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Posted: 5/7/2015 11:25:48 AM EDT
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I have been reading a bit, and it seems to me that a majority of the issues that folks have with their assembled (built) .308 AR's is the BCG.
I am a fan of being frugal, but, I don't think a BCG perpetually on sale is a very good deal... I also don't think that $550 for a Bolt Carrier only (KAC) is a good deal either. Is there something that can be articulated? Or is it going to be materials & craftsmanship, with attention to detail and tolerances? QUESTION #1: WHAT MAKES A GOOD BUY IN A BCG? QUESTION #2: Is the KAC BC worth it? (If one can be found) QUESTION #3: Is there SR-25 field repair kit at $250 a good buy? QUESTION #4: Is the Lewis Machine & Tool BCG a good buy? QUESTION #5: Is POF's "Ultimate BCG" for impingement a step forward or to the oblique? 
The Ultimate Bolt Carrier Group was developed to solve simple issues that plague the standard direct impingement bolt carrier group. Our Ultimate Bolt Carrier Group is machined from a solid piece of alloy steel, eliminating the need to stake the gas key and deleting the ability for gas key screws to come loose under operation. The carrier itself is NP3 coated and features a chrome plated bolt. This group features a stainless steel gas inlet tube that is pressed and pinned into the solid gas key. This tube has been designed to allow ample clearance for the removal of the roller cam pin during maintenance. |
| I think most problems are with the bolt itself rather than the entire BCG. For my Maten (my first large frame) I went with a cheaper BCG with a good rep with AR15s with all the right specs. I did this with the plans of getting a better bolt if needed. I can buy both for less than the kac BCG or the same as a jp fmos. Well I got the BCG in and it head spaced with zero failures so far (300rds). Now I can use that money for something else I want and get another bolt later and I'll have a spare. Some people expect ar15 type plug and play but I fully understood the chance I took and it worked out. If money isn't a concern, you want it to work instantly, or you are an operator this approach might not be for you. |
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KAC carrier is not worth it UNLESS it's the carbon cutter version. Otherwise, is pretty much the same as the Armalite bcg but without forward assist, and i think they don't have the firing pin spring. I think only Armalite and LaRue use the firing pin spring.
POF offering seems like a gimmick to me. Solid gas key, but a threaded portion for the gas tube? Seems redundant to me. The LMT is good, but i think they make it like an AR15 semi auto bcg. That's what it "looks" like from pictures, but I've only seen one picture from an upper angle, the one of LMT's site. If building a large frame AR10, i say go with the Armalite bcg. It's very well made, very durable, the bolt design is superb, you can't really go wrong. Just use the entire bcg, don't mix and match bolts. In my opinion, the only thing that could be better on the Armalite bcg, is hard chrome or melonite treatment. Just for the ease of cleaning. I personally don't mind scraping at the carbon, i bond more with my guns that way. Cleaning time is my personal one on one time with my guns. A good buy is something known to work. Stay away from the newer 308 bcg offerings. Most are being made by ToolCraft, which is good. But with so much rebranding, it's hard to keep track of QC. Lots of bad parts get out there this way. This is the main reason i say sick with what's known. Armalite, DPMS, or JP. LMT is good too, but pricey. The bolt is a very important part, and should not be skimped on. |
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Quoted:
KAC carrier is not worth it UNLESS it's the carbon cutter version. Otherwise, is pretty much the same as the Armalite bcg but without forward assist, and i think they don't have the firing pin spring. I think only Armalite and LaRue use the firing pin spring. .. And HK-417 of course! |
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The BCG is not often the main problem, unless buying some no-name, slack-jawed garbage that attempts to jump on the coat tails of quality units.
