A Few AR-15 Build Questions

[allivak]

hey guys I am doing my first AR build and I've actually run across a couple questions that I've been unable to resolve through google searches etc....

so the first thing I'm wondering about is Buffer Tube Assemblies.....I've read/heard conflicting information such as "all buffer tubes are the same and its not a critical part, go as cheap as possible" at the same time I've heard the exact opposite, ie. "its not a part to skimp on, spend the extra $30 or $40 and get a Spikes etc etc etc". Like most things, I'm sure the truth lies somewhere in between....but I am basically wondering if there is anything to look for or to AVOID when buying a buffer tube kit? specifically I found a buffer tube kit for significantly cheaper than anywhere else at(don't laugh) http://www.deltateamtactical.com/Mil-Spec-Buffer-Tube-Kit--Heavy-Duty_p_3582.html

ok my second question is whether I need to worry about headspacing if I'm using my own BCG, with an assembled barreled upper(minus BCG)...even if they specifically say all their uppers are properly assembled, headspaced and test-fired??? How can they be sure if you're buying it without their BCG???

third and final question....what is the best budget magazine on the market?


for what its worth, this gun will mostly be a range toy and possible home defense weapon, so its not like I'm building this to go to war or use in the field.
Thanks for any input!

 

[burrhead]

I'm not an operating operator in the midst of operations (one will be along shortly) but I've built a few ARs. As to the buffer tube, I find the stock I want and buy it as a kit. I do prefer milspec.

Head space. I've always built my uppers from disparate vendor's parts. I don't have head space gauges and, though it's a good idea, I've never checked head space and never had a problem. Maybe I'm just lucky but it doesn't worry me. That said, it's not a bad idea to check if you want to be sure.

Mags. Just buy Pmags and be done with it.

 

[WestKentucky]

Yes on pmags.

I'm starting a build and was looking at a few parts. Looked like it was going to be within a few dollars (like within 5) of getting a buffer tube kit and a buying a separate stock or getting a stock and buffer kit all in one package. I got lucky and scored a nice used stock with tube assembly.

From what I have seen and read you need to figure out which stock you want, buy it as a kit, and be happy. Tolerances are tight, but if you buy part a that comes with part b you are most likely going to easily have assembly c. If you buy a here, b here and try to assemble parts on opposite tolerance ends your going to have problems.

 

[SuperNaut]

For all of my builds I've been able to find milspec buffer tubes for the same price as commercial, so I just went milspec. Am I ever going to have to clear a jam by slamming? Who knows? But I'd rather have the ability than not, wouldn't you?

 

[lysanderxiii]

With receiver extensions (the official term for a buffer tube), there is "Mil-Spec", and there is "mil-spec diameter"...

"Mil-Spec" is made from a 7075-T6 forging and machined to shape and has the threads rolled in.

"Mil-spec diameter" is made from either 7075-T6 or 6061-T6, usually an extrusion of either alloy, and has the threads either rolled or cut.

There is a fairly significant strength difference between 7075-T6 and 6061-T6.

There is a measurable difference between cut threads and rolled threads, especially in fatigue life.

There is a very slight difference between an aluminum forging versus an aluminum extrusion.

Commercial receiver extensions are almost exclusively made from 6061-T6 extrusions with cut threads. Commercial extensions are larger in diameter, and have a slightly different shape so butt stocks will not interchange between the two.

A 6061-T6 extrusion with cut threads is perfectly adequate for 98% of the civilian population. However, it's up to you what you want.

The one you linked to appears to be a extension made from 7075-T6 with rolled threads, whether or not it is forged or extruded is unknown as you can tell the difference once its been finished. However, extrusion vs forged is minor.

 

[carbine85]

Most of us can get by just fine with a commercial receiver extension but the Mil Spec tubes are stronger. When you purchase a stock it needs to be the correct diameter for the tube. There is a big difference between commercial tubes. I'll just say you can't buy a well made strong tube for $20.
Check the dimensions of the tube before you buy it. A lot of companies sell "Mil Spec" tubes that are actually commercial diameter.
Pmag, C Products, Brownell's and Military mags all work well. AR mages are cheap.
The barrel should head space with most bolts if the barrel is spec. I wouldn't rule out the need to check it but you rarely hear of head space problems with new AR barrels. If you want the most accuracy you typically don't want chrome lined. 4150 Nitride barrels are easy to come by. 4140 is GTG also. Don't get hung up on 1:7 twist barrels either. A good 1:9 or 1:8 will provide the best accuracy.

 

[MistWolf]

With receiver extensions (the official term for a buffer tube), there is "Mil-Spec", and there is "mil-spec diameter"...

