Community for Kel-Tec Shooters banner
1 - 10 of 10 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter · #1 ·
Just put together my form 1 can and was wondering what everyone likes to feed suppressed 9mm
 

·
Registered
Joined
·
905 Posts
Just put together my form 1 can and was wondering what everyone likes to feed suppressed 9mm
I understand that 147 grain is subsonic so lends itself well to suppression.
 
  • Like
Reactions: BJK

·
Registered
Joined
·
1,007 Posts
Yup, standard pressure 147s are subsonic. I have no idea about +P or +P+. But you don't want to feed the sub2k a diet of them anyway. At all? IDK. Can you buy special 9mm for can use? Sure, but why? Esp' if it's more expensive. Heavier bullet weights will also be subsonic.

I reload my own and was told that my suppressed SBR (not a sub2k), was ridiculously quiet at the last "anything goes" outlaw rifle match. But accuracy suffers with the load and can. I need to revisit the load.
 

·
Registered
Joined
·
18 Posts
Yup, standard pressure 147s are subsonic.
I was wondering about that. If they come out of a pistol barrel at 1,000 fps, wouldn’t a 10% increase from a 16” carbine barrel increase velocity to over 1100 fps breaking the sound barrier?
 

·
Registered
Joined
·
1,007 Posts
I haven't tried all commercial 147gr loads, very few in fact. Maybe some are supersonic out of a long barrel, but I doubt it very much. There's only so much room for powder in a 9mm case and most 9mm loads are for handguns so slightly slower powder tailored for a more efficient burn in a long barrel isn't really an option. You're correct about the velocity increase out of a longer barrel though, but it's not as much as you'd guess. The pressure drops very rapidly in the longer barrel.

Assuming peak pressure of 36k psi in 4" of barrel, it probably peaks in less barrel but we'll use 4". We double the volume to 8" and the pressure is now 18k according to Boyles Law. Double it again and the pressure is 9k. That's not much pressure to accelerate a bullet with. It might actually be decelerating at some point. But that's just a hypothetical.

You might need to test various loads to find one that stays subsonic in a long barrel. But I think it'll be more of a potential issue in winter when the speed of sound changes with the ambient temp'. What is subsonic at 90°F might be supersonic at 20°. There are speed of sound calculators online if you're interested in seeing the effect.

You'll also find that faster powders will have a huge effect on how the can works. Back to Boyles Law, if the pressure peaks at 2" down the barrel pressure at the muzzle will be even lower than in my example above, upping the efficiency of the can. I used that info' to build some ammo for an outlaw match a few months ago (mentioned above). How does one tell powder burn rate in commercial ammo? I doubt they'll let anyone in on the load info. Maybe that's why they make specially marked subsonic loads for cans, faster powder? Just speculation. But if I do it for quiet ammo I'm certain they can figure it out too. But this paragraph only deals with muzzle blast that the can needs to handle and not velocity.

Since I don't buy ammo but make my own I can't help beyond theory. Keep waiting and maybe someone will turn up who has tested different commercial loads. But with a can on you will know immediately if the bullet is supersonic. I would be extremely surprised if you found any standard pressure ammo to be supersonic with a 147 or heavier bullet.
 

·
Registered
Joined
·
18 Posts
But with a can on you will know immediately if the bullet is supersonic. I would be extremely surprised if you found any standard pressure ammo to be supersonic with a 147 or heavier bullet.
Thanks for the super informed post. I ordered some 147 fmj so we'll see. I'm not sure I can tell wearing hearing protection. As mentioned elsewhere I tried Stelth 165gr and it was super quiet and accurate, but underpowered to cycle the action (thanks for the education on PF) I can still shoot those for sound comparison.
 

·
Registered
Joined
·
1,007 Posts
160-165 loads... In the past I'd use them because of the gentle push on the shoulder. Same minor PF though and the Sub2k loved them. The sub2k never malfunctioned, well it did if I used alum' cased ammo. But brass cases? Never, not once. Then I switched to the B&T GHM9 SBR and it would randomly malfunction. Understand they were butterfly fart loads designed to just make minor PF. I grew tired of that and made 147gr BF loads, again random malfunctions. Sure I could go back to the sub2k but there were other issues with the long barrel and barricades and such. Now I just use full power loads and suck up the additional mousegun recoil. Now the GHM9 doesn't malfunction. But competition is a game of split seconds and that's why I used the BF loads. I've often pondered what it would take to make a short barreled sub2k. I'll leave it to KelTec since I don't have the resources. It would be a nice gun to have IMO; light accurate, easily packable.

Today if the zombiepocolypse were to happen either firearm would work for me. With a can. Zombies are drawn to sound or so I've seen in the documentaries.

Please let me know how you make out. Others read these threads and might benefit from your data. Just be aware that it's hard for the ear to discern minuscule differences in dB and the gear to accurately measure it is quite expensive. My ear only detects, "Hey, that's quiet!".
 

·
Registered
Joined
·
229 Posts
Sharing data.

124g NATO (supersonic)


147g Federal HST (subsonic)


147g Freedom Munitions (subsonic)


147g Speer Gold Dot v2 (subsonic)


124g HST (supersonic)


All data collected at sea level. Hope it helps. I also have labradar reports for Sig 365 ammo and Blazer 115g - both are still supersonic at 50 yards.
 

·
Registered
Joined
·
18 Posts
So I got some 147 FMJ and brought it to visit my jailed CQB. Very quiet and no malfunctions but I can’t seem to get tight groups. I’m not ruling out operator error but next outing I’ll shoot a mag each of 147 and 115 grain to compare and see if it’s just me. I also ordered couple of boxes of federal syntec 147 to see if thats any better.
 
1 - 10 of 10 Posts
Top