Mutant Project 🤔

[mtnGhost]

Took the plunge a week or so ago and decided to add a bipod rail to my little Mutant. I've never been a fan of shooting from bags, so the rail is ideal for me. I have to say, this stock has to be some of the densest wood that I have ever seen on a PCP. I think it's beech, but I'm not totally sure. It's strong enough that I probably could have got away with the drilled and tapped threads alone for the rail, but I don't trust them for longevity and I use T-nuts when I can.

I seated the T-nuts in wood filler, the sanded and stained them afterwards. The stain came out decent, but I just wanted to keep that area nice and flush for the air cylinder:

So now that I finally have a rail on this thing, I'm debating on what I should do next - if anything at all. It was setup by Charlie Freer to shoot 18gr JSBs in the low 800's. I had tested 20.2gr NSAs and 22gr FX Hybrids with the CZ barrel when I got it from the original owner, and they were slow - but very accurate with this barrel.

I'm debating on whether or not I should build a new valve for it. I would probably be able to drop the reg pressure significantly if I did (and likely get a few additional shots out if it per fill). It would also give me the option to shoot slugs (much flatter), and provide greater versatility for hunting / pesting / BR. On the other hand, it is incredibly quiet (the quietest that I own) and has a decent enough shot count as it sits. 

It's a tough decision. Anyone have thoughts?

 

[mr.grimm]

When you make a new valve for it make 2 so I can by one from you. As far as your Mutant goes try to crank some more power out of it and let the slugs fly

Phillip

 

[biohazardman]

Nice professional looking job on the rail install. Actually probly better than most professionals would do from my past experiences. Whenever there is a modify it decision to be made my default is always set to modify. ;^) Anytime something can be made better than it is and the thought comes into view it really needs to be done or I spend entirely to much time, with much mental anguish involved, debating it with the addiction.

 

[Motorhead]

I had done a full tuning and modification to my personal Mutant Standard @ 4 years or so ago and shared the mods with pictures over on the TALON forum.

It covered modifying the valves throat size to equal that of the @ .200" transfer path already there. Made a PEEK poppet and a bit later another poppet utilizing the COBRA tech "Air Spring" mods. Plenum space was increased by moving the reg forward to the limits of the vent hole while using a thinner wall tube for the standoff. Vent placed on the HST thimble hole to eliminate suction created as hammer travels away towards the valve when fired.

All done the gun gained IIRC @ 5-6 FPE

Playing with reg pressure was a no win minimal gain game quickly creating VALVE LOCK due to these guns having VERY light hammers in them. Came to the conclusion there PELLET shooters and EXCELLENT at that designed task ... Sluggers IMO they are not really suited. The Mutant SHORT as your picture shows even Less So !!



Scott S

 

[mmahoney]

I agree with Scott. If more power is wanted you are better off moving up to the standard or long versions of the gun.

 

[mtnGhost]

Nice professional looking job on the rail install. Actually probly better than most professionals would do from my past experiences. Whenever there is a modify it decision to be made my default is always set to modify. ;^) Anytime something can be made better than it is and the thought comes into view it really needs to be done or I spend entirely to much time, with much mental anguish involved, debating it with the addiction.

Thanks man. I'm my own worst critic, but I think it turned out alright. If anything, function over form and I don't see this thing going anywhere lol

I had done a full tuning and modification to my personal Mutant Standard @ 4 years or so ago and shared the mods with pictures over on the TALON forum.

It covered modifying the valves throat size to equal that of the @ .200" transfer path already there. Made a PEEK poppet and a bit later another poppet utilizing the COBRA tech "Air Spring" mods. Plenum space was increased by moving the reg forward to the limits of the vent hole while using a thinner wall tube for the standoff. Vent placed on the HST thimble hole to eliminate suction created as hammer travels away towards the valve when fired.

