Who Will Be The First To Put A SD Front End On Their Mac Style RR?

[A&S Conversions]

There have been so many threads about a SD barrel and suppressor for a Mac style upper here. But the SD ports would be inside a standard upper where the bolt needs to go. I know there are some that have looked into 9mm for the Lage Max/15 uppers. I think that it would be cool to combine the HK SD ported barrel and suppressor with the Lage upper.

This is something that I would like to do with my Tenko 10-16. Funds have been very short, so I have not done it yet. But I have the SD style suppressor which would be the biggest hurdle. So who will be the first to have a SD Mac? There is the recent FW video about an AR style SD upper.

Scott

 

[slimshady]

On a stock upper you could do like the Stetchkin silenced bbl, ports at the rear, reduced diameter bbl, and a sleeve over everything, maybe? Second set of ports near the muzzle dump the gas back into the bbl ahead of the projectile.

 

[A&S Conversions]

On a stock upper you could do like the Stetchkin silenced bbl, ports at the rear, reduced diameter bbl, and a sleeve over everything, maybe? Second set of ports near the muzzle dump the gas back into the bbl ahead of the projectile.

That sounds like a huge project. I looked up the Stetchkin silenced pistol. The ammo isn't commercially available. Then there is the barrel porting. Where would you start with the porting? It just seems like you would have to start from scratch.

I was thinking of the AR platform. There is a commercial ported barrel and several SD suppressor manufacturers with cans available. After I bought a sear in a converted 94. One of my first host guns was a 9mm SD clone. It is fun to shoot. I have been wanting to buy one of the new SD AR uppers. I just think that the ported SD ported barrel with the specific SD can is pretty cool.

After finding out about the manufacturer of the AR SD upper, I wanted to get one. But I got more fired up about getting one afterwatchingthenew "Gun Jesus" video. I just think that the system is cool. And the manufacturer has both simple blowback and rotary delayed blowback.

Scott

 

[Deerhurst]

An integrally suppressed barrel for M10 doesn't sound all that difficult. Little machine time and some research into how to build integral cans and I could probably slap one together. As long as I started with enough barrel!

 

[Hey...]

The telescoping bolt over the long internal barrel is a feature on the Uzi/MAC/etc… that is NOT on the MP5SD.

Good luck getting past that WALL that is the barrel trunnion welded into the upper…inches ahead of the chamber.

 

[Deerhurst]

The telescoping bolt over the long internal barrel is a feature on the Uzi/MAC/etc… that is NOT on the MP5SD.

Good luck getting past that WALL that is the barrel trunnion welded into the upper…inches ahead of the chamber.

Barrel length would have to change and suppressor be external to the upper receiver.

Why would you want to put it inside the receiver? Seems like a nightmare in every way.

It really is just more practical to thread a can on.

 

[MitchWerbellsGhost87]

I have seen numerous examples over the years of integrally suppressed Ingram uppers. Most of them utilize a long 11-13” barrel, ported about 3/4 of the way, with a barrel nut bushing like an UZI and an aluminum tube/sleeve that threads on over it, with a series of baffles slipped over the barrel of course. I believe I have pics of something like this saved in my archives, I’ll have to dig. The same kind of suppressor build could be accomplished using the newer replacement uppers from FTF industries that utilize an AR15 barrel nut, with various different extended barrel lengths. Port the barrel, slip baffles over it, thread a tube with an end cap onto the AR barrel nut and viola.

Edit: found some pics. It’s an M11/9 integrally suppressed upper, and it’s excessively long, damn near 18” carbine length with the tube, probably about 10” without it. I bet it’s quiet though, end cap looks like its a standard MAC/sionics type wipe cap.

I have to agree that it’s much more practical and convenient to just thread on a suppressor. It was kind of the whole point of the package in the first place with the threaded barrel, though more reliable attachment methods have since been devised. The removal of the suppressor and resulting compact size is one of the biggest plus sides to the platform and was its primary selling feature. To attach permanent huge suppressor kinda defeats the purpose if you ask me

 

[Gaujo]

Barrel ports are a design compromise to compensate for the fact that govt users couldn't get subsonic ammo at the time. Just run subsonic ammo, short barrel, and a thin suppressor under a handguard and you have a superior gun.

