Author Topic: 45/50 sabots and 1-28" barrels (Read 747 times)

EZshot · « **on:** March 26, 2004, 06:40:00 AM »

I know every barrel is unique but is seems to be less than the exception that people are getting good to excellent accuracy in fast twist barrels (1-28" and faster) with 240gr - 44/50, 250gr - 45/50, and 260gr - 45/50 even while pushing some impressive velocities. This seems to contradict some of the bullet/twist compatability formulas and even the prbullet chart. Anyone have any insight on why this is the case?

Thanks.

RandyWakeman · « **Reply #1 on:** March 26, 2004, 06:54:36 AM »

Quote from: EZshot

This seems to contradict some of the bullet/twist compatability formulas and even the prbullet chart. Anyone have any insight on why this is the case?

Thanks.

What contradiction? Bullet RPS is rate of twist and muzzle velocity, nothing else does it.

EZshot · « **Reply #2 on:** March 27, 2004, 08:25:02 AM »

By contradiction I mean: just by glancing at Cecil's bullet selection chart, they don't even make a 45/50 bullet weight less than 275gr, and even the 275gr 45/50 QT only yeilds 2 "*" so per the table it wouldn't be the first choice to try in a 1-28" twist or faster barrel. Yet, many posters here and elsewhere are reporting great accuracy/velocity with 45/50 - 250gr SST's, 44/50 - 240gr XTP's, or 45/50 - 260gr WinPT's out of Encores/Omegas/Knights/Savages with 1-28: or faster twist barrels. Why is it less than the exception vs. what Cecil's testing has indicated. What gives?

RandyWakeman · « **Reply #3 on:** March 27, 2004, 08:40:54 AM »

Quote from: EZshot

they don't even make a 45/50 bullet weight less than 275gr, and even the 275gr 45/50 QT only yeilds 2 "*" so per the table it wouldn't be the first choice to try in a 1-28" twist or faster barrel. Yet, many posters here and elsewhere are reporting great accuracy/velocity with 45/50 - 250gr SST's, 44/50 - 240gr XTP's, or 45/50 - 260gr WinPT's out of Encores/Omegas/Knights/Savages with 1-28: or faster twist barrels. Why is it less than the exception vs. what Cecil's testing has indicated. What gives?

It is a very general guide, nothing more. Muzzle velocity + rate of twist= RPS which stabilizes a projectile. Make of gun, barrel length + powder charge are all in your hands. At present-- no bullet or gun manufacture begins to give you nearly this much info, or this variety.

Of course they make .45 weights less than 275: they will make whatever you want! If you want light bullets, go 40 / 50 200, 220, 240 ------------ and enjoy the flatter trajectory.

AndyHass · « **Reply #4 on:** March 31, 2004, 06:48:21 AM »

The PR chart is for PR bullets. If you look carefully, some bullets of the same rate behave differently in the same twist. This is because of bullet length.
The RPS are just a factor of velocity and twist as Randy said. However, the RPS required to ideally stabilize a given projectile varies according to the length of the bullet (and shape too). So you cannot accurately assess the performance of a 250 grain SST by comparing it to a 250 grain QT.

Underclocked · « **Reply #5 on:** March 31, 2004, 07:33:58 AM »

Is there a twist formula that at all takes into account the addition of a plastic sabot?

RandyWakeman · « **Reply #6 on:** March 31, 2004, 07:45:24 AM »

The sabot has nothing to do with it.

Underclocked · « **Reply #7 on:** March 31, 2004, 05:09:17 PM »

I'm calling you out, mister!!! :wink: The sabot HAS to have something to do with it. The formulas may ignore it but it's there, it has mass, it has length, and frictional effects.

If I'm wrong, please tell me why?

RandyWakeman · « **Reply #8 on:** March 31, 2004, 05:28:28 PM »

Quote from: Underclocked

The sabot HAS to have something to do with it. The formulas may ignore it but it's there, it has mass, it has length, and frictional effects.

It is also not a projectile; stabilization of the bullet is what counts. We aren't trying to stabilize plastic.

1:28 is just that, regardless of actual bore diameter-- .45 / .50 / .54. Those who note Cecil's experiences will see rate twist by bullet-- not sabot or bore. Bore buttons and powder charges have mass; they do not affect RPS of the bullet. Frictional effects? So does anything in contact with rifling, lead, bullet lube, gilding metal jackets... or sabots. The torque value to spin a bullet is exceedingly low.

The only consideration with sabots loaded from the muzzle is that current polyethylene formulations, according to Del Ramsey, do not tolerate rate of twists tighter than 1:22 well.

Greenhill would be pleased-- it a specific gravity ratio of projectile to atmosphere, little else.