.303 British Seating depth variance (rimmed cartridges)

[Conman50]

Hello! New here, just wanted to pick your brains on something I've notice while loading .303 Brit.

I load primarily soft point 150 grain projectiles and I know because they are soft point my Cartridge Overall Length will vary somewhat. But I'm noticing a pretty good spread of my COL. I don't remember the numbers now but I can measure a few to find out. I just thought it was a pretty large spread, around 10 to 15 thousands.

Is the large variance in COL caused by this head spacing off the rim of the case? I know there can be some differences on case rim thickness so I'm wondering is this cause of my large spread in COL?
This also applies to any rimmed case correct?

Thanks!

 

[AJC1]

Col is one of the most basic measurements that there is and seemingly one of the most inaccurate. Cartridge base to ogive is the current standard 4 measurement. This takes out all the tip irregularities that are common in everything but the new plastic tips. You can use another cartridge or the Hornaday a tool to measure a consistent place on the bullet that will give you more accurate readings

 

[Conman50]

Col is one of the most basic measurements that there is and seemingly one of the most inaccurate. Cartridge base to ogive is the current standard 4 measurement. This takes out all the tip irregularities that are common in everything but the new plastic tips. You can use another cartridge or the Hornaday a tool to measure a consistent place on the bullet that will give you more accurate readings

I dont think they make a comparator specifically for .303. Could I use one in .308 size? Usually bullets I use are .311 or .312.

 

[FROGO207]

The one for 308 will be close enough. Remember you are going from the base to the ogive NOT to the tip of the bullet. Also some of the problem could be a dirty or incorrectly sized seating plug. Stand some of the bullets up on the bench and put a straight edge across the tips. All the same? Gaps on some? If some are using the bullet tip as length adjustment and some another are on the ogive area to index off of that might be your answer. I have had to drill a center hole deeper in a seatimg plug before when using long boat tail bullets. Time to measure things.

 

[AJC1]

I dont think they make a comparator specifically for .303. Could I use one in .308 size? Usually bullets I use are .311 or .312.

A consistant place on the ojive will work.