Ruger at 556 troubleshoot

[68w]

Hey all. I got a nib Ruger AR 556 and bought some 55gr PMC bronze fmj to zero it with. It was about 2" groups at 50 yards prone with a rest using vortex 3x ballistic reflex. Had some possums and racoons cleaning out my chickens and got some fiochi 40 gr. VMAX and some 62gr. Federal fusion for larger fanfare. All this ammo is .223 REM. It was grouping dinner plate at 50 yards with both 40 gr and 62 gr. I got the .243 out and dispatched the varmints but was very unhappy. I have coming 55, 67, and 77 gr. In both .223 REM and .556 since it's at .556 chamber I thought maybe it didn't like .223 ammo. I will of course strip and clean before testing, but I shot Vietnam era m16 so abused you had to hold the upper and lower receivers together while you fired, and I had no problem hitting 300 yards iron sights.... I couldn't hit a possum at 25 and about threw the rifle at it. Any ideas? (Other than a new upper which is my next stop if ammo testing fails.)

 

[mtwarych]

Iron sights or scope?

I agree with you on the AR platform, I have never fired an AR that shot as bad as your Ruger.

Something is really wrong.

 

[TJAY]

Put a scope you know is good on it and make sure it not a problem with your reflex sight.

 

[Waynzee]

I wouldn't go as far as a whole new upper, maybe a new barrel. But first see if there is any wobble where the barrel slides into the receiver if there is that might be your problem and that can be tightened up some.

 

[68w]

It feels really solid, no discernable wobbles. I will take it apart and do a good clean and inspect and then try irons to see if maybe it's a problem with the optic.

 

[Outlaw6.0]

Definitely make sure you clean the crap out of it. We also need some additional info. What is your twist rate? Although I do have a 1-7 that will shoot light bullets, it can be difficult at times. Shooting with a red dot/reflex sight can be irritating for those who don't have a lot of experience. I agree with the above statement about putting a tried and true scope on it to validate any accuracy concerns.

I too have had some accuracy woes with 55grn PMC... or any other plinking ammo. They go bang and they are cheap however, they have never brought out the best accuracy of any of my AR15's.

As far as shooting .223 ammo in your 5.56 chamber: You're fine, it won't hurt a thing. You have a different throat than the .223 but as far as exterior dimensions go, the actual ammo is identical (with the same bullet of course). The most profound difference I can think of is true 5.56 ammo will usually have a crimped primer and thicker case head. I've used both .223 and 5.56 in my AR's with different load with no trouble at all.

Hope that helps some,


t

 

[Jerry M]

What is the twist of your rifle? You could be over spinning the bullets. Speer use to put a warning on their varmint bullets, TNT I believe about shooting in fast twist barrels.

Good luck

Jerry

 

[Outlaw6.0]

You're right Jerry, a fast twist can make a frangible bullet come apart however, I've never encountered an FMJ that would. It'll be either 1-7 or 1-9 (I have seen a few 1-8's). A 55 grain pill will be redline for sure but I can see a problem. We shoot 55's out of a 1-7 all the time. It took a bit of load work to get them to shoot right but they hold together.


t

 

[68w]

It's a 1-8 twist that is stated to be able to stabilize from 35 gr. To 77gr. Safely. I have tried 40, 55, and 62 gr. And accuracy has been deteriorating with all. Leads me to believe something is loose or improperly put together that's not readily visible. Going to work on it to ight and then do some test groups and see what happens.

 

[68w]

Well, update... Took it apart and cleaned it, really barely had any residue. Took apart bcg took off handguards, looked it over. No wobbles noticed so I put it all together and took the optic off to try iron sights at 25. Wasn't really taking my time shot .5-.75 inch groups with irons at 25 in 3 different bullet weights. I thought surely it was the optic, so I put the optic back in, and it still shot around half inch groups. I realize that's a 2" group or so at 100 yards, but a vast improvement over where it was without doing much other than taking it apart and putting it back together. May float the barrel later but seems like whatever was going on miraculously resolved itself.