So you want to buy an AR-15, huh?

[chris falk]

BCM Bolt Carrier Group vs. CMMG BCG

jwise et al:

Making the final decisions before ordering from CMMG in the recommended manner. Given the probable backlog, there's no need to rush the order and end up not having made the best choices. To that end, I have a couple of questions. Here's the first one, which is pretty straight forward:

Earlier in the thread ( http://forums.officer.com/forums/sho...=81462&page=10 ), the merits of the Bravo Company bolt carrier group were discussed and it was suggested as a economical and effective way to fix many of the perceived shortcomings found in some of the AR-15 style weapons from less recommended manufacturers. Of course, CMMG is reported to not have these problems, so the Bravo Company bolt carrier group might be a solution in search of a problem in this case.

The Bravo Company bolt carrier group is $160 when it's in stock. Leaving out the CMMG bolt carrier group when you order gets you a $85 credit and the savings from not paying for the EGRESS upgrade (if you were going to, and you've expressed your opinion that adding an o-ring is a more economical route) is another $30 savings - so the net difference is $45 plus the shipping from Bravo Company. In other words, enough to be worth spending for a clear upgrade and enough to be worth saving if there's no benefits. So what do you get for the money?

Both the CMMG and Bravo offer the full auto carrier that seems to be recommended.

The Bravo Company bolt carrier group has:
MPI Bolt (Magnetic Particle Inspected)
Shot Peened Bolt
Chrome Lined Carrier
Chrome Lined Gas Key
Gas Key Hardened to USGI Specifications
Grade 8 Hardened Fasteners
Key Staked Per Mil-Spec
BCMâ„¢ Extractor Spring
Black Extractor Insert
Mil-Spec Crane O-Ring

CMMG's bolt carrier group has:
MPI Bolt (Magnetic Particle Inspected)
Shot Peened Bolt
Key Staked Per Mil-Spec
I can only imagine that CMMG could also claim:
Gas Key Hardened to USGI Specifications
Grade 8 Hardened Fasteners
The EGRESS upgarde would have added the:
Black Extractor Insert
Mil-Spec Crane O-Ring
Better extractor and ejector spring
as well as one piece gas ring
I don't see anything about chrome on the CMMG parts

So it looks to me that your $45 plus shipping gets you chrome lining on the carrier and key and costs you the better ejector spring (of possible worth) and the one piece gas ring (of little to no worth).

So what does the chrome in the carrier and in the gas key that you're paying for do for you? Easier cleaning? Less wear? Longer functioning between lubrication/cleanings? Enhanced corrosion resistance?

[jwise]

Nearly every bolt carrier that I know of is chrome lined.

Get the standard CMMG bolt/carrier, and stick an O-ring in there. You're done.

The BCM bolt/carrier is ONLY for those who want to fix a lesser rifle system. There is no reason putting a BCM bolt/carrier in a CMMG, LMT, or Colt, etc...

[chris falk]

Nearly every bolt carrier that I know of is chrome lined.

Get the standard CMMG bolt/carrier, and stick an O-ring in there. You're done.

The BCM bolt/carrier is ONLY for those who want to fix a lesser rifle system. There is no reason putting a BCM bolt/carrier in a CMMG, LMT, or Colt, etc...

An answer that keeps money in my pocket or let's me spend it on something worthwhile instead! Now, that's a thing of beauty. Sorry to bother you with something that was so obvious. I guess chrome lining of the bolt carrier is so common that nobody bothers to list it for those of us at the entry level. Thank you, and I'll work on my next question.

[chris falk]

buffer/spring/bolt carrier/extractor/gas system/ammunition question

Bear with my pea brain here and show me where I'm being an idiot.

It seems that when you mix all these parts together, you need to end up with a harmonious system or there will functional issues that will make you pull your hair out and not trust your carbine. It sounds as though you can end up with two problems: you could either get "short-stroking", which I take to mean the bolt carrier group does not go far enough to the rear and/or for a long enough time to strip the next round out of the magazine and/or eject the fired case fully OR you can get "hard extraction" which I take to mean that the fired case is not extracted (the rim is ripped off or the extractor otherwise doesn't otherwise do it's job).

