Looking for 9mm PCC input

[ReluctantDecoy]

I just ordered a CMMG. They built their own delayed blowback system which reduced recoil.

I'm starting to think I should have ordered a CMMG complete AR9 upper for this reason. I just ordered a Tacom 2 stage buffer, so maybe that might soak up some of the bounce I'm getting right now on my build. I mean, the 9mm blowback isn't crazy, but it is just enough of a jolt to make acquisition between shots kind of lengthier than I would have hoped. I'd be curious what you think of the CMMG though, particularly if you've ever shot roller delay in contrast to see if it is anything close to that.

 

[Davidk]

I'm starting to think I should have ordered a CMMG complete AR9 upper for this reason. I just ordered a Tacom 2 stage buffer, so maybe that might soak up some of the bounce I'm getting right now on my build. I mean, the 9mm blowback isn't crazy, but it is just enough of a jolt to make acquisition between shots kind of lengthier than I would have hoped. I'd be curious what you think of the CMMG though, particularly if you've ever shot roller delay in contrast to see if it is anything close to that.

I have an MP5 (full auto) and the recoil is a fraction of my standard 9mm AR. I expect the CMMG will be close to the MP5. Recoil is not much, but like you said, it does increase shot-to-shot time due to recovery. If it wasn't for the awful mag changes and lack of bolt hold back, I would shoot my MP5 in competition. Other than those two things I love that gun.

 

[ReluctantDecoy]

I have an MP5 (full auto) and the recoil is a fraction of my standard 9mm AR. I expect the CMMG will be close to the MP5. Recoil is not much, but like you said, it does increase shot-to-shot time due to recovery. If it wasn't for the awful mag changes and lack of bolt hold back, I would shoot my MP5 in competition. Other than those two things I love that gun.

My current AR9 isn't my first blowback 9mm carbine, but I've been shooting an MP5 clone primarily for about a year, so it was kind of a shock when I finally got to firing this new build. I built it for the exact reasons you mentioned. LRBHO and AR ergonomics. It's just not nearly as fun to shoot as the MP5 clone. I wish I could mash up both in one build. Angstadt has the UDP-9 now, which apparently uses roller delay and a MP5 barrel, so maybe that's another avenue to venture down if they are compatible with AR9 lowers.

 

[Davidk]

My other 9mm is a Angstadt, but its not roller delay. I didn't know that they came out with one. Just checked their website. It seems they only have pistols. IPSC does not allow pistols

 

[ReluctantDecoy]

My other 9mm is a Angstadt, but its not roller delay. I didn't know that they came out with one. Just checked their website. It seems they only have pistols. IPSC does not allow pistols

I'm hoping they release it as a stand alone complete upper, as it appears to be compatible with existing 9/40 lowers. Not familiar with IPSC requirements, but the current model has only a 5.83" barrel. Definitely geared towards PDW subgun territory rather than comp.

 

[Davidk]

My only purpose for 9mm is IPSC. I use 300BLK for serious purposes. IPSC does not allow pistols, only rifles and SBRs. I really dont want SBR, so Im sticking with rifles.

 

[PappyM3]

I have an MP5 (full auto) and the recoil is a fraction of my standard 9mm AR. I expect the CMMG will be close to the MP5. Recoil is not much, but like you said, it does increase shot-to-shot time due to recovery. If it wasn't for the awful mag changes and lack of bolt hold back, I would shoot my MP5 in competition. Other than those two things I love that gun.

Have you tried only loading 28 rounds in a magazine and doing tactical reloads when possible?

 

[Davidk]

Given the fact that MP5 loading and reloading is more time consuming since I can drop an AR mag with a my right hand while grabbing a new mag with my left simultaneously, Im better off with the AR platform

 

[PappyM3]

Given the fact that MP5 loading and reloading is more time consuming since I can drop an AR mag with a my right hand while grabbing a new mag with my left simultaneously, Im better off with the AR platform

Makes sense. I’m building a MP5 mag AR9 with a CMMG upper and was curious about the efficacy of that technique since there’s no easy way to open and lock the bolt on an AR with just my left hand.
Bonus though is that I can drop a mag with an AR manual of arms.

 

[ScottS]

I'm starting to think I should have ordered a CMMG complete AR9 upper for this reason. I just ordered a Tacom 2 stage buffer, so maybe that might soak up some of the bounce I'm getting right now on my build. I mean, the 9mm blowback isn't crazy, but it is just enough of a jolt to make acquisition between shots kind of lengthier than I would have hoped. I'd be curious what you think of the CMMG though, particularly if you've ever shot roller delay in contrast to see if it is anything close to that.

For what it's worth, I've switched to Armaspec Stealth Recoil Springs in both my AR9 carbines. It's a captured recoil spring system, and I find it softens the blow-back impulse significantly. The 9mm version is spec'd at 6.4oz, and it's noticeably smoother than my previous setup, which was a Spike's ST-9X heavy buffer.

 

[ReluctantDecoy]

For what it's worth, I've switched to Armaspec Stealth Recoil Springs in both my AR9 carbines. It's a captured recoil spring system, and I find it softens the blow-back impulse significantly. The 9mm version is spec'd at 6.4oz, and it's noticeably smoother than my previous setup, which was a Spike's ST-9X heavy buffer.

Funny you mention that one. It was one of the three I was selecting from. The only reason I didn't buy that one is because I couldn't find any definitive information if it was short stroke or otherwise ruins LRBHO. I figured if you have to remove the bolt weight, it was probably going to be short stroke. But I was finding conflicting information, so I passed. I really like the captive spring ideal though.

