View Full Version : Need help on something relatively simple....
I have used the search function repeatedly and have found many threads on this topic, all with varying responses. I bought a Bushmaster carbine a while back and have been modding it. I didn't know of some of Bushmasters shortcomings with the lack of staking of the bolt and castle nut, commercial buffer, and weak extractor spring/buffer. I just ordered an LMT h buffer and BCM extractor spring upgrade kit. I think the h buffer will be perfect, but am not sure what to do as far as the kit. Should I use the Crane o ring along with the BCM spring and black buffer? There seem to be some varying responses in other threads and all of them seem to be pertaining to mid length rifles. Thanks in advance guys.
Also, I've never had an issue with this rifle. I just want it to be as reliable as possible.
Is yours a carbine or mid-length? If carbine, use the O ring and test it. Bushies are usually overgassed. If a middie, try it without the O ring and test that.
Thanks. It's a carbine. I just ordered the stuff from G&R (first time w them) hopefully I'll get it soon and I'll try it w the o ring.
Rather than me search through all of the previous hundreds of Bushmaster threads, I will tell you some of the things I had to do to our carbines back in 07-09.
1. I would get rid of the bolt and get a real HP/MPI tested bolt.
2. Replace the extractor spring assembly. I would only use the O-ring if you experience failures to extract when using 5.56 ammo. If you do add the O-ring. Be advised that this till may not cure the problem.
3. Replace the carrier key screws with proper ones and then torque and stake.
4. Bushmasters are usually all overgassed enough that you could use an H2 buffer. I would also look at a blue Springco spring.
5. Tighten and stake the castle nut. Be advised that you also have a commercial receiver extension so if you plan on changing stocks, make sure you get the right one.
Rather than me search through all of the previous hundreds of Bushmaster threads, I will tell you some of the things I had to do to our carbines back in 07-09.
1. I would get rid of the bolt and get a real HP/MPI tested bolt.
2. Replace the extractor spring assembly. I would only use the O-ring if you experience failures to extract when using 5.56 ammo. If you do add the O-ring. Be advised that this till may not cure the problem.
3. Replace the carrier key screws with proper ones and then torque and stake.
4. Bushmasters are usually all overgassed enough that you could use an H2 buffer. I would also look at a blue Springco spring.
5. Tighten and stake the castle nut. Be advised that you also have a commercial receiver extension so if you plan on changing stocks, make sure you get the right one.
Thanks for the input. I have replaced the commercial buffer tube with a mil spec one and installed a Magpul STR. Why MPI tested bolt? I'm sorry for the questions but I am really interested and would love learning about this. What is the advantage? Would you recommend just replacing the bolt and taking care of the screws on the carrier and staking them or replace the bolt carrier as well?
Because I have seen first hand BM bolts break (premature) in my opinion and because they only batch test them you have no idea what you have.
Do you want to spend 50.00+ on a carrier plus a bolt or would you rather pay 50-60.00 for a bolt and 8.00 or so for some screws? Once you have replaced the screws you can then field stake them or have it staked with a MOACKS.
Thanks for the input. I have replaced the commercial buffer tube with a mil spec one and installed a Magpul STR. Why MPI tested bolt? I'm sorry for the questions but I am really interested and would love learning about this. What is the advantage? Would you recommend just replacing the bolt and taking care of the screws on the carrier and staking them or replace the bolt carrier as well?
Because I have seen first hand BM bolts break (premature) in my opinion and because they only batch test them you have no idea what you have.
Do you want to spend 50.00+ on a carrier plus a bolt or would you rather pay 50-60.00 for a bolt and 8.00 or so for some screws? Once you have replaced the screws you can then field stake them or have it staked with a MOACKS.
If there is no real advantage to replacing the carrier once the screws have been replaced and staked on the bushmaster I would like to keep the bushmaster and replace the bolt w a BCM. Would you replace the carrier or fix the bushy?
Once again.
1. Replace the bolt with a quality bolt- BCM, DD, Colt.
2. Replace the screws in the BM carrier with correct ones, torque and stake.
If there is no real advantage to replacing the carrier once the screws have been replaced and staked on the bushmaster I would like to keep the bushmaster and replace the bolt w a BCM. Would you replace the carrier or fix the bushy?
Once again.
1. Replace the bolt with a quality bolt- BCM, DD, Colt.
2. Replace the screws in the BM carrier with correct ones, torque and stake.
Thanks for the help. I appreciate you taking the time and helping me out. I really came to this forum thinking I had a perfect rifle. I wasn't aware that Bushmaster cut corners. Overall I am still very pleased with my rifle. I think after staking the castle nut, gas key, and replacing standard buffer with an H buffer and the Bushmaster bolt with a BCM bolt the reliability will be improved quite a bit. This is extremely important to me. However I did buy this just after Obama had been elected and ARs were no where to be found in FL. I was lucky to get one at the time lol.