Assuming that I've got that much right (big assumption), that many parts is a lot of variables. Lets try to narrow things down some. Let's start by assuming a true 16" barrel carbine with a midlength gas system and the standard buffer return spring (since CMMG doesn't give you a buffer return spring choice). It also seems a common thought that most AR-15s are already "over gassed", which I take to mean have larger than needed or optimal gas ports.

If I haven't screwed up so far, that leaves us with ammunition, extractors, bolt carriers and buffers to monkey around with to achieve the best shooting carbine that doesn't sacrifice reliability.

Of course, we want good reliable functionining with the full range of ammunition from what I understand is the rather anemic Wolf through M855 and the new 77 grain OTM rounds so we can't narrow down the ammunition.

Obviously, we do what we can to enhance the extractor's performance with better spring, o ring/Defender, the insert (that some claim does something and some claim does nothing) and that's the best we can do there.

This leaves us with bolt carriers and buffers, where the weight of each component is the last variable. You could have any combination of light, medium or heavy weight buffer and light, semi auto (middle weight) or full auto (heaviest) carrier.

Here's where I really go out on a limb with my guesswork. I'm guessing that it's the overall combined weight of the buffer and carrier that matters. If you get too heavy, you don't have enough energy to drive the bolt carrier and buffer back far enough and you'll get the short stroking problem. If you're too light, the bolt carrier and buffer go to the rear so fast that the extractor is trying to drag the fired caring out of the chamber while it's still swelled tightly against the chamber walls (and probably bottoms out against the back of the buffer tube to boot). If by some fluke, I'm not off track here, how do you figure out the right combination?

I suppose that you could put in the heaviest buffer and bolt carrier you can find and try some Wolf with a really loose hold while the carbine is dirty and when that short strokes (and I'm assuming that it will), try lighter and lighter combinations until there's no short stroking. I guess that combination would give you the slowest cycling, softest ejecting possible, but it's certainly not condusive to ordering something right from the get go. On top of that, I've read that the competition action shooting folks (e.g. three gun, etc.) favor special reduced weight carriers/buffers etc. It seems their theory is that less reciprocating mass leads to faster, better shooting. This sounds good but would seem to be at odds with avoiding "hard extraction" and lead to less reliability unless they really put time into tuning the gas system on these rifles, which they probably do. On the other side of the coin, this thread favors the full auto carriers for more weight. I guess the theory here is that more weight counters any over gassing and leads to more reliable extraction (and to hell with faster shooting if it comes at the expense of reliability in a duty weapon.)

All that said, please correct me where I went wrong in theory and explain the rationale behind choosing which buffer to order with a 16" barrel length (exclusive of flash hider) midlength gas system carbine with a full auto carrier or with a semi auto carrier? (I don't see how it could be perceptible, but using a heavier buffer and a lighter carrier would shift a few ounces rearward in a platform that is always getting stuff stuck to the front of it.)

[Omega Man]

Still like to hear any thoughts on the Daniel M4. Anybody?

I just found out via an email from Daniel Defense, that thier rifles are not 2 stage triggers.

[chris falk]

I should add that there is buffer advice out there that's all over the map from standard carbine to H3 to 9mm buffer:

http://www.ar15.com/forums/topic.html?b=3&f=4&t=450219

https://www.snipercentral.com/forums...79936e86c26f46

and many more.

I found a couple of articles on operation and short-stroking that look like they've gotten passed around and sure sound like they know what they're talking about (not that I could tell the difference):

http://www.ar15barrels.com/prod/operation.shtml

and near the end of this thread:

http://www.thehighroad.org/archive/i...p/t-80843.html

Between dwell time, over gassing and under gassing both being able to cause the same symptoms and all the other things discussed, I think I'm still in the "knowing how little you know" phase of learning.

The bright side is that the mid length gas system 16" carbine seems to be the most forgiving platform short of the original rifle length 20" rifle and will probably work with almost any buffer, but who doesn't want the best possible combination of reliability and "shootability".

I assume that you'd get this best combination if the buffer spring was compressed to the point where the coils almost came in contact with each other and that the buffer doesn't have to actually rebound off a fully stacked spring to work. If that's the case, I'm trying to figure out if there's some way to figure out how far back in the tube the buffer goes after a shot.

