Is this a common round in bolt/single-action rifles?
I've heard about this round, and are courious about the performances it delivers.

About a 10-12% average gain would be a good guess. I thought about one, for a couple seconds, once:

quote:

My gunsmith has had a 50 bmg improved reamer for about 10 years! He says that it will push a 750 Amax at 3350 from a 32 inch barrel. I have held the round in my hand and it is AWESOME! It eliminates all the case taper and looks like it is ready to kick some serious butt! He has reamers, dies, and all the know-how to put one together for you! His name is Brad Stair and he runs a shop called, "performance guns". He's from Texas, then moved to Colorado, and now he's in Utah.

[url]http://longrangehunting.com/ubbthreads/showflat.php?Cat=0&Number=59075&Main=58793[/url]

According to die maker CH/4D, there are five (5) versions of the improved BMG out there, so you have to be careful and I'd expect performance to vary slightly.
[url]http://www.ch4d.com/catalog/reload_dies/reload_dies_12.htm[/url]

quote:

a 750 Amax at 3350 from a 32 inch barrel.

Suicide Special?

I did some quick doodling in my design software.

50BMG AI (my quick version) - reduce taper, blow shoulder forward, 30° - gains 32 grains water capacity or 10%. Leaves all other dimensions the same (case length, neck length)

With 32" barrel, looking at about 2700 fps for the 750 Amax IF LOADED TO SPEC PRESSURE. If you load it hotter, which newer bolt guns can handle, you can drive it faster.

Hey Marty, What is spec pressure? And can you work some algebra to see what it would take to get to 3350

The pressure level you are using Marty must be quite different; the Hornady manual and Hodgden data both show attaining (at least) 2800 with ju7st the standard version and an A-Max.

Doesn't seem possible to "improve" it 10% and then get 100 fps less . . . .

Hodgden

Ahhhh, I get it. If you increase the charge, the additional pressure is released by the split barrrel resulting in lower velocity.

If the powder charge is kept constant, then velocity will decrease with the increase in combustion chamber volume . . .

In the typical "Ackley Improved" cartridge, there is velocity loss when using the originally configured cartridges in the improved chamber, and there is also a velocity loss when using reloading data intended for the parent cartridge in the improved chamber.

In all cases, due to increased capacity, it is necessary to increase the charge *just to get back to the original performance level* of the parent case. The increased potential of the improved version is not achieved until it is loaded back to full permissible (original) pressure and the added case capacity is then occupied with powder.

Collins, even as physically large as this cartridge is, pressures are not unusually high at 55,000 PSI (US milspec), nor should pressures be any greater in the improved version. Your chances of blowing a case or barrel is no greater than blowing one with a .30-06 case . . .

Actually, I did increase the charge. However, the OFFICIAL pressure to which the 50BMG is to be loaded to be safe in all weapons is 53600 psi max.

I entered the Barnes data (got the manual as I am on the Advisory Staff) for the 750 solid from the 30" barrel using 225.0 gr H870, it leads to 2625 fps in my software as opposed to the 2769 listed by the manual. Pressure is calculated as 51700 psi.

Similarly, Hornady manual data, 36" barrel, 750 Amax, 224 H870, book says 2800, software says 2640 fps with 44800 psi.

If I let the software optimize for the 750 AMax in a 30" barrel and run pressure to the max (53600) it renders 2750 with H50BMG as the preferred powder.

So it gains 100 fps over the other loads according to the software with about 35 gr more powder. It also shows the limitations of the software. And the software suggests that with the larger AI case, a longer barrel would be better suited to this version as muzzle pressure is high and there is more room for powder to work with ....

Hey, it's not me, it's the computer, I have no dog in this fight, just wanted to tell folks what the computer predicts. Heck, I have seen claims the 50 Spotter AI duplicates 50 BMG loads in short barrels ....

The "BS" flag is spot-on. The difference between 2700 FPS and 3350 FPS is about 50% in kinetic energy. Ergo, you would need about 50% more case capacity to get there. (Assuming same powder, same pressure, etc.)

