Suggestions for mis-feeding CMMG MKG 45acp?

[sloppyjoe]

Thanks for sharing your journey. I built a .45 RDB upper but paired it with an Angstadt Glock lower. I haven't had a chance to shoot it yet, but I'll let you know when I do. If you want to go shooting in the Indy area sometime, I would be happy to swap uppers/lowers with you to help toubleshoot.

 

[STFU]

Called CMMG, sent them pictures and the info I posted, they think it’s the magazine catch and spring, sending me new ones.
Not sure I buy that answer, but I’ll swap them out and give her another go. I’ll update after.

Hope I get it 100%, it’s a very fun gun to shoot.

Thank you for sharing butch. I look forward to the next update.

 

[Karl-just-Karl]

I pulled the buffer and weighed it.

It is stamped "H" and is 4.635 oz.

It is a larger diameter than the buffer/spring combo used in an M&P AR-15.

I have been under the impression that it was a .308 buffer that CMMG uses.

Off to do more research...

 

[Karl-just-Karl]

Since people like pics:

 

[Karl-just-Karl]

Update from my issues:

Took freshly cleaned Banshee and well lubed out....

Any opinions/feedback?

Sorry, I guess I never did comment on the pictures of your misfeed.

That's what I meant by the "nose down" misfeeds. There was usually a notch in the bullet that would frequently break through the plating on the projectile.

The leading edge there of the feed ramp seemed to be pretty sharp on the barrel extension. I took a small needle file and just worked it enough to break the edge. It was with hope that it would stop cutting into the projectile. For the most part I do not have that kind of stoppage anymore.

That seemed to be one tough piece of metal. It took some persistence but maybe it was because the jeweler's file I used isn't very aggressive.

 

[profjeremy]

First of all, really sorry to hear about this, as I know how frustrating these issues can be. Especially when it isn't exactly a cheap gun!

I'm following this thread with interest, as I have a Banshee in 10mm that I absolutely love and hasn't had a single misfeed in over 600 rounds so far. I'm blown away to hear this about the MK45 and am wondering if there isn't some crazy issue with a component (like bmbutch suggested) or if it's perhaps some error in the design of the MK45 itself. Definitely sad to hear it though, when it has the potential to be such a great gun.

 

[LEaSH]

I'm following this thread with interest, as I have a Banshee in 10mm that I absolutely love and hasn't had a single misfeed in over 600 rounds so far.

So I'm interested, too. I was really considering a mk45 but maybe not now.

Is your 10mm a later production run? What sort of ammo are you feeding it? Thanks.

And I hope butch and karl get their models sorted.

 

[profjeremy]

So I'm interested, too. I was really considering a mk45 but maybe not now.

Is your 10mm a later production run? What sort of ammo are you feeding it? Thanks.

And I hope butch and karl get their models sorted.

I bought my Banshee 10mm in August, I think. I haven't shot any steel cased ammo in it, but it's eaten everything I've thrown at it so far. Not even a single misfeed in probably close to 1000 rounds. Sellier & Bellot, Magtech, CCI Blazer, Defender, Underwood, etc.

Interestingly, it looks like the MK45 is being offered online at significantly lower prices than any of the other Banshees. I wonder if this is just a known issue with the MK45 now. If so, CMMG should definitely be handling it better than they have, judging by the info in this thread. God knows they're raking in the cash based on their high prices!

 

[bmbutch]

11-18-20 Update:
Installed the new mag release and spring and took the Banshee out to gun range:

Same issues, oddly, maybe worse, as the aforementioned Federal Red Box, which had been 100%, gave me issues.
My reloads, using both RMR Plated and Blue Bullets Coated ran 100%, both 230gr.

Just contacted CMMG for next steps, will update further.

PS: Did mess around with newly acquired linear comp for Banshee, and while not a "game changer" did soften the shooting some. Made no difference in Fail to Feed issues, but since I wanted to try it out, added it into the mix.
Here's what I purchased:
https://www.joeboboutfitters.com/Articles.asp?Search=KVP-LINEAR-45-40-10MM-.578-28&ID=301

Couple more pics of "post malfunction" cleared ammo looks, you can see one of them suffered significant bullet set back. (Both factory Aguila 230gr)

 

[bmbutch]

CMMG wants me to send the entire firearm to them, they are sending me info/instructions. I'll update when I know more.

 

[Karl-just-Karl]

Sorry to hear that the mag catch didn't fix your problem.

It didn't fix my issues either.

I was shooting Independence and ended up with a bunch of those. Independence seemed to be real bad for nose-down misfeeds and bullet set-back.

Best of luck to you working with Brian and CMMG's CS.


I am supposed to sit down with a friend of mine today that has done some AR-10 builds and discuss buffers.

