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BobbyZ
05-04-2011, 12:49 PM
Can anyone tell me the difference in quality for different BCMs? I understand the wear and tear comes into play so a good quality one may last longer but that's all I can gather. I'm sure there are limitless answers as it is the heart of the gun. Does the trigger and bolt need to 'get along'? Is it the upper and BCG that need to 'get along'? I'm guessing these are super noob questions.

So far I have:
JD Machine Upper
JD Machine Lower
Gonna order a LPK with 3lb trigger from Bill Springfield. Should I ask him?

CK_32
05-04-2011, 12:57 PM
Just the logo and testing... But most companies do HPT AND MPI testing these days so it pretty much just comes down to company logo... Some do stake their gas keys differently and that causes problems too if done wrong or not a good method... Other than that they are about the same.

I just stick with BCM or LMT.. good reputation and have and proven track records...

goodlookin1
05-04-2011, 12:59 PM
- Whether or not the gas key is properly staked
- Different coatings (Chrome, FailZero, Phosphate, etc)
- Milspec and within spec

That's pretty much it. The only other thing you may want is a bolt that is headspaced specifically for YOUR barrel. This gives better accuracy. Make sure you headspace any Bolt/Carrier assembly that you buy if your not buying it already assembled as a complete upper. Do this BEFORE shooting it......Just buy or borrow a set of GO/NO-GO gauges. If it fails, then DO NOT use it.

BobbyZ
05-04-2011, 1:16 PM
Okay, so....Thanks for the posts guys. I have read about HPT and MPI on that spreadsheet going around.

I'm going to get a BCM or LMT but would like a smaller company to support if possible. I just see these all over the forums with BCM boys and such. Then again they may not do the HPT and MPI.

I guess I need to do some headspace research. Any links or info would of course be appreciated. The go/no-gos are the bullet shaped guages correct? and you have to get them to match the barrel? clueless...I'll be reading.

AeroEngi
05-04-2011, 1:24 PM
Okay, so....Thanks for the posts guys. I have read about HPT and MPI on that spreadsheet going around.

I'm going to get a BCM or LMT but would like a smaller company to support if possible. I just see these all over the forums with BCM boys and such. Then again they may not do the HPT and MPI.

I guess I need to do some headspace research. Any links or info would of course be appreciated. The go/no-gos are the bullet shaped guages correct? and you have to get them to match the barrel? clueless...I'll be reading.

This might help you in understanding headspace.

http://www.rifleshootermag.com/gunsmithing/headspace_0612/

BobbyZ
05-04-2011, 1:38 PM
Okay, I get it....more $$$$$.

I read an older thread that had Calgunners saying if it's all new then don't worry about it. Is this being irresponsibly and cutting corners? I would have to buy a BCG just to do the test right? Do people take their guns to stores to test BCGs?

motorwerks
05-04-2011, 1:42 PM
There is also the debate of Young BCG's. They are supposed to lock up a little tighter, and I know mine functions a little smoother. Whether or not it does anything better or worse then my milspec ones I couldn't tell you but it does clean up really easy, and its like gun jewelry. They also do not stake their keys but they do use some sort of a thread locker. Mines been 100% flawless, and if I have the money I'll buy more someday.

dieselpower
05-04-2011, 2:36 PM
Its not really cutting corners. Its a philosophy of manufacturing.

Two companies make a chair. Company A wants a 250lb person to sit in the chair for 10 minutes to prove it can support the weight. Then stamp the chair 250lb. Company B only test every other chair and dont stamp anything.

Now salesman C says chair A is better than a Chair B. Why?

There is no non-bias document supporting the salesman claims. In fact it has been shown that both chair A and Chair B are used by the Military.

The best BCG is the one in your gun...thats been working for you. Either can fail.

BobbyZ
05-04-2011, 2:59 PM
Sorry dieselpower, I meant if I didn't do the headspace check with the go/no-go guages and just bought a decent BCG because people said that new parts don't need the headspace check, would that be cutting corners? I can't see everyone buying these $50 guages. but hey..?

mrvash
05-04-2011, 3:12 PM
I don't know whether my CMMG BCG is chrome lined or has any other fancy features or tests, but after nearly 2,000 rounds it has function flawlessly. The whole rifle has functioned flawlessly as a matter of fact.

rareair
05-04-2011, 3:24 PM
I don't know whether my CMMG BCG is chrome lined or has any other fancy features or tests....


If you're BCG is Black, is Phosphate coated. If it's been MPI tested, it will be stamped into the bolt. Look in the cavity of the Bolt Carrier where the Bolt is inserted into. If it's Chrome lined, it'll be in this area.

Chromed BCGs (or any other coatings ie NP3, TiN, Nickel Boron, Diamod Coat etc...) are all designed to reduce friction. Less friction = less heat. Less heat = less wear/longer longevity.

mrvash
05-04-2011, 3:35 PM
If you're BCG is Black, is Phosphate coated. If it's been MPI tested, it will be stamped into the bolt. Look in the cavity of the Bolt Carrier where the Bolt is inserted into. If it's Chrome lined, it'll be in this area.

Chromed BCGs (or any other coatings ie NP3, TiN, Nickel Boron, Diamod Coat etc...) are all designed to reduce friction. Less friction = less heat. Less heat = less wear/longer longevity.

It's not black, more like a dark grayish color, and the inside where the bolt goes into is more of the same.

BobbyZ
05-04-2011, 3:39 PM
So you get what you pay for.

mrvash
05-04-2011, 3:45 PM
So you get what you pay for.

Very true and I agree, I must have been lucky to get a really good standard non-fancy BCG. Mostly dry, nearly 2,000 flawless rounds.

