Bushmaster Upper Reliability Problem

S

SA Scott

New member
I posted a while back on the pre-ban Colt AR-15 Match HBAR I bought. I've been very happy with it, but I really wanted a lightweight carbine upper as a shooter. So, I bought a Bushmaster 16" M4-profile barrel flattop upper at the January SAXET show here in San Antonio. $500 all in.

Finally got to the range Sunday, and fired a total of about ten rounds, no more than two in succession, because the upper wouldn't feed/extract reliably. Two ammo types and several different magazines were used. Casings would remain in the chamber or get caught sideways in the ejection port by the returning bolt. Three casings had crush points. I experienced no malfunctions with the Colt upper. Both are small front pivot pin.

I've talked to the seller and he promises to make good with repair or replacement. He seems to think the gas port may have been drilled too small out of the factory. Does this make sense? Are there other common problems I should explore?

Thanks for any advice/feedback.

SA Scott

P.S. I also bought a Trijicon Reflex and the thing is cool!
 
easy solution

just go to the Fulton Armory website and punchup "Defender Ring". they'll explain your prob and sell you the fix (for jus 12 bucks).
 
Seems to me that Bushy would be more than happy to correct the problem if it was brought to their attention.

kgs.
 
The Colt factory uppers have a .062 gas hole. Many of the shorter barrels must be drilled out. I have seen some as large as .125 on a 10.5 " barrel.

It is not hard to drill out. Simply remove the front sight roll pin and pull it straight off of the barrel. You will see the gas hole. If it is .062 it may be too small for the lenth of your barrel. I would reccommend drilling a .010 larger hole and then replacing the gas tube and front sight and then function firing for reliability. If it still fails to be reliable, drill larger . Just be patient and take your time. Be sure not to let the drill pull itself thru the hole and into the other side of the barrel or you could put a burr in it that cant help the accuracy.

I'll go out on a limb here and say that it'll probably take about a .093 hole to get it to function correctly. If you get in a rush and drill the hole too big, the added gas pressure will make for very brisk ejection and will add to recoil. It will overwork the bolt and eventually cause cracking of the bolt and the upper reciever. Just be patient and dont go too big. Do a little at a time and fire it each time. It will be well worth the effort if you do it correctly.

Hope this answers your question.
 
Allow me to second the suspicion about the magazines.
I have or have had a couple Bushy's with very similar
occasional problems. Each time, another magazine was
added to my 'scrap pile', and the problem went away.
DanM
 
How is the gas tube fit?

Remember, the carrier key has to be "function fired" ten times upon replacement to "crud" it up and effect a seal. I've used Permatex gasket compound (could also try gasket shellac)to eliminate this step. Of course this is on the lower pressure end (trust me on this one, the gas tube provides a BIG pressure drop)but I've seen guns with big front sight gas tube holes that leaked like sieves until a few rounds were fired.

How is the fit? Its a PITA to check W/O taking the roll pin out. Take my word on it, the roll pin comes out easy, often with hand pressure alone. Use a pin punch with a tiny blob of soft solder on the tip. While you are at it, take a look at the fouling pattern on the tube with respect to the hole. Remember, we are talking about high pressure gas at high velocity and ANY resistance to flow makes for a HUGE pressure drop.

My guess it a little misalignment coupled with a tight bolt is short cycling. Don't go to the point of drilling the barrel. Its too easy to screw it up and you never know what kind of burrs you are creating. The factory has a reamer they use to chamfer this hole.
 
You did not specify whether the M4 upper you purchased came with its own bolt carrier. If it did, have you swapped-in your original to check? Failure to extract with two different bolt assemblies would seem to point to the gas port . . . but let Bushmaster dick with it.
 
Thanks for all the help, guys.

Magazines were Colt 20s, Sanchez and Canadian Thermold 30s. Ammo: S&B 55gr. and American Eagle 62 gr. I cleaned and lubed prior to firing (perhaps not the best job as I'm a relative novice with ARs). The bolt & carrier may or may not have been mated out of the factory. I don't know enough about the gas system to recognize a potential problem.

I'm a little concerned about putting the Colt bolt/carrier on the Bushy upper as a test. Should I be?

I don't want to deal with Bushmaster directly yet. The seller seems honest & knowledgeable, and promises to resolve the problem (Gerald Swank, GDS Enterprises, if anyone knows him).

Keep the feedback coming and I'll keep you posted on my progress.

SA Scott
 
SA Scott wrote:

...The bolt & carrier may or may not have been mated out of the factory...
Click to expand...

Bushmaster's website made reference to "Bushmaster Rifles" being sold at gun shows that were actually just Bushmaster lowers assembled by parties unknown with parts of uncertain pedigree. Before you contact Bushmaster, take a look at their website; they used to have a guide somewhere about how to recognize "parts guns." FWIW, I've seen some uppers at the SAXET show in Austin that, even to my "non-AR15 expert" eye, looked like workbench specials . . .

I also think the FAQ at Bushmaster's website had some troubleshooting tips . . .
 
Check the buffer tube assy to make sure its lubed properly and moves freely. If not this can cause
"short stroking".
 
HankB makes a great point...

The "Bushmaster" in question may not actually be a Bushmaster. The following is from the the Bushmaster website:


Q: I bought what I thought was a Bushmaster at a gun show. It has a lot of problems, and I think I got taken. How can I be sure of buying a Bushmaster?

A: We have seen this happen many times here. We get rifles all the time for warranty service that have our lower receiver, but every other part is a gun show special. Before purchasing, look things over carefully. You are about to lay down a sizeable chunk of money, so take a minute to be sure of what you are buying.
Bushmaster's identifying marks are:
1. On the barrel, in front of the front sight, it will be stamped:
"B MP 5.56 NATO 1/9 H BAR" (exactly that way). On some barrels, it may be under the handguard, but it will still say that exact thing. The only difference might be a 1/7 instead of a 1/9 . This denotes the rifling twist.
2. Our front sights are held on by two taper pins, one through each of the bands of the front sight. We do not use hollow roll pins, never have - never will.
3. Our handguards have aluminum heat shields in them.
4. Our barrels have the correct gray/green manganese phosphate finish, not black.
5. Our tele-stocks have a small roll pin holding the nut on under the sliding latch. If it's not pinned, it's not ours.
6. Our hammers and triggers have polished contact surfaces.
7. Our bolt carriers have the gas key staked on by 4 V-shaped stamps.
8. We always use aluminum delta rings to retain the handguards.
9. Our buffers have a gold-colored finish on them, which is easy to see inside the stock.
10. Our aluminum parts all have the mil. spec hard anodized flat or matte finish to them, not shiny. This includes the receivers, the charging handle, and the delta ring. However, oil on the surface might make the normally flat or matte finish appear shiny.
The best insurance is to always buy from a local dealer, someone you can go back to if you have any problems. Most of them are reputable, and will at least help you contact the factory for service problems.



kgs.
 
I have a similar situation.

I am buying a Bushy DCM upper sans bolt and carrier. So I email Bushmaster and ask if I can get a bolt and carrier for this upper. They reply that

"... DCM barrels have bolts that are matched to the chambers of the barrels...DCM bolts are matched to the barrel extension for maximum strength and accuracy. Each barrel has it's own custom matched bolt".


But they also said ".. It would be a good idea to check the headspacing. I don't expect there would be any problems with the new carrier. You should be able to "drop it in and go". Headspace check would be recommended for safety reasons."

So, maybe a headspace check is in order as well. Or did you already say that you have and I just missed it?

Keep us posted. I haven't received my upper yet and have not yet ordered the B/C either.

Steve
 
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