Here is a picture of my most frequent problem:

 

[Karl-just-Karl]

So, my buddy with AR-10 experience has been sidelined by the Covid.

I've been looking at the Odin Works adjustable buffer since it is an AR-10 Carbine design.

It is only 2.7 inches in length however. The current buffer I have is 3.25 inches. The adjustable weight range seems a little limited compared to the Ar-15 length buffers.

My first approach would be to try a little lighter buffer and it covers this. But I am confused as to if that would make it cycle faster when what I am looking for is slower. The Radial Delayed Blowback seems to be the wildcard in the mix.

If I use something heavier, it seems to me it would delay the opening of the bolt until there is even less remaining pressure in the chamber. CMMG offers additional weights that can be added to the BCG for use with suppressors, so that is the basis of my thinking.


My lingering question is: Does one-half an inch make a significant functional difference in overall buffer length?

I've also found heavier springs available, but that doesn't seem like the direction I want to head in.

 

[sloppyjoe]

You dont want to run with an AR10 buffer. Those buffers are shorter because the .308 bolt carrier groups are longer and most people use standard AR15 buffer tubes on their AR10s. What buffer weight and spring are you using now? I would think you would want to run in the 3 to 5 ounce range for .45.

 

[Karl-just-Karl]

You dont want to run with an AR10 buffer. Those buffers are shorter because the .308 bolt carrier groups are longer and most people use standard AR15 buffer tubes on their AR10s. What buffer weight and spring are you using now? I would think you would want to run in the 3 to 5 ounce range for .45.

The AR-10 buffer I'm running is OEM. The BCG is based upon an AR-10, probably due to the size of the cartridge base.

The CMMG MKG is based upon an AR-10 upper, so I'm kind of locked into using, modifying or discarding what I have. My current buffer is 4.635oz. The spring is just a standard carbine length AR-10 buffer spring as far as I can tell.


I finally got to talk with my buddy. His help was marginal at best but he did promise to check the length and weight of the buffer he used in his builds.

 

[sloppyjoe]

I guess I havent seen a MKG in person, but the CMMG RDB .45 ACP is based off AR15. The bolt carrier is the exact same size as an AR15 carrier, but the bolt face is bigger, and you have to run a "XL" upper with a wider ejection port to allow the fatter .45 ACP brass to make it out of the upper during ejection.

Can you take a picture of your MKG bcg next to an AR15 bcg?

 

[Karl-just-Karl]

I guess I havent seen a MKG in person, but the CMMG RDB .45 ACP is based off AR15. The bolt carrier is the exact same size as an AR15 carrier, but the bolt face is bigger, and you have to run a "XL" upper with a wider ejection port to allow the fatter .45 ACP brass to make it out of the upper during ejection.

Can you take a picture of your MKG bcg next to an AR15 bcg?

There are buffer pics up-thread if you would like to get a start there.

Whatever it is CMMG put in there isn't an AR-15 buffer. It has a larger OD as well as its accompanying spring.

One of my earliest attempts to troubleshoot involved some AR-15 parts. Things weren't fitting like they should so I did not proceed with parts-swapping.

 

[bmbutch]

I haven't forgotten about this thread, my Banshee is still @ CMMG, it's been there about 2-weeks now, but with Thanksgiving Holiday, that doesn't mean much time wise. It got there the Monday before the holiday, based on tracking.

 

[sloppyjoe]

There are buffer pics up-thread if you would like to get a start there.

Whatever it is CMMG put in there isn't an AR-15 buffer. It has a larger OD as well as its accompanying spring.

One of my earliest attempts to troubleshoot involved some AR-15 parts. Things weren't fitting like they should so I did not proceed with parts-swapping.

Sorry for missing your earlier comments. I now see that you are running a heavy buffer.

I just measured some standard AR15 buffers and they match your measurements. The AR10 buffer is shorter like you mentioned. You dont want to run the AR10 buffer or you run the risk of your bcg going back too far and getting caught on the detent pin. Since you had better luck with hotter reloads, I would suggest trying a standard AR15 weight buffer. It should match your current buffer in size, but weigh less. I have a handful of extra standard AR15 buffers if you need one.

 

[Karl-just-Karl]

I guess I am just stuck on a buffer stamped "H" being 4.635oz. That is H2 range in AR-15 world.

Thanks sloppyjoe, I appreciate your offer. I'm gonna have to mull this around for a while to figure out where I want to go with this.

My buddy is digging out some extra parts for me now.

For reference, the buffer and spring diameter are smaller in S&W ARs...FWIW.

 

[sloppyjoe]

I took my RDB upper to the range for the first time this morning. I only tried S&B ammo, but had no failures. I am running an Angstad Arms lower with SGM 23 round magazines. The only issue I had was no lrbho but I was running a 5.6 ounce buffer. I'll try it next time with something in the 3 to 4 ounce range.