Highlights from an initial acceptance inspection of an officer’s Bushmaster carbine. Photos included below are of anomalous items, or items of particular common interest. Photos copyright by me, all rights reserved.

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Manufacturer: Bushmaster
Type: Carbine
Model: Undetermined (Pending)
Serial Number: L452###




Lower Receiver:

    L-prefix serial number. Standard single stage semi-auto fire control group. Note seam on hammer and possible mold mark on left side of hammer. Mil dim receiver, hammer, pivot, and takedown pins. Drain hole in magazine fence. Hex bolt in grip screw.








Buttstock Group:

    Common Bushmaster type. Commercial dim receiver extension. Circumferentially larger and longer (3/4") than mil dim. 6-position. Hole spacing uneven. End of extension cut at angle. Buttstock plastic. Form of current mil type . Loose fit. Receiver extension (castle) nut unstaked. Nut could be unscrewed without tools after two attempts. Standard carbine buffer, correct weight.  






Upper Receiver:

    Flat top. Eotech 553 mounted. BUIS is flip-up, Bushmaster OEM, retained by allen screws. No addressing on rails. Extended feedramp machined pre-anodizing.






Bolt Carrier Group:

    Bolt bears “CM” engraving. Extractor spring assembly 4-coil spring with blue insert. Carrier key bears small rectangular indents for staking with no material intrusion on carrier key screws. Bolt carrier includes shrouded firing pin and semi-auto rear tang.










Barrel Assembly:

    16” barrel, marked “B MP 5.56 NATO 1/9”. Chrome lined chamber and bore. M4-type step on barrel. A2-type flash hider installed and timed correctly. Gas block shaved style with Bushmaster OEM flip-up front sight installed over the top of the gas block. Sight retained by allen screws. Gas block and pins installed prior to parkerizing. Sling swivel installed with rivet. Barrel extension cut for extended feedramps prior to parkerizing. Handguards M4-dim, lightweight plastic, single pair black heatshields.








Gauging:

    Passes pertinent gauges.


Other:

    Michiguns Ltd. 5.56mm NATO chamber applied to chamber. Small amount of material removed from chamber.


Function Testing / Live Fire:

    Pending


Required corrections:

    Stake carrier key screws. Stake receiver extension nut to receiver end-plate. Replace OEM extractor spring assembly with carbine extractor spring assembly. Replace grip screw with slotted screw. Apply thread locking compound to all sight components supporting optic. Corrections for Eotech optic as per standing order concerning same.


Recommendations:

    Conditional approval. Return for inspection at every 500 round and 60 day interval(s).

*END*
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So is Bushmaster now doing extended feedramps?

Quoted: Model undetermined? What he couldn't read the receiver?

Most of the BM carbines are so marked, all I've seen IIRC.

What is undetermined is the moniker it would be assigned, such as "Superlite", "Patrolman's Carbine", etc.

Quoted: So is Bushmaster now doing extended feedramps?

Observed on certain contract guns. The Texas DPS guns are an example.
Observed on certain NFA guns.
An exception, not the rule, and no indication of change to the line as a whole by BM.

Quoted: Other:     Michiguns Ltd. 5.56mm NATO chamber applied to chamber. Small amount of material removed from chamber. /////

You ran a chamber reamer into a chrome chamber?

And it was out of spec!

Quoted: Quoted: Other:     Michiguns Ltd. 5.56mm NATO chamber applied to chamber. Small amount of material removed from chamber. ///// You ran a chamber reamer into a chrome chamber?

Pretty common.  Several makers guns end up with undersized chambers and you have to ream them slightly...lose some chrome, get a correctly sized chamber.  

Chamber size is more important.  

Quoted:..... Apply thread locking compound to all sight components supporting optic. Corrections for Eotech optic as per standing order concerning same. //

Does this involve throwing the ARMS mount out of a window?

Quoted: M4 feedramps on a privately purchased Bushy ORC? I've never seen that before...

There's your model, an "Optic Ready Carbine"

This is a factory complete rifle? I assumed all complete rifles sold had B-prefix serial numbers, and all lowers sold had the L-prefix.

The L prefix means the lower was made by LAR, B means Bushmaster and a few CM mean CMT.

So, what happens when the chrome you cut in the chamber starts to flake? Also must be hell on your reamer.

So you don't really know if it came from Bushmaster like it is or if it has been messed with? What kind of 'officer' had it?

height=8

Quoted: M4 feedramps on a privately purchased Bushy ORC? I've never seen that before, but hell Colt has mixed and matched whatever was in the bin on plenty of rifles.

all the bushy ORC's ive seen up here recently have the m4 ramps, weird huh?

