Sounds about right Ash. I learned that despite the marketing we must choose... zero with can or without.
Sounds about right Ash. I learned that despite the marketing we must choose... zero with can or without.
That was a good thread. "Go Shoot the Gun" is some of the best advice to be given.Originally Posted by rob_s
We wish to thank the United Network Command for Law and Enforcement, without whose assistance this program would not have been possible.
I thought I'd gotten this thing all sorted out. I even un-mounted and re-mounted the can in my previous range session (as posted earlier in this thread) to confirm. Apparently, though, something is still off with the mount and now I'm beginning to question whether it was the culprit all along. Yes, there were marks inside the rail, but I think that may have been from the round hitting the suppressor endcap and popping the barrel around rather than just the harmonics of the shot.
I hit the range with Karmapolice last Saturday AM and he ran me through a new rifle exercise he's working on. Should've been pretty straight forward, but I had some random misses just winged out there like "WTF?" Figured it was me just having a bad day until I went to re-shoot the 25yd portion and couldn't hit shit. Took the can off the gun and had zero additional problems getting the hits.
Today I took 2 rifles and 2 cans to the range to try and figure this out once and for all. Rifles consist of Colt uppers with Colt SOCOM barrels, one cut to 10.3, the other is the problem gun pinned/welded on 14.5". Suppressors are AAC M4-2000 and AAC SDN-6.
My hypothesis was that the mount on the pinned gun is compromised such that it's causing slight tilt of the can such that it sometimes creates minor impact of the bullet into the endcap and slings the wild round. I further hypothesized that using the SDN-6 with it's larger .30 cal bore would negate these issues. It seems I was right. I further confirmed this by firing the 10.3" gun with both cans as well as sans can to remove the M4-2000 can itself as being the issue.
Path forward: since I've already taken the pinned gun back to the shop who did the work and they claimed the mount was fine; I'm done with them. I've emailed Steve @ ADCO and expect that having him cut off the existing mount and pin/weld a new mount properly will solve the issue.
Endcap strike:
Mount (see that material missing between the shoulder and the last thread? My guess is that's the issue.
Shiny spot on back of the thread is interesting:
Targets these are 10-shot groups standing at 25yds with AE 55gr. I know benching would be more precise, but I'm looking for a trend, not zeroing the gun. The problem is still plenty evident:
Last edited by ASH556; 02-04-2019 at 02:49 PM.
Food Court Apprentice
Semper Paratus certified AR15 armorer
Just as a bit of follow up, I pulled the barrel this morning to send to ADCO to have the brake cut off and replaced with a 51T FH, and observed no marks of interference with gas block and rail. I'm convinced this is and always was 100% a mount issue.
Food Court Apprentice
Semper Paratus certified AR15 armorer
I received the barrel with newly-pinned brake from ADCO yesterday and slapped it together (I mean, properly assembled, torqued and re-torqued 3X to 40 ft/lb, even used a fresh gas tube roll pin)this morning. I hit the range over lunch today and confirmed that all is good to go.
10 rds, 25yds standing, NX8 on 1X illuminated, rapid fire aiming at top of 2" dot (noted by red mark).
5 rds, 25yds, standing, NX8 on 4X, no illumination, slow fire aiming center of 2" dot (noted by red mark).
I'm pleased that the gun is now GTG. I'll get it out to 100yds and re-zeroed with Gold Dots, then confirm suppressor shift; if any.
Food Court Apprentice
Semper Paratus certified AR15 armorer
Zeroed at 100, no can
SDN-6 shift 3” (.8mil) straight down:
M4-2000 shift 2.5” down, 2” left:
SDN-6 with .8 mil elevation dialed (mirage getting to me by this point, but basically there.)
I’m good with this. The elevation correction is simple and not that much with the N6. That lets me keep the M42K on the 10.3, where I like it better anyway, but if I had to use the M42k on this gun it would work. Bottom line the mount and endcap strike issues are solved!
Last edited by ASH556; 02-14-2019 at 08:41 PM.
Food Court Apprentice
Semper Paratus certified AR15 armorer
Good stuff Ash. Glad you got it worked out.
Curious that the contact between the cut FSB and rail is at the top. This problem is more often seen on the bottom, when barrel droop is introduced due to adding a heavy can. I have no doubt that you had a mount issue, but could the upper contact have been caused by preloading a bipod?
Yep! Absolutely and that's probably what caused it. At the time the shop showed me the rail contact I was baffled because I've shaved literally dozens of gas blocks for myself and others and never had a problem. Bipod load makes sense.
Food Court Apprentice
Semper Paratus certified AR15 armorer
Also, for the CDO among us, I was a little rushed at the range yesterday evening, but when I got home and looked at the pics some more I decided to add 1 click (.2 mil) rightward windage and re-zeroed the turret. That should take care of the left bias you see in the groups!
Food Court Apprentice
Semper Paratus certified AR15 armorer
Reply With Quote
