A few big bore PCP projects

Forums Big Bore Airguns A few big bore PCP projects

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    Wingman
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    Some of you may have already seen a few of my big bore build threads on other forums but thought I share a few here for those that are interested.   My mission is to build a lightweight short .30cal big bore PCP from scratch suitable for taking deer and pigs with cast projectiles.    I have 3 different barrels to test with a range of twist rates and bore diameters for the range of .308 cast projectiles which are in themselves tunable in weight and balance with an adjustable depth hollow point.Ive got my money on the 1-14" twist .307.5 match barrel for the 105gr cast projectiles but also have a 1-18" twist for 80gr -120gr projectiles and a 1-10.5" twist shallow cut microgroove for up to 160gr projectiles.   This is the bullet I have chosen, it is a 115gr Lyman bullet     The mould has been modified into a hollow point that now casts a 95-110gr HP pure lead bullet depending on hollow point depths.    My goal is to get about 170-180ftlbs from this rifle so although making a bullet for a barrel before the rifle is even built may seem a little backwards but it was a big part of the R&D process for this project and I needed to be very sure there was a bullet that would suit my needs and will be stable at a lower than intended velocity range in one or more of my barrels. I pushed a sized one through the microgroove bore to get a feel of the bore friction and check out the rifling groove cuts in the bullet.. the weight and balance can be fine tuned by altering the hollow point depth and diameter at a later date if needed.     For the action I cut a piece of 1-1/4" 6061 T6-51 alloy to length and skimmed one side down on the mill to 1" to form the start of the receiver.    Then I marked the barrel/bolt centre, fitted up my 4 jaw chuck and drilled the pilot hole with a long series 8mm drill bit..    Followed by the 1/2" barrel clearance size drill and a 10mm bore for the bolt.I then cut the loading port for the feed tray and the 45 degree chamfers to pretty it up..     A little more milling and the basic shaping is done.. It will get a raius to mate up with the cylinder, transfer port and then the bolt and cocking pin cut outs on the underside..     A few more components to the list.. the rear plug is yet to be bored out and threaded for an external power adjuster/spring guide and the bolt still needs the probe, O ring groove and handle to be made.The 1-14" twist match barrel has been pre fitted and is ready for the transfer port to be drilled. I have decided to use a modified German made Gecardo trigger because Im too lazy to make one from scratch.. :)   Progress has been a little slow this week as I have been a little pre-occupied but I spent a little time on the lathe tonight and made the bolt handle.Because of the heavier hammer springs needed on big bore airguns, there is a trend to have a separate cocking handle directly into the hammer and protruding from the cylinder but I'm not a big fan of that "double action" system.     This is normally done to lessen the cocking pressure but I have decided to have the hammer cocking of the bolt so it had to be built tough and of a big enough diameter to take extra load After shaping and trimming to length I heated it red hot and put a nice bend in it. It is drilled into the bolts shaft and held tight in place by a recessed 4mm cap screw.     Next up the high flow valve.. I cut a length of 6061 T6 bar a little longer than I need for the valve but Ill use the other half on the front plug/fill valve.After turning to the inside diameter of the air cylinder I drilled a 5mm pilot hole right through and then parted it off a little over the length it will end up and bored the various port, valve shank and seat internal diameters.           Once all the internal bores were cut I measured up and drilled the transfer port and then milled a counter sink for a transfer port tube.    The valve was then slipped into the air cylinder and located it with the transfer tube. Once locked in place I drilled the holes three valve retaining cap screws and countersunk them with a 3/8"mill cutter so the heads of the cap screws are in shear load not the threaded shanks. This "pinning" system is far stronger and safer that threaded end plugs that can strip out and thin the cylinder walls in the threaded sections.       Back in the lathe for a polish and to cut the O ring grooves     Then a hole and 1/8" BSP tapered thread to fit a downward facing manometer.       With a final polish and clean it is ready for assembly.   