I've weighed out the full case capacity for .223 Rem. It's about 32.5 gr. for X powder.

So, I'm gonna punch the chamber out to Ack. Imp. which will give me more case capacity.

Shooting a Rem. 700 PSS, heavy, bull bbl. Heavy action, heavy duty gun. This is the same hardware as the 22-250 which holds a LOT more powder than any Ack. Imp. case in .223.

So, question is . . .

Insofar as the 22-250 holds a comparatively larger charge than the .223 Ack. Imp. why should there be a "maximum" load weight on the .223 Ack. Imp. if the case won't hold powder equal to the capacity of the 22-250?

I understand about the issue of case capacity, seating, and the volume in the chamber affecting pressure. Still, seems like the .223 Ack. Imp. in a solid, heavy gun would safely accomodate all the powder one might be able to dump into the brass.

BE ADVISED . . .

This is all hypothetical speculation. I'm not "topping off" -- but I'm looking to toss a 40gr. bullet at 4000 fps. in .223 Ack. Imp. and wonder about the theoretical limits of loading this caliber in a strong, bench grade gun.

[This message has been edited by Genghis (edited 01-16-2002).]

Propellant burning rate,is the variable,you omit. A 223Ackley case full of Re-25 is sedate,at best. The same filled with Unique,may kill you...............

I think I see where you're going with this. Your reasoning is right in some ways and wrong in many. I'll try to keep it as "non-technical" as I can.

If you take one action chambered for 460 Weatherby, and an identical action chambered for .223 AI, yes the .223 would hold a much higher pressure before it simply blew up than the same action in 460 would. You could say you have a much higher margin of safety before ultimate failure with the smaller round.

Here's why you don't want to use that margin:

The metal immediately surrounding the chamber doesn't know that there is a "bunch of extra metal that will hold if it fails." This metal doesn't care. All it knows is the chamber pressure acting against it. That pressure puts both compressive and tensile stresses on it at right angles--it's the tension you need to worry about most.

The closer the stress in tension comes to its yeild limit (measured in PSI--Not total force) with each cycle, the shorter the fatigue life of the structure.

So, just because the action will withstand one shot at say, 100,000 psi where a smaller action will only withstand 90,000 psi...doesn't mean you aren't doing damage when shooting at 70,000 psi.

By increasing the stress in the action at the chamber with every shot you take, you are increasing the chances that an imperfection (stress concentration) so small you wouldn't see it without an electron microscope will propogate--turn into a crack and get bigger and bigger with every shot you take.

Eventually, even a shot at 65,000 psi will blow it up after such abuse.

Here's a stupid analogy that should get some chuckles.... Imagine pressing on a balloon with your open hand. You can press pretty hard (lots of force) but since it's distributed over a large area you aren't applying much pressure to the skin. Simply touch it with a pin (very low force but high pressure due to the low area) and POP!

I know that's fundamentally wrong on many fronts but maybe it will help you get the point.

There's a reason SAAMI allows the same pressure from big magnums as standard rounds even when used in the same actions. That's what's safe.

So that's why you can't simply up the pressure becuase you're using a smaller cartridge in the same action as a larger one.

In addition, there's this:

If you could stuff a 22-250 load into a 223 AI case behind the same bullet you would get MUCH! higher pressures because you have a smaller chamber. How much higher would depend upon the load...but I'd guess you'd be blowing primers at the least.... There's a reason you can't load a 30-06 to 300 Win Mag velocities even though they may be built on the same action. It just doesn't work that way.

Does this make any sense?

Yes, makes perfect sense. But I couldn't explain it at the molecular level like you have. That's why I hang out in here!

Thanks.