FX Impact. Enough fpe for .30 slugs?

[Virginia_Joe]

Cool, do you have any info on that... ?

 

[Airgun-hobbyist]

Here's a picture of said hammer weight if you have a friend who could machine one for you. The print of the hammer weight does not show the inside through hole that needs to be drilled between 3.5mm and 4mm. It seems that the 8mm dimension should 7.4mm, and the 5mm dimension was a bit thicker than need be for hammer spring preload. The outside diameter can be checked against the diameter of the spring and plastic spring guide that will be removed upon installation of the new brass weight.

View attachment MTU3MDg0NDQwOF8xODcyMzg1NzI4NWRhMTJlZjgyZjEyODQuOTA3MDYwOTFfU2NyZWVuc2hvdF8yMDE5MTAxMS0yMTM3MjV+Mi5wbmc=

 

[heavy-impact]

I have a theory, and I base this on evidence of my FX Impact MK2 .25, Cal 700 mm, using NSA 36.2 gr. slugs. When I got the MK in July I tuned it in for the Jumbo MK II JSB pellets, and it didn't take long before I was shooting with great accuracy... right around 915 FPS. Then came the slug liner, and from the get-go I had trouble tuning it in. But I will make a long story as short as I can. While FX had increased the capacity to move air, they did nothing for the hammer spring... it's the same hammer spring used on the old FX, the smaller calibers, etc... and that used to be fine. But, the slug liner creates more resistance, the slug has more surface area in contact, the slug does not squish, and the slug is heavier... all in all the amount or air to move this slug has dramatically increased as expected. What I found is there is a DP across the valve; one side is the regulator pressure, the other side is atmospheric. To open that valve, the hammer has to have enough velocity to overcome that DP on the valve. What I have found is to increase the regulator pressure you must also increase the hammer spring pressure; they go hand in hand. I can tell you with my impact, I am currently getting about 915 FPS with the hammer spring at .585 inches. The maximum I can go is .560 inches. So I don't have much room, nor do I want to sit on the tightest setting either. The current regulator pressure is 148 BAR. I walked that hammer spring from sloppy lose to .585, so I know that I only increased in speed... meaning that the valve did not open too much. Now I will tell you part II. Last week while trying to tune it in, I got some erratic behavior. I suspected too much hammer spring. At the end of the day I was at 165 BAR, with the hammer spring maxed out and only getting 400 FPS; I will re-type..not a typo... 4000 FPS. It was pitiful. The key came when I looked at the reservoir pressure. After 28 shots I only used 25 BAR. In other words, the valve was not opening very far, or for very long. The 165 Bar was too much pressure for the spring to overcome. It seems to me that the design of the MK2 failed in the strength of the hammer spring. Shooting slugs, or getting a slug liner should come with a beefier hammer spring.

Slugs do "squish" or they wouldn't pass through the choke. They're pure lead and soft.

4 grams of added hammer weight works well.

My setup..

.30 700mm slug liner

Elongated brass port and half pellet probe

6.35mm valve + 4 gram hammer weight, OEM spring

95cc total plenum space at 150 bar

50gr jsb 1072 fps, 66gr NSA 948 fps

These numbers were just testing. I haven't been to the range yet for tuning.

 

[Virginia_Joe]

Thanks Airgun Hobbyst & Heavy Impact; ... I live in an area where I'm the only one I know of that has any air rifle (springer or PCP) so info is limited.



So what I'm getting is that I need to machine a small additional hammer weight (around 4 gr give or take). I actually asked a similar question in a forum overseas. Their answer is to replace the C3 bumper with a Delrin substitute... which will also have to be manufactured. I ordered a 8mm Delrin rod, and various sized drill bits in and around 3.13-3.5 mm based on feedback (no real clear answer on the hammer slide rod diameter). Their beef was the original o-ring is absorbing to much energy of the hammer spring. And to a point I get both jobs are probably necessary. And of course there are people who insist that a beefier spring is the answer. I've read that adding mass will increase the dwell time, but has no effect on the valve cracking. And a beefier spring will crack the valve better, but does nothing for the dwell time. I'm an engineer, unfortunately an electrical, and that does zip here, but I do understand the principles in play. However, we are dealing with many variables, many of which are completely unknown.. such as the friction, accuracies, etc... so I think it will boil down to a little experimentation of added mass, a more robust and better transfer of energy bumper, and possibly a beefier spring.

Heavy Impact - Wow I like your numbers; good job Sir. BTW I realize the slug I have chosen squishes compared to hard lead, or other metals... my point (albeit written poorly) was the slug design does not have a hollow area like a pellet, where if squishing was necessary (and it is to a degree) it is much more resistant to squish than a pellet. I am making the case that slugs require more energy, and that energy is stored air. In short pellets are easy-peasy compared to slugs. 

