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Posted: 10/6/2007 1:17:54 PM EST
[Last Edit: 10/6/2007 4:29:38 PM EST by DeltaII5]
So I'm awaiting my 762SD right now.

I've read that you aren't supposed to use subsonic ammo in a fluted chamber? Is this true, I've only come across this advice once though.
Link Posted: 10/6/2007 5:24:23 PM EST
[Last Edit: 10/6/2007 5:24:56 PM EST by MisterPX]
Got no idea why not. Use 9mm subs through my PDW clone all the time.

BTW, you're the first person I've heard say that about fluted chambers
Link Posted: 10/7/2007 9:37:56 PM EST
[Last Edit: 10/7/2007 9:38:50 PM EST by Tactical_T]
Well, that sux. Guess I better scratch the can idea.

Is the common to all .308 gas guns (AR-10, FAL, etc.) or just the delayed blowback system on the HK-91 rifles?

I know the FAL have some sort of adjustable gas system to dial it in for the ammo you are using. I've heard of guys using an adjustable gas block on their AR-10's (JP) so they can use them with cans, though I never asked if a re-charge was still required after every shot.
Link Posted: 10/8/2007 6:11:44 AM EST
Isn't subsonic rifle caliber ammo designed to work that way on all rifles. Even 5.56 subsonic is the same way. You can do it but it's probably best shot out of a bolt gun...because that's what you'll have anyhow.
Link Posted: 10/10/2007 7:25:32 AM EST

Warning! Do not fire any subsonic rifle caliber ammunition in H&K firearms or any firearm which has a fluted chamber, This type of chamber prevents cartridge case obturation, allowing propellant gasses to escape out the breech, and possibly sticking a projectile in the bore. Subsequent firing with a bore so obstructed can cause serious injury or death.

Will any subsonic .308 cycle? Same goes for 5.56 as i'm gonna be switching the can between.
Link Posted: 10/10/2007 8:22:25 AM EST

Originally Posted By DeltaII5:

Will any subsonic .308 cycle?

Not to my knowledge.
Link Posted: 10/11/2007 4:28:34 AM EST
Standard .308 muzzle velocity is somewhere in the 2800-3000 FPS.

To get "sub-sonic," you have to drop that velocity to roughly 1000-1100 FPS depending on conditions.

I've never hand loaded a round in my life and know nothing about it, but for a .308, 1100 FPS is almost 1/3 the standard velocity so... 1/3 the charge?

Either way, it's significantly lower pressure.

That's why, as it's been suggested, you probably won't find a subsonic round to cycle the action.
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