Seating Depth - .303 Brit, 185 grn .312 bullet

[bluemike807]

So I've taken to casting these:

Its a .312 (though they drop around .3115), 185 grn, with obvious lube grooves and a socket for a Gascheck. How deeply do I seat these? The topmost groove resembles a cannelure as much as anything - and I've seated to this depth for some 7.62x54R I've loaded up, but it looks very deep.

How deeply should I be seating these?

 

[ben hunchak]

Ideally you seat them as far out as your chamber will allow for best accuracy, at least it is a good place to start. Hopefully the loaded round will then still fit in the magazine. In any event, you still should not have the gas check below the neck of loaded round. Sometimes the bullet one chooses does not fit all these criteria....Ben

 

[bluemike807]

Will there be any detriment to having exposed lube grooves then?

 

[44Bore]

exposed lube grooves may pick up grit and lint etc. You have to take care to keep them clean. Not a problem for range use but if you are going to hunt with them it is better to have the lube grooves inside the neck.

 

[Cactus]

Do as Ben suggested...

Load a dummy round with no crimp and gently chamber it. Examine the tip of the bullet, if there are marks on it, it has been pushed in to the max the chamber will take seat it a bit deeper and test it in your mag. If it is too long for the mag, seat it in a bit more untill it fits the mag.

Crimp it at the point where it fits both and you have a test round to adjust your dies to when you reload. At that point you can load a few rounds and test them then a few more seated a little deeper untill you find the depth that works best for you.

I use a GC Lee cast 180gr RN, the manual says 3.075 max length, factory rounds I measured were 3.048, my rounds are 2.880 and they work great in my rifle. This is where reloading is fun, testing for the best round you can make. My rounds may be seated a bit deeper than others, all but 1 of the grease groves are mostly in the neck of the case and as I said they function and fire well out of my rifle

Dont forget to adjust your dummy round to what ever you decide is the best for your rifle for reseting the dies as needed. This is helpful when you cast more than one weight of bullet for the same rifle.