New Impact not shooting to spec (low & eratic velocity)

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Doug-T

Doug-T

Member
Feb 19, 2019
287
17
Orygun, United States
I received my new .22 Impact about two weeks ago. The regulator was set at about 105 BAR and it shot JSB 18.1g at a very low velocity, 600 and something fps. I turned the reg up to 145 BAR, maxed out the hammer spring tension and opened the valve until it touched the shroud and it would only shoot about 880fps. That didn't seem right. When I went to zero and test for drops at different ranges it seemed the velocities weren't consistent. Tonight I pulled out the chrono and my velocity, with no adjustments was about 715fps and were varying by 30+fps. I fiddled with the hammer spring tension and valve and velocities were inconstant. Tonight I pulled out the barrel and looked very clean. I maybe have 300-400 pellets through this thing and this low/inconsitent velocity doesn't seem normal.

Any advice?
 
I stopped by our local hardware store and picked up a 7mm OD, 3.5mm ID, 1.5mm thick nylon spacer. I swapped in my slug liner and it was shooting about 720fps last night. After the new spacer velocity went up to 920fps and was pretty consistent with 18.1g pellets out of a slug. I still feel this is a bit slow with the reg at 145 bar, hammer tension at max and the valve adjustment all the way out.
 
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Brass pellet inlet and pellet probe mod will have it shooting way faster at lower pressure. Both parts can be replaced by ordering them from fx usa if you ever needed to return to an unmodified state.

Never make the brass port wider, just make it a little longer and flared to cover the 7mm port that feeds it. Pellet and slug feeding remain unchanged. I can give more details on doing this mod if you need them.

1570814052_3612213255da0b86475d435.16036272_Port1 - (2).jpg
1570814052_18948973155da0b864a24ad3.38412677_Port2 -.jpg

 
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Good News!

I spoke with an air gun friend, Mike, last night. He mentioned that you can adjust the allen head screw in the hammer spring slide. I turned that in about 2 turns and my velocity went up from 920fps to 1003fps average with JSB 18.1g. That's more of what I'm expecting. The trajectory looking through the scope was impressive when being used to mid-800's velocity. I found that the valve adjuster didn't seem to make as much velocity difference as I thought it would.

I started slug testing but it started raining and I stopped.
 
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@marcobet38 The o.d. should be the same diameter as the slugs, so .217" for the 22 caliber. The length is probably going to be the same as the other caliber it's replacing. The .30 probes I made I tapered ever so slightly so it was a few thousandths larger on the back end so it sealed well on the o-ring inside of the brass transfer port.
 
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Thanks...good idea with "tapered " things...my hesitation was "the brass inlet inner oring size for .22 is 5.50 x 1.50 mm NBR70"....so i guess it must be 5.55 mm or 5.57mm at oring position...but 5.55- 5.57 mm is slightly bigger than .217 ( 5.52 mm)
Click to expand...

You can measure the inside diameter of the brass chamber and compare that to the installed o-ring diameter. Making the probe diameter somewhere in between those two dimensions should be good.
 
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Maybe it's just me, but it seems a rifle in this price range should be reasonably expected to shoot as received. The late generations of FX rifles seem totally focused on features of adjustability. Some of them work. There are much simpler rifles in the same price range that are rock solid. They might not offer 10 features that you don't need, but they work, and they don't need to be treated with kid gloves to maintain reliability. I recently bought a Taipan Veteran, mostly out of curiosity regarding bullpups. It probably has about 1/3 the number of parts as the Impact. Power is easily adjusted by a thumb screw in the rear of the action, and that's it. The barrel attaches with a solid threaded shank, and is a traditional solid, Lothar Walther barrel, no sleeve/liner assembly. The trigger is a true two-stage, fully adjustable, and of match quality. I think you could hammer nails with this rifle and maintain zero. If everyone whose posts I read regarding issues with FX rifles would send them back and demand the quality and features for which they paid, we might see some changes. If folks continue to buy them, and then figure out how to make them work on their own, seems FX doesn't have much incentive for improvement.
 
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