 

[Slowmo]

Or convert it to .380. A warm .380 load is not too far off from a ported 9mm load, and you're generating less gas to manage due to the decreased powder load.

 

[Hey...]

Why would you want to put it inside the receiver?

I don’t.

 

[A&S Conversions]

Thank you for the pictures of the ported barrel/suppressor upper. The whole point of the HK SD is that the porting is close enough to the chamber such that 115 grain ammo doesn't go supersonic. Yes, 147 grain plus is subsonic, but is much more expensive. The the really long ported barrel would be required to be a drag on the bullet with no real pressure behind it.

Certainly with enough time and money all of the options are possible. The reason that I brought the SD ported barrel with a SD suppressor is that this is an off the shelf system. I find that my SD system seems quieter to my ears than a 6" barrel with an attached suppressor. Again, thank you for sharing the long ported barrel with extended suppressor.

Scott

 

[LawBob]

Blazer Brass 124 or Lawman 124 is

… subsonic. It’s not advertised as such but it turns out it is. Its also not more expensive.

You can get the lawman in TMJ which keeps the lead down

“Lawman 9mm Luger 124 grain ammo offers a muzzle velocity of 1090 feet per second and a muzzle energy of 327 ft lbs.”

I mean with a long barrel it prob goes super but not in a blowback gun.

Speer Lawman 9mm Luger Ammo 124 Grain Total Metal Jacket - Ammo Deals

Speer Lawman 9mm Luger Ammo 124 Grain TMJ at Target Sports USA with free shipping availble. Enjoy great deals on 9mm Luger ammo for sale online

www.targetsportsusa.com

 

[LawBob]

Vs federal
The Federal 9mm 124 Grain ammo offers a muzzle velocity of 1160 feet per second and muzzle energy of 344 ft. lbs


The lawman has a lower energy so the RPMs will be reduced also. Slower fire.

 

[MitchWerbellsGhost87]

Vs federal
The Federal 9mm 124 Grain ammo offers a muzzle velocity of 1160 feet per second and muzzle energy of 344 ft. lbs


The lawman has a lower energy so the RPMs will be reduced also. Slower fire.

that might explain it. I always wondered if the 147gr reloads I was shooting were responsible for the damn near full-size Uzi Rate of fire I would achieve through the single feed SWD 9mm M10. I always assumed it was a combination of the heavy bolt, a little bit of feedlip drag from the zytel mags and maybe the suppressor bleeding off some of the gas pressure. Didn’t even consider that the ammo could be the cause for this.

 

[A&S Conversions]

Thank you for the numbers of the 124 grain. I will stock up on some of the lower power Lawman 124.

Scott

 

[LawBob]

that might explain it. I always wondered if the 147gr reloads I was shooting were responsible for the damn near full-size Uzi Rate of fire I would achieve through the single feed SWD 9mm M10. I always assumed it was a combination of the heavy bolt, a little bit of feedlip drag from the zytel mags and maybe the suppressor bleeding off some of the gas pressure. Didn’t even consider that the ammo could be the cause for this.

Completely unscientic explanation:

If 147 has the same powder charge as 115, the heavier bullet will travel slower, but think of newtons law about action reaction.

It’s pushing a heavier bullet and the bolt is reacting rearward more so

Now it all depends but I’d suggest that a 147 subsonic prob has a little more powder than your typical 115, bc it’s 27% heavier but only 12% slower (I know it’s not a direct correlation - but just for illustrative purposes) to get it to 1050fps or so. (115 is typically 1190)

If you want more power and faster shots, go with 124 NATO

It’s pushing 124 at 1200. So heavier bullet near same speed as typical 115

Caliber Multi: 9mm NATO
Muzzle Energy: 396 lb/ft
Muzzle Velocity: 1200 fps

Compare to 124 lawman 1090 and 124 federal 1160

Wwb115 is 1190
362 lb

So nato is about same speed w heavier bullet so see the energy rating.

Energy won’t necessarily mean what you feel but when comparing similar loads it’s probably a good proxy

 

[sigstroker]

9mm NATO is +P, the last thing you want to use if you're trying to be quiet.

