I took my new Rock River midlength AR to the range this weekend. I worked up some loads using a Hornady 55gr FMJ and Ranshot x-terminator. I started at 22.8 grs. and worked my way up to 24.8 grs. in .5 gr increments. Distance was 50 yds. and I was using a red dot scope. With the starting load, the first three holes were touching and the fourth opened the group up to 1 in. I figured that I pulled the shot. However, all the successive 4 shot groups displayed the same pattern. The first 3 shots grouped under .5", with the fourth shot opening the group up to 1.5" or so. The fourth shot was always 1 in. low and a little to the left. I have experienced fliers before, but they were random, not consistent like the ones I experienced with this rifle. What could be causing this? Could it be vertical stringing due to barrel heating?

Sounds right. You can prove it by shooting 3 and letting the barrel cool, then shoot that fourth one. The barrel might be touching something when it expands.

quote:

Originally posted by bfrshooter:
Sounds right. You can prove it by shooting 3 and letting the barrel cool, then shoot that fourth one. The barrel might be touching something when it expands.

Are you single loading or loading from the magazine. Might be varying pressure from the magazine.

quote:

Originally posted by ireload2:

quote:

Originally posted by bfrshooter:
Sounds right. You can prove it by shooting 3 and letting the barrel cool, then shoot that fourth one. The barrel might be touching something when it expands.

Are you single loading or loading from the magazine. Might be varying pressure from the magazine.

I am loading from the mag.

shoot 6 in a row. See what happens

Just some info if interested-
I manufactured barrels for the military for 25+ years, and this was always a sign of a barrel where the bore is not concentric to the outer diameter within tolerances. That being, there is to much material on one side of the bore than the other; which I beleive you have surmised. Sometimes the OD/bore is fine, but if a fluted/ribbed barrel, the depth of the flutes would not be equal giving the same results.
If a defective barrel somehow got through our process, during testing on single shots with time in between shots the defect would not show up. However, when repetitive/low/high rates of fire were being done the first few rounds (4-6) would be perfect and then the barrel would instantly warp from heating and the next round and susequent would be off target. The dispersion results repeatable again with further testing...(barrel not suitable for sale by the way, and would be scrapped, or used for gun function testing only)
I don't have a clue what that company says about the performance of its barrels/guns, guarantees etc., but asking for a replacement barrel from them might not be out of the question...? It seems excessive to me, and I would imagine at further distances than 50, the group would be "out there"..?
Take care.
PS- The comments about it touching something may be in play here; don't want to sound like an "expert" in AR's and am just sharing info; but it does sound exactly like barrel problems I have seen/had like mentioned above. I also have an AR (diff manuf), and for what it is worth doesn't do that.

I would suggest dumping the red dot and using a scope. Even at 50 yards, if you have to crank up the brightness on the red dot, you may not have a precise enough aiming point.
Peter.

I took the gun to the range and ran some factory ammo through it. Rem UMC 55gr FMJ, AE 55 gr FMJ, and Wolf millitary classic 55gr FMJ. Distance was again 50 yds. The interesting thing was that I did not experience many fliers this time. Much to my surprise, the Wolf ammo gave the best group. Go figure. Anyway, I am thinking about trying a slower burning powder like TAC or Varget and seeing what kind of groups I get.

quote:

Originally posted by molar1:
I took the gun to the range and ran some factory ammo through it. Rem UMC 55gr FMJ, AE 55 gr FMJ, and Wolf millitary classic 55gr FMJ. Distance was again 50 yds. The interesting thing was that I did not experience many fliers this time. Much to my surprise, the Wolf ammo gave the best group. Go figure. Anyway, I am thinking about trying a slower burning powder like TAC or Varget and seeing what kind of groups I get.

It may be that it doesn't get as hot with that ammo? Out of interest, when it did do it with the factory ammo, did they tend to be to the same direction?

Unit5A, I fired a 6 shot group with the Rem UMC, 4 of which were tighly clustered less than .5" from center to center. The other two holes were touching as well, but were 1.25" to the left, while at the same POI vertically. This differed from the fliers I experience with the reloads, which tended to go down and to the left. The AE acted in a similar fashion as the UMC's. With the Wolf, I only had one flier and it impacted 1 in. low and at the same level horizontally. I went back and looked at the targets I shot with the reloads. At 22.8 gr X-term.(starting load), 3 holes were touching, with the 4th being 1.2 in to the right. At 23.3 gr, I could not determine that there was a flier. All 4 holes were in a cloverleaf pattern spanning a little less than 1" from center to center of farthest holes. At 23.8 gr, it is easy to see the flier about 1.5 in. low and to the left. The same pattern is noticeable with the next two loads, with groups opening up significantly. It is hard to describe this in words. If only I could figure out how to post pics here, I would show you the targets.