Main Problems We're Seeing With Builds: Chamber dimensions below SAAMI minumum due to incorrect or worn reamers Materials selection Bolts not matched up well to extensions, since both are often independently sourced Fitting issues with the new wave of el cheapo 308 AR receiver sets Balancing the gas system and recoiling parts Small parts issues not common on AR15's Magazines Aluminum gas blocks Incorrect length gas tubes Excessive extractor spring tension Ejector channel burrs Substandard spring quality Lack of dimensional uniformity due to poor machining, lack of QC Incorrect dimensions in critical aspects of the operating system Incompatibility with popular and proven parts like BCM charge handles Variation in upper receiver rail heights causing headaches for the handguard and front sight alignment Buffer and recoil systems not working, even when using the recommended parts from the manufacturers, many of whom don't know what they are doing and have incorrectly labeled or misunderstood the differences between gas system lengths and manufacturers Magazine catch shaft length not long enough, since most LPK's use AR15 catches, not AR10 length Pivot and takedown pin dimensions all over the map from one company to another Incompatible barrel nut thread patterns between makers etc. etc. A new problem I've never seen (after working with AR10's/SR-25's/LR-308's etc. for years and years now) shows up about once a week, usually with PSA builds, followed by LR-308 and Aero M5 builds. Pick any combination of problems from the list above, and you'll see them frequently here on the board, over and over and over again. |
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The BCG is not often the main problem, unless buying some no-name, slack-jawed garbage that attempts to jump on the coat tails of quality units. Main Problems We're Seeing With Builds: *snip*. Why don't people read? I hate books, but love reading tech manuals, articles, all that crap. The FAQ up top is filled with extremely useful info. Same with all these new mfgs, the info is here, easily accessible, very simple to understand, and proven to work, time and time again. Why don't they read the FAQs and go from there? Who should the blame goto? The builder? Their parents? Society? The schools? Haha! I think the FAQ should have is label changed. Something v like "So you want to build a 308AR? READ HERE FIRST! " do what it takes for that to pop up under any search containing 308, AR, and/or AR10. Maybe that'll get people to actually read it. Most problems posted about would be solved from reading the FAQ. |
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This. -Stooxie Quoted:
Quoted:
Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie That looks like the Rainier branded one for 259$. This is what i don't like, the constant rebranding. Of all the different bcgs I've seen come out over the years, the only one that looks like it would be any type of enhancement is the Lantac bcg. But, that requires their upper i believe to work correctly with their cam pin. |
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Quoted: That looks like the Rainier branded one for 259$. This is what i don't like, the constant rebranding. Of all the different bcgs I've seen come out over the years, the only one that looks like it would be any type of enhancement is the Lantac bcg. But, that requires their upper i believe to work correctly with their cam pin. You are comparing your speculation against people with field experience. Rainier doesn't make the BCGs, or much of anything as I understand it. It is they who re-brand. The RCA 308+ BCG is already engineered to handle anything in the 308 case cartridge family and has close tolerances around the firing pin and firing pin hole to avoid primer issues. Look on the threads here, lots of complaints about "why do my primers look like this with XYZ bcg?" You can lead a horse to water... -Stooxie |
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I went with the AIM Surplus Nitride BCG $169.00 shipped and have had no issues with it.
Granted I only have about 80rds down it, and 40 of that supressed. |
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Also, I just googled that SR-25 field repair kit, and no way is that shit worth $250. Might as well just get a backup bolt or another BCG for that price. 
That is a tougher looking firing pin. I wonder if it would fit in a NON-KAC bolt? SR-25 Field Repair Kit comes with: P/N 99077 - Firing Pin P/N 91428 - Cam Pin P/N 99076 - Ejector Spring P/N 99080 - Ejector Retaining Pin P/N 99075 - Extractor P/N 91492 - Extractor Spring P/N 94065 - Extractor Pivot Pin P/N 99164 - Extractor Buffer P/N 21002 - Gas Rings DPMS Bolt Parts Kit: 
Includes Three Bolt Gas Rings Extractor Extractor Pin Extractor Spring Ejector Ejector Pin Ejector Spring Firing Pin Firing Pin Retaining Pin Cam Pin Wow. When you break it down like that... Over 6x the price for KAC ! The DPMS kit comes with MORE! [Firing Pin Retaining Pin, Ejector!] |
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Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had to problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. You will have no regrets! |
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I don't get why people read someone's question/questions and wonder why they don't read the FAQ's first. I know if I wanted a one sided conversation I'd just google what I wanted to know and be done with it. But if I wanted a back and forth dialogue, I'd go to a forum like this. I've noticed this a lot about forums (this one particularly) Instead of harping on someone for not using Google or FAQ's first, let it go?