 

[ReluctantDecoy]

Makes sense. I’m building a MP5 mag AR9 with a CMMG upper and was curious about the efficacy of that technique since there’s no easy way to open and lock the bolt on an AR with just my left hand.
Bonus though is that I can drop a mag with an AR manual of arms.

At one point, I was seriously looking at this route myself, as I have 6 date stamped preban MP5 mags. If I was going to do it that way, I think I was going to look at something like a BAD lever. It's shame MP5 mags don't hold the bolt open when dry. That's really the only reason I chose Glock mag. Kind of ironic that LRBHO is my current issue with my lower though.

 

[Rob Boudrie]

1) I don't really have much experience with the select fire group, but can think of no reason why it wouldn't work.

AR15 select fire weapons that use the standard system (not sure about kludges like the lightening link) need a full auto bolt carrier that will strike the lever that is tripped by the carrier when it slams forward. Most semi-auto AR15s don't have this (makes both conversion, and allegation you have an unregistered full auto weapon more difficult) on their .223/5.56 bolts, so there is reason to suspect that 9mm bolt carriers won't either.

 

[ScottS]

Funny you mention that one. It was one of the three I was selecting from. The only reason I didn't buy that one is because I couldn't find any definitive information if it was short stroke or otherwise ruins LRBHO. I figured if you have to remove the bolt weight, it was probably going to be short stroke. But I was finding conflicting information, so I passed. I really like the captive spring ideal though.

LRBHO works perfectly (well, at least for my Colt-style lower. My Glock-style lower has no LRBHO). I'm a fan, and the price is right, especially if you catch one on sale.

 

[hv55maxx]

Anyone seen any replacement colt mag followers? looking to get around no LRBHO on my converted uzi mags

 

[ReluctantDecoy]

Anyone seen any replacement colt mag followers? looking to get around no LRBHO on my converted uzi mags

Yes, but not sure if 100% legit. Neither look completely identical to me, and the price on the specialized one is like buying a new free state mag.

Specialized Armament

9mm Magazine Follower

www.sarcoinc.com

 

[hv55maxx]

Yes, but not sure if 100% legit. Neither look completely identical to me, and the price on the specialized one is like buying a new free state mag.

Specialized Armament

9mm Magazine Follower

www.sarcoinc.com

Trapezoidal tho. Wonder if they'd work in a rectangular mag like the colt/uzi.

 

[PappyM3]

At one point, I was seriously looking at this route myself, as I have 6 date stamped preban MP5 mags. If I was going to do it that way, I think I was going to look at something like a BAD lever. It's shame MP5 mags don't hold the bolt open when dry. That's really the only reason I chose Glock mag. Kind of ironic that LRBHO is my current issue with my lower though.

Yup, it’s been a debate for me for the same reason. I have BAD lever that will be my temporary solution. I found an ambi-bolt catch lever that required cutting a slot in the top of the lower so it could pass through. I really liked that solution, but it appears they’re not made or sold anymore.

 

[ScottS]

Yup, it’s been a debate for me for the same reason. I have BAD lever that will be my temporary solution. I found an ambi-bolt catch lever that required cutting a slot in the top of the lower so it could pass through. I really liked that solution, but it appears they’re not made or sold anymore.

Be careful: "Once you go BAD, you never go back." I have them on all my ARs. You get mighty used to being able to rack/lock the bolt without ever moving your right hand from the firing position.

 

[ReluctantDecoy]

Be careful: "Once you go BAD, you never go back." I have them on all my ARs. You get mighty used to being able to rack/lock the bolt without ever moving your right hand from the firing position.

Wonder why with all the "ambi" crazy in recent years that no one has come out with an ambi bolt release. Doesn't seem like that much of an ask, mechanically.

 

[ScottS]

Wonder why with all the "ambi" crazy in recent years that no one has come out with an ambi bolt release. Doesn't seem like that much of an ask, mechanically.

Aero Precision sells a lower that has one. I think you can get it either as a complete lower, or buy the release lever and install it yourself (requires modding your lower).

 

[ReluctantDecoy]

Aero Precision sells a lower that has one. I think you can get it either as a complete lower, or buy the release lever and install it yourself (requires modding your lower).

Funny that the Aero website doesn't show a top view to see how the magic happens. I'm sure that was strategic.

It would seem like a tiny bit of lower milling and one of their ambi bolt release bars would almost work on any lower. Thanks for the tip! I may have to experiment.

 

[ScottS]

Funny that the Aero website doesn't show a top view to see how the magic happens. I'm sure that was strategic.

It would seem like a tiny bit of lower milling and one of their ambi bolt release bars would almost work on any lower. Thanks for the tip! I may have to experiment.

There are a number of vids on YT that show how to do it. I think you can DIY with a file/hacksaw/Dremel. The ambi BHO is like $59 (kind of pricey), but it looks pretty easy to install.

 

[PappyM3]

Funny that the Aero website doesn't show a top view to see how the magic happens. I'm sure that was strategic.

It would seem like a tiny bit of lower milling and one of their ambi bolt release bars would almost work on any lower. Thanks for the tip! I may have to experiment.

 

[ReluctantDecoy]

Now that I'm seeing it, I'm not sure it would help me. Extra weight on that side might exasperate my LRBHO issue, as the problem seems to be the catch isn't riding enough as-is.

 

[PappyM3]

Now that I'm seeing it, I'm not sure it would help me. Extra weight on that side might exasperate my LRBHO issue, as the problem seems to be the catch isn't riding enough as-is.

Yeah, I was actually just reading a review where the guy was having LRBHO issues after installing, and it also apparently isn’t too handy for manually locking the bolt open. It’s really only helpful for releasing the bolt.