Bolt carrier comparision, any difference?

[markm]

Used to be you could steal COLT bolt groups for a modest premium over the aftermarket poop. It’s not so easy any more.

[MassMark]

Thank you all gentlemen - one of the most informative posts I’ve read in a long time, (anywhere). Gives me superb food for thought as I approach my build and cements the logic behind joining this forum. Thanks again.

Mark

[toddackerman]

@gotm4

Which then quickly results in shooting loose, broken or damaged key or broken carrier key screws which totally sucks.

So then IF you buy a Colt, or LMT BC you shouldn’t have these worries?

[markm]

@toddackerman

So then IF you buy a Colt, or LMT BC you shouldn’t have these worries?

I’d say one greatly reduces the likelyhood of these problems with a good carrier. But nothing is 100%

[g3driver]

I have 3 Bushmasters BCG’s all have over 2000+ rnds not one problem. I am not sure why people bash bushmaster, I have not had any problems and the customer service is great.

E

[markm]

@g3driver

I have 3 Bushmasters BCG’s all have over 2000+ rnds not one problem. I am not sure why people bash bushmaster, I have not had any problems and the customer service is great.

E

There’s thousands and thousands of functional bushmaster carriers out there. The bottom line, however, is that there are higher quality options.

[C4IGrant]

@g3driver

I have 3 Bushmasters BCG’s all have over 2000+ rnds not one problem. I am not sure why people bash bushmaster, I have not had any problems and the customer service is great.

E

Honestly, your round count is low and you have a very low statistical sampling.

BM’s CS is great. I would MUCH rather seem them spend the money on better components and higher levels of CS though.

C4

[Shihan]

@g3driver

I have 3 Bushmasters BCG’s all have over 2000+ rnds not one problem. I am not sure why people bash bushmaster, I have not had any problems and the customer service is great.

E

Nobody bash’s them but simply states fact. 2000rds is very low, how many of those rounds were shot through a short amount of time like in a training senario? People need to get away from the I own it and therefore it is good stuff mentality and look at facts.

[ksa464]

I too own a Bushmaster M4 and love it. I also own a Colt M16 type, and love it too. Both have provided me with flawless service and there is no difference in the shootability in them. Functions without a hitch.

I believe what you are refering to when you say about the comments that “Bushmaster sucks” is not really that. The more accurete description would be that the chances are greater of receiving a quality weapon (QA and top shelf components, assembly pratices, etc) from a Colts PT Manufactuing vs. a Bushmaster.

A quick look at the gas keys for example in my two rifles reveals the Colt has a noticably defined stake as where the Bushy is not as defined and deep. Are they both staked? Well (with some debate) yes. Is one done better than the other? Probably so. Many will contend that a “proper” stake is very important. It may not be for a rifle for 5,000, 10,000, 20,000 rounds, maybe never. BUT is that a chance worth taking? Maybe, maybe not. Again, it may nerver be an issue with the reliability. Its these things that also drive the costs up. Its what you pay for.

Now with that said, and for instance, 99 out of 100 Colts maybe problem free. 92 out of 100 Bushmaster/Stag/RRA/XXXX/XXXXX maybe problem free. One Colt would go back under warrantee service, eight of the BusyRRAag’s would be returned. In other words, you take a greater chance on XXXXXX vs. the Colt. That I believe is the chance you take/price differance. Otherwise, I dont believe that you would find anyone ( well maybe some) who would honestly say flat out across the board that “Bushmaster sucks”; because they dont. They are very good as many others are as well.

Now Olympic on the other hand…

[usmcvet]

@ksa464

I too own a Bushmaster M4 and love it. I also own a Colt M16 type, and love it too. Both have provided me with flawless service and there is no difference in the shootability in them. Functions without a hitch.

I believe what you are refering to when you say about the comments that “Bushmaster sucks” is not really that. The more accurete description would be that the chances are greater of receiving a quality weapon (QA and top shelf components, assembly pratices, etc) from a Colts PT Manufactuing vs. a Bushmaster.