The gauge will get a brass extension to drop it down flush with the walnut stock so I haven't wound it tight into the tapered threads        A little more progress in the last few days…I decided to use a fill probe rather than a foster fitting to keep the cylinder shorter and tidy so started by turning a fill probe out of a piece of 12mm brass hex rod and milling a blind 8mm hole into another chunk of alloy bar. I wanted to leave it "blind" so the fill port was only visible from the underside of the cylinder and lessen the risk of introducing debris in to the air cylinder and valve etc.          Once the plug was turned to a nice slip fit into the cylinder and fitted with an O ring I centre drilled the 3/32" air inlet port with a long series drill bit into the 8mm fill probe port and cut a 3mm thread for a countersink head cap screw to create the one way fill valve.      I assembled the simple one way valve design consisting of a 3mm countersunk cap screw with the thread filed flat on one side snugged down on a 005 O ring and tested/adjusted its flow rate on the dive bottle.. I adjusted it to a restriction pressure of 500psi on a fully open dive bottle valve (3200psi) which will be enough to let air in slowly but completely seal and not let air back out when the probe is removed. Works a charm.. ;D    The front plug is held in place by three countersunk 12.9 grade cap screws like the valve body again with the heads in shear load not the threads.    A small mod was needed after initial testing as it was hydraulicing the air in front of the probe which prevented me from pushing it all the way home.. a 1mm vent port drilled into the top side of the fill probe hole sorted that out and allowed the probe to seat all the way home.     So with both shiny new parts fitted up to the air cylinder I filled it with air and submerged it in a bath of water to check for any leaks then left it over night to check for any leak down.. Sunrise came and the cylinder hasn't dropped any pressure at all.  With the air cylinder sealed up and the valve working I moved onto fitting the receiver to the cylinder.The transfer port was used to centralise the action on the cylinder which consists of a steel transfer tube compressed between the two parts in blind counter-bores sealed with external O rings.         Once the transfer port was mated up I drilled the action for four flush fitting 4mm cap screws to lock it all down in place     After some careful measuring of the hammer travel and total spring compression range I then cut a slot for a cocking pin and mated it up with a second slot in the receiver for the opposing cocking pin/bolt lock up. I have used a much bigger cap screw in the bolt and recessed the head a little as it is subjected to a lot of rearward pressure on discharge, I will also be adding a second smaller "safety screw" on the bolt in case the main locking screw ever failed and tried to exit the action rearward. Its not as much as a safety hazard in a bullpup as it would exit over top of your shoulder and probably leave you with a ringing ear but in a conventional rifle set up the bolt is right in front of your nose  ūüėĮ ūüėģ              The action works smoothly but it does takes quite a bit of effort to compress the hammer spring with the added side loadings of the cocking pins etc so regretfully I think I may have to cut a second slot in the side for a stand alone direct cocking handle.  On a positive note: the proportions look pretty sweet in its walnut bullpup stock. The .308 match barrel is currently cut to 23 inches, this cast bullet barrel will be a deer, pig and goat slayer so noise is no issue and will probably stay unsuppressed.. I may make a nice break for the muzzle though.         Ive had a few emails from guys asking where I got this bullpup stock from, it is one I made a couple of years back for a .25cal Marauder but it is a bit of a cupboard queen at the moment so I have decided to share the stock and the forward scope riser mounts/trigger group with my new .30cal build. So for those of you that missed that build thread here's a brief look at the making the stock.. (sorry to all those that have seen it before) The stock started as a large 6 foot long 2.5" thick slab of 120+ year old black walnut.. I spent about an hour moving the template around the slab trying to envision the finished stock… Im very happy with the chosen piece but wont really see the true grain until I start the shaping. I should have taken a pic of the vast array of router guides and jigging I had set up to get the inletting right, It looked awkward to put it best.. This is my first stock Ive made by hand that is not to be a painted finish so Ive been sooooo careful not to slip with any power tools..that said there's a lot of work to do on it yet so if you see a sudden shift from the idea of polished walnut to a nice olive drab paint job, you can assume Ive muffed it up and had to bog something….     