Anyone try one of CMMG radial delay blowback 9mm's?

Status
Not open for further replies.
someguy2800

someguy2800

Member
Joined
Sep 16, 2015
Messages
8,694
Location
Minnesota
Hey guys, I am doing some thinking about what I want to do for firearms in 2020. I would like to trim down some of my stuff collecting dust and focus on the stuff that I actually use. Well my 9mm AR15 is by far my favorite firearm to plink with so it makes sense to me that if it gets the most use perhaps it should get an upgrade. The only thing I don't really like about it is that its a little jumpy with factory ammo because of the bolt mass and high spring pressure. I am also contemplating switching to a glock mag lower because I think they would be more reliable with hollow points. So that leads me to think about building another AR with the CMMG delayed blowback parts, or maybe just buying a complete CMMG banshee. Question I have is how effective is the CMMG setup at reducing the muzzle jump and how do they feed with hollow points? Anyone have one?

My current 9mm is built with a colt style lower which will not work with the CMMG parts, so if I go that route I will sell my current setup and build a totally new upper and lower.
 
I see it still has the tail-weight in the carrier but the statement: "Requires enlarged ejection port for reliable operation." implies to me that it ejects earlier than a *Colt pattern* 9 with the classic system.

This alone gives me pause.

I don't see the advantage to the added complexity of a rotating bolt but am open to learning.

Todd.
 
ApacheCoTodd said:
I see it still has the tail-weight in the carrier but the statement: "Requires enlarged ejection port for reliable operation." implies to me that it ejects earlier than a *Colt pattern* 9 with the classic system.

This alone gives me pause.

I don't see the advantage to the added complexity of a rotating bolt but am open to learning.

Todd.
Click to expand...

The ejection timing will be different than a typical 9mm AR because this uses a normal AR15 spring ejector in the boot face rather than a fixed blade ejector. Actually I like that because you should be able to get the cases to fall closer to your feet. Mine launches brass into orbit.
 
OK, I'd like to make a few comments on this subject. Over the last 6 to 8 years I've learned a lot about 9 mm, AR based, PCC's, mostly though the school of hard knocks.
First, yes the CMMG delayed radial blowback system is softer shooting than the straight blowback designs. I am running an 8", 45 ACP Banshee and it is a softer shooter than my 9 mm guns. However, in a 9 mm gun I question whether the increased cost and complexity is really justified.
Second, NO, a Glock lower will not be more reliable with HP's. Some guns built specifically for the 9 mm and Glock mags may be HP reliable, but those built with standard AR dimension parts are not. There is just to much unsupported jump from the mag to the chamber. In the best case, the HP will just cause a stoppage, in the worst case the bullet will set back during feeding, causing extreme over pressure and case head failure when fired. And no, my CMMG will not reliably feed HP's.
The only way I've gotten 100% reliable and safe results with HP's is to mate a standard 5.56 AR lower with my 9 mm uppers and use the MeanArms Endomag conversion. The converted Pmags provide a feed ramp right to the chamber. The converted mags also allow 100% reliable bolt hold open on the last round. Only down side is you lose mag compatibility with your Glock handgun (if that's important). Some do not like the plastic ejector associated with the Endomag, but I have had no failures, nor seen any ware in hundreds of rounds. In addition, the CMMG version does not use the ejector on the mag as they use a standard AR style spring loaded ejector.
Basically your decision comes down what is most important; Recoil? Glock mag compatibility? or HP reliability?

JAC
 
Rangegod said:
OK, I'd like to make a few comments on this subject. Over the last 6 to 8 years I've learned a lot about 9 mm, AR based, PCC's, mostly though the school of hard knocks.
First, yes the CMMG delayed radial blowback system is softer shooting than the straight blowback designs. I am running an 8", 45 ACP Banshee and it is a softer shooter than my 9 mm guns. However, in a 9 mm gun I question whether the increased cost and complexity is really justified.
Second, NO, a Glock lower will not be more reliable with HP's. Some guns built specifically for the 9 mm and Glock mags may be HP reliable, but those built with standard AR dimension parts are not. There is just to much unsupported jump from the mag to the chamber. In the best case, the HP will just cause a stoppage, in the worst case the bullet will set back during feeding, causing extreme over pressure and case head failure when fired. And no, my CMMG will not reliably feed HP's.
The only way I've gotten 100% reliable and safe results with HP's is to mate a standard 5.56 AR lower with my 9 mm uppers and use the MeanArms Endomag conversion. The converted Pmags provide a feed ramp right to the chamber. The converted mags also allow 100% reliable bolt hold open on the last round. Only down side is you lose mag compatibility with your Glock handgun (if that's important). Some do not like the plastic ejector associated with the Endomag, but I have had no failures, nor seen any ware in hundreds of rounds. In addition, the CMMG version does not use the ejector on the mag as they use a standard AR style spring loaded ejector.
Basically your decision comes down what is most important; Recoil? Glock mag compatibility? or HP reliability?