[jwise]

I should add that there is buffer advice out there that's all over the map from standard carbine to H3 to 9mm buffer:

http://www.ar15.com/forums/topic.html?b=3&f=4&t=450219

https://www.snipercentral.com/forums...79936e86c26f46

and many more.

I found a couple of articles on operation and short-stroking that look like they've gotten passed around and sure sound like they know what they're talking about (not that I could tell the difference):

http://www.ar15barrels.com/prod/operation.shtml

and near the end of this thread:

http://www.thehighroad.org/archive/i...p/t-80843.html

Between dwell time, over gassing and under gassing both being able to cause the same symptoms and all the other things discussed, I think I'm still in the "knowing how little you know" phase of learning.

The bright side is that the mid length gas system 16" carbine seems to be the most forgiving platform short of the original rifle length 20" rifle and will probably work with almost any buffer, but who doesn't want the best possible combination of reliability and "shootability".

I assume that you'd get this best combination if the buffer spring was compressed to the point where the coils almost came in contact with each other and that the buffer doesn't have to actually rebound off a fully stacked spring to work. If that's the case, I'm trying to figure out if there's some way to figure out how far back in the tube the buffer goes after a shot.

You are definitely getting into the nitty-gritty of the platform. You hit the nail on the head in your previous post, when you were expounding on the numerous ways that an AR-15 can malfunction. With that being the case, there is no ONE best buffer. You should use the heaviest buffer that the REST of your platform supports. This could be the H3 buffer. This could even be the 9mm buffer. I recommend the H or H2 buffer, until you figure out that your rifle either (1) needs, or (2) can handle a heavier buffer.

With a full-auto, this changes. With a match gun that is for competition and not the street, this changes (somewhat).

The most important thing that you noted was what I highlighted. This is why I recommend the Midlength.

[yaktamer]

Any idea how long CMMG is running on orders these days?

[WinterBoarder]

BCM Standard 20" Government Profile Upper Receiver Group

Wasn't sure if I should create a new thread, so I thought I would post in here instead. These are in stock...

http://www.bravocompanyusa.com/BCM-M...urg-gov-20.htm

[WinterBoarder]

Anyone have any experiences with these BCG's?

http://www.failzero.com/armory/ar-15.html

A completely assembled, ready to install AR-15 Bolt and Carrier System. Kit includes six critical parts that are treated with EXO Technology, a revolutionary surface technology that provides permanent dry lubricity, radically improves the performance of your AR-15 and eliminates the need to apply oil or grease to treated parts for the life of the weapon. Treated parts include; Bolt, Bolt Carrier, Hammer, Extractor, Cam Pin, Carrier Key. This kit has fired over 11K rounds in a standard anodized upper. Quality features include:

* Case Hardened, Shot Peened and MPI Bolt (Magnetic Particle Inspected)
* EXO Coated Bolt (40% more wear resistant than Chrome with a very Low Coefficient of Friction)
* Mil-Spec Gas Rings
* EXO Coated Carrier
* Chrome Lined Gas Key
* Gas Key Hardened to USGI Specifications
* Grade 8 Hardened Fasteners
* Blue Extractor Insert
* Mil-Spec Staked Gas Key
* Firing Pin and retainer

[PatFWC]

Anyone have any experiences with these BCG's?

http://www.failzero.com/armory/ar-15.html

A completely assembled, ready to install AR-15 Bolt and Carrier System. Kit includes six critical parts that are treated with EXO Technology, a revolutionary surface technology that provides permanent dry lubricity, radically improves the performance of your AR-15 and eliminates the need to apply oil or grease to treated parts for the life of the weapon. Treated parts include; Bolt, Bolt Carrier, Hammer, Extractor, Cam Pin, Carrier Key. This kit has fired over 11K rounds in a standard anodized upper. Quality features include:

* Case Hardened, Shot Peened and MPI Bolt (Magnetic Particle Inspected)
* EXO Coated Bolt (40% more wear resistant than Chrome with a very Low Coefficient of Friction)
* Mil-Spec Gas Rings
* EXO Coated Carrier
* Chrome Lined Gas Key
* Gas Key Hardened to USGI Specifications
* Grade 8 Hardened Fasteners
* Blue Extractor Insert
* Mil-Spec Staked Gas Key
* Firing Pin and retainer

Absolutely. My local armorer puts these in all of his rifles(Tactical Machining). They are amazing. Even just feeling the outside of the bolt you immediately know it's different, it feels slippery. I've heard that the only thing that makes this bolt fail is due to the fouling created by the rounds. I can't wait until they make one for a 92FS.

