My 16" Preban Bushmaster will run about 300 rounds on any ammo then it starts to short srtoke.  Then if I switch over to Q3131a it will go another three mags.  Once it starts short stroking with Q3131a, I can go to xm193 and it will go another couple of mags.  Is 450 to 500 rounds w/o a cleaning too much to ask of any AR or is mine just a dog.

If it is my rifle, what can I do to fix it?

Edit to add: I use break free as my lube.

Derrick Martin once put way over a thousand rounds through one of his match modified AR15's without cleaning and without a hitch and still shooting High Master scores...

My suspicion is that your gas rings and/or the gas tube are wearing out and/or perhaps the chamber did not really start clean. One other is the security of your carrier key...

Pull the bolt and carrier and see if the bolt can move by gravity alone. If it can either clean or dirty, replace the rings. Some High Power shooters do this every season.

Check out the gas tube. if it looks like the little bulb that slips into the carrier key is worn, it is time for a replacement. Us High Power types replace the tube with the barrel, but change barrels at less rounds than you would with a barrel where battle grade accuracy is desired.

If you start with the chamber less than clean, it can give dificult extraction and short stroke...

Carrier key screws should be tight and staked.

Good Luck.

Billski thanks for the response.

I recently put in Mcfarland one piece rings and my key feels tight.  My gas tube however is older than the hills.  I never thought about it wearing out.  I'll try replacing it.

Kris

The 6,000 round milspec test requires that the rifle start clean, is cleaned after the first 600 rounds then every 1,200 rounds after that. That's a reasonable expectation.

Have you checked the tightness of the carrier keys with an allen wrench?

I'm not a fan of the one piece rings as they cause the bolt to bind in the 45 deg military test. Besides, the original parts were designed to be cheap and easily replaceable, unlike the McF ring.

Have you checked (per the Checklist) that you are experiencing short strokes?

As a start I'd change the rings (back to original style) and the gas tube as Billski recommended. Those parts are designed to wear out and do.

I once fired about 700 rounds of the wolf in a session. Had the worst jam of my life. MAXIMUM stick case(on the last round I shot). Gave the remaining 200 some odd rounds away. The inside of the rifle looked like chewing gum, black chewing gum. Rifle functioned flawless up to that point.

I also shot a case of q3131a over the course of 3 days without and cleaning or adding any clp. Functioned flawlessly.

I was stand- offish about buying an Ar for many years, because I bought into the B.S, about how JUNKY, finicky they were. Boy WAS I mistaken. Wish I'd have bought one 15 years ago.

My bushy eats anything I feed it, I feed it anything but WOLF. The single stuck case is the only hiccup I have had.

I have seen McF rings that looked great, and the rifle was short stroking. The rifle was a Scott Medesha space gun, big bucks, and the owner was fit to be tied. Replacing the tube did not fix it, but swap in a set of GI gas rings, and it ran like a champ. A whole bunch of us got convinced that day...

I had a franken-AR using an Oly lower and Colt upper that I fired 1k with and never had a problem.  This 1k was done in a one day period and only a small amount of lube was added twice.

That rifle ran like a champ, but was forced to sell it to pay a bill.  Wish I would have sold another and kept it. Oh well...

I typically fire 300-400 rounds through each AR on an average range trip.  

I know of a few guys that clean their AR's once a year and shoot all the time.

TS

I go about 250 rnds, drop a few drops of CLP where the bolt enters the carrier, and a few in the weep holes, and keep going to 500 or so, then clean it at home.  My son did a test, just adding oil, up to about 1000 rnds.  All ammo was SA.

I have been told I "over-lube" but any excess will blow out the first few shots.