Also, Trucker3573 has a good idea to try some pellets (jsb33.95gr) just to see if they group well. 900fps is a good speed for those from my experience with 25cal. That would tell you a lot about the barrel itself.
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Brand new Impact M4 not grouping at all
- Thread starter NelisBaas
- Start date
You may have to up your regulator, for those heavy 36 gr slugs. Slug kit with heavy hammer. Make sure the barrel is turned for slug position. I just got a FX Impact M4 compact 25 cal. Shooting great groups after tuning, don’t like the way it sounds with 110 reg. Going to raise reg to maybe give it some breathing room. I have slug kit.
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Try 26-30 grain ammo. The NSA or H&N I’m getting 54.0 ft with NSA 26.8 slugs and 57.3 ft lbs with 25.4 JSB pellets.
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I thought of 1 more thing, is the liner facing the correct direction? https://fxairguns.com/wp-content/uploads/2019/06/liner-replacement-eng.pdf
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As others have said, try pellets first. Then try slugs. Multiple slugs. I've only ever had a few barrels that like both and multiples of either.
Also need to look into the twisting rate and actually do a push test to see which diameter slugs it needs. .249 vs .251 will have a big difference.
Also need to look into the twisting rate and actually do a push test to see which diameter slugs it needs. .249 vs .251 will have a big difference.
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Try pellets like others have said. Shooting them from a heavy slug liner they will shoot great at 50 yards if all is well.
When you put the carbon fiber sleeve on did it fit tight?
I just put one on my M3 and the fit was a bit sloppy. I didn’t have and don‘t want to use epoxy on it. Shot it and this gun has never shot worse. Took it off and put the O rings back on and it shoots fine now. I am sure if the CF liner was snug it would have shot much better
When you put the carbon fiber sleeve on did it fit tight?
I just put one on my M3 and the fit was a bit sloppy. I didn’t have and don‘t want to use epoxy on it. Shot it and this gun has never shot worse. Took it off and put the O rings back on and it shoots fine now. I am sure if the CF liner was snug it would have shot much better
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Special thanks to Trucker3573. Tried shooting pellets, the JSB 33,95 gr. At 880 fps I got a perfect group.
It was the slugs all along as many of suggested. Weirdly the pellets shoot these perfect groups out of the slug liner, with the slug transfer port in use. Also overwhelmed by the amount of fast and helpful comments. Faith in the gun is restored.
This is a 5 shot group at 35 yds (top right)
I guess the hunt for the perfect slugs continues. I'll give the JSB knockouts a try first. After I return my 10 boxes of javelins, that is...
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Dude the JSB King heavy's 33.95 and MK2s are lights out. I have put them down an empty 12gauge shell at 135yards. Glad you found the problem. Enjoy your new wonder gun.
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I had the same problem with the .25 cal Javelin slugs, terrible shotgun-like groups. I switched to Zan 37 gr and have been very happy.
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I've got even money you had too much air behind the slugs, the pellets don't give a hoot. Even bad slugs won't shoot THAT badly with the proper amount of air behind them. Matt Gruber's thing is just enough air to get the slug out of the barrel and not a molecule more. Works like a champ.
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Which particular liner do you have? Is it the one in sixteen or the one in eighteen?
Also, If available in your country, try getting sample packs of slugs. It'll make it much cheaper and easier for you to figure out what works.
Also, If available in your country, try getting sample packs of slugs. It'll make it much cheaper and easier for you to figure out what works.
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Okay, I need to show my ignorance here. I don't understand the meaning of "too much air". I assume it's not just a reference to velocity. ?
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I think he meant the valve dwelling was too long, or at least longer than it need to be, causing turbulence at the muzzle, destabilizing and affecting the trajectory of the slugs. That type of scenario is tuning related. you could try to adjust the valve in conjunction with the hammer and reg setting to only have it it open just long enough for a shorter burst, so the valve is closed before the projectile leave the barrel. Generally, you could achieve that with slightly higher reg pressure and lower hammer strike instead of the other way around, have to find the balance depending on many other factors.
Matt Dubber explained it in detail a few years ago:
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Yep, that's pretty much it. It's illogical until it's not. I'm pushing .25 hybrid 26 gr at 1020ish out of my Maverick VP600 getting nice consistency, I can run 32gr slugs slightly slower with good results. I believe it's easier to creep up on it than to go down but you can do both. If your speeds seem ok, then back off some and see what happens for a group of 5, do it again and see where it goes, it'll give you a trend. I'll bet you are close, the final is a very very very tiny adjustment.
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