"Mil-Spec" is made from a 7075-T6 forging and machined to shape and has the threads rolled in.

"Mil-spec diameter" is made from either 7075-T6 or 6061-T6, usually an extrusion of either alloy, and has the threads either rolled or cut.

There is a fairly significant strength difference between 7075-T6 and 6061-T6.

There is a measurable difference between cut threads and rolled threads, especially in fatigue life.

There is a very slight difference between an aluminum forging versus an aluminum extrusion.

Commercial receiver extensions are almost exclusively made from 6061-T6 extrusions with cut threads. Commercial extensions are larger in diameter, and have a slightly different shape so butt stocks will not interchange between the two.

A 6061-T6 extrusion with cut threads is perfectly adequate for 98% of the civilian population. However, it's up to you what you want.

The one you linked to appears to be a extension made from 7075-T6 with rolled threads, whether or not it is forged or extruded is unknown as you can tell the difference once its been finished. However, extrusion vs forged is minor.

This is a pretty good summation. Milspec receiver extensions don't cot much more than commercial REs and it's easier to find stock to fit milspec REs.

AR bolts and barrel assemblies are designed so that when made to spec, headspace will be within allowable limits. New, in spec parts will mate up fine.

"Just a range toy" and "not going to war" are no excuses for using sub-par parts. Sub-par parts will only make shooting the rifle a frustrating experience. You don't to spend big bucks to get good parts either, just know what your getting.

The bolt and barrel assembly is the heart of the AR. Get those right and you're most of the way there. The easiest way is to look for a bolt that's made from 158 Carpenter steel, is MPI/HTP and has been shot peened. Shot peening is more important than MPI/HTP.

The easiest way to get a good AR kit is to buy a premium kit from PSA and one of their lowers

http://palmettostatearmory.com/ar-15-05/rifle-kits.html

 

[allivak]

yeah I had already decided to go Mil-Spec for my buffer tube and stock assembly....my question was mostly centered around whether there is any difference between a $70 tube kit and a $25 one and I think lysander answered my questions in that regard.

Although I don't intend to go to war with this gun or abuse it much at all, I do intend to build the best quality AR within my budget and IF there is a good reason to spend $30 more on a buffer tube assembly, I'd absolutely do that. But it appears from my own research and the majority of responses in this thread that's not the case...of course there are always a few people who think the only good products are ones made by the big brand names and can't sleep at night unless they used premium products in their AR build.

 

[Driftertank]

I've used BCM buffer tubes on my personal gun, my stepfather's and my BIL's. Built a coworker's with a Brownells kit with Magpul stock included. They all went together and function perfectly.

I used BCM for mine because i could specify my buffer weight when ordering a kit, and vaguely recalled a stock strength test i read years ago where they had used BCM tubes and noted they were 7075 and that, while the locating pin holes had distorted, and some of the pins in stocks had sheared, the tubes survived all the testing in fully functional condition, if a little ugly. Plus the internets say "BCM doesnt make junk."

For a range toy, go as cheap as you like. As long as it's in spec, it should fill the bill. The Brownells kit we used for my coworker's was ultimately a bit cheaper, and everything Brownells sells is guaranteed by them. So can't go wrong there either.

 

[taliv]

of course there are always a few people who think the only good products are ones made by the big brand names and can't sleep at night unless they used premium products in their AR build.

i only use mil-spec receiver extensions on my ARs (except the ones that have magpul UBRs) but i won't lose sleep if you buy a cheap one.

seriously, the cheap ones will probably work just fine. I know some have broken, etc but that won't matter if it's just a range gun. I've never heard of cycling problems due to a cheap commercial tube. (though I have heard of them coming loose from poor assembly)

if you're looking to save $20, then the buffer tube is a much better place to cut corners than the BCG/barrel

 

[USAF_Vet]

I've got both mil spec and commercial REs on lowers. There is a slight difference, as mentioned. Magpul makes stocks for both. Buy what fits, what matches, what you like at a price you can afford.

I haven't had to worry about headspacing so far. Maybe I've been lucky with my builds to not need it. I'm too cheap to buy a set of headspacing gauges, and bookmarked the RE kit you linked for under $25. So that my opinion for what it's worth.

As far as mags go, Magpul Pmags will serve you well. Lancer and Hexmags are also quite good. I also use aluminium USGI mags. Most of mine are marked Colt, Adventure Line, or FN. Most USGI aluminum mags will serve you well, if you can get them cheap, do it and upgrade to an anti tilt follower if it doesn't already have them.
Don't cheap out on mags. They will be one of your biggest points of failure.

