USAF_Vet
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Does a 9mm AR upper require M4 feed ramps? I'm thinking probably not, but want to make sure before I go and buy a receiver I may need to mod.
9mm AR quick question
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USAF_Vet
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Nevermind, looks like all the dedicated 9mm uppers are cut for M4 feed ramps. Guess the ones I'm looking at won't need to be modded. I'm good to go.
Mods, feel free to close this one.
Mods, feel free to close this one.
USAF_Vet
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Another quick question
Had the mods reopen for another question.
Does anyone make a 9mm AR bolt that does not utilize the buffer tube?
With my slightly crazy 9mm pistol build, I want to eliminate the buffer tube. The Sig MPX bolt uses a recoil spring and guide rod over a short bolt, but uses an upper receiver that is similar to, but quite different from a standard AR upper.
Something more like the CZ Scorpion, I guess.
Needs to feed from double stack mags, too.
Should still be able to use the standard AR charging handle, as well.
Does such a thing exist?
If not, what is the shortest tube, spring and buffer available for a 9mm AR?
Had the mods reopen for another question.
Does anyone make a 9mm AR bolt that does not utilize the buffer tube?
With my slightly crazy 9mm pistol build, I want to eliminate the buffer tube. The Sig MPX bolt uses a recoil spring and guide rod over a short bolt, but uses an upper receiver that is similar to, but quite different from a standard AR upper.
Something more like the CZ Scorpion, I guess.
Needs to feed from double stack mags, too.
Should still be able to use the standard AR charging handle, as well.
Does such a thing exist?
If not, what is the shortest tube, spring and buffer available for a 9mm AR?
USAF_Vet
Member
I'm looking at the New Frontier Armory 9mm Modular BCG.
Does anyone have experience with this particular bolt?
Do the alignment pins go all the way through, or does it bottom out?
I'm thinking of using just the front portion and fabricating a pair of guide rods with captive recoil springs and a rear plate, turning this into something more like an Uzi style bolt. The only issues would be the lack of mass, and on a blow back system, I'm afraid a light carrier will not stay closed until chamber pressure drops to safe levels. A heavier spring might alleviate that, but generally for a blow back, its bolt mass that matters.
Any suggestions for a 9mm AR bolt that lacks a buffer tube? I'm not coming up with many ideas.
Does anyone have experience with this particular bolt?
Do the alignment pins go all the way through, or does it bottom out?
I'm thinking of using just the front portion and fabricating a pair of guide rods with captive recoil springs and a rear plate, turning this into something more like an Uzi style bolt. The only issues would be the lack of mass, and on a blow back system, I'm afraid a light carrier will not stay closed until chamber pressure drops to safe levels. A heavier spring might alleviate that, but generally for a blow back, its bolt mass that matters.
Any suggestions for a 9mm AR bolt that lacks a buffer tube? I'm not coming up with many ideas.
USAF_Vet
Member
Nothing? No one has any sort of input?
I recently put together a 9mm AR.
The M4 feed ramps aren't an issue as my lower has it's own feed ramps into the chamber. The M4 ramps on my lower are present, but unused if that makes sense.
Can't answer your question about the bolt and buffer but I'm not aware of any 9mm AR setup that doesn't use a buffer tube. Because it's a blowback action, you want a heavier bolt, heavier buffer, longer buffer or spacer, and a carbine length buffer tube. At least that's what I found in my research and is working well for me.
The M4 feed ramps aren't an issue as my lower has it's own feed ramps into the chamber. The M4 ramps on my lower are present, but unused if that makes sense.
Can't answer your question about the bolt and buffer but I'm not aware of any 9mm AR setup that doesn't use a buffer tube. Because it's a blowback action, you want a heavier bolt, heavier buffer, longer buffer or spacer, and a carbine length buffer tube. At least that's what I found in my research and is working well for me.
USAF_Vet
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That's what I've been coming up with, too.
Was wanting to do something like the gilboa in a pistol platform, so no folding stock.
If 9mm bolt faces were separate from the carrier, I could use a piston system with a spring like a PLR-16, but again because its a blowback, mass is going to be an issue.
Looks like I'll have to settle for a carbine buffer rear end with a spacer and a standard 9mm bolt.
Might as well go with a 16" barrel, too then.
Unless of course I can fabricate an upper and get an Uzi bolt to function with an AR lower and hammer.
Was wanting to do something like the gilboa in a pistol platform, so no folding stock.
If 9mm bolt faces were separate from the carrier, I could use a piston system with a spring like a PLR-16, but again because its a blowback, mass is going to be an issue.
Looks like I'll have to settle for a carbine buffer rear end with a spacer and a standard 9mm bolt.
Might as well go with a 16" barrel, too then.
Unless of course I can fabricate an upper and get an Uzi bolt to function with an AR lower and hammer.
Lead filler? Bore out the carrier and fill it with lead? More weight, stiffer spring, shorter travel. It might be tricky to work out, but there is no reason the travel for a 9MM AR blow back action couldn't be shortened.
USAF_Vet
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I've got some hardened tool steel from high tonnage injection mold presses.
If I could run a rod of that through the gas tube and attach it to the bolt, I could have a recoil spring around that. I'd still need to beef up the bolt with some lead filler as Walkalong suggested, but it would operate in a similar way as the Olympic OA-93 pistol, but with the recoiling guide rod inside the hand guard using the space provided by the gas tube hole.
I'm not engineer, so I'd have to play around with different springs, to find the best length/ strength, but that's all part of the fun.
While I'm at it, I could eliminate the standard charging handle and mill out a slot in the hand guard to run a reciprocating handle to the guide rod.
Ok, my gears are turning now for new designs.
If I could run a rod of that through the gas tube and attach it to the bolt, I could have a recoil spring around that. I'd still need to beef up the bolt with some lead filler as Walkalong suggested, but it would operate in a similar way as the Olympic OA-93 pistol, but with the recoiling guide rod inside the hand guard using the space provided by the gas tube hole.
I'm not engineer, so I'd have to play around with different springs, to find the best length/ strength, but that's all part of the fun.
While I'm at it, I could eliminate the standard charging handle and mill out a slot in the hand guard to run a reciprocating handle to the guide rod.
Ok, my gears are turning now for new designs.
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