I know it's capable of smaller groups as I've shot smaller groups with a 6933 without the can. I'm not terribly worried about the group size as I know it was operator (and weather) induced on that day.![]()
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I know it's capable of smaller groups as I've shot smaller groups with a 6933 without the can. I'm not terribly worried about the group size as I know it was operator (and weather) induced on that day.![]()
With my relatively heavy SpecWar2 on the 10.5" CL MRP barrel I get about 1 MOA shift to 6 o'clock.
The same can on my fluted SS 14.5" WOA barrel gives me about 5 MOA shift. I've mounted both the old and new style BiLocs on it and the shift was consistent (it's a SBR lower) regardless of the mount.
Last edited by edwin907; 08-07-07 at 06:53. Reason: .
RobS: How does that flashhider mount work without the can? What about price? I need to meet you over at Markham and shoot that beaut! I'm doing the SBR thing right now, and with the short little barrel I know I'm gonna need a can! What's the price on that can? I'm going to have to hold off for a while on it, but one it is on the list.
Your barrel should be checked as well. Its not uncommon for Colt barrels to have bores as much as 7 thousandths off center. A perfectly concentric bore plays a significant factor in minimizing POI shift with a suppressor. If you can remove the barrel and send it in, we can tell you how concentric it is.
I have a 15th model as well, on a 16" gov't middy barrel (Sabre). I zeroed it with the can off at 50 yards (with irons), checked it on the 10" 200 yard steel (ding ... ding ding ding), put on the can and still hit it. Shooting for groups on paper at 100/50, I can't shoot well enough to notice a POI shift.
Once I'm finished moving and find a new range I'll try a more organized test on paper, but it'll only be with irons/4moa Aimpoint.
Bigbore - didn't some of your testing show that the flash hider mounts increased the dB on the cans by a small amount?
I'm using the regular 2-port brake, and after months of being ambivalent about it, I've really started to like it. It works really well with my mid gas, M16 carrier, and standard buffer.
Ron from Ops sent me a "used" muzzle break mount to try out in lieu of the A2 flash suppressor mount that ADCO sent with the can. I just got back from the range testing out the new mount. The difference was HUGE. Virtually no shift this time at 50 yards. I used a Leupold 3-9x optic and a bi-pod this time so the groups are slightly better (I'm not used to magnified optics and bipods, I need work). Pics to follow, but I would call the shift virtually nil at 50 yards now.
In other news, Black Hills 75 grain is well worth the cash. I would say it groups half to a quarter as tight as all the others I tried.\
One note. While the brake did appear to greatly improve the POI shift with and without the can, it is HUGELY louder, even to the shooter. and with XM193 it is loud enough that I would not want to shoot it.
Which creates the conundrum; the brake offers the least shift, but is essentially useless (to me) without the can, meaning that it's only useful with the can on. So it's usefulness is somewhat questionable IMHO. It is supposed to better protect the baffles, however, so I suppose it's worth it in that respect.
Pics to follow.
Interesting thread. I am willing to be that the majority of mass produced barrels are not perfectly centered (as Steve pointed out).
I have done some POI shift testing with my SF 556K and a Noveske 18" barrel and found almost no POI shift.
C4
Updated pics. Again, no appologies for my ability as a shooter. Running a magnified optic and bipod and trying for the best possible accuracy is very new to me as I'm generally content if I can hit a 6" steel at whatever range I'm engaging from and do so as quickly as I can. I certainly didn't take the time I should to try for groups in this test. I think you'll be able to tell the potential of each ammo type, and pick out the shooter errors. Each group was 10 shots. With all but the Barnaul, I'd call anything outside the 10-ring a flier, and with the Black Hills I'd call anything outside a 1" circle a flier (shooter error).
Since people keep asking....
I fired 30 shots of XM193 to get the scope on paper (scope is turned sideways, took me a couple of tries to figure out how to adjust for that), and then 10 shots of Black Hills to get zeroed. After that I shot the suppressed groups, BH & W first, then reload (I only had two 20-round mags with me) & shoot XM & Prvi, then reload and shoot B. I then let the gun cool enough to remove the suppressor, and fired 10 rounds of XM to heat the barrel back up, then followed the same shoot/load schedule above. Without a temp sensor I guesstimate that the barrel was kept as close to a constant temp as I could.
After all of this, my conclusion is that the muzzle brake mount definitely makes for less of a POI shift than the A2.
This was my first time shooting the gun with the brake mounted but without the can. The brake is LOUD, especially so with the XM193, even with my Sordins on. If I was going to be shooting just milspec ammo with only the brake on I would double-up on plugs & muffs. It was borderline painful to shoot (and probably affected the unsuppressed XM groups because of it to some extent). Because of this, I found an interesting conundrum; if you want to shoot the gun both suppressed and unsuppressed and see the least amount of POI shift, you need the brake, but shooting unsuppressed with the brake can be borderline intolerable, making the A2 a much better choice.
For me, I only ever intend to shoot this particular rifle suppressed. That's in fact the whole purpose for this particular rifle. In which case it really doesn't matter which mount I use, except to say that the brake allegedly both better protects the baffles and provides better sound suppression than the A2 mount. The other school of thought would be that even in my previous test the shift was acceptable for the range at which an 11.5" barrel AR would be effective, so the A2 is certainly serviceable if the user needs to have both suppressed and unsuppressed capability. For me, I'll keep using the brake on this gun since it stays suppressed, and I've mounted the A2 on my other 6933 just in case I ever want to put the can on it. I'd like to try the 3-prong mount I see on ADCO's site now, but not bad enough to pay for one.
It does bear mentioning that the A2 mount that I received with my can sells for $75, and the brake mount sells for $185. I am unsure if this savings was reflected in the price I paid for the can or not, but it's somewhat of a moot point now as Ops at least sent me out a free muzzle break mount after seeing the first post in this thread.
Thanks again to Ops for all the help, and hopefully the new results are more in line with what they would expect to see.
The ammo used
The gun (with suppressor and without)
Suppressed groups
Unsupressed groups
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