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Page AR-15 » AR Basics
AR Sponsor: bravocompany
Posted: 9/19/2017 12:28:59 PM EDT
Hey guys I picked up two new bolts for my rifles one is a daniel defense and one is a BCM. Both great bolt carrier groups however I have a question I hope someone can answer. On the DD bolt you can see a thick chrome plating without taking the carrier out but on the bcm you cant see anything unless you take the carrier out and then its just a little chrome lining. What is the difference and is the bcm not considered chrome lined?
Link Posted: 9/19/2017 1:50:56 PM EDT
[#1]
Link Posted: 9/19/2017 2:00:46 PM EDT
[#2]
I will post two pictures of what I mean to give some context I am somewhat new to the top tier ar parts so I am just trying to learn as much as I can.  In the last image that thick silver lining is different on the dd than the bcm why is that? DD BCG BCM
Link Posted: 9/19/2017 7:33:40 PM EDT
[#3]
Quoted:
Hey guys I picked up two new bolts for my rifles one is a daniel defense and one is a BCM. Both great bolt carrier groups however I have a question I hope someone can answer. On the DD bolt you can see a thick chrome plating without taking the carrier out but on the bcm you cant see anything unless you take the carrier out and then its just a little chrome lining. What is the difference and is the bcm not considered chrome lined?
View Quote


The BCM bolt, and the BCM bolt carrier are mil-spec parts, built per the TDP.

What do you mean when you say "you can't see anything unless take the carrier out"? You seem confused about what you are attempting to talk about. Can you post pictures of the individual parts you are concerned with?
Link Posted: 9/19/2017 8:52:26 PM EDT
[#4]
Link Posted: 9/19/2017 10:44:38 PM EDT
[#5]
I would imagine variation in application.  FWIW, I've seen that much variation in factory carriers pulled from the same top tier brand.
Link Posted: 9/19/2017 10:52:34 PM EDT
[#6]
Not uncommon at all to see some chrome on the front of the carrier. It varies from brand to brand and batch to batch even. Chrome planting can be somewhat unprecise. BCM and DD are top of the line and made to meet mil spec fit, function and finish on them will be 110%.
Link Posted: 9/21/2017 5:38:34 AM EDT
[#7]
The carrier is the chromed part.  The functional area is inside the carrier bore and the gas key to facilitate cleaning and prevent corrosion. The difference is simply a cosmetic one and doesn't imply a difference in plating thickness.
Link Posted: 9/23/2017 11:32:14 AM EDT
[#8]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
The carrier is the chromed part.  The functional area is inside the carrier bore and the gas key to facilitate cleaning and prevent corrosion. The difference is simply a cosmetic one and doesn't imply a difference in plating thickness.
View Quote
Makes total sense to me. I agree.
Link Posted: 9/24/2017 4:51:55 PM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
The carrier is the chromed part.  The functional area is inside the carrier bore and the gas key to facilitate cleaning and prevent corrosion. The difference is simply a cosmetic one and doesn't imply a difference in plating thickness.
View Quote
Very well said....Seems the OP is confused about what he was talking about and looking at but you explained it perfectly.
Both the Daniel Defense and BCM bolts and bolt carriers are g2g.
Link Posted: 9/30/2017 11:39:11 AM EDT
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Very well said....Seems the OP is confused about what he was talking about and looking at but you explained it perfectly.
Both the Daniel Defense and BCM bolts and bolt carriers are g2g.
View Quote
That's the second time you've said the OP is confused. No offense but my one take at reading his post made perfect sense. BCM appears to have a thin interior carrier lining while the DD has a thicker, almost solid chrome look. He's just using the wrong terminology otherwise...so let's help him.
Link Posted: 9/30/2017 11:53:32 AM EDT
[#11]
Quoted:
Hey guys I picked up two new bolts for my rifles one is a daniel defense and one is a BCM. Both great bolt carrier groups however I have a question I hope someone can answer. On the DD bolt you can see a thick chrome plating without taking the carrier out but on the bcm you cant see anything unless you take the carrier out and then its just a little chrome lining. What is the difference and is the bcm not considered chrome lined?
View Quote


OP, what you mean to say is when the bolt is removed from the carrier, that's where you see the difference in chrome lining. The bolt is the smaller component which contains the gas rings, blocky lugs, extractor, etc. The bolt rides inside the carrier, which is the larger of the group. Inside the carrier near the face (end with the staked gas key) is the chrome lined area you're referring to. The chrome lining is done via an electrical process when submerged. The chrome itself has a higher hardness rating and reduced friction coefficient, and as others have said, more resistant to corrosion.....all in comparison to steel of course. Hope that helps. DD produces their own BCGs however I cannot speak for BCM.
Link Posted: 10/1/2017 12:35:58 AM EDT
[#12]
haven't seen the OP reply back yet...

I will pipe in though.

Using the picture posted above, from my reading and understanding of the OP, that pic is representative of what he is asking about.

The chrome lining of the carrier from both manufacturers is likely similar in thickness. The interior of the carrier is the critical chrome lined part, the front of the carrier is a non-critical area.

The difference is down to differences in manufacturing. The inside is the important part, the front is overlap... Think of it in a similar manner as "overspray" in painting. One manufacturer's process resulted in more of the chrome sticking to the, non-critical, front of the carrier, than the other manufacturer's process... Like they didn't mask off as much area to protect from overspray.
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