Henry Tatro M16

[Fishman]

It will never be as smooth as a MP5 SD. I think that the CMMG RDB has more potential as a SD.

I have a ported integral CMMG RDB SD. If anybody wants to lend me a RLL or RDIAS, for science, let me know.

 

[amphibian]

I have a ported integral CMMG RDB SD. If anybody wants to lend me a RLL or RDIAS, for science, let me know.

Ohhh....please do tell....
I have been wanting to get my CMMG integrally ported....
Please share some pics and details.
Who did the work?
Baffle material?
Modified factory barrel?
How many ports?
Overall impression?
Ammo used?

I have an old LRM integral can which is built around an old straight blowback RRA barrel that is plain chrome moly steel. I want to go SS for the integral RDB for corrosion resistance.
I've already had 1 custom SS barrel made for my CMMG Guard and need to find some time to make sure it groups well and then thinking about sending it off to get it modified for my integral build.
I have another 9mm SS blank that I may use as well.

I reload strictly 9mm subsonic 147Gr. LRM had ported mine less than typical and I chrony'ed it and was still losing too much velocity and so he put a bushing on my barrel to block off 2 of the 4 ports.
I see some manufacturers are threading the ports so you can add/remove set screws to control the bleedoff. I'm considering that too. I honestly am not sure how much I will use an integral setup as I am very happy with my short custom Curtis Tactical can and 8" barrel.
The velocity and sound are where I want it with my 147Gr loads.

It is more for the curiosity to see how smooth it can get with a ported setup.

Sorry can't lend you a RDIAS but let me know if you are ever in FL to do some testing.

 

[A&S Conversions]

Man, I have to ask, why go through all the trouble of making a SS barrel from scratch? Factory SD barrels are not SS. I would think a collar added to the CMMG barrel with the thread pitch for the can and porting the barrel like Ralph at RDTS would be an easier way to go. He drills holes in the groove of the barrel. Since I want to use a SD suppressor, I thought it would be easier for a machinist to make a collar to fit an SD barrel with the CMMG barrel extension. At least that is the direction I was going to start.

To me threaded ports sound very problematic. It is hard enough to clean smooth holes in a SD barrel, let alone threaded holes. I would think threaded holes would gather unburned powder deposits quickly in the threads. Once those deposits start, I would think the build up of deposits would be faster than the build up in a smooth hole. There would also be a wear factor. I would think the high points of the threads would wear quickly. So if you did want to plug a hole later because of wear in the holes, how well would a plug stay in a worn threaded hole?

BTW, as I recall Todd's roller locked barrels are SS. If you have a SD can, you might try posting a WTB ad at HK Pro. Just a thought. Someone might have a SS SD barrel tucked away. A back burner project I have is replacing the CA5 SD barrel with a K barrel and use my Raptor can, that will fit inside the SD cage.

Scott

 

[amphibian]

Man, I have to ask, why go through all the trouble of making a SS barrel from scratch? Factory SD barrels are not SS. I would think a collar added to the CMMG barrel with the thread pitch for the can and porting the barrel like Ralph at RDTS would be an easier way to go. He drills holes in the groove of the barrel. Since I want to use a SD suppressor, I thought it would be easier for a machinist to make a collar to fit an SD barrel with the CMMG barrel extension. At least that is the direction I was going to start.

To me threaded ports sound very problematic. It is hard enough to clean smooth holes in a SD barrel, let alone threaded holes. I would think threaded holes would gather unburned powder deposits quickly in the threads. Once those deposits start, I would think the build up of deposits would be faster than the build up in a smooth hole. There would also be a wear factor. I would think the high points of the threads would wear quickly. So if you did want to plug a hole later because of wear in the holes, how well would a plug stay in a worn threaded hole?

BTW, as I recall Todd's roller locked barrels are SS. If you have a SD can, you might try posting a WTB ad at HK Pro. Just a thought. Someone might have a SS SD barrel tucked away. A back burner project I have is replacing the CA5 SD barrel with a K barrel and use my Raptor can, that will fit inside the SD cage.

Scott

I want to go SS because I periodically put suppressor internals in my ultrasonic cleaner as well as physically scraping carbon off the barrel. I don't want to be scraping on parkerized or even nitrided surface. SS and I don't worry about any corrosion....and if I do end up adding ports or whatever, there is no concern of protecting the holes from corrosion since the entire barrel would be SS.

I thought the same about the threaded ports clogging up and was thinking I could chase it with a tap and was also thinking to just get some holes dimpled only...so drill right through for 2 ports then just dimple the barrel for 4 more ports or whatever if I wanted to increase the ports.

Nah, I don't have an MP5SD.

 

[Jmacken37]

Man, I have to ask, why go through all the trouble of making a SS barrel from scratch? Factory SD barrels are not SS. I would think a collar added to the CMMG barrel with the thread pitch for the can and porting the barrel like Ralph at RDTS would be an easier way to go. He drills holes in the groove of the barrel. Since I want to use a SD suppressor, I thought it would be easier for a machinist to make a collar to fit an SD barrel with the CMMG barrel extension. At least that is the direction I was going to start.

To me threaded ports sound very problematic. It is hard enough to clean smooth holes in a SD barrel, let alone threaded holes. I would think threaded holes would gather unburned powder deposits quickly in the threads. Once those deposits start, I would think the build up of deposits would be faster than the build up in a smooth hole. There would also be a wear factor. I would think the high points of the threads would wear quickly. So if you did want to plug a hole later because of wear in the holes, how well would a plug stay in a worn threaded hole?