[Barnacle Bill]

jwise, really a great thread! I found it very helpful. I found it over a year ago, but have just now registered so I can ask questions. I'm not new to AR's - built one from stripped receivers 25 years ago, but I was totally out of date on what constitutes quality and what companies deliver it. The guide at the beginning was perfect, but I probably should have read the rest of the thread before now

Last July I ordered a rifle from CMMG using the guide for internal stuff, but the pupose was to add an M16A2 (lookalike) to my military rifle collection while I still could so the outward features were somewhat different. Not having read the full thread, I didn't understand that the cost difference was tax and you still got the lifetime warranty on separately orders uppers & lowers, so I ordered a complete rifle. After the election, I still didn't have it. Apparently there was a problem with 20" barrels. So, I had them split my order and send me the lower. I still don't have the upper, but have received an email that it is in production and they charged my card for it about that time, so hopefully soon.

A few weeks ago I got an email from UPS saying a shipment was going from CMMG to my dealer, so I (and the dealer) figured it was finally my upper. When the package came, they didn't even open it. When I did - surprise, surprise, surprise! That's not my upper - it's a whole carbine pretty much like what this guide's about. I got to hold it, but there was paperwork inside identifying the rightful recipient. Bummer...

That got me thinking, though, about how sweet it was & how my 50 year old eyes are getting too tired for iron sights & maybe a flat-top AR mounting optics would be just the ticket. So, I talked myself into looking for one. However, I wanted to find something that was in stock someplace, not wait another year. So, matching what you wrote in the guide to what I found available, later this week I expect my dealer to receive a Colt LE9620 for me (it shipped from the distributor Friday). Now I have some questions...

I wanted an illuminated reticule 1-4x because - optics vs iron for the aging eyes, illuminated for low light, with flexibility to leave it by default on 1x but have 4x on tap for longer shots. I researched the ones mentioned way early in the thread and others, decided that the Meopta K-Dot looked like the best bang for buck (I'd love the S&B but I could buy a whole 'nuther rifle for the price difference between that & the Meopta and I can't believe it's that much better). OK, so LaRue had a package deal with the scope & mount, with your choice of of the SPR or SPR-E mount. I asked Larue about it and they said the E was for more eye relief if you shoot "nose to charging handle". I honestly never thought about it, but after much thrashing with the rep on the phone I went with the non-E one. Scope & mount should sarrive Weds, if UPS isn't lying. Later I went & broke out my old AR (fixed A1 stock), but found that I wasn't necessarily consistent (at least while thinking about it) and seemed able to get a comfortable cheek weld with my schnozola anyplace from the charging handle to a couple inches aft thereof. Then I got farther into the tread and read where you wrote "I would recommend a Meopta K-Dot (or S&B Short Dot) in a LaRue SPR-E mount" Then I saw an Army pub online that was saying you should shoot nose to charging handle. Apparently that's how the Army & Marines train, but I'm retired Navy and they don't train us shipboard types just issued weapons for security details if you could hit the paper enough times during the qual shoot (litterally hit the paper, it was blank and a hole anyplace in it counted as a hit). Did I mess up & order the wrong mount?

Related but just curiosity since I'm not in LE - is the collapsable stock in practice used as an adjustable (set it where you like it & forget it), or do you collapse it for storage in the cruiser & extend it when you break it out?

Another place in the thread, your recommended "C-Products USGI 30rd mags with Magpul followers". Is this the same thing as green-follower USGI mags from other manufacturers, like the D&H mags that 44MAG sells, or something better. If better, why & how much difference does it make. As in I already bought a mess of the the D&H ones while waiting for the CMMG rifle...