An LEO's rifle?  Then reliable operation is a necessity.

The seam on the hammer does not bother me.  The notch does.  Ditch the notched hammer and replace with an unnotched hammer.

Bolt carrier includes shrouded firing pin    

Good!  Along with an unnotched hammer this will give smoother operation, it can't hang up from the notch dragging on the firing pin or bend and damage the fp retainer.

This is one of my pet "things" about AR's... that damned notched hammer and "ramped" bolt carrier.

Drain hole in magazine fence.  YES.  A dead end hole lets dirt and moisture collect.  The drain let's oil flush it on down and out each time it is lubricated.

Hex bolt in grip screw.  You are correct, change that out for slotted.  A real pain to find a long allen for that.

Apply thread locking compound to all sight components supporting optic.

You bet!  BUT, guys... BLUE ("service removable") Locktite, not red (permanent).

Quoted: The L prefix means the lower was made by LAR, B means Bushmaster and a few CM mean CMT.

Right, I assumed they used the bushy lowers on complete rifles but sent out the L's for stripped/incomplete lower sales.

holly crap. So now I have seen a Bushy with m4 ramps.  My god!!!

i have never really cared for the notched hammer either.

Quoted: Quoted: Quoted: Other:     Michiguns Ltd. 5.56mm NATO chamber applied to chamber. Small amount of material removed from chamber. ///// You ran a chamber reamer into a chrome chamber? Pretty common.  Several makers guns end up with undersized chambers and you have to ream them slightly...lose some chrome, get a correctly sized chamber.   Chamber size is more important.

Um, no, having a correctly sized chamber with chrome is more important.  Reaming a chrome lining is stupid.

Quoted: Um, no, having a correctly sized chamber with chrome is more important.  Reaming a chrome lining is stupid.

Very true.

If I found out someone took a reamer to my chrome lined barrel I would demand that they replace it. If it didn't have extraction issues before it soon will when the chome starts to flake leaving a very uneven surface in the chamber.

Quoted: The L prefix means the lower was made by LAR, B means Bushmaster and a few CM mean CMT. So, what happens when the chrome you cut in the chamber starts to flake? Also must be hell on your reamer.

Flaking hasn't been a concern with many other users.

Reamer is taking it just fine. Doing chrome chambers will accelerate wear on the reamer. When it does, no problem. It will be replaced.

The advantage of a correct chamber that will prevent other issues is worth it.

Quoted: So you don't really know if it came from Bushmaster like it is or if it has been messed with?

What made you think that? There are no questions of origin, beyond the uncertainty of it's common name (and part#).

What kind of 'officer' had it?

LEO

Quoted: Right, I assumed they used the bushy lowers on complete rifles but sent out the L's for stripped/incomplete lower sales.

The last 5-10 BM I've seen were all complete, factory assembled, with L-prefix. These include but aren't limited to Superlights, Patrolman's Carbines, and others.

Quoted: Quoted: Um, no, having a correctly sized chamber with chrome is more important.  Reaming a chrome lining is stupid. Very true. If I found out someone took a reamer to my chrome lined barrel I would demand that they replace it. If it didn't have extraction issues before it soon will when the chome starts to flake leaving a very uneven surface in the chamber.

Interesting feedback. Would you guys mind sharing what your experience is in reaming chambers, esp chrome lined chambers, and the effects you've observed on servicability of the barrels thereafter?

Radiant556, the employee submitting the carbine for approval indeed had a choice: Subject it to corrective processes, or submit a more acceptable, pre-approved sample from a list he had already been provided. There were no surprises.

I have never run a reamer into a chrome chamber for a few reasons.

1. I have never had a chrome chamber I felt was undersized to the point that it wouldn't run.

2. The chrome is going to tear up the reamer.

3. The reamer will probably scratch, gouge and chip the chrome leaving a very rough chamber that will lead to problems.

I have lengthened the throats on some non chrome chambers (mostly DPMS). Remember, there is very little difference between a .223 and 5.56 as far as chamber dimensions. The difference is in the throat/freebore. That's why you can use a .223 reamer with a seperate throat reamer.

I have seen chrome lined barrels cut down and recrowned with mixed results. Sometimes the chrome will start to flake at the crown.

Randall put together this excellent reamer comparison.

ar15barrels.com/data/223-556.pdf

Your best bet is to use a bore scope and see what kind of damage the reamer did to the chamber. You will probably want to replace the barrel especially if it is a duty gun.