 

[A&S Conversions]

I agree, but I think that since the SD design bleeds off propellant gasses just beyond the chamber, it is my understanding that the SD system was designed around supersonic standard pressure ammo. There have been quite a number of SD barrels ruined because subsonic ammo was was used which bled off so much gas that a bullet was slowed down so much that the bullet didn't leave the barrel. Other bullets came behind the bullet lodged in the barrel and bulged the barrel.

This thread is specifically about using the SD system on a Mac style RR machinegun. I have been unfortunate enough to have had a squid load in a semi automatic handgun. I noticed a sound difference and stopped. I was able to push out the squib load bullet from the barrel with a cleaning rod without damage. It would be very difficult to realize that there was an underpowered load and let go of the trigger midmag dump and not have at least fired another round, which could damage the barrel. At least with my HK clone 9mm SDs, standard 115 grain ammo seems to work pretty well and is quiet. The whole point of the SD is to dump a lot of the propellant gas in the expansion chamber down near the chamber end of the barrel. I have seen some HK clone SD builds that have drilled a couple of extra holes on the muzzle end of the barrel up against the other ports. Then those holes plus a few more were threaded. The owner could take a specific ammo and tune the speed of the bullet by installing Allen screws in the threaded holes.

The SD system tends to be a little quieter than muzzle mounted cans. Certainly some modern cans can out preform a SD system to the shooter's ear, because the end of SD can would be closer to the shooter's ear than a full size MP5 using subsonic ammo and a modern can. The original HK SD cans sucked. But modern SD cans are very quiet. I will have a SD upper on the Tenko. Hopefully I have one by this fall. I already have the SD suppressor. So all I need is the Broad River Tactical rotary delayed blowback SD upper.

Scott

 

[slimshady]

The original SD was created with the ports close to the chamber to reduce velocity because the end user, the military, didn't want to have to add a subsonic round to their supply chain. A civilian doesn't have that requirement, subsonic ammo is easily sourced. I would think a more efficient design would be with a series of holes further down the bbl, but retains the rear expansion chamber and modern baffles up front.

On a MAC this could be accomplished by putting the mounting point on the trunnion and turning the bbl down in front of a minimal amount of threads to secure the bbl in the trunnion with a pin to lock it in place. Then port up there, bleeding into the suppressor.

As for tuning, I recall a few integral suppressors for things like a Swedish K had the bleed holes down by the chamber and the ones closer to the muzzle. A threaded collar screwed over the bbl to block the chamber end holes for subsonic ammo, or left off to drop supersonic ammo to .380 levels.

 

[A&S Conversions]

So we are all on the same page, yes the original design of the HK SD was to use the 115 grain 9mm ammo that was in stock in Germany. Yes, a collector can buy subsonic 9mm ammo. I have found that subsonic 9mm ammo tends to be 20% more expensive than standard 115 grain standard 9mm ammo.

To be clear a SD system for a Mac style family of RRs is for fun. Is it a practical system? No, but I think it is cool and a lot fun. A SD can is a specialty can. It is designed for use with the ported barrel. But there is some standardization. Unless there is a standardized barrel that can be purchased off of shelf that work would need to be done by a Gunsmith that understands the how and why of porting a barrel. Then needs to create a can for that specific application. The custom long barrel version posted earlier in the thread is a unique way of combining the Mac style of mechanism with a ported barrel.

I have had some experience with getting custom projects done, like my water cooled M16 upper. It is very hard to find someone with the skills, the time, and the interest in doing the project. That is a tough combination to find. There is also the expense. I would think that $75 to $100 per hour would be about as inexpensive as most would find. A ported barrel would not be a 10 minute project. Neither would a custom suppressor. Because of the tight fit between the factory style bolt and barrel, a off the shelf SD barrel could not be used as a starting point. We could go down the rabbit hole of what could be do. Whatever custom solution would be used, custom would not be cheap.

So who will be the first to post themselves shooting a Mac style RR with a SD upper? There are piles of Mac style RRs shooting suppressed, but I couldn't find one with a SD style ported barrel.

Scott