Whats the story with gas checks , are they to be used with lead bullets when you reach a certain velocity? Ive been shooting cast performance 460 WFNGC from 1200-1500 fps, and was thinking on tring some 500 grain bullets from Oregon Trail but i noticed they were plainj base not gas checkes.

I am not sure what cartridge or gun you are loading for?

In my 38-55 schuetzen rifles I shoot plain base and in my .375 H&H and Improved I use gas checked bullets. I don't have a cut off number where to use them or not but the handbooks might suggest one.

Plain base ought to work fine at those load levels.

My version is that you use gas checks when the mold is cut for them, but you usually don't need a gas checked design for loads less than 1600 fps in a rifle. I have never had any luck shooting gas check bullets without the gas check except in extremely mild loads.

In a straight case, if the bullet you want is only available in plain base, you can go a good bit hotter by using an upside down gas check. I only do this when the GC will touch the powder.

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Unfortunately it isn't as simple as saying you need gas checks at a certain velocity.

The point at which a gas check provides a benefit to prevent leading is a factor of the guns dimensions, ie throat and bore, bullet dimensions, bullet hardness, operating pressure of the cartridge, and velocity.

As a general rule, plainbase bullets require (I hasten to say tighter) a better match of chamber/bore dimensions, and a more limited range of velocities. Gas check bullets are more tolleranct of dimensional variances in the gun, and can generally be run faster w/o leading.

I'm assuming from your post that you are shooting a 45-70. I'd also guess that at the velocities you are running, you shouldn't have problems with leading.

One thing to note, if you do get leading with the plainbase bullets, run a few gas check bullets through the gun, and they'll take the leading right out.