Wednesday, May 15, 2013

AR range report

I took my AR to the range, finally.  The purpose?  Function check it, as I assembled the lower myself and modded the upper a bit, and to sight it in.

First of all, I took it to Clark Brothers.  You have to buy their ammo, generally, to shoot at their free range.  So I didn't bring my own (or much of my own)  They had .41 colt, but no .38 or .45 ACP.  They were out of .22.  They had over a dozen boxes of 5.56 .  Cool!  I'll get 4.  Nope, restricted to one per customer, but they were forgiving of using your own ammo from home.  Dang!

Well, the first thing I found out is that I should have marked the gas block better.  I musta lined it up poorly.  The AR is a single shot (Maryland, if they knew, would be ecstatic...)  The gases in my gas operated rifle are not operating.  Well, shucks.  I don't even know how to adjust that to be sure I am doing it right.  Any help?

The EOTech was shooting low and right at 25 yards.  I figure zeroed at 25 means zeroed at 250, and shooting high at 100.  It took MAJOR adjustment to get that sight dialed in.  Full turns of the dials adjusted with a tool made for the job.  A Jefferson nickel.  I got that done, one shot at a time.  a few rounds out at 100 to confirm I am way high out there, but still pretty centerline, vertically.  Good.  So, solve my problem with the gas cycle and I have a carbine that works as advertised.  No other flaws noticed.

Luckily, I had some .38 and some loaded .45 mags.  I thought my new snubbie had a better trigger than my current snubbie, but now I can't tell the difference.  Good.  I want them to be twins.

The new 70s era Colt Commander surprised me.  It shot VERY well.  I am very happy with that. 


Geodkyt said...

Yeah, barrel gas port and gas block port not lined up is overwhelmingly most likely cause, followed by gas tube obstruction.

Pinned on gas block? Replace with bolt on block. (Which can be pinned in a different location that the earlier holes, AFTER it is bolted on and confirmed correct -- no point in doing two pins on a bolt on, no matter how worried you are about shifting, BTW.)

Bolt on gas block? Remove, measure hole locations on both block & barrel, make sure when you reinstall it, you have your longitudinal position correct as well. Especially if you aren't using an handguard endcap because you aren't using traiditional handguards, it's easy to screw up longitudinal position.

If necessary or desired, take a ball end burr and break the edges of the gas port hole on both barrel and inside the gas block -- just break it; this will provide more slop.

After assembly, you can try blocking one end of the barrel, removing the gas tube, and trying to blow pressurized air through the other -- does it come out the gack of the gas block smartly? If not, something isn't lined up well.

If it passes the pressure test, add the gas tube, rerun -- is air coming out the gas tube? If not, it's blocked somehow. Replace, and dry fit the tube to the gas block and run presssure test before fitting the pin, just in case. (I've never seen it happen myself, but it is possible the pin location is upgefucht from missed QA. Super low probability, but possible.)

Old NFO said...

Geod is right, and it IS a PITA to get them aligned...

Geodkyt said...

Even though I am neither a gunsmith nor planning on doing a squad's worth of barrel assemblies, I bought the gas block jig from Bravo Company. It has settings for rifle, mid-length, and carbine gas systems. Do two ARs, and it's paid for itself.

Frozen said...

also, check your gas tube, make sure you didn't install it upside down (i have seen this before on home builds).