I have seen that both shoot 700grains at 2400FPS!
Is it the same bullet diameter???

.500 A-Square = .510", standard load shoots a 600 grain bullet at 2450 fps

.550 Magnum = .550". It is a wildcat so there is no standard load.

They are not the same. The biggest difference, as has been pointed out above, is that the bullet diameters are different.

But both the .500 A-Square and the .550 Magnum are based on the big Weatherby belted case, i.e., the one used for the .378, .416 and .460 Weatherby Magnums, among a couple of others.

The standard .500 A-Square loading will launch a 600 grain bullet at 2,500 fps. I have done that with mine using RL-15 and H4350 both.

It should be possible to get at least 2,300 fps from the .550 Magnum with a 700 grain bullet.

BTW, Art Alphin of A-Square fame is apparently back in control of the company and is now in the process of relocating from Bedford, Kentucky to Glenrock, Wyoming.

I hope he can get hold of some quality control in the ammo bearing his name.

The 550 magnum (techinically a proprietary case) is a 3" weatherby basic, but functioning cases can be made from weatherby brass, you just seat the bullet a little long.

one CAN hit 2400 FPS with a 700gr bullet, and since the round is currently at a pressure lab, we'll have "real" data, i HOPE, soon.

RNS will have to post the details in the matter.

Like the 308 and 358 winchesters, there is some formula (which I have forgetten) which tells you how much faster the same case and pressure will make the same bullet weight go in different bore diameters.

I have found that BASICALLY (a generalization) that one can make the same SD bullet go about the same speed from the same case, in different calibers ... again, basically.

Neal has nudged 2400 FPS with a 700gr bullet in the 550 magnum over a chrono.

jeffe

quote:

The 550 magnum (techinically a proprietary case) is a 3" weatherby basic, but functioning cases can be made from weatherby brass, you just seat the bullet a little long.

So is there another "orginal case" for the .550 Magnum?? or is it the Weatherby biggest case the orginal???

//Ok

The .550 Magnum case is based on the big Weatherby case, given the common meaning of the term "based on" - as in derived from, generated from, used with modification, etc.

Put another way, it is identical in every respect to the big Weatherby case (blown out, of course) except that it is 0.09± inch longer.

The 550 Magnum will have true chamber pressure from a lab. True meaning the reading will be true case pressure.

RNS

Neal,

Kudos on having the .550 lab tested. Are you also doing the Express?

I'm sure I'm like a lot of experienced reloaders in thinking that I'm capable of judging pressures by "feel" but real data doesn't have an agenda.

Thanks,

Mike