Reduced 223 load with 22 supressor

[historicfirearms]

I've been playing with reduced power 223 loads out of my rifles to find a replacement for 22lr. So far I've had pretty good luck with around 2 grains of Red Dot and a couple different boolits. Velocity is around 900 fps and accuracy is acceptable.

I am wanting to try shooting some of these loads out of my Gemtech 22 suppressor, but would like to make sure I'm not going to blow it up. Does anyone have a formula for figuring out estimated muzzle pressure? I am thinking that a HV 22lr round out of a 3" pistol barrel would have a higher pressure than my reduced power 223 round out of a 20" rifle barrel, but want to see some numbers before I try it.

The boolits are not tumbling at 25 yards, so baffle strikes shouldn't be a problem. Any other things I should consider before trying this?

[Lonegun1894]

I wouldn't think the muzzle pressure would be anything to worry about considering what you're doing. Now if you were to use full power .223 Rem loads with a .22LR can, then I would be asking you not to do this. You also hit on the main thing I was worried about when I first started reading your post, and that is baffle strikes. Since you said it is stable at 25yds, I would say you should be safe to assume that it is also stable for the first 6" or so that most .22 cans are long. What I would do is fire a handful of rounds through the can and check the target again to make sure that you don't have any turbulence in the can causing the bullets to be unstable, but you should be fine. I would check this with mine but my .223 Contender isn't threaded, yet. I have been playing with the same kind of thing as far as .22LR replacement loads in .223, would you mind if I ask what other bullets you'be been playing with? So far, my experimentation has been limited to the Lee Bator and the Lyman 225450, and I need to do quite a bit more testing before I can help with load data, cause so far, I have good results at 50yds, but my low velocity loads seem to fall apart by the time they get to 100 yds.

[kencha]

FWIW, Quickload gives calculated muzzle pressure.

If you give me the specifics (load data and barrel length) I can tell you what it guesstimates. I don't know what muzzle pressure of a 22lr is though (and I sure as heck am not smart enough to know how to calculate it), so with nothing to compare it to, I'm not sure it would be of any help.

(e.g. Using 16" barrel, with 2.0gr Red Dot, Lyman 57gr 225462, 2.16" OAL, and everything else left at default, QuickLoad says it should be about 1190psi at the muzzle.)

You might want to just contact the suppressor manufacturer.

One other thing to consider is muzzle thread length. Some 22 suppressors are meant to be used only on a barrel with 0.4" thread length, while 223 are usually threaded 0.6". They do make spacers for just this purpose (just flat ground washers, essentially), and some suppressors will work fine with either length.

I've worked up something similar for 25-20, which was easy with its small case volume, and am in the process of doing the same with 300BLK using light cast bullets, just because. I don't have any Red Dot, but found the powders I tried to be very position sensitive (Unique, Clays, and Trail Boss). Some had as much as 300fps variance in limited tests comparing powder forward and powder rearward. Not wanting to use any filler with a suppressor, Trail Boss and enlarged flash holes (which renders the brass unsafe for using with standard loads) has been the only way I have found to achieve consistent velocities.

Since the 223 is going to have even more case volume than the 300BLK, powder position sensitivity may be something for you to look at as well. (Not an issue if you don't mind the possible velocity differences or the PITA procedure of making sure you always point your barrel up or down before shooting.)

[historicfirearms]

I have been playing with the Bator and the NOE 37 grain boolits. 20" 1-9 twist barrel with 2.0 grains Red Dot.

[sackot]

I agree with Lonegun1894: absolutely nothing to worry about with loads like that. You could use a silencer made from cardboard and get away with it.

The way I've seen it calculated is open to criticism, but just take your expected peak pressure within the cartridge (I would guess less than 10k psi for 2gr Red Dot) and decrease it by a factor based on the ratio of your cartridge volume and the total volume of cartridge+barrel+first chamber in silencer. Then calculate hoop stress for the tube wall thickness of your silencer (calculators and formulae found online) and compare this to yield stress of tube material. Then realize that paper would have been just as good as cardboard.

It's a good thing if the silencer can be dismantled for cleaning. IMO you're more likely to have problems from build up of carbon and unburnt powder than anything else, and I'd be happier if I thought I could recover any errant filler or gas checks.