View Full Version : Commercial RE failure
I understand the threads on Milspec RE's are bigger in overal diameter thus engaging your lower's threads better.
Question is, since you do have ".sumthing" less on a commercial RE's overall thread diameter, how big are your chances of actual RE failure on a F/A carbine? Has anyone ever actually had these things ripped off their lowers?
Im trying to see whether I should just go for the commercial CTR set or the milspec MOE set. -- The only choices I have at the moment.
Well I have seen broken and bent ones in the mil so I would say the weaker commercial tube could become FUBAR.
I'd go Milspec MOE because it gives you more options down the road.
This is one of those things where you're never going to find "XYZ Company tested 1000 receiver extensions and found that of the 500 milspec only 10 failed, and of the 500 commercial 57 failed" kind of testing.
Robb Jensen
02-07-09, 06:46
Commercial vs. mil-spec.
This is one of those things that matters really only to the owner of said gun.
I've never had failures with commercial extensions but I have had problems with them. Most don't have the extended bottom lip so that the buffer retainer is trapped into the lower well like it is on good mil-spec ones. On some lowers with commercial tubes I've had to remove metal from the top of the mouth of the tube to get the buffer retainer trapped in the lower. The metal has to be removed so that the upper can close onto the lower. Commercial tubes also have a shallower notch for the locking end plate. This can allow the tube to turn with the castle nut when removing the nut from the gun. It causes it to gouge the tube. The external length of commercial tubes vary as well. This usually isn't a problem but with some stocks and can make them not collapse all the way.
Just for those reasons I always prefer a mil-spec tube on my guns. And to repeat what rob_s said it give you more options down the road since more stocks are available in mil-spec sizes, and most if not all new ones are made for mil-spec sizes first..
If you never plan to remove your carbine receiver extension (buffer tube) and trust that it's installed correctly then just leave it.
Thanks for your responses everyone!
Ive decided to go with the milspec MOE set and will just purchase a milspec CTR stock when theyre back in the market.
I just upgraded to Mil-Spec 2 weeks ago. Everything gotm4 said I had, and for the price you cant go wrong.
One other thing I had with the commercial stock even with the castle nut as tight as I could get it (and staked) I could twist the stock off, it doesn't seem to be a problem with the Mil-Spec.
One other thing I had with the commercial stock even with the castle nut as tight as I could get it (and staked) I could twist the stock off, it doesn't seem to be a problem with the Mil-Spec.
Things that make you go hmmm.
How about a "commercial" A2 for $75 versus a forged Colt from SAW for $135 (complete stock ass'y prices)?
I got both, and other than visual differences, the buffer which goes into the stock before the RE is metal on the "Comm" one and plastic on the Colt. Seem the metal would be tougher, but perhaps that defeats the purpose...:confused:
Decided too late on the milspec MOE. :(
What do you guys think of the RE that comes with the complete commercial CTR Kit?
Coming from Magpul, less issues as compared to other commercial tubes perhaps? Im particularly concerned about the issues brought up by gotm4 but I looked at the photo of the complete kit on pkfirearms and it looked like it had a lower lip. One concern left I suppose is the shallow notch for the endplate, keeping in mind that it is a F/A carbine.
spamsammich
02-08-09, 18:29
Looks like G&R has CMT receiver extensions available. That would pair nicely with a MOE stock.
MisterWilson
02-08-09, 18:53
How about a "commercial" A2 for $75 versus a forged Colt from SAW for $135 (complete stock ass'y prices)?
I got both, and other than visual differences, the buffer which goes into the stock before the RE is metal on the "Comm" one and plastic on the Colt. Seem the metal would be tougher, but perhaps that defeats the purpose...:confused:
Commercial & MilSpec are referring to the diameter of the tube past the threads. There is no "commercial" rifle tube.
As for the "buffer" that goes into the stock, are you referring to the spacer that goes on the back of the tube?
