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Suppressed M1A Ammo


Rekraps
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So, for a long time I have shot my M1A (Scout Squad) with a GemTech One (.30) can. As described in another post, there is no way to make this gun run semi-auto with subsonic ammo.  Anyway, I've got it tuned in with S&B 200gn 7.62x51 and it shoot stabile and accurate to 100 yards no issues. S&B stopped making the ammo and it's almost impossible to find now, so i found some Privi Partizan 200gn 7.62x51 with the same ballistics. Shoot identical. Well made.

Note that if you shoot with a barrel less than 18", the round will tumble. 

I'll post a video of me shooting the gun with subs.... very easy on the ears, quieter than 9mm subs through a smg. 

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I tried to muffle mine with the adapter that replaces the flash hider and a Gemtech Sandstorm.  I think the adapter was Smith Enterprise?

Long story short, I ended up getting some rub and sold the adapter.  I don’t recommend using it for anything beyond a brake or hider.  I also don’t recommend the Sandstorm or Outback II…another long story.🤣

 I load my own subs for my bolt gun and Encore pistol.  I primarily use 180’s with Trail Boss and haven’t encountered any stability problems.

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1 hour ago, Don. said:

I tried to muffle mine with the adapter that replaces the flash hider and a Gemtech Sandstorm.  I think the adapter was Smith Enterprise?

Long story short, I ended up getting some rub and sold the adapter.  I don’t recommend using it for anything beyond a brake or hider.  I also don’t recommend the Sandstorm or Outback II…another long story.🤣

 I load my own subs for my bolt gun and Encore pistol.  I primarily use 180’s with Trail Boss and haven’t encountered any stability problems.

Very good. Your M1A a std, scout squad or Socom?

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19 hours ago, Rekraps said:

Very good. Your M1A a std, scout squad or Socom?

Just a standard.  I’ve had it for about 25 years and bought it used.  I’ve hammered thousands of rounds of SA a Injun surplus through it and it still shoots great.

 May try to adapt it again.  I want to face the muzzle and make sure it’s square to the bore first.

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5 hours ago, Don. said:

Just a standard.  I’ve had it for about 25 years and bought it used.  I’ve hammered thousands of rounds of SA a Injun surplus through it and it still shoots great.

 May try to adapt it again.  I want to face the muzzle and make sure it’s square to the bore first.

I mention concentricity in my previous post about these guns. They are not manufactured to readily adapt to cans. Of the nine M1A's that I have, using GemTech adaptors/mounts, only four passed the concentric bore gage test. DO NOT bypass this. The doggone flash hider threads are just not that square to the barrel. I use Geissele bore gage rods work well.

My first real gun was my SA M1A standard, bought in 1986 at Ft. Benning. I used to shoot on the weekends on the ranges and one time the AMU was there practicing and they took my gun in and "adjusted" the trigger. Wow. Very nice gun. 

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Guys, after further shooting, the Privi Partizan 7.62x51 200gn, subsonic is not really subsonic. Out of my M1A Scout Squad, the rounds are shooting right at supersonic... too much. 

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3 hours ago, Rekraps said:

Guys, after further shooting, the Privi Partizan 7.62x51 200gn, subsonic is not really subsonic. Out of my M1A Scout Squad, the rounds are shooting right at supersonic... too much. 

How cold was it?  I’ve had my subs go super when the temperature and humidity drop.

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12 hours ago, Don. said:

How cold was it?  I’ve had my subs go super when the temperature and humidity drop.

It was in the 20's (I'm in Atlanta). I never thought of that. I looked up the specs of the ammo and it said 950 - 975 fps, which should have been fine out of my 18" M1A, but they went super (to the shagrin of my neighbors). Do you think it makes that much difference?

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20 hours ago, Don. said:

How cold was it?  I’ve had my subs go super when the temperature and humidity drop.

I looked up PPU 7.62x51 200gn specs, and the company says 1050 out of 22". I then looked up the impact on cold on the speed of sound, and it moves it just a little, maybe just enough to do the trick. So I'll wait till it warms up and try again.

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On 1/22/2025 at 1:10 PM, Rekraps said:

I looked up PPU 7.62x51 200gn specs, and the company says 1050 out of 22". I then looked up the impact on cold on the speed of sound, and it moves it just a little, maybe just enough to do the trick. So I'll wait till it warms up and try again.

I’ve had weird stuff with minor temp and humidity shifts.

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Final determination for my Scout Squad (18”) and Privi Partisan 6.62x51 200gn subsonic ammo.  
 

It’s not.  15 rounds over three days using a GemTech One. Goes super every round.  Shot S&B at the same time, hugely different and the S&B run subsonic every round. 
 

That’s all I have to say about that. Glad I only bought one box. 

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Good to know.  I wonder how much faster they are going over the sound threshold.  One day I’ll get a chronograph, but it’s not a priority for me.  10.2gr of Trail Boss under a 180gr keeps quiet for all conditions for me.

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4 hours ago, Don. said:

Good to know.  I wonder how much faster they are going over the sound threshold.  One day I’ll get a chronograph, but it’s not a priority for me.  10.2gr of Trail Boss under a 180gr keeps quiet for all conditions for me.

Excellent.  I’m just glad I did not order a case of the PPU ammo.  Unfortunately, S&B has suspended making the 7.62x51 subs for now.  I have 500+ so I should be okay. 

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On 1/26/2025 at 5:48 PM, Rekraps said:

Excellent.  I’m just glad I did not order a case of the PPU ammo.  Unfortunately, S&B has suspended making the 7.62x51 subs for now.  I have 500+ so I should be okay. 

They take all of the fun out of it.

If you do any refilling, that recipe holds true in all weather conditions at around 4K feet of elevation.  You could probably crank it up to 10.5gr at your altitude.  I’ve had them periodically break the barrier in colder temps and low humidity when warmer.  I’ve yet to have one go super at any temperature at 10.2.👍

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