Ops 15th shift

[rob_s]

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.

[Derek_Connor]

Very interesting.

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...

[rob_s]

Eventually I'll go back and see if I can shoot from prone to tighten up the groups and shoot a gridded target to better document the MOA shift.

[SHIVAN]

Do you have any way to attach a more magnified optic??

To be more consistent, and give really solid results, I would suggest using match ammo.

I'd do the following if I wanted to get good usable data:

1) Zero the rifle without the suppressor on.

2) Print the best group you can with match ammo @ 100yds using a more "precise" magnified optic and no suppressor.

3) Install the suppressor and shoot again, from the same batch or box, on a 1" grid target.




My speculation: The ammo selection, ambient heat, "thin" barrel, and suppressor conspired against you in accuracy.

[rob_s]

I'm just not interested in all that science.

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.

Beyond that my interest completely falls apart.

[SHIVAN]

Something like a 4+ MOA shift would piss me off enough to get interested.

[rob_s]

Something like a 4+ MOA shift would piss me off enough to get interested.

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.

The 100 degree heat had alot to do with reducing my interest as well.

[SHIVAN]

...and this gun is really only ever intended to be fired with the can on....

That's how I zeroed my 10.5" Noveske, with the intention that the can would be on it.

I have not yet check the zero shift.

[Derek_Connor]

I have not yet check the zero shift.

Christ, I couldn't agree more.

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

[ashooter]

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.

1) Zero shift is not a big deal as long as it's repeatable.

2) 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...

3) 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".