I TALKED TO THE LAB TODAY AND THEY STARTED TESTING THE 550 MAGNUM FOR ME. I ONLY HAVE BASIC INFORMATION RIGHT NOW AND WILL HAVE THE FULL REPORT IN SEVERAL WEEKS.

800gr jacketed soft point
24" test barrel
2100 fps
7833 ft/lbs of muzzle emergy
63,000 psi
240 Momentum
132 Taylor KO
116 recoil Energy
24 fps recoil Velocity
0.378 Sec. Dens.
1861 Efficacy (energy * area)

Figures for a 12.25 # gun and 120 gr of powder

Neal, did you mean to type 700gr, or is it correct @ 800gr?

Keith

Keith

800gr is correct. which is the first weight they started with. After every shot I was told they have to move the bench back in place.

700gr and 600gr will follow soon. This is true chamber pressure as the barrel and cases have a hole drilled into them which line up. Then a pressure transducer is fixed to the barrel and actual chamber pressure is read.

.378 s.d.! Wow, cool.

Please pass the Ibuprofen.

Neal,

you are 'Da Man!!! Wish you well on the testing.

Rich
DRSS

quote:

Originally posted by 500grains:
Please pass the Ibuprofen.

Make that Prescription strength, (600mg)

RD,

based on this data we will figure out my 550 loads for the rifle you should build me. Included is a plastic pill bottle with 800 650Mg Acetaminophen, and a tube of Preparation H, since regulating this will likely stick your a$$ up around your shoulder blades! Or vice versa.

CONGRATULATIONS AGAIN NEAL!!!!!!!!!!

Rich
DRSS

quote:

Originally posted by RNS:
After every shot I was told they have to move the bench back in place.

Bet that is something "NEW" for the lab, at least with a "sporting round".

Keith

715gr at 2200fps in a <11# rifle aint bad to shoot!!

It just BETTER fit you!!

Outstanding, Neal!

I am sure it is a first for the lab

Excellent indeed.
The 550 Magnum will not be a bolt thrust issue if it is kept under 75,000 psi.

Quality brass can certainly handle 63,000 psi.

.550cal/800-grain bullet is way more than enough bullet with SD = .378, and 2100 fps is enough for classic ballistics, so ...

This all adds up to more than enough whomp with whatever weight bullet between 650-grainer and 800-grainer: SD from .307 to .378, pick your poison.

If I were less of a whimp I would build a 550 Magnum and load a 650-grainer to 2400 fps (SWAG). I would want an FN copper solid and a copper monometal like a GSC HV for the "soft."

At the rate Stuart Satterlee is going, my 500 Mbogo will be a CZ and the Satterlee action might have to be turned into a 550 Magnum.

I see that the GSC HV is 600-grains and the GSC FN is 700-grains:

.550cal/600-gr = .284 SD
.550cal/700-gr = .331 SD

That'll do, averages out to 650-grain.

My burning question now is what Twist for the barrel of a .550 Magnum? 1:18" standard?

I SWAG my barrel to be 24" stainless with a 1:12" twist, and 3" Knoxform of 1.250" diameter with a straight taper to about .835" to .850" muzzle diameter in a McMillan stock and 10.25 lbs bare weight. No Brake. With a 2.5x Leupold, rings, 4 rounds of ammo, buttstock ammo carrier, a light sling, and two recoil pads, ought to be about 12.25 lbs field ready and recoil like Neal's test gun.

This really is the maximum stopping rifle in a bolt action. No doubt about it.

Still portable, still manageable. No skeletonization of the common bolt face. Easy 4-round capacity in the common CZ action which can handle more pressure in this cartridge than any brass would ever allow. Easy brass from blown out 460 Weatherby.

Brass availability with proper headstamp.

Now real pressure data.

unless you get a CUT RIFLE your choices in twist are 16, 18, and 20 ... unless one wants to pay about 300 bucks for a faster twist button. as all button rifled require a specific button.

cut rifle? badger and cutrifle can probably cut you anything you like.

if mcgowen gets bauska's button, it's an 18 twist.

not a twist war, just cold hard facts

RIP,

NOBODY has ever accused you of being a whimp, a horse's a$$ once or twice, but never a sissy around recoil.

Join the club, build one of these, and go happy.

Rich
DRSS

I would like to know what twist rate Neal's test barrel was for that pressure data.

Not to start any "twist war," just curious.

I know Rob liked a 1:16" twist on the 600 Over Kill.

Way to go Neal and great data! Congrats-Rob

It was from PACNOR and it's a 20"

Neal,

Do you have barrels in stock? I noticed that the only one listed on the site is 16".

thanks

Les
want to shoot a 550 expres? btw, I used to live in Deer Park..
jeffe

quote:

Originally posted by jeffeosso:
Les
" I used to live in Deer Park.."
jeffe

I'm sorry you have to admit that

The express is what I plan on building. I got a Mark X with nothing screwed on the end.

I will try to take you up on the offer though. When I get back to the states we can see if we can work out a time.

Congrats, Neal. 116 ft.-lbs. of recoil energy ain't bad at all, considering that you are launching 800 grains of bullet at 2,100 fps.

I would think that the 700 grain load would be the one I would want, however, and I eagerly await your results.

I checked it 20"

Neal, did you get the pictures of my 550 from a month or two ago? Got a new camera and I'm setting up to photograph a bunch of rifles to sell. I can do another, better one.

Hey hey hey. McGowen Precision Barrels is indeed shipping barrels now. I have a .308 barrel on the way from them, for a .300 Lapua. I asked about the rumored acquistion of the Bauska tooling for .550 barrels, and it seems they have made an offer to buy the tooling. That would be a quick transition from defunct Bauska barrel to McGowen barrel in .550.

Now if they will offer a 12" twist ... those .550/800-grainers might shoot staight.

Neal,
What powder is that 120-grain load for the 800-grain bullet?

quote:

Originally posted by RIP:
Now if they will offer a 12" twist ... those .550/800-grainers might shoot staight.

All you got to due is buy the button, and I bet they'll do it.. or order 15 barrels.

Well heck, why not fully modernize this wonderful new stopping rifle and give it a 12" twist? Pressure and velocity differences from a 12" versus 20" twist ought to be less than 1/2 of one percent.

Also the sensation of increased torque in the hands will give the illusion of greater killing power.

RIP,

a suggestion that the slower twist might be a lot easier on those inexpensive cast bullets for us po folks practice loads!

Rich
DRSS