The Down Range Forum
Member Section => Tactical Rifle & Carbine => Topic started by: alfsauve on May 04, 2010, 05:34:33 AM
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Okay, so I should probably take this to the AR-15 board, but it's so hard to read. Maybe someone here can clear this up.
There seems to be two sizes of AR-15 butt stocks. "Commercial" and "Mil Spec". One says it's 1.168" the other 1.148"
What the heck are they measuring? Is it the thread dimension? Is it the buffer tube.
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Alf, these are the diameters of the buffer tube. It makes a difference since the buffer tube screws directly into the lower receiver.
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Alf, these are the diameters of the buffer tube. It makes a difference since the buffer tube screws directly into the lower receiver.
But exactly where do I take the measurement?
Is it the tube itself somewhere after the threads? Or the outside diameter threaded part of the tube? Or the inside thread diameter of the lower threaded part of the lower? or something else.
When I took measurements on my A2 National Match (supposedly Mil-Spec) none of them match the 1.168 or 1.148.
Let me pose the question another way. If I have a lower that's not marked what do I need to measure to determine whether to buy a "commercial" or a "mil-spec" stock?
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I think the #s refer to the O.D. of the buffer tube. As far as I know it only applies to collapsible stocks. I don't have any way to measure mine.
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From Brownells..
Magpul Original Equipment (MOE) carbine buttstock provides the quality, durability, and ergonomic benefits of Magpul’s CTR stock in a rugged, economical, drop-in package. Strong, A-frame design is lightweight and comfortable, yet provides operator with plenty of support. Comb contour is wider than standard issue M4 stock to help shooter maintain a solid, consistent cheekweld. Streamlined exterior and protected release lever won’t snag on clothing, gear, vehicle interior, or vegetation. Heavy duty, spring-loaded release lever allows fast length-of-pull adjustments and won’t dig into your hand. Impact- and heat-resistant, polymer construction includes molded-in reinforcements at stress points, plus two slots for web slings and a hole for a toe-mounted sling swivel or clip-on sling. Soft, synthetic rubber buttpad increases comfort and helps prevent slippage. Mil-Spec fits 1.14" O.D. buffer tubes on Colt-manufactured M4 and similar mil-spec tubes that accept both four- and six-position collapsible stocks. Commercial fits larger, 1.17" O.D. commercial carbine buffer tubes. Buffer tube, carbine buffer, receiver extension nut, and carbine-length action spring not included. Available in Black and three popular tactical colors, Dark Earth, O.D. Green, and Foliage Green.
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And this..
(http://i384.photobucket.com/albums/oo283/tsbevins/CTR_Stock_Specs.jpg)
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But exactly where do I take the measurement?
Is it the tube itself somewhere after the threads? Or the outside diameter threaded part of the tube? Or the inside thread diameter of the lower threaded part of the lower? or something else.
When I took measurements on my A2 National Match (supposedly Mil-Spec) none of them match the 1.168 or 1.148.
Let me pose the question another way. If I have a lower that's not marked what do I need to measure to determine whether to buy a "commercial" or a "mil-spec" stock?
I think the threads will work on either. I thought I remember reading some place one time that even though the Milspec buffer tube was a smaller diameter it is stronger and more costly to manufacture than the commercial version.
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I think the threads will work on either. I thought I remember reading some place one time that even though the Milspec buffer tube was a smaller diameter it is stronger and more costly to manufacture than the commercial version.
http://www.ar15pro.net/2008/09/milspec-buffer-tubes-vs-commercial.html
Different materials, 7075 forged vs 6061 extrusion.
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Quaker, who has just gotten a headache from all the techno speak, would suggest the following. Write down the serial number and call whoever made the reciever. They should be able to tell you. This seems a lot easier than measuring fractions of an inch on a threaded tube. ;)
FQ13
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Quaker, who has just gotten a headache. would suggest the following. Write down the serial number and call whoever made the reciever. They should be able to tell you. This seems a lot easier than measuring fractions of an inch on a threaded tube. ;)
FQ13
Twenty thousands difference on an O.D. is pretty easy to measure, even with a tape measure with 1/32 graduation.
Measure the circumference and divide by pi...
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Twenty thousands difference on an O.D. is pretty easy to measure, even with a tape measure with 1/32 graduation.
Measure the circumference and divide by pi...
Yes, but you paid attention in math class. ;) Me, a perfect 800 verbal, 540 in math and they give you 300 just for showing up. :-[ I is not so good with numbers, but speak English pretty goodly. ;) Anyway, I still think the call to the factory, BEFORE paying X dollars to buy an after market stock is worthwhile.
FQ13 who has a not so small box of various slings, holsters, sight rails etc that just didn't work as advertised.
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A lot of 4 position and 6 position stocks are available as a kit that includes the buffer, tube, and spring, so you can change from a fixed stock. It's only confusing when changing to an aftermarket stock on a carbine that already has a colapsible stock.
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FQ.
http://www.midwayusa.com/viewproduct/?productnumber=119190
They are actually probably decent calipers, the reason they are Midways lowest priced is because they are only 4 inches.
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A shout out to Timothy for the picture. The dimension that I really need is the thread diameter. Mine is 1.184. Mystery solved.
Also a shout out to CTR for the clear explanation of their products. Just for that reason, I may go with their stock.
Thanks, Alf
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A shout out to Timothy for the picture. The dimension that I really need is the thread diameter. Mine is 1.184. Mystery solved.
Also a shout out to CTR for the clear explanation of their products. Just for that reason, I may go with their stock.
Thanks, Alf
Yer most welcome... ;)
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Alf, here are a couple of links.
The first one is a link to the installation of a Magpul brand CTR stock.
http://www.riflegear.com/t-howto-ctr-stock.aspx
The second is a generic thread about changing a stock. It has some observations about staked end plates, castle nuts, locktight, and problems that may be encountered.
http://www.thehighroad.org/showthread.php?t=327420
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Thanks for the links, Blackwolfe. (It's been in forever since I went over the THR forum.)
My problem isn't in knowing how to change them or having the tools, but was in what the heck they were measuring. Measuring my other AR didn't help because i's tube was 1.111 which didn't match anything.
I have a bare lower, so I'm shopping for stock that comes complete with buffer, buffer tube and spring. I could care less what size the tube is, but I do care that the threads match my lower.
I went by two gun shops today (had my day off today since I'm working the weekend) and examined several stocks. Haven't found exactly what I want yet. I may just go with "stock" A2 at least for now. Everybody's into "carbine" and I'm building a varmint rifle. Full size stock please.
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I had a chance to shoot the SIL's Bushmaster a few weeks ago and even though I don't shoot long guns too often, I was able to kill a couple of clay pigeons at 100 yards with iron sights. Used only five rounds to kill two birds.
Piqued my interest in the platform. I suppose, if I did enough research, I would consider buying but I've got other priorities at the moment. I've always liked the M16 look, full size, irons, nothing fancy..
Let us know what you finish Alf, I'd be interested in whatever you come up with.