Good conversation guys.... today I'm off to increase the reg pressure just a tad. I still have about .025 worth of hammer spring adjustment left to work with. 

 

[jaird]

V_J if you are located in Virginia, what general area? I live in SW Va. Have not found other airgun people around here.

 

[Virginia_Joe]

Jaird, - I'm in Hampton Virginia. I do plan on being out at Halifax next week for bow hunting (i.e. headed SW). I was hoping to have the FX tuned in and ready for squirrels, but right now (today, moments ago) I finished up tuning for a bit, I'm not sure it is ready. Currently I'm at 152 BAR, with the average speed about 927 (until I run the numbers that's a ball park).The hammer spring is getting close to that max value... it should be less, which is why I jumped into this conversation. The groups did improve a hair, seems to me the low 930's is about right for the NSA 36.3 HP. I'm shooting at 30 Yards and getting about a .33 " 5-shot group. Previously with pellets and the pellet liner I was one hole grouping and .25 was about average groups. I think with a little tweaking this FX will do well. I see these guys in South Africa hitting doves in the head at 150 yards. That's pretty damn impressive. I'd like to see if I can do similar to some tree rats. Shooting is not hard, tuning...well that shouldn't be hard either, but I think I'm at the boundaries of the design.... I'm thinking that I need to get in the gun and change out the C3 bumper, and put in a heavier spring, and maybe some mass as well; the mass however is dicey. I see trouble on keeping it snug. If it comes lose from the hammer, I see trouble.

How far West are you? I actually went to school probably a tad bit further west.. ETSU in Johnson City I went there on a shooting scholarship back in 1980-1984. Things in the air gun world have really improved since then. Back then I was required to shoot an air rifle in competition; but they were prehistoric compared to what is out there now. I've been waiting to jump back in (for fun, no more competitive shooting for me) , watching the PCP evolve. When the Impact MK2 came out, and the Nomad II came out... well it was time.

Glad to know there is another air gunner in the state... excuse me The Common Wealth. By the way my goal is accuracy more than power. But these slugs need the speed to fly well. I'm just not positive I'm at that point yet. My regulator does weird things... I call it slipping. For no apparent reason it seems to be set and shooting at X- BAR, and 20 shots later it may or may not be at X-BAR . Once it's set and has been there for awhile, then it is rock solid. So when I had it up earlier today.. I was shooting one hole groups when the speed were at around 933, but then it slipped, and I am around 927 FPS. Doesn't seem like much, but the groups are much better. I think the slug is flying well at that speed, and my harmonics may minimal at that speed... 

 

[heavy-impact]

I'm thinking that I need to get in the gun and change out the C3 bumper, and put in a heavier spring, and maybe some mass as well; the mass however is dicey. I see trouble on keeping it snug. If it comes loose from the hammer, I see trouble.

A brass hammer weight replaces the plastic spring guide inside the hammer and is captured between the spring and hammer. It can never come loose. You can make it yourself by drilling a piece of brass rod to 3.5mm (5/32" will work) then chuck it in a drill and cut the OD with a file to fit inside the spring leaving a flange on one end like a nail head equal to the spring OD. Around 4 grams works well. If you have a 5.5mm valve seat you can drill it to 6mm (15/64"). Do a little port work on your brass inlet and probe. Do not make the brass port any wider, just elongate it and flare the entrance enough to cover the 7mm port that feeds it. Pellet and slug feeding remains the same as OEM.

 

[Virginia_Joe]

Heavy Impact.... OK.. now I see the bigger picture. Duhh. Once you see it makes sense. You are replacing the spring guide with a brass spring guide, and because it has a flanged head it gets propelled too.

As far as the port... I don't think I'm brave enough to start drilling into existing material. The FX is literally weeks old, and as you can see I'm not yet up to speed with you AGN guys.

Thanks for the help. I do have one more question. I asked these guys over in the UK that sell beefier springs; unfortunately they only sell OME or the infamous 12 FPE spring. However he did say "The .30 cal rifles have an extra Delrin washer behind the hammer spring to put more tension onto the system". Have you seen or head about that?



Thanks

Joe

 

[heavy-impact]

Heavy Impact.... OK.. now I see the bigger picture. Duhh. Once you see it makes sense. You are replacing the spring guide with a brass spring guide, and because it has a flanged head it gets propelled too.

As far as the port... I don't think I'm brave enough to start drilling into existing material. The FX is literally weeks old, and as you can see I'm not yet up to speed with you AGN guys.

