Hi

I am talking to Pac nor about a barrel for a 500 A2 build on a CZ 550 (416 Rigby) action.

Pac nor suggest a 1:15.

Cartridges of the World state 1:10

RIP has in several posts maintained 1:10 as the go and I believe the origonal A2 rifles were too.

Considering the wide range of bullets available for the .510 cal and given that I would probably not shoot the 600 grain at more than 2200 fps do I split the difference or go with the origonal 1:10?

Pac nor suggest more pressure with the 1:10, but then given the size of the case and the fact that I will not be really stoking the cartridge up is it ever going to be an issue?

All advice and opinions appreciated

Oh, I was going to look at 23", any comment positive or otherwise?

Cheers

Stu

I have never build a rifle in 500 A2. But I would go for the faster twist barrel for sure. And a barrellength between 22-24" should work fine..

1:10 works, and 1:15 works, with almost all bullets, incuding BMG bullets.

pick one, you'll be happy with it

Thanks gents

Interesting to see what A2 have in the current crop of barrels?

Stu

1 in 10" twist for me. , Rodney.

Mine has a 1 in 14" twist and works quite well.

my 500 Jeffe is 18, my first 500 AR is 15, my latest is 10 .. i run them pretty mild pressures.

My .505Gibbs has a 1 in 10" and I ordered a 1 in 10" for the .500AccRel. The Gibbs literally drills holes with Macs solids and McGowens fast twist barrel. Rodney.

Thanks very much guys.

Interestingly CZ have a 1:16 in their 500J. Why would one manufacturer be so different to another?

What twist do AHR run in their barrels?

The general concensus is 1:10, any strong opinions otherwise?

Regards

Stu

CIP probalby calls for a 1:16 twist .. but it doesn't matter

Not another twist thread.

1-15 for the BMG

Keith

quote:

Originally posted by stuey:
The general concensus is 1:10, any strong opinions otherwise?

Regards

Stu

Would'nt twist be more determined by the design and weight of the desired bullet? Just an opinion but are not most barrels and twists determined by what is most used? The most common typically being a jacketed softpoint of some kind. For myself I prefer a faster twist barrel for heavy unleaded bullets. Rodney.

You know personal choice I suppose.

I like the idea of big cal splat bombs. Not real keen on slow moving heavy pills.

I run a 235g in the 375 H&H at about 2800fps, I run 340g in the 416 at about 2600 fps, in the 458 AccRel I run a 400g at 2650fps and in the 500 AccRel I will be running 535g at .....( as quick as Jeffe thinks is safe)

So slow twist doesn't worry me in the least because I use the lighter projectiles

regards
S&F

Being based in Australia my options are obviously the Woodleigh projectiles.

Correct me if I am wrong the A2 ammo is of monometal projectiles.

Is the 1:10 ok for the jacketed lead ie Woodlieghs?

Stu

I've had great results with the .500a2 with a 1:15 twist. A 1:10 will also work just fine. This has been beaten to death before. It probably just doesnt matter enough to discuss any further. -Rob

Stu,
If you want to limit yourself to 535, 570, or even 600-grain cup&core leaded bullets, a 1:15" twist is fine.

A-Square "Triad" bullets should not influence you. The Lion Load (frangible soft), Dead Tough (poorly expanding soft),
and Monolithic Solid (bronze round nose monometal solid)... they are an antiquated sales gimmick
that no person of normal intelligence takes seriously.

Woodleigh FMJ solids plus Weldcore softs are a better choice.

Art Alphin did put together a great reloading manual with plenty of good info.

He also created the best big bore cartridge name ever: 577 Tyrannosaur

His 500 A-Square was a rework of the .510 Wells.
J. D. Jones of SSK did the similar 50 Peacekeeper.
Me too cartridges, but the most practical of all the sporting 50-cal cartridges, .510/460 Weatherby's all.
Why, I even beat J. D. to it with my .510 JAB.

Alphin seems to have pioneered the 1:10" twist in the .510/460Wby.
I followed suit.
Then so did J. D. Jones.

Jones wanted to use the 750-grain Hornady A-Max, and 700-grain AP milsurp, both at 2200 fps from a 23" barrel.
This is realistic.

These slower velocities than the 50BMG will require a faster twist to produce the same revolutions per second as the 1:15" 50BMG does.

Actually, 1:12" would do that.
1:10" is more than enough.
Better more than enough twist than not enough.
Use enough Gun. Use Enough Bullet. Use Enough Twist.

Twist may not have a lot to do with penetration of solids inside game after the process starts,
but it may play a part in the transition from air flight to a good start in-target on a straight line.

570-grain GSC FN monometal copper solids at 2400 fps from a 1:10" twist will zip straight through 8 feet of bison butt to neck and exit reliably.

There is always some nonsense apparent when you study the twist standards of CIP:

500 Nitro express: 1:15"
.505 Gibbs: 1:16"
500 Jeffery: 1:20"
50 BMG: 1:15"

Lighter cast bullets might do better with a slower twist.
1:15" if all you want to do is Woodleighs and cast bullets.

1:12" if you want to run 750-grainers at 2200 fps for 1000-yard work.

1:10" if you want to use all sporting jacketed bullets inside of 500 yards to best advantage,
including Woodleigh softs and solids, and every monometal soft or solid available,
as well as lobbing the heaviest available bullets near or far.

I need to get some of those 975-grain/50-cal Ranger Rick gas-checcked lead bullets and try them in my 1:10" twist at modest speed.
I'll bet THOSE cast bullets would be the cat's meow in a 1:10" twist.

Just beating Rob's dead horse.

RIP, thanks very much.

Thanks to every one for their input.

Stu

I have a 1-15 Pacnor on my 500A2.

Thanks fla3006

What bullets are you shooting with your rig?

Stu