 

[Tirod]

If a choice is to be made (the OP did) then "milspec" is the better option as more stocks are available in it - including all the military ones. As an AR is used by a builder he does change things and sticking to the military diameter allows changes where commercial can limit him. You can't install a surplus stock on one.

The reason headspacing isn't a major issue comes from the unique different way the AR is designed. It uses a barrel extension screwed onto the barrel which is set and pinned. Some will tell you it's torqued in place but I still can't find where that is a military spec assembly operation. It's a popularly linked private gunsmith webpage, not necessarily what Colt does. Headspace is set by screwing in the barrel extension, then pinned, and the barrel gas port drilled after orienting the feed ramps down to verify vertical. It has nothing to do with how it's assembled to the receiver, which is mandatory with most other firearms. Conventional guns get the barrel pressed into place with the bolt locked into the receiver lugs, making it a skilled and difficult operation. The AR is much simpler.

Because the assembled barrels are shipped headspaced to spec, there's not much need to do more about it unless you find evidence in the ejected brass of an issue. Let's not forget reading around the net of conventional guns being shipped with issues, too - none of the makers care to let that happen, and it's equally rare. For AR shooters gas port diameter is a bigger issue.

Mags? Pmags? They are commonly available but there are issues. One, cold weather durability has come up. Another is that they have thicker walls and constrain handloaders with a shorter overall length. And last but not least, you get what you pay for - cheap isn't a good quality for the AR magazine as it's already under engineered and too much has been taken out. They were once considered to be part of a disposable preloaded supply system where you shot them once and threw them away. It's interesting that a lot of the western armies have standardized them with a Stanag spec when in reality they are the weak link in the functioning of the gun, rated as the #1 malfunction cause because of the thin construction and lack of resistance to abuse. You can't even drop one from shoulder high, loaded, onto concrete without damaging them. On the other hand, issue AK mags are the exact opposite - practically body armor when stacked in chest carry and virtually unaffected when driven over.

Issue Brownells mags with tan followers are the currently preferred GI models, with Okay recently deciding to sell to civilians they will be snapped up for quite a while. In the meantime you will continue to see plastic mags on store peghooks and they are ok, especially in the rare ten rounders that cost double in sheet metal. Lancers are also well recommended as they have steel feed lips. But, Pmag as an absolute standard, no. They are readily available and affordable nonetheless.

 

[allivak]

thanks for the excellent responses and in particular, Tirod's response was very helpful. I had no idea that magazines were one of the most critical parts of an AR build...glad I mentioned them.

great forum! thanks again to everyone who responded

 

[Driftertank]

I favor the Lancer L5 AWM. Pmags are awesome, but i like not having to store with "dust covers"

 

[MistWolf]

"Conventional" rifle barrels are torqued into place, not pressed.

The reason you cannot find a military spec for torquing the barrel extension is because that's not something military armorers do. They don't build up barrel assemblies or replace barrel extensions. They would simply replace the barrel assembly in its entirety

 

[tiamat]

If you want some durable mags, I'd offer the suggestion to check out Cammenga mags - heavy duty steel (with emphasis on the *heavy*), and offer an interesting quick-loading/unloading 'feature' (one could also replace that term with 'gimmick', but so far in my experience it does work). There are youtube videos of them.

 

[lysanderxiii]

"Conventional" rifle barrels are torqued into place, not pressed.

The reason you cannot find a military spec for torquing the barrel extension is because that's not something military armorers do. They don't build up barrel assemblies or replace barrel extensions. They would simply replace the barrel assembly in its entirety

Pressing and pinning barrels is a relatively new idea with the intent of reducing cost. AKs and new Chinese SKSs have pressed and pinned barrels. Cutting threads is more expensive than not cutting threads. To my way of thinking, it's not the best way to do it.

The barrel assembly drawing is floating around on the internet somewhere. The extension is to be torqued to 150 +/- 5 lb-ft, the pin is not intended to prevent rotation of the barrel relative to the extension, it is there to align the barrel assembly to the upper. In fact, if the pin is installed to the maximum allowed height, it will not even contact the threads.

 

[lysanderxiii]

....It's interesting that a lot of the western armies have standardized them with a Stanag spec....

There is no STANAG specification on magazines. STANAG 4179 was never ratified.

Ammunition - yes

MG links - yes

Magazines - no

In any case, STANAG 4179 was an interface standard, it only identified magazine catch location, bolt stop bearing location and feed lip geometry, it did not identify performance or material requirements.

Lastly, if you think "cheap isn't a good quality for the AR magazine", then you must not like USGI magazine, as they are about the least expensive option for AR magazines. And, handloads to the maximum OAL still fit comfortably in a PMAG. If you are going for an OAL that just kisses the rifling of a 5.56mm chamber, chances are it won't fit in any magazine.