I spent about an hour behind the router tonight snorting sawdust and reminiscing my college wood working class…I made a good start on the inletting. Nice snug fit too.    The scary inletting job is all done, it was a little more complex than I first thought so I'm very relieved to have that stage finished..Another couple of hours behind the router and its starting to take shape..I had to shift the lateral router line down about 10mm due to the thin wood in the scope mount recesses. I wanted to be well clear so not to weaken it or in case they "broke through". It hasn't really changed the look to the original design though, they still look good.I really wanted to stray away from the "chunky" looking bullpup designs commonly seen and endeavour to produce a thinner, slick, light weightand more ergonomic stock.    I finished cutting the basic outline now and have started roughing out the contours.. Its starting to show some really nice grain now..   I've got it all shaped out now which only leaves the sanding part… lots and lots of sanding!I'm really loving the lines of this stock, the grain follows the curves just as I hoped it would whenI laid out the template. I have tried to keep the Eastern European stile lines which I'm quite fond of.Probably not every bodies cup of tea.. but then again nor are bullpups    A total of 20 hours work and the stock is finished just applied the final coat of oil. with the recoil pad fitted the stock weighs 980 grams.  …and here's the forward trigger group and scope mount risers I will also be re-using:                                A little more progress in the last few days.. Regretfully I cut another slot in the side of the cylinder to add a stand alone cocking handle, not really my preference but it is much better in terms of smooth operation. it cocks with very little effort now and the cocking handle has added weight to the hammer which may eliminate the need for an internal tuning weight. I have left it quite long but will cut it down a little once I shoot a few strings. I also spent a little time polishing the machining marks out of the various parts, eventually after all testing is done the external alloy parts will be bead blasted and anodized flat black.          I cut the bolt probe to length and fitted two 007 O rings (cool size huh) :mrgreen: to it, it seals just inside the breach against the receiver itself ant the other sits just outside the transfer port in the barrel. I am a fan of at least two O rings in this position as there's nothing worse than a breech leak on a bullpup.. loud and uncomfortable is the best case scenario and a permanently flared nostril and an eyelid turned inside out is the beginning of something quite dangerous..      I have shortened the bolts stroke to just allow a bullet in the loading tray by a second safety cap screw in the bolts shaft and added a sprung ball bearing with a detent in the bolt shank to positively lock it up in the closed position. It all runs very smooth now.      The 26".308 match barrel started its life on a .308 win target rifle and after the .308 Win chamber section was removed it showed signs of a section of throat erosion which is common and it had a an inch or so or wear at the muzzle end too probably from excessive cleaning from that end.I have trimmed both ends back to remove the bad sections and have ended up with 21" of good strong shiny rifling to work with.. I have added a muzzle break to keep the aesthetics looking right because it ended up an inch and a half shorter than I'd hoped but"accuracy first"  :D       Thanks to my gunsmith friend for the loan of a piloted .308 tapered throat ream I have the cast bullets slipping in with perfect resistance and a nice gradual taper from the lands to the groove without any angled shoulder to gather lead.This match barrel is tight, it slugs at .3072" so I will be sizing my bullets to .308" not .309" like I had intended for a .308 bore. Ill be very keen to see these on paper..      Nearly finished.. I still have to modify the scope riser mounts for this barrel and set up the trigger linkage..It is VERY light and will be a pleasure to carry, it is 30" over all length.      I test fired a few shots out of the stock and all is well.. no leaks and the breech seals perfectly. I filled it to 3000psi and fired its first string over the chrony without any hammer weights fitted.. 105gr cast HP bullet 3000psi: FPS = 921, 929, 916, 896, 881, 840, 829. 1700ish psi end pressure, not bad.. I need to fill my dive bottles to try a full 3500psi fill which should show the top of the curve rising slightly and 10-13 usable shots. I will aim to peak the thread at 900fps so will drop the hammer spring tension slightly too.Realistically this build will be usd a 50-100 yard deer gun so 3 high power even shots is plenty but I will tune the flattest consistent string out of interest. 200ftlbs in a bullpup certainly puts a smile on my face!  :D  Just for shits and giggles I put a 44gr .30 cal JSB pellet over the chrono..3000psi fill got 1176fps and it sounded like a .223rem letting rip! These pellets are too small for this bore and the twist is too fast but it was entertaining. Finally got it fully assembled and in the stock with the forward scope mounts set up, Ive just got to do a small job on the trigger linkage tomorrow and its ready for tuning and hope to get some groups on paper.I have backed the power off to a maximum of 915fps to help flatten the string a little more too so I'll also run a few more strings over the chrony..         Weight was something I was thinking of throughout this build as it is a deer rifle which means it will be carried through the hills for hours on end. I just weighed it and it is 3.5kg with the scope (7.7lbs).. much lighter than all me other bullpups. :D Its showing some very good groups at 100 yards too.. shot several groups around 1.5" today with the 105gr HP but they should get even better once my .308 bullet sizing die turns up and I can size this lead a little smaller for this tight match barrel..  I finished it  all off yesterday by attaching the new trigger linkage and polishing all the parts ready for anodizing.       Here's the results of it first 100m field test.. I tested two bullets, my 105gr HP and a 85gr HP      I shot prone of my rest and there was a strong gusty wind up the gully I was shooting through so I expected a little horizontal patterning, I'm a little over waiting for the weather to clear so I can test this build so pushed on..     After getting the scope zeroed at 100 yards I shot the following 5 shot group with the lighter 85gr HPs      I then topped it up to 3000psi again and shot these 10 shots consecutively of that fill… the wind had really picked up at this point ::)      So although a windy and rainy day I have the confidence I can get 5 shots inside an inch at 100 meters on a still fine day with both these bullets…  I will try again when the weather settles. ::) This was the first 5 shots I put on paper at 100m the other day when sighting and tuning..    With a huge THANK YOU to my big bore buddies Neil and Danny, I now have a good selection of .30 bullets to test in the pup today.. the sun is shining and there is not a breath of wind..  I will tether it and unleash the thunder on paper.. Heres the line up, Danny made me a double mould cavity with a 85gr HP and a 105gr HP to try too.The first two bullets beside the .30cal JSB pellet are both his designs one has a bigger hollow point than the other. The 5th from the left is his new 105gr HP with a larger hollow point than my one which is an attempt to get a better performing deer bullet. All the rest apart from my duller looking 100gr HP in the middle are Neils bullets. L/H to R/H: 47gr JSB, 85gr HP, 85gr bucket mouth HP, 118gr Flat Point, 105gr HP, 100gr HP, 128gr HP 132gr Spitzer, 158gr Spitzer, 163gr HP,  and for a scale reference 8.44gr .177 JSB 18.1gr .22 JSB      To say it was nice to get out of the house and put 100+ shots through the .30 would be an understatement..      Here's the results from several groups from each bullet at 100 yards prone of the rest.. some could be refined with velocity adjustments and different hollow point and sizing options but Im happy with the results I got.              Top group of the three     Middle group of the three     Bottom group of the three           Two groups from JSBs which are actually far too small for this barrel, they are designed for a .300" bore not my .3074" bore.. they did quite well considering..            The clear winners were the 100gr HPs with a 3/4" group!        Top group     Bottom group, these new 85gr HPs from Danny consistently printed 1" to 1.5" groups and will be my "go to bullet for lighter game like rabbits and goats as they have better expansion and velocity advantages over the 100gr that I will use on larger game.         It seems to like the spitzers too, particularly the heavier 158gr which brings the theoretical down range energy up a touch but in real world tests on game the tend to pass through with little terminal damage unless tipped over and sent tumbling by contact with bone.. Still they have a draw card for me and the lower muzzle report, the increase in recoil and loud thump from down range from this heavier pill just seems to feel right in this pup.. the lighter bullets seem softer to shoot but really crack in comparison. I think its time to strip it down for anodizing black then get it out bush ;D This 7.62mm will be a bit of work horse so I didnt spend a lot of time on finishing etc but have plans of some really ornate and unique work on a future build.. I've just got done giving it a registered identity (legal requirement in arms manufacturing here).. but still haven't filled out the "model" box yet.. I'm stuck for a fitting name…   

