Blah, point of impact shift 3 inches to the right at 100 yards? New SDN-6

[grumper]

Went out and tried out the 7.62 SDN-6 today.

I expected the shots to be a bit off, but not this much and was hoping it would shift vertically instead of left-right. The shots were grouping at 3:30 O'clock about 3 MOA from the point of aim with the suppressor mounted.

Is this normal?

To battlesight zero the 6920 at 25m I had to crank the BUIS to the maximum left setting and back off 1 click.

Seems to be pretty consistent, on the 10.5" rifle it was also shooting to the right about 2-3MOA at 50 yards where I last zero'd the red dot.

 

[grumper]

Hrm, I guess it's normal.

Seeing lots of posts on other forums saying stuff like 0-3MOA is about normal. 6+ MOA shift is when it starts becoming unacceptable. Just wish my shift was up or down instead of to the side.

 

[40Arpent]

Might be a dumb question, but could removing and reinstalling/re-torquing the muzzle device make a difference, or try a different one (I know they're not cheap, though)?

 

[grumper]

Might be a dumb question, but could removing and reinstalling/re-torquing the muzzle device make a difference, or try a different one (I know they're not cheap, though)?

Maybe, but the muzzle brake/adapter has to be installed the same way with the openings level on the sides. So might not make much of a difference.

I read somewhere how concentric the threads are cut to the bore makes a difference with POI shift. Might just be coincidence that both my rifles shifted to the right.

Not sure what to do now, get new barrels and send them off to ADCO to thread more concentrically? Might just live with the POI shift, zero all the sights to the new impact point and only shoot suppressed.

 

[1slow01Z71]

That is quite a bit for sure. How are your groups looking?

 

[grumper]

That is quite a bit for sure. How are your groups looking?

I got a few 3 shot groups that were about 1 - 1.25" wide. It surprised me because I was using ordinary Federal XM193. The suppressor seems to have tightened them up.

 

[1slow01Z71]

If its shooting better than normal then it sounds like you've just got a good bit of shift. I had about 3" of shift with my yhm til I noticed the teeth weren't quite locking in on the last notch. After that it shoots 3 shot groups awesome, 4th and 5th shot spread out though for some reason. Havent figured that one out yet.

 

[SC-Texas]

how tight is the sdn6 on the mount?

 

[Sugar Land]

Could be the shooter...lol duck

 

[grumper]

Could be the shooter...lol duck

Maybe. Ran out of damn ammo trying to sight in.

The suppressor rotates a little bit on the 6920. On the 10.5" rifle it rotates and wobbles. For some reason I got two AAC 51T brakes that are completely different. The threads are all different in starting/ending position and length.

Going to the next show to see what's up with that. Want to take the shitty loose adapter off and replace it with one like the other rifle has.

 

[Sugar Land]

Sounds like something fishy up.

 

[SC-Texas]

Nothing fishy. this is a common issue or the 51tooth mount system

 

[SC-Texas]

Some cans and mounts lock up tight. Some don't.

Of the ones that do not lock up tight some have no group size issues and some have issues.

Some have consistent POI and some don't.

There is a fix that involves relieving the shoulder of the mount until the can hops that last tooth.

 

[SC-Texas]

It is odd that the group is 3" left though.

 

[Sugar Land]

Sounds like you would be better off with a threaded can. IMO. It would really suck if the two I have coming are going to be that bad. That is the first time I have heard of that 51T problem. Guess I should of done more research before I bought them.

 

[1slow01Z71]

Sounds like you would be better off with a threaded can. IMO. It would really suck if the two I have coming are going to be that bad. That is the first time I have heard of that 51T problem. Guess I should of done more research before I bought them.

Might want to do a lot of reading then because the AAC 51T mount problem is well documented. Its probably the worst QD design on the market at the moment. Sorry to hear you bought into them. Like SC said, there are fixes for it though. After my accuracy issues with my yhm qd, Im swearing off teethed qd systems except for the specwar Ive got coming as it seems to be the only one thats rock solid.

 

[40Arpent]

Sounds like you would be better off with a threaded can. IMO. It would really suck if the two I have coming are going to be that bad. That is the first time I have heard of that 51T problem. Guess I should of done more research before I bought them.

Chuck, I did the research and still went with the SDN-6. Feel the luck, Chuck, feel the luck.

 

[grumper]

I'll pick up some coarse sand paper and a new bastard file after work and go to town on the loose shitty mount.

The mount on the Colt seems ok. There is only a little rotational play and almost no wobble.

The shitty mount on the 10.5" MG rotates an entire tooth's width and wobbles like a drunken hobo. Ima file that bitch down until it engages the next tooth.

I got the SDN-6 because it was the only one in stock at the dealer and I wanted to get my paperwork approved before any possible NFA rules changes. Also wanted to get some of that 99 day eFile goodness.

I got both so I can't complain, just need to wail on this mount til it catches the next tooth and everything will be fine. The Colt's mount seems fine. With the SDN-6 mounted was able to shoot a few 1-1.5" groups with garden variety ammo.

 

[grumper]

Went back out with the SDN-6 today and did much better.

I'm glad I didn't file on the adapter yet because it did exactly what the other dude on SnipersHide said it would do: After putting another 60 rounds through it, things DID loosen up enough that I could turn the suppressor 1 more notch.

Now it locks up very snugly on both rifles and the accuracy is acceptable. Shot these targets real quick at 100 yards with the 6920SOCOM, and 50 yards with the CQBR using standard XM193 ball.

Got the sights all adjusted and satisfactory now. Not going to worry about the POI shift because I'll probably never shoot those guns unsuppressed. The first trip out with the SDN-6 was disappointing, I spent 100 rounds chasing the seemingly random POI around. The targets had holes sprayed all over them. But now that it's broken in and fits more snug on the mounts I'm happy with it (if it stays this way).

 

[Tejano Scott]

That's good news.