Just my $0.02 
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| Anybody know what that RCA bolt weighs? I'm building two new uppers for my Armalite and may rework my 16" .308 into an 18" lighter weight hunting rifle. That Armalite BCG weighs a pound! An 18" pencil barrel and a lighter BCG would make a difference. I've looked at JP's light weight BCG but can't find a weight spec anywhere. I emailed them asking but got no response. |
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Quoted: The BCG is not often the main problem, unless buying some no-name, slack-jawed garbage that attempts to jump on the coat tails of quality units. Main Problems We're Seeing With Builds: Chamber dimensions below SAAMI minumum due to incorrect or worn reamers Materials selection Bolts not matched up well to extensions, since both are often independently sourced Fitting issues with the new wave of el cheapo 308 AR receiver sets Balancing the gas system and recoiling parts Small parts issues not common on AR15's Magazines Aluminum gas blocks Incorrect length gas tubes Excessive extractor spring tension Ejector channel burrs Substandard spring quality Lack of dimensional uniformity due to poor machining, lack of QC Incorrect dimensions in critical aspects of the operating system Incompatibility with popular and proven parts like BCM charge handles Variation in upper receiver rail heights causing headaches for the handguard and front sight alignment Buffer and recoil systems not working, even when using the recommended parts from the manufacturers, many of whom don't know what they are doing and have incorrectly labeled or misunderstood the differences between gas system lengths and manufacturers Magazine catch shaft length not long enough, since most LPK's use AR15 catches, not AR10 length Pivot and takedown pin dimensions all over the map from one company to another Incompatible barrel nut thread patterns between makers etc. etc. A new problem I've never seen (after working with AR10's/SR-25's/LR-308's etc. for years and years now) shows up about once a week, usually with PSA builds, followed by LR-308 and Aero M5 builds. Pick any combination of problems from the list above, and you'll see them frequently here on the board, over and over and over again.  All that makes me feel good that my parts and pieces .308 build runs like champ with a cheap DPMS BCG. I blame most issues on the buffer/spring or gas system before the BCG! |
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Quoted: That looks like the Rainier branded one for 259$. This is what i don't like, the constant rebranding. Of all the different bcgs I've seen come out over the years, the only one that looks like it would be any type of enhancement is the Lantac bcg. But, that requires their upper i believe to work correctly with their cam pin. Quoted: Quoted: Quoted: Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie That looks like the Rainier branded one for 259$. This is what i don't like, the constant rebranding. Of all the different bcgs I've seen come out over the years, the only one that looks like it would be any type of enhancement is the Lantac bcg. But, that requires their upper i believe to work correctly with their cam pin. That's because it is.   |
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Quoted: All that makes me feel good that my parts and pieces .308 build runs like champ with a cheap DPMS BCG. I blame most issues on the buffer/spring or gas system before the BCG! The DPMS 308 BCG has long been a go-to part. Seems odd with DPMS's AR15 reputation (rightly or wrongly), but the 308 stuff was always on a different level. It's also not so cheap, if I recall. Usually $225 or so for the parkerized and $250+ for the chrome. -Stooxie |
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Quoted:
This. -Stooxie Quoted:
Quoted:
Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie Any of you know if this works well with the mega maten? Thx |
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Quoted: Any of you know if this works well with the mega maten? Thx Quoted: Quoted: Quoted: Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie Any of you know if this works well with the mega maten? Thx I called Jason@MEGA and asked him which BCGs they recommend. They said RCA. I have two MEGA builds with RCA BCGs and both work perfectly. -Stooxie |
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I called Jason@MEGA and asked him which BCGs they recommend. They said RCA. I have two MEGA builds with RCA BCGs and both work perfectly. -Stooxie Quoted:
Quoted:
Quoted:
Quoted:
Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie Any of you know if this works well with the mega maten? Thx I called Jason@MEGA and asked him which BCGs they recommend. They said RCA. I have two MEGA builds with RCA BCGs and both work perfectly. -Stooxie Mega told me pretty much the same thing: "RCA and Leitner-Wise are what we use, I haven't had a JP but know they are very good quality." Clarified: RCA for .308 and Leitner-Wise for 5.56. EDITED: I do still wonder about the KAC 3 gas holes in the side of their carrier as well as their dual ejectors. 