Thanks for the help. I do have one more question. I asked these guys over in the UK that sell beefier springs; unfortunately they only sell OME or the infamous 12 FPE spring. However he did say "The .30 cal rifles have an extra Delrin washer behind the hammer spring to put more tension onto the system". Have you seen or head about that?



Thanks

Joe

The head on a brass hammer weight acts as a spacer for extra spring preload. The pellet probe and brass port are available from FX USA for about $50 if you ever wanted the gun to be in original condition again. Modifying those two parts are the key to power.

 

[Skidoo165]

I used washers in my hammer before I got edosan's hp kit, seemed to work just fine...

 

[jking]

I elongated my 30cal brass port yesterday. I think it turned out pretty good going very slow with a dremel. Really didn't see much of a increase in speed but I think the hole in the 30 is near full bore already. Also modified the probe that I had double ported to a single port with the top half removed (thanks Edosan). Currently with the 6.48mm VS with these two mods at 160bar and the stem limiter at would be at a 5th line its running 1010-1015fps. Back on the 4th line abut 995-1000. It actually shoots really well at that velocity. Hoping to do some coyote hunting in the near future with it.

jking

 

[Virginia_Joe]

Heavy Impact... My guess is this is what you had in mind. The cost is reasonable given I really don't have a lathe, and by hand I don't think I could do as well. So I just ordered it . About $40 + shipping/taxes. I found on Ebay By next week, the squirrels had better be focused . Thanks again. By the way I did watch some videos on enlargening the that brass port and pellet probe. Doesn't seem hard as I first thought.

 

[heavy-impact]

Heavy Impact... My guess is this is what you had in mind. The cost is reasonable given I really don't have a lathe, and by hand I don't think I could do as well. So I just ordered it . About $40 + shipping/taxes. I found on Ebay By next week, the squirrels had better be focused . Thanks again. By the way I did watch some videos on enlargening the that brass port and pellet probe. Doesn't seem hard as I first thought.

That's a really high price but it will work.

 

[teufelhund84]

What is your barrel length? Would you mind sharing your settings for this tune? Reg press., hammer spring tension length, valve setting. thanks 

 

[Virginia_Joe]

Sorry Teufelhund84... I somehow missed your e-mail. Sure I will share.

Barrel 700MM

Wheel always on MAX

Regulator is at 160 BAR

HS is at 0.60

VS is at .355 on the flange (There is a small flange in front of the FX body, it is more accurate to measure from there)

Average FPS = 928 FPS



I shoot at 30 yards (my range) and I'm grouping about .25" The pellets were better (scary good) in the pellet liner, but I'm committed to the slug MO.

 

[MonsterMaxx]

My .30 Impact was tuned for 1000fps w/ the 44.75 gr. It was at 155b. Accuracy beyond 50yds was not good at all. It looked like the pellets were tumbling.

I detuned it and ended up at 110b moving at 880fps on the min hammer setting with some respectable accuracy at 85 yds. I'm thinking of turning the reg down a little more so I can get more hammer spring engaged.



I have ordered a 700mm, slug liner and 580cc bottle. I think it'll throw a pretty heavy slug and would like to try some neilson slugs. 



Reading your results with great interest.

 

[Virginia_Joe]

I've learned thru experimentation that slugs like a speed in the hood of 935 FPS (at least in my .25 cal). I've also learned there is a give and take relationship... if you go too slow on a slug, the groups suck, my guess is you are not getting sufficient spin. And if you try to get to fast ...well there are limitations to the airgun, and a toll of wear to be paid. I really don't dare go above my current setting (just under 930 FPS). Besides you start entering the transonic range, and that does weird stuff to the projectile. You want to be above it or below it. The results I posted above for ten shots are very similar in more ten shot groups... my Excel is just set up for 10 shots at a time... keeps things tidy. But I assure it is repeatable. However, there is hope for both shot count and reg pressure: just announced by FX this month a Power Plenum kit. Essentially you have a larger storage area behind the regulator with the new plenum. Theoretically, you should be able to use less pressure on the regulator and have a higher shot count. With pellets (JSB Exact King Heavy at 33.95 gr.) and the pellet liner I was getting about 50 shots on the fill, and like I said perfect accuracy within 30 yards (I did not go beyond that range). With slugs ... well I'm a little disapointed with shotcount. I got on the list for the Power Plenum; should run $300 unless you have purchased relatively recent (6 months I think); then they cut you a significant break. The Power Plenum will be a kit, and install new parts, it looks like the kit has the spacer (very similar to the one I posted above (in brass). Should be interesting in tuning in after the Power Plenum kit. My tuning MO is exactly like Uncle Hodge... if you haven't seen him, look up the Meathead Marksman on YouTube, and look under harmonics. We had similar weapons, and pellets, and results. He uses little cartoons at the begining of his video... very helpfull. In Monster Maxx above... he had trouble with too fast a projectile... I'm guessing based upon them videos, he may have had an air push at the muzzle (i.e. the valve seat was not closed). That tends to kick the projectile and possible start off a wobble.