A quick look at the gas keys for example in my two rifles reveals the Colt has a noticably defined stake as where the Bushy is not as defined and deep. Are they both staked? Well (with some debate) yes. Is one done better than the other? Probably so. Many will contend that a “proper” stake is very important. It may not be for a rifle for 5,000, 10,000, 20,000 rounds, maybe never. BUT is that a chance worth taking? Maybe, maybe not. Again, it may nerver be an issue with the reliability. Its these things that also drive the costs up. Its what you pay for.

Now with that said, and for instance, 99 out of 100 Colts maybe problem free. 92 out of 100 Bushmaster/Stag/RRA/XXXX/XXXXX maybe problem free. One Colt would go back under warrantee service, eight of the BusyRRAag’s would be returned. In other words, you take a greater chance on XXXXXX vs. the Colt. That I believe is the chance you take/price differance. Otherwise, I dont believe that you would find anyone ( well maybe some) who would honestly say flat out across the board that “Bushmaster sucks”; because they dont. They are very good as many others are as well.

Now Olympic on the other hand…

I like the way you put that! And that quote from Pelosi is priceless.

[d30gaijin]

@Bill_Alexander

Bolt carriers need a little examination.

Bores, concentricity aside, need to be chromed as these are running surfaces. The bolt tail which is nominally 0.2503" diameter runs through a 0.2510" diameter ring at the back of the carrier that provides the gas seal. This is a mechanical clearance so there is naturally some gas leakage during operation. The chrome in this area must be smooth to allow the bolt tail to run as the first alignment surface and also resist gas erosion (hard chrome is between HRC68 and HRC72 if correct) The second diameter within the carrier is the area that the gas rings run on. Gas rings are 302 stainless and as such are not particulaly hard. The surface must be smooth to prevent excessive wear on the rings. This said they are a sacrificial item and replacement between 2000 and 3000 rounds should be a consideration in a working gun. New rings will show slight shear marks when installed. After break in the edges should be square. If any rounding is observed the rings should be removed and discarded. Linear striations on the rings indicated the chrome bore is not smooth enough. The third diameter in the carrier is also a bearing surface. The bolt is supported in this area by the raised ring seen about half way down the bolt body. Again a smooth hard surface is required. In examining the bores the chrome should appear uniformly light grey and have a slight sheen. Carriers with polished bores usually result from a secondary operation to polish off excessive chrome or hide a defective finish. It is also a consideration in examining the chrome that there should be a witness visible between 1/3 and 1/2 into the cam pin path. This prevents the exposure of an edge at the point where the cam path breaks through the bolt into the bore, where chipping would occur.

Carriers are produced from AISI 8620 and typically case hardened. Specification carriers should not be subjected to secondary straightening. I have no evidence of the detrimental effects of this process beyond the induced stress in the part but would aviod such carriers.

Externally the carrier base should be smooth as this is the surface that runs over the rounds presented by the magazine. A rough base will act as a linear brake on the carrier and the speed of the carrier will change as the magazine tension relaxes. This is not conducive to reliability. The back of the carrier again should be smooth and correctly chamfered on the external and internal diameters. Lastly the front rails should be well defined without blurred edges that indicate excessive blasting of the part prior to phosphate.

Someone posted that the carrier is akin to the crankshaft in an engine. This is not a bad analogy

Bill Alexander

Incredibly great information! Thank you for taking your time to share it here with us.

Don

[KevinB]

This is a DPMS chrome bolt carrier that I used in a SR16 (non E3) for well over 18k rounds.

I cleaned up really easily, and I (statistical sample of 1) was impressed.

Beyond the ability to be cleaned and not pick up carbon build up, I’m not really sure what the gain was.

[Boss_Hogg]

KevinB, thank you for taking time to post pictures of a DPMS chrome bolt carrier with a high round count.

The chrome DPMS BCG was recommended to me in 2007 by another SME, and he put over 50,000 rounds through it before the extractor broke. No other problems.