PDA

View Full Version : Groups open up quickly - heat?


HelluvaEngineer
September 26, 2017, 15:42
I have a homebuilt FAL with a cut-down 18.5" barrel. I seem to recall it being a new Argy barrel but I could be wrong. It's been years and through a few "rebuilds". Entreprise receiver (had all kinds of issues now fixed) and a 3x fixed optic on a DSA mount.

I took it out this weekend. It was hot - high 80's. Shooting MEN ammo I was initially really happy - getting 1.5" groups. Then it just all went downhill after zeroing in my optic and putting a few more shots downrange. Suddenly it was grouping more like 4-5".

So I checked the mount screws and everything was fine. I let it cool down and took it to the steel plate range. It was ringing steel 100% at about 220 yards consistently until about 10 shots. Then it starts opening up again. My dad was spotting me on a big Konus watching the bullet trace.

Any obvious things to check? I know FAL barrels don't like heat but usually mine just string vertically. Thanks as always.

kev
September 26, 2017, 15:55
Could be that it's just going to do that. Gunplumber reported a lot of Argy barrels that had chambers and muzzles both centered but when cut back to 18" the bores were off-center to the new muzzles. Pretty sure those were nos Sarco Argy barrels. That means the bore never was centered in the barrel and if you've got a barrel with more meat in one side than the other it's bound to wander around as it heats up. Or it's bent. Or it was bent and later straightened.

HelluvaEngineer
September 26, 2017, 16:15
Could be that it's just going to do that. Gunplumber reported a lot of Argy barrels that had chambers and muzzles both centered but when cut back to 18" the bores were off-center to the new muzzles.

Well, unfortunately that totally makes sense. Glad I spent that time cutting it down and threading it. Thanks for the info.

4markk
September 26, 2017, 20:31
"optic" as in scope?

That is where I'd look first. Far more likely the scope is wandering.

Shoot 5 5-shot groups at 50 yards with open sights. See what you end up with.