~Will |
| The carbon cutters are crazy cool. I wonder where I could get my RCA cut like that. About a week ago I ran just shy of 500 rounds through my Maten. Not a lot by some other people's standards. I lubed vigorously and it created a ton of fouling. It was a mix of PMC Bronze and FGMM. I didn't have any stoppages, but I imagine that if it ever got to that point the carbon cutters would make a difference. |
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JP Rifles is the only outfit that makes a large frame BCG worth the money. IMO. I'm building an AR 10 in 6.5 Creedmoor and was choking on the fact JP were asking $471.00 for their JPBC-4 stainless .308 Low Mass Carrier and JPEB-308HP JP High Pressure EnhancedBolt™, cam pin, firing pin and firing pin retainer. I just purchased this from Dvor for $359.00 earlier today. (Just looked and their are a few left at that price. Sale runs for another 2 days). =2248-0-1220204]JP Enterprises JPBC-4A: Complete JPBC Bolt Carrier Group, JPBC-4 .308, Black |
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That's because it is.
<a href="http://s43.photobucket.com/user/unclemoak/media/20140614_125012.jpg.html" target="_blank">http://i43.photobucket.com/albums/e398/unclemoak/20140614_125012.jpg</a> Quoted:
Quoted:
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Do what I did, but a Rubber City Armory bcg for $300 and call it a day. I've had no problems with my build whatsoever. http://i.imgur.com/XuZ209k.jpg This. -Stooxie That looks like the Rainier branded one for 259$. This is what i don't like, the constant rebranding. Of all the different bcgs I've seen come out over the years, the only one that looks like it would be any type of enhancement is the Lantac bcg. But, that requires their upper i believe to work correctly with their cam pin. That's because it is.
<a href="http://s43.photobucket.com/user/unclemoak/media/20140614_125012.jpg.html" target="_blank">http://i43.photobucket.com/albums/e398/unclemoak/20140614_125012.jpg</a> For clarification, are you saying that the Rainier bcg is made by Rubber City Armory? |
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Quoted: The serrated rails on the new KAC BCG do at least two things: Deal with debris like dust and sand Enhance coefficient of drag It also provides less bearing surface. I would dispute that drag is reduced. But it's marketing vs theory so it's pointless anyway. -Stooxie |
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Quoted: It also provides less bearing surface. I would dispute that drag is reduced. But it's marketing vs theory so it's pointless anyway. -Stooxie Quoted: Quoted: The serrated rails on the new KAC BCG do at least two things: Deal with debris like dust and sand Enhance coefficient of drag It also provides less bearing surface. I would dispute that drag is reduced. But it's marketing vs theory so it's pointless anyway. -Stooxie Coefficient of friction is not dependent on surface area. |
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Quoted: Coefficient of friction is not dependent on surface area. Quoted: Quoted: Quoted: The serrated rails on the new KAC BCG do at least two things: Deal with debris like dust and sand Enhance coefficient of drag It also provides less bearing surface. I would dispute that drag is reduced. But it's marketing vs theory so it's pointless anyway. -Stooxie Coefficient of friction is not dependent on surface area. Exactly the point. -Stooxie |
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I went with the AIM Surplus Nitride BCG $169.00 shipped and have had no issues with it. Granted I only have about 80rds down it, and 40 of that supressed. i used aim as well. i built my 18 in ar 10 with all aero parts except for the bcg. i used aim for that. i have about 150 rounds through it with no problems. i would rather put the extra money into my next build. i also have an aim 556 bcg that has 1000 rounds through it problem free. aim bcgs are good to go in my book. |
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