Mixed Cases

[ColonialBuff]

I have W-W cases in both nickel and brass. After weighing a sample of 10 cases of both nickel and brass, my results show they all were within .6grs of each other. Can I make a leap and use the cases interchangably? Or, would that be serious case of brain damage. /ubbthreads/images/graemlins/tongue.gif

 

[Bart B]

You can use the same loads, but ones in the nickel cases may have a little different muzzle velocities.

 

[EddieHarren]

Why?

 

[Bart B]

Nickel's more slippery than brass. All other things being equal, bullets will slide out of a nickel plated mouth a bit easier. So muzzle velocity may be a tiny bit different.

 

[EddieHarren]

Oh, now I understand.

 

[ColonialBuff]

Bart thanks for the info. I will crono and see if that is universally true. /ubbthreads/images/graemlins/grin.gif

 

[EddieHarren]

Yes, please check this out. I'm looking to get 10 or 12 more FPS out of my 30BR.

 

[davewilson]

could i ask why you'd like to get 10-12 more?

 

[Bart B]

If you want a dozen fps more bullet speed, size your case necks so they are tighter on the bullet. Chronograph the loads to see how much differene there is.

Or, hold the rifle much tighter into your shoulder. That'll increase the speeds bullets leave by about 10 to 12 fps. And you don't have to change your reloading process.

 

[EddieHarren]

BartB, I was being a smart *** with your reply about nickel cases giving more velocity than brass. I assumed you were being a smart *** too.

I shoot my 10lb. Varmint Hunter class (IBS) free recoil. I've been shooting this rig that way for many years. It does not like to be held.

 

[Bart B]

No, I wasn't being a smart *** about anything. Holding a rifle tighter will increase the load's muzzle velocity. And case neck friction changes will also change it.

Glad to hear you're shooting the rifle free-recoil. Most folks don't realize how much the way they inconsistantly hold a rifle reduces its accuracy. And if you're group shooting, free recoil (or a proper machine rest) does indeed produce the smallest groups.

 

[EddieHarren]

Sorry I mistook your scientific responses for humor.
IBS Varmint Hunter class matches are all score matches. Front rest ie. Hart, Bald Eagle, Farley and others are allowed but no mechanical rear rests of any kind.

In your opinion how much of a velocity gain would one expect to realize by holding the rifle tighter?

 

[Bart B]

I've got as much as 60 fps difference with a .308 Win. Two people I know got about 90 fps difference between them shooting the same rifle and ammo off sandbags atop a bench.

When I shoot the same .308 Win. rifle/ammo standing and prone, bullets leave about 20 fps faster from prone.

 

[EddieHarren]

That's some difference! How much affect coes it have on shot placement at, say, 300yds.?