All done the gun gained IIRC @ 5-6 FPE

Playing with reg pressure was a no win minimal gain game quickly creating VALVE LOCK due to these guns having VERY light hammers in them. Came to the conclusion there PELLET shooters and EXCELLENT at that designed task ... Sluggers IMO they are not really suited. The Mutant SHORT as your picture shows even Less So !!



Scott S

Ok, Scott is not optimistic so now I have to do it!

The real itch / motivation for this is turning this 50y gun into a 100y shooter. My original idea behind scoring this Mutant was pesting 25-40y (max). The varmints somehow figured out that they're safe beyond that distance. I'd like to get it shooting the FX Hybrids or getting the 18gr pellets at 30-35FPE without it pulling a groin muscle.

I boosted my Vet 25FPE for the H&N slugs, there's some differences with the Mutant's porting, but I'd be hedging on squeezing another 5-10FPE using that valve design customized a little for the Mutant. Worst case scenario - I swap in my 500mm FX barrel to make up for any shortcomings on power, but I think I could get there without it.

 

[mercado]

I was thinking the same about my 177 cricket compact I wanted to shoot 13g slugs but is so quiet shooting 10.34 g at 900fps thatI decided to test 11.g slugs the awesome acurate up to 90y so I will leave it like that because the point was to have a compact gun....maybe try to shoot the lightest slug 17.5g the fastest you can...my greatest longer kill was made will a .22 cricket compact with the 17.5 Nielsen at 910 fps 210y stock gun.. 

 

[Motorhead]

FWIW when i tried to shoot slugs from it, replaced the CZ barrel with a 24" HW 6 groove no choke. * Tho in factory trim as set with the oem CZ barrel in place & shooting JSB 18's it mustered @ 35 fpe maxed out with 18 grainers and just shy of 40 ft lbs with 21 grainers & with the longer 24" barrel a bit more speed 30-40 fps IIRC telling that the valve dwell just did not cater in delivering more air volume to take advantage of more barrel length.

Adding a SLUG in either being aware of the "IN BORE" drag being more so than a pellet, for comparable weight ( pellet / slug ) there were losses and not gains in FPE obtained.



GOOD LUCK !!!

 

[mtnGhost]

FWIW when i tried to shoot slugs from it, replaced the CZ barrel with a 24" HW 6 groove no choke. * Tho in factory trip As set with the CZ barrel in place & shooting JSB 18's it mustered @ 35 fpe maxed out & with the longer 24" barrel a bit more speed 30-40 fps IIRC telling that the valve dwell just did not cater in delivering more air volume to take advantage of more barrel length.

Adding a SLUG in either being aware of the "IN BORE" drag being more so than a pellet, for comparable weight ( pellet / slug ) there were losses and not gains in FPE obtained.



GOOD LUCK !!!

Thanks. I just cracked this Mutant open for the first time, I'm poking around taking measurements. The valve body, pin, and poppet looks the same as the Vet.

The buck stops there though, everything else looks completely miniaturized . Bummer, I machined a valve spring stop for the Vet with an adjustable spring tension feature (I got real tired if making springs and little PEEK valve spring bushings which were about impossible to fine tune). Needless to say the OD is too large for the Mutant, so I'd have to make another one.

The poppet head looks somewhat optimized compared with the Vet's, but what bugs me most is the teeny tiny port in the block. That thing is small.

I knew this thing wasn't built for power, but I still have some ideas that should get me close to my goal. I have a couple of things that I can do to test those theories in the short term, so I might as well give it a go and see what happens 

I was thinking the same about my 177 cricket compact I wanted to shoot 13g slugs but is so quiet shooting 10.34 g at 900fps thatI decided to test 11.g slugs the awesome acurate up to 90y so I will leave it like that because the point was to have a compact gun....maybe try to shoot the lightest slug 17.5g the fastest you can...my greatest longer kill was made will a .22 cricket compact with the 17.5 Nielsen at 910 fps 210y stock gun..

I had some surprisingly good results with the 20.2gr Nielsens @110y when I tested them (on a real windy day). They weren't under 1/2" by any means, but they were relatively tight up to 930fps - certainly good enough for hunting small game. I can't see shooting any 22 cal slugs lighter than those though.