Is there any such thing as quality free-float carbine-length handguards w/o rails? I'm not really looking mount anything, but wouldn't mind increasing accuracy. If not, how much weight do the rail ones add vs stock? What's the scoop on rail covers & ladders? I think I see rail handguards with covers on the picture of your carbine with the Meopta setup.

At what range do you typically zero? From what I've seen playing around with a ballistic calculator, a 50 yard zero looks pretty good for a carbine shooting either of the military loads - MPBR (no more than 4" high or low) at around 300 yards for M193 & around 285 for M855. Don't know about the heavier OTM bullets like the 75 gr TAP you recommend.

Speaking of which, from what I've read on AR15.com & elsewhere the M193 would be better for self defense than M855 because it has a longer fragmentation range. However, the 75 gr Hornady and 77 gr Nosler & SMK loads are considered "best". Some of that stuff is unobtainium for the unbadged, and the rest looks to be sold out all over the net except for a SMK load from Silver State Armory (that supposedly mimics military-only BH MK 262). On another web sight I read that also has lots of LE folks, they love Corbon DPX but that affection seems rooted in its performance against car doors & windows - probably not a likely scenario for a non-LE civvie. Some folks seem to like Prvi Partizan 75 gr match. What would you choose if you couldn't have TAP?

[beavo451]

Wow, giant first post.


Shooting nose to cheekweld is not about comfort. It helps with getting close to the same cheekweld each and every time. As you have pointed out, you can get a comfortable cheekweld just about anywhere, but the positioning is inconsistent. Doing the same at the rifle also helps translate into consistent shooting stances.

Wait until the SPR mount comes in before deciding. You can always get a SPR-E mount. LaRue Tactical has excellent customer service.

I leave my collapsable sotck in one position for all shooting and storage. I have it collapsed one notch in for on-duty use (to compensate for body armor). I also leave my Aimpoint on. Grab, charge, and go.

Magpul followers have more anti-tilt properties than the USGI green followers. Not that I've heard or seen a lot of failures related to the green followers, but it's better right? I would just skip the aluminum mag/upgrading follower business and buy Magpul Pmags.

D&H magazines are excellent. I wouldn't worry about it if you have a bunch already.

The Daniel Defense M4 7.0 rail (replaces standard carbine length handguards) weigh less installed than the plastic handguards. 8.5ozs

Clark carbon fiber handguards are probably the lightest at 6ozs installed for a 12" (rifle length) handguard. No rails though.

Rail covers and ladders protect the rails and your hands. Different styles for different missions/taste.

50 yards is a good zero for a fighting carbine.

As far as defensive ammunition goes, pretty much any quality 75gr or 77gr round will be sufficient.

[jwise]

jwise, really a great thread!

Thanks! I'm glad you finally registered.

Last July I ordered a rifle from CMMG using the guide for internal stuff, but the pupose was to add an M16A2 (lookalike) to my military rifle collection.

I've got one, too! I love having it, even if I don't shoot it that much.

I wanted an illuminated reticule 1-4x because - optics vs iron for the aging eyes, illuminated for low light, with flexibility to leave it by default on 1x but have 4x on tap for longer shots. I researched the ones mentioned way early in the thread and others, decided that the Meopta K-Dot looked like the best bang for buck (I'd love the S&B but I could buy a whole 'nuther rifle for the price difference between that & the Meopta and I can't believe it's that much better). OK, so LaRue had a package deal with the scope & mount, with your choice of of the SPR or SPR-E mount. I asked Larue about it and they said the E was for more eye relief if you shoot "nose to charging handle". I honestly never thought about it, but after much thrashing with the rep on the phone I went with the non-E one. Scope & mount should sarrive Weds, if UPS isn't lying. Later I went & broke out my old AR (fixed A1 stock), but found that I wasn't necessarily consistent (at least while thinking about it) and seemed able to get a comfortable cheek weld with my schnozola anyplace from the charging handle to a couple inches aft thereof. Then I got farther into the tread and read where you wrote "I would recommend a Meopta K-Dot (or S&B Short Dot) in a LaRue SPR-E mount"

Haha!! I guess you should have read it all the way through, first!

