end cap strike?

corey4

Sergeant
Feb 11, 2012
1,269
54
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38
pittsburgh pa
#1
just got in from shooting my scar 17. i was zeroing my new trijicon 1-8 and i figured i'd try my tbac ultra9 instead of my saker 762. i was getting erratic shots, even at 50yds. totally not normal. when i got home i noticed this. on the inside of the can, at 3:00, it looks like it was beat with a brass hammer. i only shot 20 times because i didn't feel like wasting ammo. this probably explains the erratic shots.


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#6
I don't know how I missed the additional details in the OP or if there was an edit, but the SCAR 17 does not have a shoulder of a large enough diameter to mount the CB brake or a DT can directly and ensure alignment. The jam nut is bad news. There are a couple adapters on the market, or we could probably install one of our face-mount brakes on it.
 
Likes: Dan M and Fig
#9
I don't know if it's the exact same one, but we've had a few customers use something very similar with good results. There are some that report backing the jam nut all the way back to where it stops and tightening against that. There is also a Gemtech adapter that provides a proper 5/8-24 interface. The bottom line on all those methods is that you're going to have to make sure it ends up straight (there are a couple threads on it on our forum). I think we could do a face mount brake as well.
 

corey4

Sergeant
Feb 11, 2012
1,269
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pittsburgh pa
#10
i had the jam nut all the way back. i figured that was the safest way to get the can centered. im wondering if the extra length is just enough to cause an issue. i didn't have any issues with my saker, but id rather use my tbac.

what is a face mount brake?

edit to ad:
this thing?
https://gemtech.com/scar-pof-thread-adapter.html

edit to ad again:
just measured the end caps holes
tbac .350
saker .370

so im thinking the extra length and obviously the opening compounded the fact i was out of alignment.
 
Last edited:
Feb 15, 2005
129
40
28
Mission, KS
www.donttouchme.com
#11
Suggested to me were these, which give options and are vastly cheaper than any purpose-built ones I have seen:
for 5.56 https://www.mcmaster.com/#8893K193
for 7.62x51 https://www.mcmaster.com/#8893K219

They have many other sizes though. Get the right size for your bore, cut them down to a few inches longer than the suppressor (and clean up the ends) so they snugly fit into the bore. Short enough, they won't droop any significant amount, so you can tell whether the suppressor is installed properly.

They are STEEL. Be slow and careful sticking them in your muzzle.

McMaster Carr is a generally awesome place to shop. If you have never seen it before, be careful, go slowly and remember to breathe.
 
Likes: 2ndamendfan

corey4

Sergeant
Feb 11, 2012
1,269
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pittsburgh pa
#12
i was just looking at those

im trying to figure out why people are using the .281 rod instead of the larger one like you suggested.

and why not use the next size up, the .302 one.

alignment rods.png
 

Waorani

Back to the Island
Feb 14, 2017
681
314
63
Auburn, AL
#19
The KBAC shoulder ring that PMM and Silencer Shop sell works fine and provides a flat, perpendicular face for brakes, direct thread, etc to tighten against. The jamb nut does not. It's a well known issue. By face mount I assume he means it tightens against the muzzle face vs shoulder.
 

EXTREMEPREJUDICE

Online Training Member
Oct 21, 2008
1,748
72
48
SE MICHIGAN
#22
Two potential issues, the face on the jam nut may not be square and secondly you would be aligning off the thread(s) rather than the shoulder. In both cases there is a greater risk of misalignment. It is done though and successfully. I wouldn't, but hey opinions vary.
 

Strykervet

Resident Phoenix Eye and Dim Mak Instructor
Jun 5, 2011
2,810
957
113
42
Pierce County, WA
#26
I've seen this on one of my .22 cans, I think it came from firing the weapon with the can loose. Sometimes it shoots loose, gotta remember to keep it snug.

It's like you can't win sometimes, either it shoots loose or it seizes up!

There was a video on here a while back, I'm sure you can find it on YouTube, where they test the run out of several popular cans (they were supposed to test even more, don't know if that happened, I ought to look myself). Anyway, the results were surprising, some popular cans were WAY off, others a bit off, almost none dead on. At least one was so far off that even if it was installed on a perfect barrel with zero run out, it would have guaranteed an end cap or baffle strike.

If you have access to a shop or know someone with a lathe and tools, that's a fairly quick check that won't cost anything.
 
Feb 15, 2005
129
40
28
Mission, KS
www.donttouchme.com
#27
i was just looking at those

im trying to figure out why people are using the .281 rod instead of the larger one like you suggested.

and why not use the next size up, the .302 one.
I'd have to redo the math to find out why I got the ones I got, but they totally work. And barely. No wobble at all. Up a size at all seems like it would not fit in the bore.

But they are cheap, also. Try several.
 

corey4

Sergeant
Feb 11, 2012
1,269
54
48
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pittsburgh pa
#28
took a trip to the local archery store. i didn't want to deal with ordering a few different sizes of rods from mcmaster-carr. the archery store was kind enough to let me mic and cram a few different arrows down the rifle to get the best fit. you should have seen the look on his face when i was explaining what i wanted lol.

carbon express mayham hunter 250 camo...gotta get the camo. it has a coating that makes it a bit thicker. the arrow comes 50 carbon/50 camo. he cut me the camo portion to 18". the arrow mics at .2965" on the camo portion.

i didn't bother showing pics of my other tbac u9 or 30p-1 because they had the same result as the particular can in the pic.

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Likes: shoobe01
Apr 21, 2007
512
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Zachary, Louisiana
#29
took a trip to the local archery store. i didn't want to deal with ordering a few different sizes of rods from mcmaster-carr. the archery store was kind enough to let me mic and cram a few different arrows down the rifle to get the best fit. you should have seen the look on his face when i was explaining what i wanted lol.

carbon express mayham hunter 250 camo...gotta get the camo. it has a coating that makes it a bit thicker. the arrow comes 50 carbon/50 camo. he cut me the camo portion to 18". the arrow mics at .2965" on the camo portion.

i didn't bother showing pics of my other tbac u9 or 30p-1 because they had the same result as the particular can in the pic.
How did you make sure the arrow was perfectly straight and not bowed?
 

lash

Swamp Rat
Sep 28, 2012
3,245
920
113
59
Central Florida
#33
Looking at your pictures it is obvious that the arrow in the R700 with can is dead center, but in the Scar, it is off center for both cans, albeit at different positions and not as extreme on the Saker as on the Ultra. This would seem to support the view that it is a mounting issue on the Scar, as already discussed above.
 
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corey4

Sergeant
Feb 11, 2012
1,269
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pittsburgh pa
#35
so my arrow doesn't appear to be 100% straight. i don't have a good straight edge or a glass table, but laying it on one of my windows, it doesn't look 100% true, but close enough.

also, i ordered the KBA ring on friday, and i got it TODAY...on a SUNDAY thru the post office?!?!?!? but hey, i'll take it!

the pics below are my arrow with a witness mark to show orientation. the pics are kinda blurry, i think due to the reflection of the silver paint pen. you can see that it still isn't perfect, i'm not sure if it's because of the camera angle or the arrow not being 100% true, or a combination of both, but there is a huge improvement with the KBA ring. for some reason it doesn't look as bad in person. now that i think of it, i should have tried the other end of the arrow as well. maybe tomorrow...

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