 

[WillyG]

My .30 Impact was tuned for 1000fps w/ the 44.75 gr. It was at 155b. Accuracy beyond 50yds was not good at all. It looked like the pellets were tumbling.

I detuned it and ended up at 110b moving at 880fps on the min hammer setting with some respectable accuracy at 85 yds. I'm thinking of turning the reg down a little more so I can get more hammer spring engaged.



I have ordered a 700mm, slug liner and 580cc bottle. I think it'll throw a pretty heavy slug and would like to try some neilson slugs. 



Reading your results with great interest.

MonsterMaxx, All Info was tested today and there has only been about 100 rounds shot through this new liner.

I just recieved my 700mm .30 slug liner and some 47.2 Neilson Slugs. My JSB's 44.75 grain are shooting at 905 FPS avg, with Slug Liner.
The 47.2 Grain slugs are shooting at 888 FPS avg. with no changes in settings. Thats 17 FPS difference between the 44 jsb and 47 NSA Slugs.

The 47 grn slugs impact about 2" higher than the 44 jsb's. Using the same POI (Zero).
The slugs are getting an average of 3/4" to 7/8" groups CC at 70 yards.
The JSB's are grouping 1/2" or all 5 in the same ragged hole at 70 yards.

I think if I could get the FPS up on the slugs, say 50 more FPS then they may group better, but I have the MK1 Impact and it is maxed out.
HS is Full Power
Reg is 150 Bar
Valve limiter is almost all the way out. 

Also one other note: Do Not put Slugs in the High Capacity Magazines or they will flip sideways and jam things up. Use the small Magazine and you will be fine. Heavier slugs may work in the High Capacity Mags but maybe not?

Created: 01/25/20 01:42 PM

Description: NSA 47.2 Slugs using Slug liner I think it is 1:26 twist rate the Pellet liner is 1:40,

Distance to Chrono(FT): 2.00

Ballistic Coefficient: 0.110

Bullet Weight(gr): 47.20

Temp: 61 °F

BP: 1016.89 inHg

Altitude: 100.00

# FPS FT-LBS PF

10 886 82.29 41.82

9 888 82.66 41.91

8 889 82.84 41.96

7 889 82.84 41.96

6 885 82.10 41.77

5 889 82.84 41.96

4 888 82.66 41.91

3 887 82.47 41.87

2 894 83.78 42.20

1 893 83.59 42.15

Average: 888.8 FPS

SD: 2.8 FPS

Min: 885 FPS

Max: 894 FPS

Spread: 9 FPS

Shot/sec: 0.2

True MV: 890 FPS

Group Size (in): 0.75" at 70 yards.

==========================================

Created: 01/25/20 01:59 PM

Description: JSB 44.75 grain using Slug liner

Distance to Chrono(FT): 2.00

Ballistic Coefficient: 0.0420

Bullet Weight(gr): 44.75

Temp: 61 °F

BP: 1016.89 inHg

Altitude: 100.00

# FPS FT-LBS PF

10 902 80.86 40.36

9 902 80.86 40.36

8 902 80.86 40.36

7 903 81.04 40.41

6 904 81.22 40.45

5 902 80.86 40.36

4 902 80.86 40.36

3 906 81.58 40.54

2 905 81.40 40.50

1 917 83.57 41.04

Average: 904.5 FPS

SD: 4.6 FPS

Min: 902 FPS

Max: 917 FPS

Spread: 15 FPS

Shot/sec: 0.1

True MV: 908 FPS
Group Size (in): 0.40" at 70 yards.



Thats my first time shooting and testing slugs, so I hope this gives you a little perspective as where you will be. With your Higher FPS you may do better than mine.. Let us know how it turns out.

Also 880 FPS to 920 FPS seems to be the best accuracy for any JSB Pellets. Anything over that and they tend to scatter a little.

 

[MonsterMaxx]

Got my 700mm slug stuff too. Been playing with it.



Using the 65.5gr, 61.5gr and the 54.5gr. 880fps to 940fps depending.



We are shooting out to 100yds w/ a hanging groundhog. Absolutely no problem pinging the groundhog.



Bullseye paper target at 75yds and the grouping.



I've got it at 150b and it seems the 61.5 makes the best groupings. Around a dime at 75yds.



Going good so far, lots more tuning to do.



I'm going to go for the power plenum anyway. Kinda got screwed on the 'upgrade'. My gun was upgraded and after all the back and forth finished on 10/17. The cutoff for $100 upgrades is 10/30.