Casting line on hammer?  Yup ALL AR15/M16 HAMMERS (and triggers) are castings.

Ramped carrier and notched hammer? Guess Bushie is using up in stock hammers as they switch over to the more desirable  shrouded carriers.

M4 ramps? Well, if Bushie is ramping LE pieces, they sure haven't done it w/the civie market yet.  At least not on the two barrels I've bought from them in the past year,

But then that doesn't bother me at all----since I don't try to feed ammo out of crappy mags that hang too low

Running a probably max dimension chambering reamer into a less than max dimension chromed chamber? Stupidist thing I've heard of this year.

Oh yeah, you forgot one thing.  Handguards are now the same sleazy pieces that DPMS uses.  Older stock had much better quality HGs.  Didn't bother me though, since I had a Colt M4 set waiting to install.

After taking a minute to learn the deal on feedramps; I can now testify that Bushmaster recently provided me with a gas piston upper receiver with properly cut M4 feedramps.

ETA

Though while matching cuts without lips which align are in the receceiver, they don't appear as deep as some M4 fr's pictures i am now looking at.

hang on I got the answer straight from the snakes mouth.

Question
I see that you now make a carbine barrel with extended m4 feed ramps. Is this a special order? Can a regular guy order one? Will you be making them with the F marked front sight base also? thanks

    Hello,
           Bushmaster does not use M4 feed ramps. We do have barrels and flat top receivers with M2 feed ramps that are not as deep or at the same angle as the M4 feed ramps. Our barrels with the M2 feed ramps will not match a Colt upper receiver with cuts for the M4 feed ramps.
           The barrels with M2 feed ramps or barreled uppers can be ordered. They are available in the 16" M4, 16" M4 V-Match ( milled gas block ) and 14.5" M4 barrels available with permanently attached flash suppressors for 16" legal length.
           Bushmaster does not have any plans to use "F" front sight bases.
           Thank you,

Jim Eden
Technical Support
Bushmaster Firearms International, LLC
Office:  1-800-883-6229 ext. 277
Fax:  207-892-8068

Wow, they're still fucking up!

Quoted: Quoted: The L prefix means the lower was made by LAR, B means Bushmaster and a few CM mean CMT. Right, I assumed they used the bushy lowers on complete rifles but sent out the L's for stripped/incomplete lower sales.

No, BFI lowers are made in-house while L lowers are made by LAR.

I have factory complete L-prefix rifles as well as factory BFI-prefix lowers only.

Quoted: Question I see that you now make a carbine barrel with extended m4 feed ramps. Is this a special order? Can a regular guy order one? Will you be making them with the F marked front sight base also? thanks     Hello,            Bushmaster does not use M4 feed ramps. We do have barrels and flat top receivers with M2 feed ramps that are not as deep or at the same angle as the M4 feed ramps. Our barrels with the M2 feed ramps will not match a Colt upper receiver with cuts for the M4 feed ramps.            The barrels with M2 feed ramps or barreled uppers can be ordered. They are available in the 16" M4, 16" M4 V-Match ( milled gas block ) and 14.5" M4 barrels available with permanently attached flash suppressors for 16" legal length.            Bushmaster does not have any plans to use "F" front sight bases.            Thank you, Jim Eden Technical Support Bushmaster Firearms International, LLC Office:  1-800-883-6229 ext. 277 Fax:  207-892-8068

Yeah, my tax time special 20" AR has M4 feed ramps and was made by Bushy. Sometimes I really wonder about the guys that answer their phones. When I asked if I could get a full auto carrier he said I would need class three paperwork, and I said, "O.K., if that's Bushmaster's policy I won't argue." He then proceeded to inform me that the blue extractor inserts were the same as the black ones and that was the only difference. It made my little brain hurt to talk to the guy.

Fortunately the rifle runs really well. It has a 1/7 twist barrel and m4 feed ramps, and uses vanadium steel in the barrel. Nice little rifle. I'm glad they had an overrun from their military contract. It was a nice change from their standard fare.

Quoted: Quoted: Other:     Michiguns Ltd. 5.56mm NATO chamber applied to chamber. Small amount of material removed from chamber. ///// You ran a chamber reamer into a chrome chamber?

Ned Christiansen says its not an issue to worry about..

Quoted: Quoted: Um, no, having a correctly sized chamber with chrome is more important.  Reaming a chrome lining is stupid. Very true. If I found out someone took a reamer to my chrome lined barrel I would demand that they replace it. If it didn't have extraction issues before it soon will when the chome starts to flake leaving a very uneven surface in the chamber.

