10mm Long Guns

[juliang]

First post here. I have a Glock 20 which has a red dot installed by the Glock store and a G40 MOS. Pus.... I have the Mechtec carbine conversion which basically gives the rifle option but uses Glock mags.

I would love a lever action option too!

[spaniel]

I think we actually need something new in the world of design for good 10mm carbine. I've been kicking around an idea for awhile now. I really like the feel of my gas operated 10mm AR. It's just not reliable. I don't really care for the blowback designs.

So, I've been thinking of something similar to a delayed roller blowback design where the delay is augmented with gas pressure. That way the timing of the action is self adjusting to the power of the ammo. I think a gas piston driven delay system would keep enough junk out of the delaying roller(s) to make it feasible.

Anybody have a bunch of money or a really good machine shop?

Look at CMMG.  That's the one 10mm AR design I'd trust to work.

[Graybeard]

I think we actually need something new in the world of design for good 10mm carbine. I've been kicking around an idea for awhile now. I really like the feel of my gas operated 10mm AR. It's just not reliable. I don't really care for the blowback designs.

So, I've been thinking of something similar to a delayed roller blowback design where the delay is augmented with gas pressure. That way the timing of the action is self adjusting to the power of the ammo. I think a gas piston driven delay system would keep enough junk out of the delaying roller(s) to make it feasible.

Anybody have a bunch of money or a really good machine shop?

Look at CMMG.  That's the one 10mm AR design I'd trust to work.

Others here have had good things to say regarding their 10mm CMMG's reliability. IIRC, many have said they render their brass unreloadable. That's the hangup for me. I'm too cheap to enjoy one use only 10mm ammo.

I would love to have a MP5/10mm, but it too really only works with one bullet weight and power level. My gas operated 10mm AR is a joy to shoot. It drops empties in a neat pile 2-3' to my right. It won't cycle with mild ammo and the converted grease gun mags cause jams if fully loaded. But, it has less and smoother recoil than my 9mm JRC of roughly the same size and weight. But I've come to the conclusion that it will never be a bet your life on it type of gun. It's just a teaser for something better. That's how I feel about the CMMG, as well.

The wide range of bullet weights and power seem to be demanding a new system to accommodate that. Hopefully someone with more means than I will get on it!

[fltbed]

The wide range of bullet weights and power seem to be demanding a new system to accommodate that. Hopefully someone with more means than I will get on it!

Ideally, we would want some kind of self regulating operating system that could function with anything from "Fed-Lite" loads, (about 20K psi) to seriously stupid hot loads.  Say an max ideal operating pressure of 36K psi with a max working pressure of 40K psi...That's a tall order!

I think it might be possible to design a short stroke gas piston operating system with a spring loaded gas vent block.  Something along the lines of the Sig MPX comes to mind.  I suspect it would be a huge capitol investment for a very small market.

However, I don't see why you couldn't build a DI AR style rifle with a manually adjustable gas block like the new Riflespeed adj gas blocks.  With the block wide open, increase the gas port size till the action cycles with the lite loads then dial back the gas pressure for the hotter loads.  I'm sure it would take some trial and error with gas port location, bolt, buffer and spring weight.   Mated up with a large frame Glock mag lower and I think it would be a sweet PCC.  It wouldn't be the Ideal rifle but I suspect it would be easier to build.
Personally, I would opt for an 8"-10" threaded barrel for a comp, flash hider or can  and put a brace on it for even better handiness.  Call it the Handy-10.

Jeff

[challer61]

I would think the Ruger PCC would be a good starting point. SIG promised us a 10mm MPX which would be stunning.

[fltbed]

I think we actually need something new in the world of design for good 10mm carbine. I've been kicking around an idea for awhile now. I really like the feel of my gas operated 10mm AR. It's just not reliable. I don't really care for the blowback designs.

So, I've been thinking of something similar to a delayed roller blowback design where the delay is augmented with gas pressure. That way the timing of the action is self adjusting to the power of the ammo. I think a gas piston driven delay system would keep enough junk out of the delaying roller(s) to make it feasible.

Anybody have a bunch of money or a really good machine shop?

I remember hearing the original H&K MP5/10 prototype had a selector switch so it could function with Fed lite 10mm or standard 10mm.  H&K figured out, designing the action to cycle the Fed lite loads, shooting standard 10mm would drastically increase wear on the roller system so, it made sense to them to modify it to work with all of the available ammo.   The problem the FBI had was, in "standard" mode, it wasn't reliable with the Fed lite loads and they didn't want to add confusion to the firearm when the Fed lite ammo was the only ammo they issued.  The FBI settled for a last round bolt hold open instead.

If that story is true, the original prototype design may be the closest thing to what we're looking for.  At least for me.   I shot an FBI issued MP5/10mm back in the day and loved it except that, the recoil made it useless as a sub machine gun.

The other operating system H&K is famous for, the gas delayed blow back on the P7.  I don't think would work for this project for two reasons.

1. Every gas delayed system I've ever seen has a fairly narrow pressure operating window.  To lite a load or too heavy a load would cause malfunctions.  The opposite of what we're after.

2. The system is very sensitive to fouling.  Shooting dirty powder will clog the gas system up in short order and forget about shooting cast lead or coated lead bullets entirely.

I still think the recoil delayed system, like on the CMMG or the Ruger PCC is the simplest to make work because by balancing bolt mass and spring weight, you can make the system work for a given load.

However, I still have hope someone can design a self adjusting gas piston system that would work.  (are you listening SIG?)

Jeff 

[The_Shadow]

I did get a lot of the 10mm brass as shot from the MP5 -10 that were shot on the FBI range locally.  The Federal ammo was loaded with fast burning powder and that caused many of the cases to split vertically from those fluted chambers.   I had also seen many cases that were messed up being trapped at the ejection port with damaged case mouths.

At lease 60+ out of a 1000 would be split, maybe 30+ per 1000 sustained damage due to the ejection cycling.