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    hasenpfeffer
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    Wow.

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    led_lobber86
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    this is truly amazing in all the ways i can imagine :D   

    a deeply satisfying read (if one can say so)   

    realy looking forward to see more :D

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    pheelgood
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    That’s a really cool story and build! ¬† Thanks for sharing!

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    ncstan
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    May I say simply amazing.Thanks for sharing .

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    jking
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    You machinist are my heroes ! 😀 lots of time and talent shared.¬†
    Thanks 
    jimmy

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    Pfcskoug
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    Very interesting read!!

    As a gunsmith myself this type of build is very interesting to me. Definitely keep us posted on your future progress. 

    Nathan

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    Nomadic Pirate
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    Wing Brother,….that is one outstanding Build,

    Can’t wait to see some hunting pictures :) :)

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    Michael
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    Great story, great pictures, thank you for sharing.

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    PaulWI
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    The fact that you not only have the talent to accomplish something like this, but the patience and generosity to document it with amazing photography, puts you in a class by yourself.

    While reading through your post I literally started laughing at the ridiculous size of and scope of the project you have undertook and completed.

    I feel like one of the monkeys in the opening scene of Stanley Kubricks “2001”.

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    manabeknives
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    WOW!! ¬†What a ¬†Post!! ¬†A Thoroughly enjoyable read….What a Nice Rifle!! ¬†Thanks for taking all that time to post this incredible build project!
    Mike 

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    Gunnertrones
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    Beautiful woodwork, and great engenering skills as well. This was a great “inside the gun”-report!

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    Wingman
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    Thanks guys, this was an early build that I learned a lot from, here’s a couple of pistol builds that followed..

     
    This build started as I had a short off cut of air vessel tubing from a length used on a rifle build.. However it is VERY short on big bore standards as they require a large section of tube in the rear to accommodate a large valve, hammer stroke and hammer spring, in this case if I was to build the same action as the .30 cal bullpup it would account for 3/4 of the length of the tubing which would be kind of pointless as there would be no volume left for air.

      

      My goal is to keep this pistols OAL to 300mm  which means no just adding a larger rear cylinder end cap to extend the hammer springs working stroke rearward which would have been easy.This is where my challenge started and I am building a bit of a prototype to test a few new dimensions and components. The first thing I wanted to achieve was the longest barrel and the shortest receiver length I could possibly get away with which meant shifting the valve body as far rearward as I could without loosing so much hammer travel that power would suffer.   I have used a different hammer spring which is shorter and larger in diameter than the one I used in the .30 Pup which gave me 12mm less length on the springs total bind length when cocked. Also being a short barrelled pistol a lighter hammer can be used to shorten dwell time on larger valve ports to get similar velocities form a larger but shorter burst of air, this gained me another 6mm. The last and most drastic design change was the valve body its self, it is 8mm shorter rear of the transfer port than the rifle length valve and I have manage to claim back another 13mm by recessing the valve return spring into the rear of the valve. 

      

    ¬†¬†Another change Ive made is reduced the poppet valve shank from 1/4″ to 5/32″ and made a stepped collar with a retaining grub screw that locks down on a filed flat..¬†

      

     

      A recessed valve spring seat means a flat or slightly recessed faced hammer can be used meaning more weight and a shorter hammer. 

      

    ¬†¬†The new valve is much shorter in total length and still has loads of meat for countersunk retaining cap screws and still within the minimum safety measurement to the edge of the material. The smaller 5/32″ valve shank means I can use off the shelf M6 X 6mm cap screws to retain the valve in the cylinder and they still wont breech the bearing surface of the valve shanks bore like it did in the rifle valve with the 1/4″ shank which required the cap screws to be cut very short.The over all valve travel remains the same as the rifle sized valve.

