Okay guys I was recently given about 80 rounds of Lapua .220 russian. Since I dont have a rifle chambered for this caliber I have broken these cartridges down into their base components. My question is doesnt the .220 russian use a 6mm bullet? If I am correct could this bullet be used in .243 varmint type rounds? Any help greatly appreciated.

The 220 Russian is 22 caliber, not 6mm. 220 Russian brass has been used to form into 6mmPPC, maybe that's what you have. Mike the bullets.

bullet diameter .243

You have received some sort of wildcat based on the 220 Russian case. As stated above, it is most likely the 6PPC. It could, however, be any number of other experiments. Accurate case dimensions, ie. shoulder angle, overall length, neck diameter, length from bolt face to datum line etc. will be valuable in determining what cartridge you have.

Okay I think we have established based on bullet diameter (i.e. 243) that this is 6PPC.
So therefore it should be safe to fire in my .243 correct? My main reason for asking is that the length of bullet is considerably shorter.

Blackhawk

I can't see where anything has been established except that the bullet is .243 and the case is headstamp is 220 Russian. The cartridge could be any one of several wildcats. Do what DocEd said, post dimensions and someone can probably ID it. It's probably a 6PPC but be sure before you try to shoot it.

OTOH, if you are simply asking if it's OK to shoot the bullet in a 243 rifle, the answer is yes. It's probably a light bullet (less than 70 grains) which is commonly used in PPC Benchrest rifles.

Ray