Tuesday, December 27, 2011

How I fixed my AR15

So, I had this Sabre mid length 16" 5.56mm upper just sitting around.  It used to reside upon my CavArms lower and worked well for the most part in that configuration.  I had quite a few problems with stuck cases (fired and stuck in the chamber).  I tried switching to brass only ammunition (I was shooting steel cased Wolf).  The problem lessened but did not go away.

I swallowed my amateur gunsmithing pride and went and saw renowned competitor and armorer Robb Jensen at my local gunshop Virginia Arms.  He inspected the weapon and ran Ned Christiansen's 5.56 Neck and Throat Reamer through the weapon.  He said it removed a surprising amount of metal thereby bringing the chamber into 5.56 military specifications.

The rifle ran OK after that.  Bear in mind this was about 4 years ago.  I moved onto my much cheaper to shoot S&W M&P15R 5.45x39mm and pretty much ignored that poor Sabre.  Meanwhile Sabre officials were destroying a good, hard earned reputation in the firearms industry.  Cute little tricks like declaring silencers as "lawnmower mufflers" and barrels as "gear shafts."  Sabre Defense is now bankrupt.  Too bad, as their barrels and ARs had an excellent reputation.

So, after wearing out one barrel (at 11k rds) and one lower parts kit on my 5.45 AR (both replaced speedily with no questions asked by S&W), I realized that while the 5.45 is a great training weapon, I need a good 5.56mm AR in case of zombies or if the cheap 5.45 ammo runs out.  I will cover the 5.45mm AR in an upcoming blogpost.  I tried the old Sabre upper on my 5.45's lower and it turned into a single shot, manually operated weapon.  I immediately proscribed it to buffer problems (the CavArms lower had a slightly shorter buffer spring and used an unmarked carbine buffer as opposed to the 5.45's "H" (heavier) buffer and forgot about it.

I took advantage of Troy's Black Friday sale to pick up 2 of these; one for each rifle.  Reasoning behind that purchase is that I've graduated to my support hand being way forward on the handguard.  I also prefer to wrap my hand around the handguard for control.  The Sabre 5.56 upper was optic-less so I watched the equpment exchange at M4carbine.net until an excellent deal on an Aimpoint Pro with an ADM mount popped up.  A Bravo Company blemished lower rounded out my needs (I like being able to adjust LOP (length of pull) on my carbines and am saving the Sabre lower for a precision AR project down the road.  Magpul furniture finished off the lower (the Magpul Plus rubberized grip is the heat, buy one, buy two!).

Now, the Phoenix has arisen, right?  I took my rejuvenated Sabre (on top of the BCM or Bravo Company Manufacturing lower) to the range.  Shit.  Single shot, manually operated weapon, even when changing out the new H buffer and spring to the CavArms units and switching bolts (backup 5.56 bolt).  Back home to troubleshoot with much swearing.

I was certain the weapon wasn't getting enough gas to operate.  Consultation with wiser heads in the industry resulted in agreement.  Close examination of the gas system showed the below; a broken gas key screw.  It's kind of hard to see but there was evidence of a lack of seal there; shown by lube seepage under the area previously secured by the now broken screw.  Definitely enough to cause a gas leak, probably enough of a leak to cause malfunctions.

Luckily, a local gunshop had the screws in stock.  I put a light coat of Rockset threadlocker on the new screws and


those suckers down.

Another trip to the range resulted in extreme disappointment and frustration.  Even with the aforementioned repair; the Sabre was still a single shot, manually operated weapon.  Luckily, I had brought my 5.45's bolt carrier just in case.  FYI, only the bolt itself is 5.45x39mm specific; everything else besides the barrel on the 5.45 is 5.56x45mm compatible.  Swapping out BC's (bolt carriers) resulted in much joy.  The weapon functioned perfectly.  I shot almost 300 rounds of mixed Wolf and brass.  I ran that rifle hard; until the handguard was too hot to grasp without gloves.  Perfect functioning.

Now that I had isolated the problem down to the bolt carrier; it took me no time at all to find the culprit.  


had gotten lodged in the gas key.  I surmise that it was the cause for the intermittent malfunctions I had experienced over the years and carbon had built up behind it.  Also, perhaps a bit of corrosion?  Anyway, I had to lightly and carefully drill it out using ye old trusty Dremel.

Drilling it out, see the powder like substance?

Almost there.....

It's out!  What is that?

  Now, we're back in business!  Soaked the gas key in Montana Copper Killer and ran pipe cleaners through it.  Reinstalled it and back to the range.  This time, over 300 rounds of flawless functioning.  Mixed Wolf and brass.  I tried to get a stuck case by letting Wolf and brass rounds sit chambered in a hot rifle.  No dice; the weapon refused to malfunction.  I used older Lancer, a mixed bag of Pmags, US GI, and Troy magazines.  Even with old stuff like below.  I am very happy with how this ended up and enjoyed the troubleshooting process.

The finished product!

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