Highly unlikely that 10% more case capacity would get you anywhere close to that.

quote:

Originally posted by Collins:
Hey Marty, What is spec pressure? And can you work some algebra to see what it would take to get to 3350

I forgot ... to get to 3350 with a standard BMG in a 30" barrel, it would have to be pushed to 120,000 psi .... go ahead, pull the trigger, as long as I get to be behind one of Collins' shields .... I'll bring my Medic kit ...

quote:

Originally posted by MartytW:

I forgot ... to get to 3350 with a standard BMG in a 30" barrel, it would have to be pushed to 120,000 psi

If I load to that pressure level, I guess I dont have to bother to improve the case first?

Is the quality on 50BMG brass good enough to take the stress of improving the shoulder?
I have got some reports on bad brass quality, so the cases cant be reloaded more that a couple of times. Is this a common problem, or is this mostly a norwegian problem you think?
Our ammo is mostly been produced at Raufoss (Nammo).

Hey Marty, I have no dog in the fight either, I'm only passing along one of the few "Improved" references I had found. Thinking it through though, my .30-06 AI doesn't get 10% increase and the case design proportions are similar.

I got the 55kpsi pressure spec from the data sheet posted at Watson's Weapons (M2 Ball Sheet)

Forgot;
460Wby, I see brass defects in every batch I've bought so far. I closely examine every round and every case any more.

Lately:
I got a batch of "match" ammo from AmmunitionStore.Com and one of 20 had a crack in the neck neck 1/4" long.

One of a 30 round batch of AP from Watsons Weapons came with the base of the case looking like it had been "crumpled", then straightened somehow and polished. Had the same marks on the shoulder and neck as if it had entered the die crooked. Case web area looks like a piece of aluminum foil that had been smashed and re-flattened.

One from a 30 round pile from a local custom handloader had a 3/16" crack at the neck/shoulder junction.

Given the exterior ballistics of the A-Max bullet, what point is there in hot-rodding it? Another hundred or two fps won't mean doodly at the ranges where this bullet really shines.

Besides, I don't think I'd like any more powder than what my "unimproved" McBros burns with each squeeze!

Things have taken an ugly turn when mine is the voice of reason!

Redial

quote:

Originally posted by MartytW:

quote:

Originally posted by Collins:
Hey Marty, What is spec pressure? And can you work some algebra to see what it would take to get to 3350

I forgot ... to get to 3350 with a standard BMG in a 30" barrel, it would have to be pushed to 120,000 psi .... go ahead, pull the trigger, as long as I get to be behind one of Collins' shields .... I'll bring my Medic kit ...

Bring a body bag!

I was just looking at the BMG/Fisher, basically improved taper and cut down to 3.2120". Looks like the BMG has around 10% more powder room with same bullet seating. I wonder how easily one could get to BMG spec with this round, and if there's any gain to be had. Pressure might be a bit lower with a fuller case, but is there an action that could take the BMG casehead that would prefer a 4 3/4" round rather than a 5 1/2"?
Also, anyone have the length of the 750 A-Max? Axial length of the boattail would be nice, too....
Thanks.

bwanabe

The 750 A-Max UHC is 2.565" long. Not sure what you mean by axial length but the BT is .300" long and bearing length is .700", plus or minus.

I'm interested in the different BMG Improved cases. What is the BMG/Fisher? Do you have dimensions on it, other than the 3.2" length?

Ray

Thanks for the bullet specs. By "axial" I just meant not along the side, but just the lengthon along the bullet's axis.
Dims for the Fisher are .7764" at shoulder, 2.5098" from bottom; 45* shldr, neck from 2.620"-3.2120" at the mouth.
So, with the A-Max seated to base of BT and base of neck, you have a 5.885" round. I bet that has about the same powder under it as the BMG....

Oops. Make that 4.885"!
We'll say 229g of water vs 255g for the BMG.
-That's under the A-Max and seated similarly.
Looks like his design intent was to maximize the case width, sort of a WSM on steroids. Might be a little more accurate in theory, and ought to produce very close to similar velocities.
Who has QuickLoad?

For what it's worth, Powley suggests 2900fps with the 750g at 50k CUP and a 30" tube, using a compressed charge of 230g of 870. Which makes it seem right reasonable to expect 2750....

Bwana

Check your PMs.

Cheechako