The only place that reamer cuts is the throat. The chrome lining in the throat doesnt last long anyway.

He said he used a chamber reamer not a throat reamer.

Quoted: He said he used a chamber reamer not a throat reamer.

He specified the michiguns product.  that's neds throat reamer. Those familiar with the product and the issues of 5.56mm ammo in a .223 chamber knew what he meant.

Neds reamer gets a lot of use in training classes fixing guns that blow primers with 5.56mm ammo when the temps get high or the rate of fire is fast.

OK, found the link to the throat reamer. It doesn't look like just a throat reamer. I would worry about those flutes touching the chamber walls.

www.m-guns.com/tools.php

Would be interesting to use a Stoney Point comparator before and after to see how much the throat was deepened.

2IDdoc
I understand that all Bushy barrels are 4150 but not 4150 CMV.  Are you certain the tax time barrels are 4150 CMV?  I havent heared this.  

I have standard rifle feed ramps in my 20" tax time upper, not that it really makes a difference.  It is on an "L" prefix complete lower I bought directly from Bushmaster, so complete lowers can definitely be had with an "L" prefix.

Quoted: 2IDdoc I understand that all Bushy barrels are 4150 but not 4150 CMV.  Are you certain the tax time barrels are 4150 CMV?  I havent heared this.

Well, there again, that is what they told me on the phone. The guy seemed pretty excited about it. I even repeated what he said about the barrels being CMV and he emphasized it. I suppose it's possible that he didn't know what he was talking about, but it sure seemed like he did.

My thought (for what its worth) is that if their barrels had to be mil spec they would have to be CMV. They probably ordered their barrels from a different vendor for this sale. That could possibly explain the 1/7 twist and m4 feed ramps as well.

The barrel is pretty darn nice in any case. I've really been abusing it, and its performing above my expectations.

My tax time 20" upper does not have M4 feed ramps.

I have four Sabre barrels marked CMV and three Bushmaster 4150 barrels. I don't think steel can be both 4150 and CMV. I of course cannot tell a difference between them based on 4150 vs. CMV alone.

I have never had or seen a problem with a chrome lined Bushmaster barrel not running due to chamber dimensions or any other barrel related problems.

See:

MIL-B-11595 A E 1 07/26/2004 BAR,METAL AND BLANKS,STEEL UNDER 2 IN DI

Edit to add the link. Go to the bottom for the .pdf Revision E Amendment 1.

assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=9234

I have a Bushmaster AR and I never had any problems with it.  Bushmaster makes good stuff, but for the life of me I can't understand two things that they don't offer:

1.  M-4 Feed Ramps.  (although I hear that they are now offering M2 feedramps, which is even more fucking stupid because now you have three different extensions instead of two.).
2.  F-Marked Front Sight Base.  Why not have the same standard height for all the front sight bases this way you don't have to buy a a taller front sight post if you use a BUIS.  Absolutely retarded.

All the other crap I hear about I have no problem with such as the commercial buffer tubes and the fact that they don't stake the carbine stock (just put some locktite on it if you think it is going to be a problem.).

Their lowers are good-to-go, but I would never buy an upper from them until they get their shit together.

Quoted: My tax time 20" upper does not have M4 feed ramps. I have four Sabre barrels marked CMV and three Bushmaster 4150 barrels. I don't think steel can be both 4150 and CMV. I of course cannot tell a difference between them based on 4150 vs. CMV alone. I have never had or seen a problem with a chrome lined Bushmaster barrel not running due to chamber dimensions or any other barrel related problems. See: MIL-B-11595 A E 1 07/26/2004 BAR,METAL AND BLANKS,STEEL UNDER 2 IN DI Edit to add the link. Go to the bottom for the .pdf Revision E Amendment 1. assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=9234

That's interesting about your upper not having feed ramps. Strange. Did you get one of the rifles from the first batch? That makes me wonder if they ended up putting some of their standard 20" rifles in with the mix. Is your barrel 1/7? Maybe we got different barrels. I guess I don't understand why a barrel cannot be 4150 and CMV at the same time. Maybe someone could help us out.

I'm starting to wonder if its worth the effort to cal BM.

As a side note, I replaced my original Bushy 20" tax time uppers bolt with a FN bolt that had a CS extractor spring, black buffer, and a crane O ring. For what ever reason it didn't run worth a crap with that bolt. Once I put the original BM bolt back in it ran flawlessly over the next 2K rounds. That makes me wonder if it is chambered for .223 instead of 5.56. Can anyone help me out with this?