BTW, as I recall Todd's roller locked barrels are SS. If you have a SD can, you might try posting a WTB ad at HK Pro. Just a thought. Someone might have a SS SD barrel tucked away. A back burner project I have is replacing the CA5 SD barrel with a K barrel and use my Raptor can, that will fit inside the SD cage.

Scott

Scott, I have a take off Todd SS MP5 or K (?) bbl with 3 lug that is yours if you'd like it...

 

[A&S Conversions]

Scott, I have a take off Todd SS MP5 or K (?) bbl with 3 lug that is yours if you'd like it...

Thank you, that is a very kind offer. But I have a barrel for the project. I just need to get around to it. I wonder if the SS SD barrel that is in the CA SD could be adapted to the RDB system? As if I don't have enough projects already.

Scott

 

[Fishman]

Ohhh....please do tell....
I have been wanting to get my CMMG integrally ported....
Please share some pics and details.
Who did the work?
Baffle material?
Modified factory barrel?
How many ports?
Overall impression?
Ammo used?

My CMMG is a 45. I got it right when they came out. Serial number 100-ish.
Its a form 1 450 bushmaster can. Curtis tactical made the 17-4 stainless K baffles.
I shortened the barrel 3 inches, rethreaded the muzzle, and cut a shoulder and threads near the chamber. I made the tapered shoulder ring from titanium.
Then a friend of my father's EDM'd 20 ports halfway down the barrel.
The port noise and blowback are so pleasant for a semi auto. Way quieter than a blowback 9mm.
I use 230 grain handloads (with WST I think)

 

[Mackjack]

My CMMG is a 45. I got it right when they came out. Serial number 100-ish.
Its a form 1 450 bushmaster can. Curtis tactical made the 17-4 stainless K baffles.
I shortened the barrel 3 inches, rethreaded the muzzle, and cut a shoulder and threads near the chamber. I made the tapered shoulder ring from titanium.
Then a friend of my father's EDM'd 20 ports halfway down the barrel.
The port noise and blowback are so pleasant for a semi auto. Way quieter than a blowback 9mm.
I use 230 grain handloads (with WST I think)

Why do you need the porting for 45acp?

 

[Fishman]

Why do you need the porting for 45acp?

It reduces gas blowback and port noise. The ports arent super close to the chamber like a 9mm MP5SD because 45 ammo is already subsonic.

 

[Mackjack]

It reduces gas blowback and port noise. The ports arent super close to the chamber like a 9mm MP5SD because 45 ammo is already subsonic.

Gotcha. I just haven't really heard of it done before with 45, but that makes sense

 

[Fishman]

Gotcha. I just haven't really heard of it done before with 45, but that makes sense

It sure does

 

[nuge]

Will be looking at at OEM vs RDIAS lower; standard SMG bolt vs ramped/W plugged; std vs enhanced buffer; std FCG vs modified FCG; and std smg buffer spring vs the flat spring. I do have some strong hammer springs coming as well to test at some point. For measurements I will use RPM and some kind of assessment of smoothness which is TBD...

Got a plan anyway - a little ambitious and may take 700 to 800 rounds to complete. ETA probably early next year...

 

[A&S Conversions]

That is very ambitious. Good luck with the project.

Scott

 

[amphibian]

Got a plan anyway - a little ambitious and may take 700 to 800 rounds to complete. ETA probably early next year...

Do you know how you plan on quantifying the smoothness?
Don't know if you've been watching the thread on AR15.com but we have been making some progress on the accelerometer testing and I have some high speed video that I did where you can clearly see the difference in smoothness.

The videos below were done at 1000 frames per second.

Here is the 9mm CMMG RDB in factory recommended config:

And now my favorite configuration:

I'm going to do a couple more vids with a standard straight blowback 9mm M16 for comparison.

 

[nuge]

Do you know how you plan on quantifying the smoothness?

I'm going to do a couple more vids with a standard straight blowback 9mm M16 for comparison.

Thanks for sharing this here. I am looking at the possibility of using human vibration measurement equipment (tri-axial accelerometers) - hand, arm, or full body. There appear to be many options that could be used with MGs. One that intrigues me right now is the palm sensor worn under a glove on the grip hand. Have you looked into these human vibration sensors and dismissed them for any reason? Would appreciate any feedback on them if you have it.

Looking forward to your vids on the classic straight blowback comparisons...

 

[amphibian]

Interesting perspective...I never thought about putting sensors on the shooter....I have been trying to reduce the human factor as much as possible.....if you put sensors on the shooter, doesn't the shooter now become a variable? Bigger person soaking up more recoil than lighter? Fat vs skinny shooter?

 

[nuge]

Shooter could be a variable and also could be evaluated as such. For my purposes above I will use one shooter. I have more questions than answers right now about the human vibration equipment and capabilities. But it is off the shelf and used in industry for exacting measurements against ISO standards. Should be straightforward to implement. Conceptually I like the idea since it is human felt vibration that is the subject here. And I believe that choppy vs smooth subguns will line up similarly regardless of the mass of the individual shooter. Time will tell...

 

[nuge]

Got to admit that the flat spring and 5005 buffer makes a big difference. Tried it out today and felt a reduction in rate an definitely improved smoothness! No measurements, but this change is beginning to push the HT into my "favorite guns" category just from the feel of it...