Did I mess up & order the wrong mount?

No. You can adjust the optic within the range of the two rings back and forth a bit. In addition, you can mount the SPR mount all the way forward. I have my SPR-E mount NOT all the way forward, and have my optic perfectly centered in the rings. There is play in there, so all is not lost...

Related but just curiosity since I'm not in LE - is the collapsable stock in practice used as an adjustable (set it where you like it & forget it), or do you collapse it for storage in the cruiser & extend it when you break it out?

I leave it where it is (2nd notch.)

Another place in the thread, your recommended "C-Products USGI 30rd mags with Magpul followers". Is this the same thing as green-follower USGI mags from other manufacturers, like the D&H mags that 44MAG sells, or something better. If better, why & how much difference does it make. As in I already bought a mess of the the D&H ones while waiting for the CMMG rifle...

Not a big deal. The D&H w/ green followers are great magazines. The Magpul followers make a great magazine even better. The P-Mag is the best. See how that works?

Is there any such thing as quality free-float carbine-length handguards w/o rails?

Hogue makes a free float tube w/out rails. I had one (maybe I still do...), but switched it out for a railed handguard a couple years ago.

What's the scoop on rail covers & ladders? I think I see rail handguards with covers on the picture of your carbine with the Meopta setup.

Get what is available and what is comfortable. I like the full panels on the bottom and sides, and just the ladder on top (ladder is cheaper and my hand doesn't touch the top.)

At what range do you typically zero? From what I've seen playing around with a ballistic calculator, a 50 yard zero looks pretty good for a carbine shooting either of the military loads - MPBR (no more than 4" high or low) at around 300 yards for M193 & around 285 for M855. Don't know about the heavier OTM bullets like the 75 gr TAP you recommend.

I like a 100yd zero. It pretty much puts you within a few inches of POA from 0-300yds.

Speaking of which, from what I've read on AR15.com & elsewhere the M193 would be better for self defense than M855 because it has a longer fragmentation range.

That's true.

However, the 75 gr Hornady and 77 gr Nosler & SMK loads are considered "best". Some of that stuff is unobtainium for the unbadged, and the rest looks to be sold out all over the net except for a SMK load from Silver State Armory (that supposedly mimics military-only BH MK 262). On another web sight I read that also has lots of LE folks, they love Corbon DPX but that affection seems rooted in its performance against car doors & windows - probably not a likely scenario for a non-LE civvie. Some folks seem to like Prvi Partizan 75 gr match. What would you choose if you couldn't have TAP?

I find 75 and 77gr ammo in stores from time to time. I wouldn't worry too much about it, though. I'd look for a BTHP that is heavier than 69gr, and be happy.


WELCOME!

[Barnacle Bill]

Wait until the SPR mount comes in before deciding. You can always get a SPR-E mount. LaRue Tactical has excellent customer service.

Meaning they'll let me exchange?

I leave my collapsable sotck in one position for all shooting and storage. I have it collapsed one notch in for on-duty use (to compensate for body armor).

I'm assuming that the Colt comes with a GI M4 stock. Do you know if that matches the length of the A2 rifle fixed stock when fully extended, or is it shorter?

The Daniel Defense M4 7.0 rail (replaces standard carbine length handguards) weigh less installed than the plastic handguards. 8.5ozs

Clark carbon fiber handguards are probably the lightest at 6ozs installed for a 12" (rifle length) handguard. No rails though.

Are these free-floats?

As far as defensive ammunition goes, pretty much any quality 75gr or 77gr round will be sufficient.

Is Silver State Armory considered quality? Right now they seem to be the only thing anybody has, which makes me worry they might be like Wolf. I ordered a box to try anyway, because playing with the numbers it looks to have a very long fragmentation range.

Same question on Prvi, although they are sold out everywhere they are a lot cheaper than the other 75-77 gr OTM loads. I've had good luck punching paper with their ammo since Hanson used to import it back in the 80's (still have some in .30-06 & .30 carbine), but I don't know how this load's bullet compares to the big names.

One more question comes to mind (probably be a lot more as I go along)... will the Colt need the o-ring thing?