This Mutant can probably shoot the FX Hybrid slugs close to, if not beyond my goal if I upped the reg pressure, bored the valve body to form a nozzle, increased hammer weight + heavier spring, and probably swapping out the valve spring. It's set at 125bar right now, maxing out at 26FPE with 18gr pellets. If the reg goes above ~135bar, it will get ugly and won't quite be the same. My guess is that I will see +60fps with another valve, but I'll find out soon

 

[DanielL]

Nice work. I almost did something similar. Was going to order a T-nut channel and inlet it into the stock. Then I realized I'd need special longer screws and I have other guns were the rail is attached with wood screws that have never budged so I went with 3/4" long #10 philips head black wood screws. Fit the holes perfectly. 

 

[Motorhead]

Stated: The poppet head looks somewhat optimized compared with the Vet's, but what bugs me most is the teeny tiny port in the block. That thing is small.



In my Mutant standard IIRC the brass valve body THROAT was something like .215" yet the transfer path out of throat and threw the mono block was at @ .200" then the hole in barrel was smaller again. IIRC once more ... the throat was opened to @ .240" that when area figured and that of stem the resulting area was equal to the .200 transfer path.

barrel port opened up to be an elongated shape with equivalent @ area.



Did a bit of digging over on theTalon archives and found the post. See: https://talonairgun.com/forums/topic/balancing-the-flow-within-the-mutant-valve/

 

[mtnGhost]

Stated: The poppet head looks somewhat optimized compared with the Vet's, but what bugs me most is the teeny tiny port in the block. That thing is small.



In my Mutant standard IIRC the brass valve body THROAT was something like .215" yet the transfer path out of throat and threw the mono block was at @ .200" then the hole in barrel was smaller again. IIRC once more ... the throat was opened to @ .240" that when area figured and that of stem the resulting area was equal to the .200 transfer path.

barrel port opened up to be an elongated shape with equivalent @ area.



Did a bit of digging over on theTalon archives and found the post. See: https://talonairgun.com/forums/topic/balancing-the-flow-within-the-mutant-valve/

Thanks Scott, I think we're aligned a great deal. Side note, I think this would make one hell of a .177! Nonetheless, I had pretty good luck last night boring out the factory valve body for the firehose nozzle mod. I also removed the barrel and saw that the TP was crudely drilled into the bottom of the barrel. It looked like whomever setup that barrel drilled a nice port into the bore, and then rushed the chamfering on the outside. It was very rough and I had to clean it up and polish it nice and spiffy. I cleaned everything up in the valve area, swapped in new o-rings, and removed the gallon of oil that I found all inside the rifle.

Without touching the reg, it's shooting 18gr 857fps consistently. I wanted to turn the reg up from 125 to 130 or so to see if that got me where I wanted to be, and I apparently went the wrong way LOL .. it's now set at 117.5bar and shooting 815 (I don't have a reg tester this long).

 

[mtnGhost]

Nice work. I almost did something similar. Was going to order a T-nut channel and inlet it into the stock. Then I realized I'd need special longer screws and I have other guns were the rail is attached with wood screws that have never budged so I went with 3/4" long #10 philips head black wood screws. Fit the holes perfectly. 

That looks good! I wound up using longer hex button heads. Ground them down to side, filed and blued them.

 

[mtnGhost]

Talk about laborious

 

[mtnGhost]

Quick follow up on this little Mutant project of mine. I wound up having issues with the valve body and the PEEK valve pin that I made for it. There was a little spot on the edge of the input port that became non-concentric when I did one of the final operations It was enough that I couldn't get the stubborn PEEK material to seal, so I wound up putting that project to the side until the other day, when I decided to try my luck and whip up a new one using a specific type of Delrin (which is still pretty hard - but has a little more give than PEEK).