BobbyZ
05-04-2011, 4:20 PM
Very true and I agree, I must have been lucky to get a really good standard non-fancy BCG. Mostly dry, nearly 2,000 flawless rounds.

Mostly dry?? and what's a really good non-fancy BCG. A solid one without all the coatings?

evidens83
05-04-2011, 4:40 PM
I had a Del-Ton BCG that ran flawless. As long as it's properly lubed I believe most BCGs will perform exactly the same.

AeroEngi
05-04-2011, 4:44 PM
Mostly dry?? and what's a really good non-fancy BCG. A solid one without all the coatings?

BCM or LMT full-auto BCG's would probably be your best bet. I think BCM has them in stock at the moment.

mrvash
05-04-2011, 4:56 PM
Yup, dry, no lube..

vintagearms
05-04-2011, 5:01 PM
Headspacing is a non-issue with AR15/M16. Just get a BCM/LMT/CMT/RRA/BM or Colt BCG and don't overthink it. Just go shoot and don't listen to the armchair commandos.

BobbyZ
05-04-2011, 9:57 PM
Word. I like your style vintagearms.

BOFH
05-04-2011, 10:06 PM
Don't run dry..that's just silly. You don't need it to be sloppy wet either. I just grease the few contact points on the bolt with automotive grease. And headspacing on AR's is a non issue with new components, its part of the design. Buy the best BCG you can afford and go shoot it. I have BCM in my AR and its been perfect but any decent BCG will be fine.

motorwerks
05-04-2011, 10:33 PM
Its not really cutting corners. Its a philosophy of manufacturing.

Two companies make a chair. Company A wants a 250lb person to sit in the chair for 10 minutes to prove it can support the weight. Then stamp the chair 250lb. Company B only test every other chair and dont stamp anything.

Now salesman C says chair A is better than a Chair B. Why?

There is no non-bias document supporting the salesman claims. In fact it has been shown that both chair A and Chair B are used by the Military.

The best BCG is the one in your gun...thats been working for you. Either can fail.

This was an AMAZING analogy!!!!

pdugan6
05-04-2011, 10:36 PM
http://www.jprifles.com/cart_pix/ph/1368.jpg
oooh me likey

wash
05-04-2011, 11:36 PM
The only carrier breakage I've heard of is from the carrier key loosening, so make sure the bolts are good and the stakes are good and deep.

The bolt has far more breakage.

The lugs are small and highly stressed and will break eventually.

If you know what a stress riser is, you will know that is where cracks start and AR bolts have lots of edges and sharp corners which do not help.

Not all bolts are created equally. I like the ITS super bolt, it is 9310 alloy with more material around the cam pin hole, better radii around the lugs to reduce the stress risers and other features I'm forgetting.

They are more expensive than most normal bolts but I feel it is worth it since it is the weak spot in the AR design.

I hear the worst thing for bolts is swapping them between barrels, so pair your barrels and bolts.

My guess is that sharing a bolt carrier between ARs is probably fine.

IPSICK
05-04-2011, 11:49 PM
http://www.jprifles.com/cart_pix/ph/1368.jpg
oooh me likey

This is an awesome carrier as long as you don't need to use your forward assist.

Sunday
05-05-2011, 7:12 AM
BCM are the cats meow.

goodlookin1
05-05-2011, 7:17 AM
AR15's are not self-headspacing. Read through this thread:

http://www.gunandgame.com/forums/general-military/38829-ar-15-barrels-self-headspacing.html

NiteQwill
05-05-2011, 8:18 AM
98% (or 99% ;) ) of the time, when you buy a new barrel and bolt, you DO NOT need to worry about headspacing in an AR.

If either component is worn out, I would always check headspacing before replacing the components.

It really is a non-issue.

That said, if you are really worried about it... buy a complete upper from a reputable company and you should have no issues.

goodlookin1
05-05-2011, 8:49 AM
98% (or 99% ;) ) of the time, when you buy a new barrel and bolt, you DO NOT need to worry about headspacing in an AR.

If either component is worn out, I would always check headspacing before replacing the components.

It really is a non-issue.

That said, if you are really worried about it... buy a complete upper from a reputable company and you should have no issues.

THIS ^

Except that I wouldnt be willing to be that 1-2% that may learn by experience to headspace your crap before you shoot. It's usually free at any gun shop....why risk such an easy check?

But yes, if buying a complete upper, you are correct.

IPSICK
05-05-2011, 8:55 AM
What do you guys think of this Palmetto State Bolt? It seems to have the same spec as the BCM bolt with the added advantage that it is available. It is missing the BCM logo and it does not have the rep of the BCM part.

Palmetto Specs: (http://palmettostatearmory.com/929.php)

http://palmettostatearmory.com/images/929.jpg

Made of Carpenter 158 Steel
Match Grade
MPI Bolt (Magnetic Particle Inspected)
High Pressure Tested (HPT)
Shot Peened
Fully Machined 8620 Steel Extractor
Black Extractor Insert
Mil-Spec Manganese Phosphate Finish


BCM Specs: (http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm%20bolt%20assemly%20mp.htm)

http://www.bravocompanyusa.com/v/vspfiles/photos/BCM%20Bolt%20Assemly%20MP-2T.jpg

Milspec Carpenter No. 158® Steel
HPT Bolt (High Pressure Test/ Proof)
MPI Bolt (Magnetic Particle Inspected)
Shot Peened Bolt
Tool Steel Extractor
BCM® Extractor Spring
Black Extractor Insert
Mil-Spec O-Ring

BobbyZ
05-05-2011, 8:55 AM
Free at gun shops. Ahh, that's the ticket. Thanks looker.