Post Float Accuracy Problem ?

[Nylon]

I had a ban era Armalite with 20" barrel (chromed bore). The barrel was fitted with a permenantly attached muzzle brake, and the rifle had the regular handguards.

I wanted to install a YHM free float handguard (the cheap one :D ). Anyway, I drilled out the muzzle device pin, and was pleasantly surprised to find that Armalite had threaded it under there.

I removed the muzzle device, gas block and old furniture. Removed the barrel, then reassembled using the YHM barrel nut etc. I used a new crush washer and an A2 style flash hider, and leveled the device carefully so that the flats were at 90 deg to the flat top receiver.

Rifle functioned fine, no gas leaks or other problems. I scoped it up and found that it shoots about 5" groups at 100 yds with IMI M855.

Previous to doing the work it shot 1.5" with the same ammo.

The only thing I can thinkof is that the rifle does not like the A2 flash hider - is this correct ? Anyone got other ideas ?

Weather has been too bad to go out again, so I thought I'd use the computer to get some info.

thanks

[Milkman]

Shoot it without the FF and the FH and see what it does.

[LOKNLOD]

Is it possible, that because of the void left in the muzzle thread where the pin was, the stress from the tightened A2 is not being distributed evenly in the muzzle/crown?

Caution: This is a wild-ass guess.

[Nylon]

Some good thinking. I don't want to remove the handguard unless I really must - a lot of work (relatively speaking anyway). The flash hider is easy to remove, so when the weather improves i can go out and see how it shoots with that gone.

Just wondered if there was anything I was missing

[Snake RAH]

Is the muzzle device just hand tight to get the timing you wanted, or is it really on there?

I had a similar issue and found out that I didn't have the flash suppressor (3-prong) on tight enough. It turned a subMOA rifle into a 3 MOA rifle with a wandering zero.

If that isn't it, then did you torque the barrel nut on to at least 30ft/lbs?

[Nylon]

Thanks Snake

The barrel nut is very tight. It came to a comfortable stop between gas tube holes, so rather than have it too loose, I really tightened it until the next hole came around.

The flash hider is a different story. I screwed it up to the crush washer and it was about just under half a turn out of alignment. I used a wrench to take it into alignment, but it was not particularly tight. Don't know if I could get it to go another full turn ?

Someone else told me that overtightening the muzzle device leads to inaccuracy, hence my caution.

[03humpalot]

Since your rifle is only having accuracy issues and seems to be running fine i would suggest shooting as many different makes and bullet weights of ammo as possible until you find one which meets your performance requirements.

You changed the barrel harmonics by adding new parts, i would suggest different ammo before "Tweaking" your setup.

Just my 2 cents Brother, keep us updated if you would.

[Robb Jensen]

Make sure there isn't a ton of carbon in the flash suppressor, try another flash suppressor, make sure the crown is good and don't over torque the flash suppressor. If possible use a peel washer instead of a crush washer.

[Nylon]

Thanks for the input fellas. A2 flash hider is new, so no fouling problems. Crown is good too.

I tried 5 types of ammo (IMI M855, Winchester M855, Lake City M855, ADCOM UAE M855, premium handload). Non of this was the low grade PD type ammo. Groups were 4 to 5" for all types.

Will try without the flash hider to see if that is the problem. I have a spare, so if the flash hider is the problem, I will use another. I also have peel washers, so that is an option too.

One thing that just ocurred to me is that this rifle has the Armalite barrel clamping gas block. I really tightened this on there - wonder if I got it too tight ?