Thanks for the input. I have replaced the commercial buffer tube with a mil spec one and installed a Magpul STR. Why MPI tested bolt? I'm sorry for the questions but I am really interested and would love learning about this. What is the advantage? Would you recommend just replacing the bolt and taking care of the screws on the carrier and staking them or replace the bolt carrier as well?
I wold go further and say to simply the BCG with a BCM, Daniel Defense, LMT, or other known good one and keep the Bushmaster as a spare after you do the fixes that IG recommends.
IIRC, the Bushmaster is an AR style carrier and the others are the M16 style. this will improve reliability as well as add mass that can help with the issue concerning buffer weight and spring...
I wold go further and say to simply the BCG with a BCM, Daniel Defense, LMT, or other known good one and keep the Bushmaster as a spare after you do the fixes that IG recommends.
IIRC, the Bushmaster is an AR style carrier and the others are the M16 style. this will improve reliability as well as add mass that can help with the issue concerning buffer weight and spring...
Unfortunately it appears I may be stuck with buying the whole BCG. I want a BCM or Colt, but I can only find the whole BCG from BCM and can't even find a Colt bolt. Well I found one on Brownells for ~$200. No. LOL
If you want something now, check out Bravo Company USA
http://www.bravocompanyusa.com/BCM-Bolt-Carrier-Group-MPI-Auto-M16-p/bcm%20bolt%20carrier%20group%20auto%20mp.htm
~$140 for a complete BCG.
Ya, i would go ahead and just get the complete BCG you want. You should be gtg. Keep us posted.
Went ahead and got a BCM full auto bolt carrier group. Gonna fix the Bushy and keep it as a back up.
Thanks for the help guys. I'll post pics when the stuff comes from G&R.
This what I would have done to limit costs.
http://www.gandrtactical.com/cgi-bin/commerce.cgi?preadd=action&key=L7A3B&reference=/cgi-bin/commerce.cgi%3Fsearch%3Daction%26keywords%3Dbolt%26searchstart%3D0%26template%3DPDGCommTemplates/FullNav/SearchResult.html
Or
http://www.operationparts.com/AR_15_Bolt_Assembly_p/DD-9302.htm
and then;
http://www.bravocompanyusa.com/BCM-Gas-Key-p/bcm%20gas%20key.htm
Unfortunately it appears I may be stuck with buying the whole BCG. I want a BCM or Colt, but I can only find the whole BCG from BCM...
Originally Posted by ra2bach View Post
I wold go further and say to simply the BCG with a BCM, Daniel Defense, LMT, or other known good one and keep the Bushmaster as a spare after you do the fixes that IG recommends.
IIRC, the Bushmaster is an AR style carrier and the others are the M16 style. this will improve reliability as well as add mass that can help with the issue concerning buffer weight and spring...
that's what I meant - BUY the whole BCG...
Yeah I was gonna try and just get the bolt. Im happy even tho I had to spend the extra cash on the whole BCG
http://i1237.photobucket.com/albums/ff469/clj94104/Image3.jpg
Bushmaster BCG on the left, BCM BCG on the right. As you can see, the BCM has the "HP MP" markings on the bolt.
http://i1237.photobucket.com/albums/ff469/clj94104/Image2.jpg
Bushmaster BCG on the left, BCM BCG on the right. As you can see, the staking job on the BCM gas key is of a much higher quality. All four stakes are touching their respective bolts, prohibiting movement.
http://i1237.photobucket.com/albums/ff469/clj94104/Image1.jpg
Bushmaster BCG on the top, BCM BCG on the bottom. You can see the difference in the bottom of the BCGs here. Pennies were placed where the cutout starts at the bottom of the BCGs for comparison.
http://i1237.photobucket.com/albums/ff469/clj94104/Image-1.jpg
Bushmaster BCG on the top, BCM BCG on the bottom. The "BCM" logo looks pretty cool too. :cool:
http://i1237.photobucket.com/albums/ff469/clj94104/Image4.jpg
LMT H buffer installed.
http://i1237.photobucket.com/albums/ff469/clj94104/Image5.jpg
Castle nut staked with an automatic center punch from Lowe's. Awesome, easy fix.
http://i1237.photobucket.com/albums/ff469/clj94104/Image6.jpg
And we're back together. :D
Thanks to everyone for their input on helping me make this rifle more reliable and functionally sound. I appreciate you guys taking the time to help.
Photos aren't too bad coming from an iPhone 4 with relatively low light. LOL
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