JAC
Click to expand...

If I do go with glock mags it will definitely be a dedicated lower reciever, I have no interest in a mag well adapter. The couple that I have seen with dedicated billet glock lowers practically put the bullet right at the back of the chamber due to the forward angle of the glock mags. What kind of glock lower were you using that you had bad luck with feeding hollow points?

I am thinking hard about the endomags. Its good to know that you have had good luck feeding with yours. My colt style lower will not feed 100% reliably with a flat nosed or hollow point bullet and maybe once every 100 or 200 rounds the mag with double feed. The two most important factors for me are the recoil impulse and reliability. Right now its just a range toy because of the reliability, but I would like to use for home defense if I could make it reliable with the same defense ammo I load for my carry pistols.

Mag compatibility is not important because I don't have any glock pistols and don't intend to get any. I would however like to have an option for a shorter 20 round magazine. I wonder if I could modify the endomag insert to fit in a 20 round P-mag.
 
My RRA 9MM AR runs great with the modded UZI mags it came with, as well as the Colt SMG pattern mags. Most JHP loads run just fine. I would think a Glock Mag 9MM AR would run as well or better. If it doesn't I don't know how we could blame the mag, unless it just doesn't match up to the platform well. I have no idea there.
 
someguy2800 said:
The couple that I have seen with dedicated billet glock lowers practically put the bullet right at the back of the chamber due to the forward angle of the glock mags.
Click to expand...

The distance from the breech to the magazine is not the whole story, unfortunately. The common bolt style nowadays requires the magazine sit much lower relatively to the axis of the barrel than it does on a handgun. The feeding geometry must overcome that vertical distance. As you put the magazine closer and closer to the breech, the ramp has to get steeper and steeper. At about 5mm out it breaks 45 degrees.

In addition, the barrels on 9mm ARs do not have hoods. Placing the magazine closer to the breech forces the cartridge to tip up steeper. At some point it starts jamming against the upper edge of the breech.

Endomag permits designers a lot more flexibility than using a pistol magazine. In particular, the unsupported jump distance is smaller in it, primarily because its feed lips are longer.
 
I have a Banshee upper and a lower that I use with both 223 and 9mm.

The endomags work great. The Banshee upper works great although the 9mm still recoils a bit more than I would like.

I don't have a ton of rounds through it yet. Word from the high round count guys is that the Banshee uppers wear out ejector springs much more rapidly than DI 5.56 guns do.
 
IndianaBoy said:
I have a Banshee upper and a lower that I use with both 223 and 9mm.

The endomags work great. The Banshee upper works great although the 9mm still recoils a bit more than I would like.

I don't have a ton of rounds through it yet. Word from the high round count guys is that the Banshee uppers wear out ejector springs much more rapidly than DI 5.56 guns do.
Click to expand...

Resurrecting this one from the dead...

Are you saying that the radial-delayed blowback functionality in the Banshee does not take much more out of the recoil over a 'normal' AR-9?

If this is the case, I'll just build my own AR-9, as I can do it for much cheaper than what the CMMG piece will cost me.
 
Status
Not open for further replies.

Similar threads

greyling22
  • Locked
Anynody tried a Cmmg banshee/guard suppressed?
Replies
2
Views
590
MachIVshooter
MachIVshooter
E
  • Locked
  • Poll
CMMG AR-15s
Replies
16
Views
1K
Coronach
C
zaitcev
  • Locked
CMMG Guard versus Thompson Autorifle
Replies
2
Views
888
browningguy
B
B
  • Locked
Two question re CMMG
Replies
7
Views
421
B!ngo
B
M
  • Locked
cmmg 2 stage trigger, others?
Replies
17
Views
1K
Kwanger
K
Back
Top