First, I am not going to defend my groups here. It was 100 degrees at the range with no shaded shooting position and a wobbly rest. Attack the groups if you must.
Rifle & can after shooting the first groups.
Targets were 7" tall shoot-n-see. Optic was a 1.5x Compact ACOG.
The first pic is approximately 10 rounds of each of the following (from left to right) shot from a “rest” at 50 yards.
Black Hills blue box 75 grain
Prvi Partisan M193 55 grain
Wolf 55 grain steel case
Federal 55 grain XM193
The second pic is approximately 5 rounds of each fired without the suppressor mounted. After I shot the first group of Prvi, Wolf, and XM (you can see those groups just above each shoot-n-see on the Wolf and XM) and noticed they weren’t printing in the black, I fired 5 more rounds of each holding the tip of the triangle at the base of the shoot-n-see. Those are the groups you actually see on the Prvi, Wolf, and XM targets, with the BH target being shot holding center of the black.
I would estimate the Wolf, Prvi, and XM shift to be approximately 8-10 MOA to the 12 o’clock, and the BH shift to be approximately 4 MOA in the same direction.
None of this is intended to be scientific in any way, just sharing my results.
I also have a OPS 15, on a 12.5 barrel. I’ll have to redig my pictures, I did an informal 5 round x 4 shot string with the can off/on. Looking hard for those pics to see what the shift was…
I went to the range to zero the gun with the can on it with the ammo I’d using if hunting/fighting. I only printed the rest to get an idea if it would hold a close enough zero for training and competing, and it will. I thought I’d check to see what it does with the can off, and fortunately the ammo I want to have the slightest shift, does.
As I said, it’s a non-issue for me. I’m not expecting great consistency out of a .625" dia. barrel, and this gun is really only ever intended to be fired with the can on. Interestingly, and what I was most wanting to check, the cheapest ammo shoots to virtually the same POA as the expensive stuff.
I’m going to order one of the muzzle break mounts from ADCO and I’ll re-zero then. Maybe I’ll be interested enough to play around more. I have a 3x Compact ACOG mounted on another gun, but in order to test it out I’d have to zero it to this gun, and then re-zero on the other gun. Yawn.:o
The 100 degree heat had alot to do with reducing my interest as well.
Im too lazy to find the picture and search the Archive on TOS. It was my first range trip with the rifle and did the experiment to figure out what the shift was roughly so I could answer the question when asked. So much for keeping my results…
I rarely shoot my 12.5 rifle unsuppressed:
The only time I take the can off is to new shooters who haven’t seen the performance of a unsuppressed/suppressed rifle back to back.
And with the aimpoint that is now on the rifle, im not too concerned about 2moa, 4 moa, 6 moa shifted within the ranges im geared to shoot with this rifle
With my vast personal experience of owning ONE suppressor and shooting it on 4 different uppers, and knowing a couple of other guys who have suppressors… I’ll make a few observations.
Zero shift is not a big deal as long as it’s repeatable.
All cans will cause a shift in zero, unless it’s just a fluke with that can on that weapon. It’s just a matter of hanging weight on the end of a barrel. A lighter weight suppressor on a stiffer barrel would, in theory, make for an almost unmeasurable zero shift. I’m sure that’s the “magic” behind why Surefire cans supposedly cause very little zero shift - lighter overall weight than most cans and telescoping back over the barrel moving the suppressor’s center of gravity farther back…
Stainless steel flexes a LOT more than 4150 of similar contour. My suppressor weighs something like 26 oz. When I first got it, I shot it on one of Denny’s “recon” barrels which is a fairly lightweight 16" stainless barrel. I got about 7-8 MOA to 6 o’clock shift. Put the same can on a 14.5" LMT M4 barrel on the same day with the same ammo and got about 1 MOA (or less) to 6 o’clock. Stainless Noveske 16" medium contour shifted about 3 MOA to 6 o’clock. And my CMMG 14.5" M4 barrel shifts about 1-2 MOA to 6 o’clock. All are/were repeatable, so I just had to know where the zero was going to go with the can on a particular carbine and adjust accordingly.
BTW, the M4 barrels are not the heavy “SOCOM” contour. Just standard lightweight under the handguards.
Rob - Even with your “pencil” contour barrel, I’d bet that if you sandbagged it and put a higher powered optic on it, you’d find that it will shoot smaller groups with the suppressor attached simply because the added weight at the muzzle decreases inconsistent barrel “whip”.
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.
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.
In this case I’d bet it is because the brake is the first baffle in the system and baffle placement and distances are critical. The first baffle is absent when using the FH.