      

    ¬†¬†The valve spring I have used a stiff little bugger too which should help with efficiency not that that will matter much with this little pistola as it will have a low shot count with maximum power tune.The best part is the new dimensions make the back end super short which will give me a 7″ barrel and a 130mm receiver compared to the 150mm of the pups, which will be low profile and made from a smaller material than the pups, the greatest advantage is I now only have a 140mm section of tubing behind the air reservoir for the firing mechanism compared to the 200mm of the rifles design but will have the same air delivery only with the dwell tuned to a pistol length barrel.¬†If all goes to plan this will lead to future pistol builds being shorter lighter and have more air capacity for a higher shot count.I will be using a rotary multiple barrel transfer port design in this pistol which uses 3 smaller rotary ports within a cut groove rather than one large transfer port cut into the lower section of the barrel. This will allow me to use smaller cast bullets, round ball and JSB pellets without the problem of them dropping into the transfer port and jamming things up. more on that later.

    Well Ill try to cover a little of what I missed on the last bullpup build on this one so it doesn’t all just get repetitive and boring..¬†¬†I got the cylinder all marked out, centre punched and milled all the counter sink cap screw holes and transfer port into it ready to seal up and pressure test.¬†

      

      

      

      Then it was onto the fill probe so I could get air into this new high pressure vessel..I went with a different idea on this build as I want to keep smooth lines and minimal length I didnt want extra material out the front off the front plug to drill in the probe port like I did on the pup so I drilled these front plug retaining cap screws 180 degrees to the valve retaining screws and drilled an 8mm probe port between and forward of the two lower cap screws.. this puts it out of sight and no need for unsightly protruding Foster fittings.

      

    ¬†¬†Due to the new location of the port ¬†I couldnt use the probe I made for the Pup because it was longer and would have come too close to the top cap screw so I made a special “pistol” probe and included a male foster into the design to save the need for a screw on adaptor. This way it plugs straight on to my whip line.

      

      

      

      

    As most of you know wood is by far not my favourite media to work with however Im quite looking forward to making the grip for this one.. it seams a little less daunting than a full sized rifle stock and some of the past bullpup stocks I’ve tackled leave me saying “never again”..I will be making an ambidextrous target style grip for this one.¬†Part of my attraction to this dusty project is that I have been saving some very special pieces of timber for just such a project.. a really nice piece of heart walnut with some great colour and grain and also a piece of rare Wenge timber.Wenge is the product of the Millettia laurentii tree. Native of the Republic of Congo, Cameroon, Gabon and equatorial Guinea. The tree was put on the endangered list due to the destruction of its habitat and over exploitation for timber. This piece was brought to NZ by a south African Knife maker and after many years of sitting on a wood rack came to my possession.The colour of the wenge is a nice dark misty brown with almost black striped grain.. a very beautiful colour when oiled. It is VERY hard withj a tight grain and was often used for knife handles and inlaying etc.

       

    This time round I am determined to set this pistol up as a “cock off bolt” system.. the bullpups intention was there but due to design changes and the power output it was just not pleasant to use in this manner. With this short stroke pistol however I have corrected a few of the design features that worked against me on the pup such as bore hight, slot dimensions and side load/friction points which have now given me a super slick cocking stroke that I can cock by hand even without a receiver and bolt to assist.¬†The design change started with a much narrower slot cut into the cylinder for the cocking cap screw and a free rolling brass bush made to run in the slot.. both the bush and cap screw will be cut down and polished once the receiver is mated upNote: the hammer in the fist pic is not actually the .30 pistols hammer it was just one I had on the bench from another .44 build.. (my hands were too dirty to go get it for the pic from inside) the .30 hammer is the one in the bottom pics with 3 contact bands and a more central cocking pin.
      

      

      I have decided to use a Crosman trigger and grip frame on this pistola as it will do the job nicely.. They are not the toughest built frame but with a bit of sear work and some shim washers it has made a very acceptable trigger. With a quick pre-fit of all the parts and a 3000psi fill I have tested the firing mechanism and valve operation on max power and there is a very pleasing and loud discharge of air moving through the open transfer port.. It looks/sounds promising to push the 85gr HP bullets to the fun side of 100ftlbs ;D

      

    ¬†¬†So with the engine room and fuel tank completed I have moved onto trying to finalise what I want this little hand cannon to look like..¬†I have done a quick concept on Photoshop of the receiver and front shroud design I have had floating around in my head since I started this build.. it may look a little more like an “auto pistol” than the traditional exposed barrel look but Im still undecided. This target stile grip design however I have decided on and will be sculptured from the heart walnut.