I forgot to mention that the bore is chrome lined. If the chrome lining were not applied evenly, could it cause this?

molar 1-
Thanks, I can't seem to get this out of my blood, even though recently disabled/retired now from it, ha ha. It sounds like you have a warping trend to the left in general, being affected slightly differently depending on the loads/bullets used; and heating variation. Again, its up to you, but I would try and get another/better barrel I think, and your results are repeatable in nature. Can't hurt to try, and maybe you can get a really good one?
We used to make both chromed and un-chromed barrels; others "nitrided" actually. The deposition of chrome varied more with equal thickness on varying inner diameters such as when getting to the chamber etc.; than anything side to side so to say in ours. In our case making chrome barrels, it would be equal in thickness throughout the bore, getting thinner as the ID opened up in the chamber toward the breech end. We machined the chambers for chrome accordingly/differently to allow for the gradually thinner amount in chamber areas, and be to print after chrome applied. The whole process we used was much more complex than just machining all surfaces say .004" oversize, and then plating back to proper/print dimensions. Keeping the bore dims right was critical, and if a slight squeeze going forward ideal.
There are a few different ways to "chrome" though, some much better than others, but I think your barrel is as I said in earlier post, and not because of the chrome. I have to admit that I don't know for sure if bad tooling/process for the application of chrome could make the thickness so un-even as to have an ill effect? But overall, the chrome is so thin compared to the rest of the barrel material I doubt it the cause...
Sorry to ramble there some, and hope I didn't confuse the issue.
"If making good barrels was easy, everybody would do it" was an old saying we had. (after messing one up, )
Take care.

FMJ bullets might be doing it. Or you just have a 1.5" grouping gun. Try loading some match grade bullets.

Unit5A, I could not figure out how to post individual pics, but here is a link to a file containing the targets in question.

http://www.flickr.com/photos/9468750@N07/sets/72157600555732083/detail/

Try Photobucket.com for pics and videos. You have to have a Yahoo/Flickr account to view that link.

Thanks for pointing that out CharlieHo. Hopefully, this will work.

Rem UMC 55 gr FMJ
http://i181.photobucket.com/albums/x46/acline3/P6290391.jpg

22.8 gr x-terminator 55 gr FMJ
http://i181.photobucket.com/albums/x46/acline3/P6290392.jpg

23.3 gr x-terminator
http://i181.photobucket.com/albums/x46/acline3/P6290393.jpg

23.8 gr x-terminator
http://i181.photobucket.com/albums/x46/acline3/P6290394.jpg

24.3 gr x-terminator
http://i181.photobucket.com/albums/x46/acline3/P6290395.jpg

24.8 gr x-terminator
http://i181.photobucket.com/albums/x46/acline3/P6290396.jpg

Those are piss-poor groups for only 50 yards. Or should I say patterns? You might as well ram the muzzle into the ground and use that rifle as a tomato stake.

quote:

Originally posted by molar1:
Unit5A, I could not figure out how to post individual pics, but here is a link to a file containing the targets in question.

http://www.flickr.com/photos/9468750@N07/sets/72157600555732083/detail/

CharlieHo beat me to it, the link took me to some page to register with Yahoo or something.

I have to agree with onefunzer2; considering everything you have tried and the results, in my opinion I think you have a 'bogus' barrel..?
I'm sure you paid good money for it, heck it's new, and you shouldn't have to live with that.

I am going to take a Leupold scope off a 308 and see what kind of groups I get at 100 yds. Also gonna load up some 69 gr SMK's with varget. If there is still no improvement, I'm gonna try to get a new barrel. Thanks for the replies

Ask for a New Barrel !. Most " Good Company's " don't want negative publicity when it concerns quality of their product !. I assume you purchased it new ?.

Shoot straight know your target . ...

Dr. K, I purchased it new from Rock River. I was using a red dot scope with a 5 MOA dot, so to be fair, I am going to take the advice of others first and try mounting a scope to allow for a more precise aiming point. I am also going to try some match kings. Has anyone had problems with a Rock River that required remedy? If so, how is the customer service?

I think a scope will help you out.If your AR is stock(Trigger,barrel,forend)it isn`t going to shoot Match grade accuracy.

I agree, but I am not looking for match grade accuracy, just 1 MOA like RRA guarantees. BTW, I only plan on using the scope temporarily to see if the rifle is capable of that kind of accuracy. After that, the red dot will go back on since I have it set up as a CQB rifle.

Why fret over 1 moa accuracy if you intend using it for close quarters battle? That's usually spray and pray.

quote:

Originally posted by onefunzr2:
Why fret over 1 moa accuracy if you intend using it for close quarters battle? That's usually spray and pray.

Agreed, but 1 MOA off a bench will be more like 5-6 MOA under other conditions. Therefore, I believe it is important to wring every bit of accuracy you can out of a rifle.

I agree !.I would want to know the capability's of the weapon whether or not I could produce them in actual field use . I also agree with mounting a scope to insure it's the weapon and not the sighting systems fault !. In my haste I some how over looked the red Dot 5 MOA sight !. Sorry about that ...

I did not know thats what they guaranty.If there is not a free float tube on it ,shoot using The Reciever on your bags.Using the fore end can pull shots.Load single rounds.You will never get best accuracy from a chrome lined bore.Good Luck I hope it works for you .

That makes sense. I was using front and rear sandbags, and my rifle doesn't have free floating handguards(yet). I guess it's possible that using the front rest may have placed undue pressure on the barrel. When I go to the range next time, I'll take your advice and lay the receiver on the bags.