sub-sonic 9mm loading advice??

[Mobuck]

After committing to assembling a suppressed AR 9mm PDW, I've found that most of the factory ammo on the market goes super sonic from a 10.5" barrel. I haven't loaded any 9mm for a few years but the Dillon is sitting there ready to go. Looking through my data, I found a couple of loads that will utilize powder I have on hand requiring only the purchase of bullets---a far less expensive option than a new shorter barrel.
Any experience with loading 9mm 147 grainers @ 850-900 fps from a handgun length barrel? I'm just guessing these will stay sub-sonic in the 10.5". A Chrony check will confirm.

 

[mike campbell]

"Any experience with loading 9mm 147 grainers @ 850-900 fps from a handgun length barrel?"

I do, but I'm not sure it would apply to other guns. I'd be concerned about OAL. I have buddy who can't make the 147's work in a camp carbine due to OAL ... of course, reducing it alters the recipe and increases pressure.

Seems you may be in virgin territory? requiring special attention to OAL and reduced charges, etc.?

 

[Mobuck]

"Seems you may be in virgin territory? requiring special attention to OAL and reduced charges, etc.?"

I have a plan. I'm going to try a recipe using a "fast" powder like TiteGroup to achieve a muzzle velocity in the 900 fps range from the 10.5" barrel. Hopefully, this solves 2 problems by maintaining sub-sonic velocities and reducing excessive buffer slamming and recoil.

 

[Rick Courtright]

Hi,

Nothing to offer with 147 gr bullets, but a buddy used to shoot 115 gr commercial lead RN over a light load of Red Dot. At the time, he was loading for several folks who got together at an indoor range every week and all shot full sized 9mm pistols (4-5" bbl range?) What he did was to take the Alliant book load, drop 10% on powder (normal practice for anybody), then work it up 0.1 gr at a time until everybody's gun cycled reliably. I think he was about 0.2 gr below Alliant's published max when he settled on "the load" and I think that was almost perfectly in the middle between starting and max loads.

Dunno if he ever chrono'd it, but I know he could hit soda cans at close to 100 yds out in the desert without too much trouble, dispelling a myth one of the group tried to spread that "You can't hit anything with a 9mm!"

Rick C

 

[Mobuck]

I discovered yesterday that I have a box of 147 grain Speer (possibly the forerunner of the GoldDot) in a box of odd bullets I was moving while cleaning house. Got the Dillon off the shelf, sorted through my powder stash, and loaded about 20 for a test run to see if they function. Using my standby, AA7 at a book claimed 825-850 fps from a 4" barrel, may get me what I'm looking for.
Just hoping I can manage the right combination of power to cycle w/o exceeding 1050 fps. I have some TiteGroup but AA7 has been my 9mm go to powder for years. Dropping the charge from the just below max charge for 115 bullets to 5.7 grain which is middle of the road for 147 took a little fiddling but I'm right on it now-doesn't take much movement of that powder screw to make a big diff.

 

[Mobuck]

What I found today: 5.8 grains of AA7 gave me 100% function with the 8 ounce buffer @ 940 fps 5' from the muzzle of the 10.5" barrel(100 fps more than was listed from a 4" barrel). I'll bump the powder to 6.0 and do some accuracy tests. I may try to get into the 975-1025 range once I get the bullets I've been eyeballing.
For what it's worth: the AR 9mm is a totally different beast vs the common rifle calibers. I initially used the recommended 6.5 ounce buffer and got far more recoil than should have been getting. The 6.5 oz. is probably OK for the 8" and shorter barrels but on the 10.5" was not holding the bolt closed long enough and allowing the bolt to cycle too abruptly which in turn caused the buffer to pound the end of the buffer tube causing increased felt recoil.
Another interesting tidbit: The published figures on 9mm+P 147 grain HP from a 4" handgun (1000fps) shows it has as much energy as the sub-sonic loads we're killing deer with in the 300AAC.

 

[Mobuck]

The load I listed seems to be accurate enough for my purposes. No failure to function during today's zeroing of the red dot optic. I found a guy who has a 9mm muffler to "sound test" a few(his muffler is 1/2 x 36tpi so won't fit my threads) and muzzle signature is satisfactory and most assuredly ear safe.
My bullet order showed up Friday so now I can work on my final load development. Maybe try to get dialed in on a velocity of 950-975 from the 10.5" barrel with a muffler installed(when I get that out of NFA jail). At this point, it's not objectionable with a 3" "forwarder" installed but it's certainly not hearing safe.

 

[krw]

I hope you wont be disappointed when ur suppressor arrives. I have 2 300 BlkOuts. 10 1/2" upper for papered SBR and a Model 7. The AR platform makes a lot of noise. The Bolt gun sounds like a pellet gun. I also shoot HK USP Tactical w Omega 9 suppressor. It does a good job. IMO the perfect suppressd platform is 45acp. They're subsonic to start with

 

[Mobuck]

Definitely a big diff between bolt action and semi-auto on most calibers. I let a couple of friends shoot my suppressed 22/45 vs the RAR and their comment was "It's nice to shoot but still louder than the rifle". Then I shot a couple of rounds while holding the 22/45 slide closed with my thumb(not that difficult especially with sub-sonics) to show them that the sound they were hearing was mostly the mechanical operation of the pistol.
I did consider the 45 ACP but don't have a 45 pistol and no intentions of getting one. Have buckets of 9mm brass and Dillon already set up so that affected my choice. Also magazine availability and capacity made a difference.
The 10.5" 9mm suppresses well enough once the ammo stays sub-sonic.

 

[Mobuck]

I'm getting the velocity I need (approx 950 fps from the 10.5" barrel) with good accuracy and function using AA7 @ 5.9-6.0 grains. Could go a little hotter but that puts the velocity in the range for which the bullets claim bragging rights.