      

     Today I made a start on the receiver, mostly slow going where the machine set up takes an hour then the job itself is done in a couple of minutes..  ::)So after carefully marking it all out the off centre bores were drilled and threaded in the 4 jaw chuck then it was onto the milling.

      

    ¬†¬†I first drilled the 4 holes that will secure it to the cylinder with cap screws and then milled the top down for a 3/8″ dove tail to mount optics.

      

      Once roughed out with a end mill cutter I used a 60 degree dovetail cutter to cut the dovetail and get the final dimensions

      

      followed buy the loading tray, rear bolt handle cut out,  all the various cosmetic angles and the radius to mate up with the cylinder.

      

      

      

      

      

    A final push today to get this to a testing state and it is finally there..¬†I didnt take many photos during the bolt and barrel work but will snap a few more when I strip it down for finishing again..Here’s a couple of the barrel cut to length and threaded ready to be fitted, torqued and transfer ports drilled.

      

      

      Here it is with its sister .308 Bullpup all assembled.

      

    ¬†¬†Here’s the receivers side by side to show the difference in the new short stroke design..

      

      I still have loads of work to do on it with some nice walnut target grips to make and polish/stamp the receiver etc.Im very happy with the cocking action on this one, very smooth and not so heavy that its awkward.I made the bolt much larger in diameter and it stand only 5mm from the hammer so side loading is minimal.I have put about 50 shots through it and got some satisfactory chrony figures but with only 2700psi left in my dive bottles I have to do an air run to town before I can shoot some full strings and do some paper punching. Even with only 2700psi I got 5 good shots with a max of 842fps with the JSBs 44gr  and a couple of good shots with the 85gr HPs which just broke 700fps at 93ftlbsIt has a lot of recoil and is louder than my bullpup so will definitely make your ears ring without hearing protection..

      

      

      

      

    Accuracy with the 85gr bullets seems good, here’s 3 shots rested at 35 yards ¬†:)

      

      

      

    Ive been tuning this little .30 hand cannon all week with a variety of hammer weighs/strokes and transfer port sizes and have settled on a nice compromise.Currently gets 5 shots with .30 JSBs with a 850fps av, 5 shots with 55gr HPs with a 750fps av and 5 shots with 85gr Hps with a 650fps average..I had intended to get the 85gr HPs up to 750-800 for 2-3 usable shots but Im quite liking the current tune as they all shoot well and pack quite a punch. I swapped the crappy fake wood grain Crosman grips for the slightly less crappy Benjamin Marauder grips just until I get around to making the walnut ones, also tried the carbine stock on it..

     

     
    ¬†Its been another fun build and even more fun to shoot.. it LOVES the little light weight 55gr hollow points and at 75-80ftlbs it makes a mess of anything it hits.¬†Just finished building another pistol for close range deer and pigs etc.. A .44 cal that shoots 163gr custom hollow points to 150ftlbs, currently getting 5 shots on a 220bar fill with a “mild” tune but it is capable of 2 shots at 200ftlbs.¬†¬†Both pistols are now in line for some custom walnut target grips.. ¬†:D¬†¬†

     

     

     

