.172 cal Impact X

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Hobbyman2007

Hobbyman2007

Member
Nov 17, 2015
608
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Ontario, Canada
Anyone else out there interested in a .172 cal Impact ? TJ’s has an already proven liner in 5/16” OD ( 8mm) and NOE bullet molds has an already proven 24grain bullet that fit in the new FX magazines . Tofazfou’s 17HmAir used this bullet and barrel combo . Since there aren’t any barrel manufacturers interested in changing their twist ratio’s to suit bullet shooters this would appear to be the best option for the tiny bullets . 

I did successfully install a .223 cal liner and shot some cast bullets with some level of success , I just don’t have the power on tap to shoot the 40 grain bullets at reasonable speed . I’m waiting for a plenum and that should get me there at 150bar . 
 
where to get TJ's barrel ? any link of webpages ? please



i'm very interested
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I was just in touch with TJ’s and it would appear that the .172 cal barrel is not available in the 5/16” OD . They do have them available in 3/8 “ so that’s what I’ll get . There is the alternative at Brownells with liners available there in the same twist rate , just the quality is unknown and most likely button rifled vs. The TJ’s hammer forged . 

The list above is only air rifle calibers , I’m talking .172 cal which is the same as a 17HMR powder burner . 



https://www.brownells.com/gunsmith-tools-supplies/barrel-tools/barrel-liners/17-caliber-rimfire-barrel-liners-prod25219.aspx
 
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I’ve started fitting the TJ’s barrel to the Impact . I had to make a thimble , comprising of a brass piece of stock with two outer oring groves , a 4 hole transfer port section to allow as much air as possible with a grove to allow the air to travel , an inner oring grove for the probe to seal up against . The center was bored out to house the barrel to just ( .050” ) before the transfer post at .372 “ for a press fit onto the barrel . I had already made a probe for the .177 QB 78 barrel that was fitted previously . I’ll take some pics later . One thing that is really bugging me in the crappy magazine . I’ll have to address that with FX and the retailer . If anyone knows where to find a .177 original magazine let me know . 
 
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I also put one of the 17 cal replacement barrel liners from Brownells in a Impact and took a few shots with it 

over the chronograph with the reg at 150 bar and hammer maxed out it shot at 850 FPS with a 24 grain slug

I was hopping for more but you need to remember that the smaller caliber is harder to make power with so more

testing and tweaking will be needed.
 
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I also put one of the 17 cal replacement barrel liners from Brownells in a Impact and took a few shots with it 

over the chronograph with the reg at 150 bar and hammer maxed out it shot at 850 FPS with a 24 grain slug

I was hopping for more but you need to remember that the smaller caliber is harder to make power with so more

testing and tweaking will be needed.
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Were you using the original Impact's C3 o-ring or a delrin washer for a bumper with this barrel? I read that the original o-ring is needed to make good power on the lower caliber and that the delrin washer's do not work well for power. It may have something to do with the rubber o-rings giving a little when the hammer starts contact and then easing the seat open, whereas the delrin washer is barely a cushion, not giving at all really and opening the valve fast.
 
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Finally got this one just about wrapped up. I got the TJ’s liner mounted wearing a 14mm OD carbon fibre tube that was bonded with locktite bearing retainer . I received my NOE mold in 24 grain and with the initial tests got it up to 920 FPS with unsorted or sized bullets. I think I could probably get a little more out of it by streamlining the porting it the hole lined up with the transfer port but I think that is pretty good for initial , that’s still making 45 FPE . The eaglevision magazine was also received and after using it for roughly 50 shots I’m really impressed , finally a magazine that matched the workmanship of the rifle. I really don’t like the plastic FX magazines, here’s a pic of how i have it set up now. Super easy calibers changes now for 172,177,217 and 223. 
 
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Way to go Denis! W00-H00!!! I'm still trying to decide what to do with the heavier .172 barrel I got from you. I'll probably put it in the Raptor. It makes all kinds of power. 😉

Jacketed? far too much friction and at ag speeds, it will not perform correctly, acting more like a needle on impact with a varmint. Slow death by ice pick. Fail + Fail. Sorry.



Knife
 
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Way to go Denis! W00-H00!!! I'm still trying to decide what to do with the heavier .172 barrel I got from you. I'll probably put it in the Raptor. It makes all kinds of power. 😉

Jacketed? far too much friction and at ag speeds, it will not perform correctly, acting more like a needle on impact with a varmint. Slow death by ice pick. Fail + Fail. Sorry.



Knife
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They exit the barrel at approx 4000fps in my application. There is a little bit of powder and a primer helping out though. Fun times indeed.
 
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Nothing good to report after the first outing. I tried sizing the bullets from .171 ,1715 172 and then just as they came from the mold. They were all shotgun patterns. I’m going to have to check the barrel and see if I had cut the leade too deep. The other issue might be that the barrel dimensions are too big for the bullets I’ve cast. I need to look into what I can do but for now this was a bust. 
 
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Nothing good to report after the first outing. I tried sizing the bullets from .171 ,1715 172 and then just as they came from the mold. They were all shotgun patterns. I’m going to have to check the barrel and see if I had cut the leade too deep. The other issue might be that the barrel dimensions are too big for the bullets I’ve cast. I need to look into what I can do but for now this was a bust.
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It doesn't seem to me that a 18 twist is fast enough for 24gr bullets?? Might have to go really light, like 15gr.

Many .172 firearm barrels are 1-10 and the bullets are going 3000 - 4000+ fps. 

I had a 9 twist for shooting 30gr Gold's for my 17 Remington.
 
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