Realistic difference: milspec vs commercial

[Ride4frnt]

Since I sold the Sig Brace today and filed my form 1, I'm looking to round up the rest of the parts for my SBR build. Most likely going with a ALG ACT trigger and either a CRT or MFT minimalist stock.

Question is, what are the practical differences between milspec and commercial spec, apart from if I'd ever want a new stock it would need to be commercial. I have a commercial buffer tube laying in the parts box, and I'm wondering if that .02" really makes a difference? Should I just pony up and buy a milspec extension with the money, or save the money for other parts and use the commercial tube?

[Thompson]

I think I read once that there's not much of a quality difference between the two; people think that mil spec is better than commercial spec, just because it's mil spec - apparently not the case. But don't hold me to my word though; I read that a long time ago.

Practically, not a clue. I'm curious to hear the answer too now.

[UWone77]

Since I sold the Sig Brace today and filed my form 1, I'm looking to round up the rest of the parts for my SBR build. Most likely going with a ALG ACT trigger and either a CRT or MFT minimalist stock.

Question is, what are the practical differences between milspec and commercial spec, apart from if I'd ever want a new stock it would need to be commercial. I have a commercial buffer tube laying in the parts box, and I'm wondering if that .02" really makes a difference? Should I just pony up and buy a milspec extension with the money, or save the money for other parts and use the commercial tube?

Main reason,

milspec tubes are 7075, commercial ones are typically 6061. In fact places like PSA sell tubes that are milspec in diameter only, but still use 6061 aluminum. Milspec tubes are also impact extruded from what I remember, which translates to breaking strength of 45 vs. 75 lbs.

No reason to go commercial. You can find quality kits with H buffers for $50.

[Ride4frnt]

Main reason,

milspec tubes are 7075, commercial ones are typically 6061. In fact places like PSA sell tubes that are milspec in diameter only, but still use 6061 aluminum. Milspec tubes are also impact extruded from what I remember, which translates to breaking strength of 45 vs. 75 lbs.

No reason to go commercial. You can find quality kits with H buffers for $50.

Now that you mention the H buffer, am I gonna need a H for 10.5" build? I have a carbine buffer and spring at home.

[UWone77]

Now that you mention the H buffer, am I gonna need a H for 10.5" build? I have a carbine buffer and spring at home.

I always start with the H, then adjust as needed or not.

[Deckard]

I think commercial tubes also have shallower threading.

[FortTom]

I think commercial tubes also have shallower threading.

I can't remember where I read this, about a 5 page treatise on extension tubes, but commercial threads can be rolled in, or cut, but not cut to the same dia. of the mil spec. That basically just relates to less passes threading the tube, equals cheaper to manufacture. On Mil Spec tubes the threads are an inverted V shape, and the rest of the tube is undercut length wise. Not rocket science but definitely more machine/labor intensive. The commercial threads are truncated, or in other words a "v" shape where the top of the thread is just machined off to the diameter of the tube and if you view them the tops of the threads are level rather than pointed. That's also the reason why both will fit into the same lower. There is not a real difference in the strength or integrity of the thread contact, but apparently the Military feels different. I would take a wild guess, and bet that's how Stoner designed the tube in the first place, and it's just been adhered to since. On most Milspec parts, using non-milspec parts might and probably will give you fitment problems. Either buffer tube, however, will be fine, both can be broken and probably have, but it's not like you've got to conscience of your extension tube, concerned if it's going to break or not. If you're starting from scratch though, I'd just go with a MILspec tube and be done with it.

So basically, that's the long version of what Deckard just said.

[Ride4frnt]

Well I'll probably just grab a buffer kit with milspec tube and h buffer. Or get a tube and do some buffer swapping from my other rifles. All these variables along with the short barrel are making my head hurt. I just wish there was a definitive "it will definitely work 100% of the time, no malfunctions" answer.

[Computalotapus]

The buffer tube kit I picked up over the holidays is decent. Milspec 7075 and it was a steal at the price I got it for. You should look at the same kit as it is still a steal.

[DutyUse]

Hey ride I got a mil-spec dimension FDE magpul CTR just laying around if you need one.

Actually I got a moe+ grip in fde and a polymer TG if any of them could help your build along. Just pm

Either way, good luck on the shortie build :D

[Ride4frnt]

Hey ride I got a mil-spec dimension FDE magpul CTR just laying around if you need one.

Actually I got a moe+ grip in fde and a polymer TG if any of them could help your build along. Just pm

Either way, good luck on the shortie build :D

Damn, would've helped me a month ago though. Thank you for the offer, but I'll politely decline. Comp talked me into a MFT stock (on his dime) and a CMC trigger. Throw that stuff up on the pay it forward thread and it'll go to a good home.

[rob_s]

There is no justifiable reason to buy a commercial receiver extension. None.

Even if you want to buy cheap-ass parts, there are plenty of companies now days that will be happy to sell you a mil spec-dimensioned part made of craptastic material.

The above posts regarding materials, extrusion method, and the way the threads are cut in are all on-point with regards to the minutiae of the differences between the two, but nobody will notice those things in pictures on Internet forums so it likely doesn't matter for the majority of "builders".

[Deadwing]

The way i see it, you've invested $200 in a tax stamp to SBR a lower that you'll most likely own forever, so you might as well spend a few extra bucks and buy a quality milspec receiver extension. I prefer either BCM or LMT tubes, but i'm sure there are others that are comparable.