Bill Alexander
02-08-09, 19:41
In specific reference to telescoping stock tubes the specifications for the military units extend significantly beyond simply the tube diameter. Correct units use the smaller diameter tube but in addition call for 7075 material in either a wrought or extruded form. The thread form is then rolled into the tube, and while the alloy is essentially a heat treatable grade this action will create threads with a good grain patern. Conversely rolling threads to tight tolerances requires considerable attention if the benefits of the thread forming are not to be offset by a more open thread specification. It might also be argued that the forming is a moot point as the threads then mate to machined threads in the lower
Commercial tubes while generally being of a larger diameter, to allow the threads to be cut in place are usually extruded from an alloy such as 6061 which will drop the yield point by typically 50%. The problem that exists that all tubes that are mil spec diameter are not mil spec materials. Thus attention to the tube diameter does not by any means indicate the strength of the unit in the commercial market.
The same applies to A2 tubes. There are in fact a great many commercial grades. Again correct units are either forged or machined (both are accepted) from 7075 alloy with the closed end integral to the form. By comparison the commercial units are extruded from 6061 and the end plate is welded in place. Discoloration of the anodizing at the end of the tube is a clear indicator of the weld seam.
Bill Alexander
Yeah, sorry I said "buffer" when I meant spacer...is mil spec for that plastic or alum?
Being completely candid:
If someone knows enough to ask this question, with details as to the differences, they know enough to make their own decision.
FWIW, there are "milspec" receiver extensions that are extruded.
MisterWilson
02-08-09, 20:45
Yeah, sorry I said "buffer" when I meant spacer...is mil spec for that plastic or alum?
I would think that it matters not, as that piece isn't under any stress at all.
I understand and respect your view but my details are from simple online research, hence, the preference to still ask members with possible first hand experiences on the subject matter.
Sometimes the minutia is overanalyzed to the point of paralysis.
Is 1 negative experience enough to solidify your opinion? 10? 100? 1000? What will be a valid sample size?
I tend to see better finishing done on the aftermarket "milspec" tubes. So I buy them, and then buy stocks to fit them.
Sometimes the minutia is overanalyzed to the point of paralysis.
Makes me wonder what they'll do if the balloon goes up.
Bill Alexander, what kind of RE is used on your Grendel Tactical lowers?
Decided too late on the milspec MOE. :(
What do you guys think of the RE that comes with the complete commercial CTR Kit?
Coming from Magpul, less issues as compared to other commercial tubes perhaps?
Magpul does not sell the complete kit AFAIK. Dealers assemble those kits from whatever parts they want or have on hand.
In specific reference to telescoping stock tubes the specifications for the military units extend significantly beyond simply the tube diameter. Correct units use the smaller diameter tube but in addition call for 7075 material in either a wrought or extruded form. The thread form is then rolled into the tube, and while the alloy is essentially a heat treatable grade this action will create threads with a good grain patern. Conversely rolling threads to tight tolerances requires considerable attention if the benefits of the thread forming are not to be offset by a more open thread specification. It might also be argued that the forming is a moot point as the threads then mate to machined threads in the lower
Commercial tubes while generally being of a larger diameter, to allow the threads to be cut in place are usually extruded from an alloy such as 6061 which will drop the yield point by typically 50%. The problem that exists that all tubes that are mil spec diameter are not mil spec materials. Thus attention to the tube diameter does not by any means indicate the strength of the unit in the commercial market.
The same applies to A2 tubes. There are in fact a great many commercial grades. Again correct units are either forged or machined (both are accepted) from 7075 alloy with the closed end integral to the form. By comparison the commercial units are extruded from 6061 and the end plate is welded in place. Discoloration of the anodizing at the end of the tube is a clear indicator of the weld seam.
Bill Alexander
Thanks. That answers some questions I've had.
Magpul does not sell the complete kit AFAIK. Dealers assemble those kits from whatever parts they want or have on hand.
Ya, I think you're right. I got a pretty good set though.
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