View Full Version : Interesting Bushmaster gas port observation.
It seems that Bushmaster may have corrected the errors of their gas port ways. At the shop Saturday a long-time customer came in and bought a new Bushmaster "M4A3." He immediately came out of the range asking about other magazines. He said he was having failures to feed and hammer dropping on an empty chamber. Knowing the Bushmaster history of large gas ports combined with their use of carbine buffers, I assumed it was a bolt speed/bolt override issue. I went in the range to diagnose and was surprised to find that the bolt didn't lock back on an empty magazine (insert 1 round into mag, fire). So that means we're short stroking. The rifle was extracting and ejecting. I checked the gas key, gas tube, for tightness and potential leaks, everything seemed good.
The ammo the customer was using was Brown Bear nickle-plated steel case, and the BCG was not lubed well. We got some PMX Xtac 5.56 and the rifle ran perfectly. I tore down his BCG and lubed it, then re-assembled and sent him back into the range. I think after he breaks the rifle in a little it might run the weaker stuff...he said he had several hundred rounds of it.
I just thought it was interesting that Bushmaster seems to have their gas ports back inline with where they should be. As a side note, someone on another forum was defending Bushmaster and claimed he called them and they verified that their ports were .063 same as Colt...maybe so!
JBecker 72
10-14-13, 10:21
A friend of mine recently showed me his Bushmaster rifle. It had a chrome lined 1/7 barrel that was marked HP MP and it had a M16 BCG that was properly staked. I'm not sure if it came from the factory that way or if it was made right by an armorer as he got it used, but I was surprised. The thing runs great and I think he only paid $750 for it.
I wouldn't read into it without measuring the port. I recently saw one at my local Walmart that didn't have a staked endplate and the BCG looked weak as well.
I wouldn't read into it without measuring the port. I recently saw one at my local Walmart that didn't have a staked endplate and the BCG looked weak as well.
Yeah, this one was typical bushmaster in other regards:
-unstaked endplate
-weak gas key staking
-semi-carrier
-commercial RE
Heavy Metal
10-14-13, 11:30
It seems that Bushmaster may have corrected the errors of their gas port ways. At the shop Saturday a long-time customer came in and bought a new Bushmaster "M4A3." He immediately came out of the range asking about other magazines. He said he was having failures to feed and hammer dropping on an empty chamber. Knowing the Bushmaster history of large gas ports combined with their use of carbine buffers, I assumed it was a bolt speed/bolt override issue. I went in the range to diagnose and was surprised to find that the bolt didn't lock back on an empty magazine (insert 1 round into mag, fire). So that means we're short stroking. The rifle was extracting and ejecting. I checked the gas key, gas tube, for tightness and potential leaks, everything seemed good.
The ammo the customer was using was Brown Bear nickle-plated steel case, and the BCG was not lubed well. We got some PMX Xtac 5.56 and the rifle ran perfectly. I tore down his BCG and lubed it, then re-assembled and sent him back into the range. I think after he breaks the rifle in a little it might run the weaker stuff...he said he had several hundred rounds of it.
I just thought it was interesting that Bushmaster seems to have their gas ports back inline with where they should be. As a side note, someone on another forum was defending Bushmaster and claimed he called them and they verified that their ports were .063 same as Colt...maybe so!
You sure you don't mean Silver Bear? it is Zinc platerd and shiny.
It and Brown Bear both tend to be stouter than Wolf or Tula.
I would be concerned if a rifle doesn't cycle Bear ammo.
You sure you don't mean Silver Bear? it is Zinc platerd and shiny.
It and Brown Bear both tend to be stouter than Wolf or Tula.
I would be concerned if a rifle doesn't cycle Bear ammo.
Yeah, that's probably it.
According to this
http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/
The bushmaster uses .058 ports
Definitely on the small end.
Haven't seen that. Assuming it is true, then they went from way overgassed to "undergassed". I suppose it would be good if you were using a suppressor.
According to this
http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/
The bushmaster uses .058 ports
Definitely on the small end.
Lightly gassed, sure.
The guns used CAR buffers and semi carriers, a pretty light setup.
They shot 10k rounds of Federal AE223BK with 0 failures.
That was in warm conditions, so the results might have been different in the cold.
Haven't seen that. Assuming it is true, then they went from way overgassed to "undergassed". I suppose it would be good if you were using a suppressor.
GUNSLINGER733
10-15-13, 10:55
In the end just spend $2-300 more and get a Colt or BCM:D
KiloSierra
10-15-13, 11:35
My department bought 10 Bushmaster SBR several years ago. Out the one's I checked, two bolt carriers(all were semi-auto) were properly staked and one was marginal. After a few hundred rounds the marginal one shot loose. None of the end plates were staked and several shot loose. They would feed lightly loaded ammo just fine that would barely cycle my personal AR's though. Last year they bought a bunch of Bushmaster ORC carbines. Same deal with the carriers and everything else that was supposed to be staked plus no backup sights and EoTech's.
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