Wow $415 for the smithing services is a bargain. Especially from a company with experience. I also agree the .495 and .500 A-2 are the easiest fifty conversions out there. R.

quote:

Originally posted by srshooter:
RIP, how well did your 1.25" barrel fit into the McMillen stock? I had decided to go with a 1.375" diameter, 22-24" long, with the first 3.00" from the receiver a straight 1.375". Then from there, tapering to about 1.00" at the muzzle. I figured that this would get me a 11-11.5 pound unscoped rifle. How well do you think such a barrel would fit McMillen's stock? You are pretty close to my goal at 10.75 pounds though and I may go with that. By the way, nice rifles! Yours is close to what I have in mind. What's the barrel length on the Ruger No.1? Guessing.........28"?

1.25" barrel shank diameter is fine. It fits the McMillan stock better too.
Mine has 3" of cylinder shank including the threads, then straight-tapers to 0.870" at the 23" Muzzle. Screw on brake makes for 25" barrel length with brake.
This is close to the old Harry McGowen #7-26" Medium Target contour (~6 lbs. in .308 caliber) that is .875" at the muzzle.
The old Harry McGowen #8-28" Heavy Target contour that is 1.000" at the muzzle weighs 2 lbs more: 8 pounds in .308-caliber.

My Ruger No.1 in 500A2 has 6" of cylindrical 1.250" shank (Knoxform) then straight-tapers to 1.000" diameter at the 27" muzzle.

A scout scope base was put on the long Knoxform of the Ruger No.1.

Both of my barrels did have some finish turning and shortening at both ends by my smith.
They both started at 28" length and ended up 23" and 27".
The 500 Mbogo will be 25" long in the barrel, so right in the middle of these two, and it will be 0.820" at the muzzle, and a lighter sporter contour, instead of the heavy straight-taper target contour.

You better stick with 1.250" shank diameter and no bigger than 0.875" muzzle diameter at 24" if you hope to be closer to 11 lbs. rather than over 12 lbs with a CZ 550 Magnum action and the McMillan "standard fill" stock.

You can always add lead or mercury to the stock to add weight and balance.

quote:

Originally posted by srshooter:
RIP, it sounds like you ordered the Shilen #7 barrel contour from McGowan. McMillen says their CZ 550 Safari Magnum stock will only handle a Douglas #5 barrel contour. The #5 is a 1.150" stock that tapers to .700" on a 26" barrel. That seems way to thin to me, at least for a .500 A2. That may be good for a .416 but not for a .500!! What gives?

The barrel channel of the McMillan stock was enlarged by sanding and scraping to fit the approximately #7 barrel contour just fine.
I would not want to go any bigger though. another reason for you to not do a 1.000" muzzle diameter, nor shank bigger than 1.250".

My barrel channel also holds the secondary recoil lug of the barrel and there is a hidden all-thread steel crossbolt backing it up, all buried in brown epoxy.

The last word on building a 500-A2 on a CZ 550 Magnum:
Spelling corrections: "McMillan" and "McGowen"

Oh yeah, use either a 10" or 12" or maybe even an 11.7" TWIST if you want to shoot any bullet well from zero to 500 yards, and especially if you want to shoot the 750-grainers out to 1000 yards in the slowpoke.



Easier to measure on the back side of the target:


That is a 10" TWIST barrel that did that 100-yard 3-shot group measuring 0.170" with 705-grainer at a slowpoking 2126 fps.

RIP,

I thought you said at one time that your single shot ruger was a 15 twist?

quote:

Originally posted by ptaylor:
RIP,

I thought you said at one time that your single shot ruger was a 15 twist?

No way! Never! You are badly mistaken, or confusing me with some poor, unfortunate soul who haplessly selected a 15" twist for their 500 A-Square, NOT MINE.

MINE HAS ALWAYS BEEN A 10" TWIST!!!

Can I possibly make myself any clearer? Are you just ???

If so, thank you.

Yeah Dave it's weird that AHR will do your project and not mine. I don't think I even mentioned a $2000 price ceiling. They wanted me to go with the .500 AHR but when I didn't bite he emailed me saying, "Good luck with your project but we'll pass on it." They sure build some nice rifles though. Good luck with yours.

RIP, I plan on this being my "go to" stopping rifle to hopefully hunt cape buff, hippo, white rhino, and elephant if I can get over there. Most of my practice will probably be at short ranges up to maybe 125 yards with some speed drills thrown in. Accuracy with speed.

I would like to do SOME long range shooting with BMG bullets and my rifle will be throated to accept them. McGowen advises that I use the standard twist for the caliber, which is 1 in 10" twist. I'll trust his judgement on this matter and go with that twist. I know there are many opinions on what twist to use on a rifle in this caliber and most probably have validation but I'll trust my barrelmaker on this one. Worst case scenerio......I'll be stuck shooting only the heavy bullets. That's all I want to feed her anyway, 570 gr. & up.

RIP, spelling noted.... Thanks to all!

The 1 in 10 barrel is a great choice, especially when you get into the mono-solids which are long for caliber. On another thread I posted that I was using 1-24 twist barrels for a fifty project. That project is a blackpowder gun and is a different animal but I'm starting to wonder if I should have just used some worn-out surplus BMG barrels? R.

RIP, what kind of velocities are you getting with your 23" & 27" .510 JAB's using 570, 600, 700 and 750 gr bullets? I am just curious as to what it will do and what kind of velocity loss to expect using a barrel shorter than the 26" barrel that the .500 A2 is tested in. I'll be keeping my loads well under max pressures in the field, probably 2300-2350 fps with a 600 gr bullet. That is still one hell of a whallop but well below the listed max. You did say that the .500 A-Square and .510 JAB are really the same cartridge right? I still haven't decided on my barrel length. It will be somewhere between 22" & 24" though. I don't want to go over 24" on a stopping rifle but I do want it to be a bit barrel heavy.

The help I've gotten on this project has been much appreciated. I am glad there are people posting here with real big bore/custom rifle experience!

srshooter,
My Ruger No.1 in 500 A-Square was built first, born in 1999 AD. It used the standard reamer and was throated long with a separate throating reamer made by Dave Manson.

I took a cartridge formed in that and loaded it with a blacktip AP bullet and sent that to Dave Manson and requested the best throat fit for that bullet and a reamer made to fit the dummies. I did not specify that it was 500 A2. Dave made the shoulder 30-degrees instead of the standard 35-degrees of the 500 A2. His interpretation of the brass I sent to him.

Thus the .510 JAB was born, no other difference from the 500A2 other than throat and shoulder angle. Trivial differences.

Start at 105 grains of RL-15 or Varget for the 570 to 600-grain bullets. 115 grains will be safe and more than enough fun, if your rifle and bullets are in spec.

Start at 105 grains of IMR 4350, AA4350, or Hodgdon Extreme H4350, using 700 to 750 grain bullets. 115 grains will be safe and more than enough fun, if your rifle and bullets are in spec.

Now go do it and tell us what velocities you get.

Get me out of here Percy!