22 TCM barrell for a MAC

[Richard/SIA]

Just pulled the M11-9 I have in the safe for transfer out to have a look.
Seems there should be plenty of material available to turn down a TCM barrel for a MAC.
The 22" TCM barrel might be able to be cut into several blanks but only one would be factory chambered.
There is a short section at .665 before the 3/4-16 threads, then just under 1.00" at the receiver and the barrel itself is .750"
I will get back to those who have expressed interest in the order they contacted me.
Three were sent to a MAC specialist so I would expect answers to the questions of this thread pretty quickly.

 

[strobro32]

Richard @ SIA,

If you do start making 22TCM barrels for the M11 and M11A1, please don't use the OEM suppressor threads. 1/2 x 28 would be nice.

Thank you,

Matt

 

[Richard/SIA]

"1/2-28", LOL!

So far it seems I have found NINE different 1/2-28 threads depending on the suppressor manufacturer and model.
One major manufacturer alone uses FIVE different threads for 9mm!
Then there are a couple of 1/2-36 variations.
Probably a metric thread or two as well.
I personally prefer a more robust 5/8-24 but I am clearly in the minority.

I think I will just sell the take-off barrels cheap and let folk do their own modifications as I'm pretty busy with my standard products.
Being able to shorten them before shipping would be nice to save on cost.

 

[strobro32]

These would be my preference for thread specs.

https://s3.amazonaws.com/com.silenc...cs/Rimfire_O-Ring_Engagement_Thread_Guide.pdf

 

[IndustrialRescue]

1/2x28, no longer than .400" will fit the spec for the Sparrow, most other 22lr full auto rated cans, and most 9mm/45 cans with a piston. An O ring groove WOULD be nice, to ensure tension, and prevent the threads from backing off.

Longer than .400", and a spacer or crush washer is typically recommended.

What are we currently looking at, price wise, for an OEM length barrel? And for longer?

Seems that 8 or 9 inches would be ideal, to allow all the powder to burn, but with the advent of CoffeeFreak coming out with the slowfire bolt, I no longer need to worry about a Lage upper.

The spare upper I currently have has a 9 inch barrel.

 

[lokifox]

If you could leave the barrel full diameter past the trunion it might give us the opportunity to send it to TROS for three lug modding.

 

[m11stuff@hotmail.com]

Test Configuration-

MAX-11 mk2 with standard bolt assembly
8-3/8" barrel chambered in 22TCM
Ammo- 22TCM 40 gr.

Test Results-

Velocity- Standard 22TCM Round- 2,331 FPS
22TCM round compressed to 1.190"- 2,317 FPS

Rate of Fire- 892 RPM

Accuracy- as good as can be expected from an open bolt subgun. Photo is of target shot at 12 yards from a benchrest.

Shooting perception- Kicks harder than 9mm. Concerned about stress to the lower receiver. Didn't see muzzle flash, but you can see it in the video.

Slow Motion Video:

[video]http://www.max-11.com/videos/22TCM1.mp4[/video]

 

[strobro32]

Good job Richard. How does the brass look? Did the case split? Did it feed more than one round?

Dang. I think this might eliminate the OEM M11/380 upper as a host. A 22TCM Max-11A1 MK II Might be fun.

I wonder if a shorter barrel would reduce the velocity and pressure.

 

[m11stuff@hotmail.com]

The cases look fine. The case mouth occasionally gets a dent in it from ejection, forming a "D".

One of my lowers had no problem cycling the rounds in full auto, the other jammed everyone on feeding. I suspect the feed ramp is higher on the first. The 22TCM chamber has a sharp edge at the mouth and it looks like the rifles use a separate feed ramp.

I would guess a shorter barrel would have lower pressure/velocity and recoil. I am not making a shorter barrel anytime soon.

My first concern was that the barrel would split at the chamber, since it is a reduced diameter. I am going to test the barrel hardness at the chamber and about 6" from the chamber and see if the chamber area is hardened. When cutting it with the lathe, it seemed to be harder there.

My second concern was about the bolt mass/spring force. Based on what I had read, I expected the bolt to short stroke and have lighter recoil than 9mm. The opposite is true with an open bolt gun. I was surprised at the recoil.

Based on this performance, I would not want to go with any lighter bolt or shorter stroke. I am thinking about testing the 8-3/8" 22TCM barrel in my MAX-31 mk2 with a MAX-31 mk1 bolt and adding a muzzle brake to the barrel.

I am not sure what the advantages of the 22TCM in an open bolt subgun platform are going to be. The accuracy of the round is negated by the "clunkiness" of the open bolt trigger system. Recoil and RPM are higher and it is less controllable in full auto. The round probably has some impressive terminal ballistics though.

 

[ChuckB]

Is the open bolt the cause of increase recoil, or just the additional pressure combined with the blowback action (compared to locked breech)?

 

[IndustrialRescue]

The round in a MAC essentially offers the performance of a P90 with AP ammo.

 

[m11stuff@hotmail.com]

Is the open bolt the cause of increase recoil, or just the additional pressure combined with the blowback action (compared to locked breech)?

From my experience with 9mm "MAC's", the open bolt system results in lower recoil and lower ROF than closed bolt/blow back. I do not know if a locking breach closed bolt will reduce recoil or ROF.

 

[CoffeeFreak]

From my experience with 9mm "MAC's", the open bolt system results in lower recoil and lower ROF than closed bolt/blow back. I do not know if a locking breach closed bolt will reduce recoil or ROF.

What if you added a little more weight to the bolt? Do you think it would cycle OK? Improve? Are you running the unmodified 30 Oz MK2 bolt assembly?

 

[ChuckB]

Thanks Richard.

 

[CoffeeFreak]

It may sound counter productive but a heavier spring, not the 15 coils off may help tame the recoil if you hadn't tried it.

 

[okpud]

From my experience with 9mm "MAC's", the open bolt system results in lower recoil and lower ROF than closed bolt/blow back. I do not know if a locking breach closed bolt will reduce recoil or ROF.

Sounds like the barrel is not chambered for API. This would make since if it was originally chambered for a bolt action rifle. No API = 2 x recoil velocity of the bolt. Doing some rough, back of the napkin math, a 40gr bullet travelling at 2300fps in an open bolt SMG w/ a 30oz bolt and no API would result in about 50% more bolt velocity than a 115gr bullet traveling 1200fps w/ the same 30oz bolt utilizing API. If both systems had API, the 40gr/2300fps system's bolt should be traveling ~25% slower than the 115gr/1200fps system.

 

[medphys]

Use a longer firing pin

 

[IndustrialRescue]

Sounds like the barrel is not chambered for API. This would make since if it was originally chambered for a bolt action rifle. No API = 2 x recoil velocity of the bolt. Doing some rough, back of the napkin math, a 40gr bullet travelling at 2300fps in an open bolt SMG w/ a 30oz bolt and no API would result in about 50% more bolt velocity than a 115gr bullet traveling 1200fps w/ the same 30oz bolt utilizing API. If both systems had API, the 40gr/2300fps system's bolt should be traveling ~25% slower than the 115gr/1200fps system.

Armor Piercing Incendiary?

Huh? English, please.

 

[m11stuff@hotmail.com]

API = Advanced Primer Ignition

 

[lokifox]

Don't steeply necked cases have issues with API?