MP5 SD Details

[Enfield577]

Hi Gents,
Not been on here for a while but been very busy making all sorts of suppressed stuff here in NZ. The latest project I am working on is a little fully suppressed 9mm carbine. I have heaps of experience making suppressors as such but for this one I want to incorporate porting to drop the velocity of standard ammo to sub-sonic via barrel porting. I have tried one idea (see picture) but it is is still running super, then I thought of the SD.

What I am after if anyone knows are dimensions for the SD porting, i.e. distance from chamber, no of ports, diameter and spacing etc.

Thanks

https://imgur.com/ZJBOoOY

[Historian]

So wonderful hearing from you it has been a long time.

Admired your talent, work, and generosity in sharing.

Heard that suppressors have been banned in Australia and
NZ. Update us on status.

Best

[Enfield577]

Hi there, thanks for that.
Busy as ever here and pretty much full time on gun stuff now, selling heaps of suppressed 410s and other stuff.

No truth in the rumour re suppressors here in NZ, they are if anything becoming more popular, I guess I thread 3 or so guns a week for cans.

All the best

[ninoslavt]

Porting starts 35 mm from the rear of the barrel's chamber,there's 30 holes, 10 mm spacing, 2,5 mm diameter. All holes are countersunk to 3 mm, externally.

[Enfield577]

Great Thanks

[ninoslavt]

You're welcome! If you need anything else about SD...

[Enfield577]

Hi Gents,
I tried the MP5 style porting though the nearest I can get to the chamber is 60mm (not like the suggested 30 or so). With this set up it is super quiet with subs, you really just hear the hammer drop but standard 115 gr high velocity is still supersonic, I even added another two rows of holes.

Anyway all good and I would say with the high velocity the noise you hear is the sonic crack well away from the gun, for the shooter it is extremely comfortable to shoot.

I should add that the extension to the barrel is to comply with NZ laws


photo host free

photo host free

photo host free

[Historian]

Again you have outdone yourself in elegance and efficiency of design.
The visceral joy your images evoke are indescribable. One
can almost feel holding each item in hand.

Thank you for sharing your admirable and enviable talent and art.
even more so in this sad and heart wrenching time the world is experiencing.

Best to you, my friend!

[Enfield577]

Thanks for those kind words, this one is a cool little toy. If It would only drop standard ammo to sub sonic that would be the icing on the cake.

All the best

[Historian]

Thanks for those kind words, this one is a cool little toy. If It would only drop standard ammo to sub sonic that would be the icing on the cake.

All the best

An anecdote from long ago win 1960s when reloading was fun as a precursor
to wistfully wanting a lathe.

Using a tool that allowed one to remove the bullet from case and removed a few grains
of measured amount the powder:

"Kinetic style bullet puller has a one-piece body and ergonomic handle;
innovative 3-jaw chuck that firmly grips the case rim.
just tap it on a solid surface as you would a hammer, and the powder and bullet drop
into the main chamber for re-use. A soft cushion prevents any damage to bullet.
Includes three case holding chucks that will accommodate cases from 5.7x28mm and .22 Hornet up through
the Winchester Short Magnum and Remington Ultra Magnum family of cartridges."



<< https://www.scheels.com/p/rcbs-powr-pul ... gIqRPD_BwE >>

[Historian]

Example: << https://www.youtube.com/watch?v=yz30wN58kAc >>
<< https://www.youtube.com/watch?v=NV0MPcfJjew. >>
<< https://www.youtube.com/watch?v=7sYamOQ0lHQ >>

Back in '60s technique was used to make up semi-jacketed rounds
for M1 Carbine and then use extracted bullet in next regular reload.

Guys got to have fun.

[Historian]

Final note on Reloading M1 carbine round: Energy 967 lbf; 44 Magnum 1041 lbf.
Clear lethality of round especially with semi-jacket ammo.

[Enfield577]

Interesting results, I took it out over the weekend and found that with 147Gr projectiles accuracy was poor at around 4" group at 25 yards, though this got better as more rounds were fired (I don't know maybe it wore burrs from the ports or something) But this ammo was subsonic and soooo quiet, you really did just hear the hammer drop.

Now with 123Gr ammo the grouping was spot on but an obvious sonic crack by the projectile down range.

BUT the really interesting thing was when we tried the chrono, the ports were doing nothing ! with ammo velocity barely below factory specs, so I guess this proves that the ports must be very close to the chamber (I understand the SD ports were much closer but cant get much closer with this gun). These were only 60mm (just over 2 1/4") from the chamber but the ammo was obviously up to speed by then.

So my next experiment is to make an identical barrel from the same blank but with no ports and see who that compares.

Interesting stuff....watch this space