This new valve pin sealed it well enough that I could hold air and run some tests over the chrono (but is bad enough that it leaks down overnight). The results that I got from this new valve were very good though. At 130 bar, I shot a mag of each of these and got the following averages:

• 18gr JSBs at 924FPS
• 16gr JSBs at 994FPS 
• 16gr Hades at 988FPS 

That puts it just a tad under 34FPE without pushing it too hard. The one thing that I had completely forgot to test: shot count!!! I wasn't paying attention to the air consumption, but it had to be somewhere over 4 mags (12 shot mags) because I only filled once.

So afterwards, I came full circle and reinstalled the factory valve and turned the reg back down a few bar. What I am realizing is that I am enjoying a 12-14FPE tune the best.

Optic - I'm on the fence about what would be the best optic to run on something like this. I'm afraid to put a variable power scope on it (such as my NX8 1-8). I'm still running with this little tiny Burris red dot for now, but I have been able to hit 12oz cans with it at 75y with great consistency The red dot is a lot of fun, so I might consider putting something like the new Aimpoint Comp M5B when they actually become available

 

[DanielL]

4 12 shot mags doesn’t seem bad for that power level and that reservoir size.

 

[mtnGhost]

4 12 shot mags doesn’t seem bad for that power level and that reservoir size.

Right? What I found even more incredible is the shot count with this 12-14FPE tune, where I'm getting 154 shots with the smaller 16gr JSBs / Hades. It's a very light and efficient little shooter, and I would go as far as to say that I'm liking this on more than my Leshiy.

 

[mtnGhost]

I discovered this Mutant barrel REALLY likes the 20.2gr NSA slugs. Brought it out a couple of days ago to pluck some birds, but the wind was blowing 10-20mph and I was having a tough time shooting 16gr over 60y.

Loaded a couple of magazines with the little slugs, with the factory reg at 139bar (and running the factory valve), it was only sending them at 750fps. They flew true and on target though, grouping at 1.5-2" off my shakey bipod in stupid winds, but I was only running a 1-8x optic (fixed parallax at 125m). Not exactly longer range PRS glass  

I had the burning desire to pick back up on power tuning this Mutant after that day. I had left off needing to fine tune the valve body and valve poppet, and I went back and forth on whether or not I wanted to bore out the transfer port in the block.

So the first thing I decided to do was drill the block. I was going to drill it to 1/4", but decided to stay on the conservative side and went a little under:

Then I finished the valve body and valve poppet. I used the "Fatboy" design from the Veteran, but I trimmed down the head some to optimize the plenum volume. This modification had a caveat - I would lose 4.9mm of distance between the valve spring stop and the valve spring seat on the poppet, so I made a valve spring seat riser with PEEK that provides 6.5mm of spring pre-tension:

The next thing I wanted to do was make a new hammer with a few modifications to the geometry. I used high quality marine brass that gives me an additional 2 grams with some prototype features that I needed for testing:

I left the factory reg sitting at 139bar, put it all back together and tested out some new springs. When I opened it up, my chrono read 836fps max with the 20.2gr and FX Hybrids. Roughly 85fps over what I was getting before.

The next mod that I have planned is to install the Huma reg that Derrick sent me in a trade deal for my spare Veteran reg (long story lol). I should have that in the mail tomorrow, I'm targeting 145-150bar with that reg, and I'm very anxious to see the results

 

[mtnGhost]

Mission completed. I can't stress how difficult this little power tuning project turned out to be. Going from 25FPE to 32FPE (with 20.2gr NSA slugs) almost felt like trying to go to the moon on a bicycle, but I really like this little rifle and needed the options for reaching out beyond 100m on windy days with it.

In the end, I had to drill out the block to 7/32" (modifying the barrel port meticulously to match), run a slightly lighter / longer hammer spring, and increase the size of the valve spring pretension seat.

I have a new Huma regulator from Derrick, but there's something screwy with the Belleville stack and it can't be set over 140bar. This is fine though, even with these modifications, I have not lost any abilities to turn the power down for 16gr using the 125 shot 20FPE tune / 160 shot 15FPE tune