I have a CZ 550 action & stock at the smith's now for a .510/460 Long (.500 A-Square, .510 JAB, ect). The barrels should be in by the end of the month, and I need to know...

A) Diameter/Taper/Diameter of barrel at different points on the barrel.

B) Optimal barrel length for BMG mil-surplus bullets (620gr-700gr), A-Max (750gr), and hunting bullets (550gr-650gr) and for a balance point on the gun.

This is the first 'custom' job I've ever had done so all info would be appreciated. Thanks

BMG,
Good man, this is into the biggies in the best way. Wish I had had the money but I bought mine previously owned. From what I can remember my barrel is cylindrical for five inches then tapers with a reverse taper for about two inches then straight to the muzzle. The reverse taper is like the neck on a coke bottle. I hope that doesn't sound stupid. I am sure there is a technical term for it.
At the muzzle mine is 0.925". Length is 23.25 Inches. Wow, first Alaska Airlines plane in 3 days just went over.
I would go with 26" length and if you feel eccentric go with 25". See how this feels on your rifle. Long is NOT wrong and you can whack off more if you want. Besides the extra little velocity the muzzle blast will be reduced and farther from your ears. All good points.

If weight is a concern keep the barrel somewhat on the slim side but enough to make a little point heavy, this way you can play with lead in the butt to get just the right feel for your style of shooting.

Overall weight should be around 12-13 pounds ready to hunt. This'll keep recoil/recoil velocity within tolerable limits and isn't so heavy you'll want a wheelbarrow. Also get a Qwik-Set sling from Murray Custom Leather in Texas. Nice!
Good luck and keep us informed.
My two cents.

I'm having my 500 Jeffrey built with a 25 1/2" barrel, thats the length of the blank I got. The muzzle dia will be ~.875", whatever the dia of the Ruger #1 458's, as I'll be using a barrel band front sight off of a 458 #1 barrel.

I also agree with the finished weight of ~12#'s, no reason to make the gun unpleasant to shoot. I'd rather have a slightly longer and slender barrel, then a shorter stubbier one.

I'm building one of these also. I'm using a Pac-Nor barrel 26 inches long and with a KDF brake added. I want maximum weight so a barrel diameter at the crown of about 1 inch with a three inch shank of 1.2 at the receiver is recomended. -Rob

BMG,
It's about time you turned Kevin loose on that gun! Actually, he has been busy in some business dealings with a couple of other entities, setting up to produce high dollar target and hunting rifles on the likes of Nesika and Dakota actions. Better get him while he is still available.

All the guys above have good suggestions. I can just tell you what I have done and would like to do.

Both my barrels are 1 in 10 twist stainless by McGowen.

My BRNO ZKK 602 has a 23" barrel that has 3" of straight shank (1.2" diameter) and then a straight taper (target contour) to 0.875" at the muzzle. This gun weighs 12.5 pounds with scope. The second generation 510 JAB.

My Ruger No. 1 has a 27" barrel that has 6" of straight shank (1.2" diameter) and then a target countour straight taper to 1.000" at the muzzle. This gun weighs 13.5 pounds scoped. The first generation 510 JAB.

The two guns are about the same length overall because of the differnt actions, the Ruger being more compact. A detachable muzzle break screws onto each, which adds about two inches to the above barrel lengths. Kevin made these brakes.

If you want a target rifle go with a longer and heavier barrel. If you want a hunting rifle go with a lighter barrel. The thread diameter of a tank-style/clam shell brake might influence you if such is used.

If I build another, it will probably be a 22" to 24" barrel with a sporter contour down to 0.800" to 0.810" at the muzzle, and no brake. I will aim for about a 10 to 11 pound gun with no scope. The third generation 510 JAB.

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Good huntin', shootin', and spear chuckin',
RAB

On a related note...

Are there any special throating considerations if I want to "plink" with surplus .50 BMG bullets out of a .500 A-Square? My first thought is that it would have to be throated a little longer, but that's just by looking at the ogive of hunting vs. surplus bullets. I don't have a handy way of actually measuring the two to compare (or at least I don't know the technique).

SamB,
My 510 JAB is based on just this concept. To seat the 750 grain A-Max out to 4.76" COL you need 0.588" of throat.

Throat is freebore plus leade. You could do this with 0.3" of freebore plus 0.288" of leade incorporated into the reamer, which I have. Or you could take the standard 500 A-Square reamer with 0.400" freebore and little leade and just extend the freebore with a throating reamer, which Kevin Jenkins has also done for me.

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Good huntin', shootin', and spear chuckin',
RAB

To the good Dr.,
Have you tried the 705gr AAA Ammo bullets yet?

ps. The LW barrel is a SS 1:10", 8 groove, 1.25" x 28" blank

You know you could leave it at 28" like those old .425 WR's.

BMG'
I am going to be trying them in November. I will also be trying the 850 grain GS Custom HV in the 50 BMG to try to get a BC calculation for that "prototype" bullet. I will let you know.

Like you, apparently, I travel a lot and can't practice my hobby as much as I would like.

Good choice on your barrel.

You will be well armed for head shots on terrorists, if you were to get a chance to go bin Laden hunting.

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Good huntin', shootin', and spear chuckin',
RAB

If any of you guys hunt with me, please do not expect me to carry your rifle, because I won't even be able to hold the heavy rascal while you piss...1" at the crown, WOW, thats got to weigh 15 lbs. loaded with scope or maybe more...soooo this brings up the reason for this post..I happen to have a set of chrome spoke wheels that came off a model A ford that should be a viable addition to your rifles.

I also have visions of Buffalo parts hanging in the branches and scattered throughout the veld, along with bruised and battered happy hunters sipping sundowners in the everning shade.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Ray,
The 1.000" muzzle is on a Ruger No. 1 "Shop Mule" for target and load work up. It weighs 13.5 lbs with scope.

If I were buffalo hunting with the 510 bore I would would have the rifle that is 0.875" at the muzzle and weighs 11 pounds with iron sights. It is a BRNO ZKK 602 in a sedate appearing express style stock from McMillan, solid brown color like walnut. The stainless barrel (McGowen, 10 twist) is finished matte black and has a set of express sights (NECG front, Wisner rear) and a barrel band sling base. It resembles one of your nostalgia pieces if you don't look too close.

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Good huntin', shootin', and spear chuckin',
RAB