View Full Version : Overgassed 11.5?
I've been working on a department weapon that seems to be a constant headache. This rifle is a F/A 11.5 Bushmaster that has been abused over the last 10 or so years. The previous armorer had opened up the barrel port (I don't have a measurement) and put a recoil spring from hell in it with a standard carbine buffer.
I've recently replaced the BCG with a new F/A DD and the gas tube. It runs fine on our issued training round, Remington 55 FMJ, in semi auto but is failing to go into battery about every 3rd or 4th round in F/A. It feeds, ejects, and extracts fine. I'm thinking the heavy spring is too much.
I'm thinking of putting in a standard spring and H2 buffer and see how that goes. Where would a good starting point be? Should I order an H3, 9mm buffer, or is the H2 a reasonable place to start?
Get the H3 and use the weights from the H3 and CAR to mix and match the three different buffer weights. Use a USGI spring for those and then go to the extra power spring and go back to CAR through H3. Change one thing at a time and write down the results so you won't have to rely on your memory.
ETA: Here
http://i6.photobucket.com/albums/y232/Alpha-Romeo3/Hunting/ARcarrifle_buffer_exploded_view.jpg
Please check the gas port size. How is the headspace?
I'd suggest that you replace the barrel with a quality one.
I will echo Tweaks' comments. Nothing else makes much sense. BTW- are you experiencing any bolt bounce issues? My guess is that you are. I did on several 14.5" BM's we had in Iraq and the cure was a new barrel.
Agreed... I wouldn't spend another second trying to get a beater Bushy barrel to run... especially since it's been modified.
Thanks for the replies. As this is a department weapon a replacement barrel will take a PO and time. I believe that's the answer as well. The head space is good to go. I believe the port is oversize because the the recently retired armorer told me he drilled it to the next size(?). Of course then he had to get the heavy recoil spring to function. So, my initial thought is to get it running if possible by going back to basics with the spring an H2 or H3 buffer and see if that works.
I hadn't thought of bolt bounce..........Would that be from the heavy spring and return velocity and mass? It only shows on full auto. We put 120 rounds in semi auto and had no issues and the PMags all locked the bolt back on the last round. I do not have a H3 in my toy box but brought in a H2 and standard spring to see if that works today. I'll be ordering an H3 today anyway as I ought to have one for my tinkering.
This whole scenario is a train wreck. Definitely DITCH the aftermarket spring... That's never acceptable in my low life opinion...
Is there a Rifle stock F/A to try it on???
I would try and H2 and standard spring first.
Can you measure the cyclic rate?
markm, you are right but no my choice right now.
Todd, thanks for the start point.
Yesterday afternoon I went to the range with an H2 buffer and new standard spring. I fired 5 mags of 5 S/A to start, no problems. Then 3 mags of 5 with the weapon's ejection port facing up, no problems. Then repeated the same drills in F/A, again no problems. Then about 200 more rounds all F/A in various 2-5 round bursts and finally a mag dump just to see if it would, and it did.
I don't have any way of measuring the cyclic rate but it feels a bit faster than my issued 14.5". I'm going to go ahead and try it with the H3 when it arrives and see how that goes. The request for a new barrel purchase order is in. If I replace that the only Bushmaster parts left will be the lower and it's internals.
The barrel needs to be shit canned and get a replacement from daniel defense or BCM if you don't want to spend the money for a Colt 11.5"
You also need to throw away the spring and current buffer and start using a standard USGI spring and H2 buffer.
The barrel needs to be shit canned and get a replacement from daniel defense or BCM if you don't want to spend the money for a Colt 11.5"
We're in agreement Scott
You also need to throw away the spring and current buffer and start using a standard USGI spring and H2 buffer.
I already did exactly that.
CarlosDJackal
01-03-12, 09:43
...The request for a new barrel purchase order is in. If I replace that the only Bushmaster parts left will be the lower and it's internals.
Why don't you just replace the whole upper. BCM makes a great 11.5" receiver - mine has been flawless even when run suppressed.
Because I just replaced the BCG, gas tube and stripped upper with DD parts.
I would have the whole gun shit canned and have it replaced with a Colt 933 that your department can buy.
OP- Your problem is eerily reminiscent of a problem a local batch of guns had. Wouldn't run, someone opened the ports, then they had too much gas. S/A was okay, F/A produced bolt bounce and other issues. The fix was a heavier buffer. They are mostly fixed.
Echo the others: Ditch the whole gun for known-good if you can. Ditch the barrel at least and replace with a known-good. No more WECSOG.
Why don't you just replace the whole upper. BCM makes a great 11.5" receiver - mine has been flawless even when run suppressed.
By BCM 11.5 runs semi/FA without any issue at all. Running a standard carbine spring & H buffer.
Years ago I has a 10.5 BM barrel that went back 2x before it ran.
Ditched it & never looked back
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