    ¬†¬†Today I did a little bit of experimenting with the .30 pistol and JSB pellets running a milder tune…¬†Lately I have been running a 7 1/2″ long 1-14″ twist 4 groove match barrel with the cast 55gr and 85gr HP bullets but I wanted to see if I could get the JSBs to shoot better. I have found they actually shot quite well with the shorter 1-10.5″ twist micro groove barrel when fitted with a .22 silencer drilled out to suit the .308 bore. The cheap chinese .22lr suppressor although undersized and not very good at removing the bark did somehow stabilise the hefty .30 JSB pellets better and reduce the horrible groups it shot without the suppressor.It probably works by defusing the massive blast of air from such a short barrel disturbing the pellets skirt design as it vacated the muzzle causing an unrecoverable speed wobble..Never had probs with shooting the cast bullets though.¬†So today I received my $14 Airsoft 9mm silencer from Ebay and stripped it out to an empty can…Some Airsoft silencers are made from very good alloy and with a few mods can be a cheap airgun suppressor. Both the front and rear of this brand are threaded on (not glued like most) and will easily handle the blast from an air rifle and will cope with the massive blast from this big bore pcp too…¬†I removed all the foam from the inside and made up a set of baffles and spacers then made an adaptor for the rear plug from the std airsoft 14mm thread to the 1/2″ x 20 UNF of my muzzle.¬†I ended up with a very cheap .30cal to 9mm muzzle can that really shuts this thing up and squashed my 5 shot JSB groups to inside an inch at 35yds with a 745fps av ¬†;D ¬†Without the suppressor it would be lucky to put them inside 6 inchs!

      

     

      

    Really it shouldn’t be working at all and I had written the JSBs off as being too small when I first tested them and got 6″+ groups at 25 yards.. It was only by chance that I was testing the suppressor that I put a few JSBs through and was pleasantly surprised!¬†¬†The bore slugs at .307.5″ and I size all my cast bullets to .308″ with good results.¬†The JSB pellets I have here measure .302″ at the head and .309.5″ at the skirt, When pushed through the microgroove marlin 30-30win barrel the heads seem to “bore ride” leaving only very slight rub marks, however the skirts even without the shot pressure to open them up cut nicely into the rifling and ¬†turn freely through the twist with mild constant felt drag.. Heres how the pellet looks when pushed through.. Ill have to fire and recover some to see if the skirt is expanding happening also..

      

     

      I tethered it to my pony bottle on the bench holding it firmly in a front rest and cut a 25 shot ragged hole group at 35 yards with only 3 flyers just outside the inch! impossible to see the impact in the scope though as the muzzle flip even with the suppressor fitted kicks it up out of the rest! 

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    mikes
    Participant
    Member

    A great post.  Thanks for sharing.

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    Dan.C
    Spectator
    Spectator

    your guns are breath taking,  a gift for the air gun world. Im blown away by the detail and craftsmanship put into the builds. Thank you for sharing these gems.  

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    Wingman
    Affiliate
    Affiliate

    I dont have the time at the moment to put together a full build thread for this little new one but will throw a few picks up as I go.. Finally spent a couple of hours on the mill and lathe and made a good start on a 9mm pistol. I really like the way my little .30cal pistol handles but wanted a little more punch so have designed this one to shoot the .357 cal JSBs and a 125gr HP cast bullet.. It will be a little smaller than the .30 cal and will get a full length receiver/barrel shroud and open sights to give it more of an auto pistol look. 

     

      

    First pressure test 

      

    It was quite a challenge to drill the required four different sized internal bores
    with long series drill bits as all my boring bars were just not long enough..
     I will have to cut it in two parts to tread the barrel into the breech anyway
    but I will do as much of the machining I can while it is in one piece. 

     

      

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    Verve
    Participant
    Member

    Gosh! Speechless! These would be very pricey collectables one day.

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    steppenwulf
    Participant
    Member

    Incredible  posts. thanks for sharing!
     

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    ozone08
    Participant
    Member

    great thread the last time I seen a member announcing that they were going to build their own air rifle they refused to¬†give any details other than ‘it’s an air rifle’. ¬†very impressive you do good work sir I see a bit of everything in there in terms of manufactures I really like the trigger mech many companies wont make a bullpup for¬†not wanting to¬†solve that puzzle but it looks like you knocked it out of the park¬†fairly simply.¬† as for the stock that’s a bit of art well done I love it.¬†

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    Nutcracker
    Participant
    Member

    Now I do feel dumb & inferior.  However, I love to see such skill  & quality come together . Good stuff man, good stuff.

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