Thanks for the acceptance review, skintop911

I also enjoyed the one you did on the Colt LE6520, and IIRC, a RRA rifle as well.




- I don't recall the 6520 needing any addtional staking or reaming, though  

Quoted: Quoted: My tax time 20" upper does not have M4 feed ramps. I have four Sabre barrels marked CMV and three Bushmaster 4150 barrels. I don't think steel can be both 4150 and CMV. I of course cannot tell a difference between them based on 4150 vs. CMV alone. I have never had or seen a problem with a chrome lined Bushmaster barrel not running due to chamber dimensions or any other barrel related problems. See: MIL-B-11595 A E 1 07/26/2004 BAR,METAL AND BLANKS,STEEL UNDER 2 IN DI Edit to add the link. Go to the bottom for the .pdf Revision E Amendment 1. assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=9234 As a side note, I replaced my original Bushy 20" tax time uppers bolt with a FN bolt that had a CS extractor spring, black buffer, and a crane O ring. For what ever reason it didn't run worth a crap with that bolt. Once I put the original BM bolt back in it ran flawlessly over the next 2K rounds. That makes me wonder if it is chambered for .223 instead of 5.56. Can anyone help me out with this?

Well, you changed four things at once (maybe five):  the bolt, the spring, the insert, you added an o-ring and if your FN bolt came with its own extractor, then you changed that as well.

My recommendation would be to remove the o-ring from the FN boklt and run it with just the HD spring/insert.  If still no joy, then go back to original spring/blue insert.  If still no joy, go back to the BM extractor (if that's an option).  I seriously doubt your functioning issues are the result of .223 vs 5.56 chambers, if that were the acse I would have expected some problems with your stock setup.  The problems kicked in when you changed bolts/springs/inserts etc.  back those out one item at a time and see if functioning is restored.


The 20" barrel runs a longer ags system and the stock spring/blue insert is the stock package.  The HD spring/O-ring/black buffer are intended for carbines that run shorter gas systems.  I've never heard of problems when using those in the rifle-length system, but I've also never heard of instances where you need to run that setup in a rifle-length system.

2IDdoc,

I think my tax time upper was in the first 300 ordered. The barrel is marked B MP 5.56 NATO 1/7. However it does not have M4 ramp cuts. Shrouded semi carrier with no marks on either the bolt or the carrier. Staking on the key is minimal.

I have always found the chrome lined Bushmaster barrels to have chambers with long throats and they run.

Before anyone else gets carried away shoving reamers in chrome lined barrels buy the Stoney Point/Hornady gauge and measure the throat first. If the rifle is choking measure the bullet jump against one that runs.

www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=570611&t=11082005

www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=290405&t=11082005

Quoted: Quoted: My tax time 20" upper does not have M4 feed ramps. That's interesting about your upper not having feed ramps. Strange. Did you get one of the rifles from the first batch? That makes me wonder if they ended up putting some of their standard 20" rifles in with the mix. Is your barrel 1/7?

As I stated in my previous post, my 20" tax time upper doesn't have M4 ramps either.  Why would a rifle have, or need carbine feed ramps?  I'm not sure which "batch" my upper was in, but I called Bushmaster after about a month of waiting, and they said they sold more than they had on hand, and had to wait on barrels from the machine shop.  My barrel is marked B MP 5.56 NATO 1/7.

Quoted: Quoted: Quoted: My tax time 20" upper does not have M4 feed ramps. That's interesting about your upper not having feed ramps. Strange. Did you get one of the rifles from the first batch? That makes me wonder if they ended up putting some of their standard 20" rifles in with the mix. Is your barrel 1/7? As I stated in my previous post, my 20" tax time upper doesn't have M4 ramps either.  Why would a rifle have, or need carbine feed ramps?  I'm not sure which "batch" my upper was in, but I called Bushmaster after about a month of waiting, and they said they sold more than they had on hand, and had to wait on barrels from the machine shop.  My barrel is marked B MP 5.56 NATO 1/7.

Damnit! I just turned on a brighter light, and my wife took the kids out to the pool, and I can see that it does not have m4 feed ramps. Sorry for the mis information. DOH! There are grooves that are from regular feeding in the upper that made it look just like m4 feed ramps. They look squarish and the receiver looks like it has ramps. Sorry guys. I'm not full of $hit about the CMV barrels though if you can believe me after this mistake.