OzFclass

Hello after only ever having reloaded once fired Winchester factory brass i have recently just bought my first lot of Lapua .308
My question relates to initial prep and fire forming the load development.
Should I do all of my usual prep e.g. primer pocket uniform, flash hole de burr, trim length etc. Before i fireform or after?
Should i full length resize before use?
Should i use a lighter charge to break the brass in?
I will have to develop a new load for the new brass should i do this after fire forming?

There is 1000 ways to cook a cat ! But .308's are very fuss free and easy to tune! I've always just used my standard load straight up of around 46 Gr 2208 large primer (155 Gr pill). Have always case prepped out of the box . .308s with 155's don't seem to be operating under large pressures anyway. I use to weigh lap brass but gave up as they were always consistent in weight .
Regards Graham.

Do you think its necessary to FL size before i use the brass or just fire form it to begin with?

If it chambers, it won't be better full sized. However, one other thing, I find that new brass has more neck tension than I want. Perhaps a FLS die with button would relieve that. In my case, I have a K & M plug that expands up after which I use a Lee collet die.

I deburr the flash hole and check the internal chamfer with my preferred tool, load and shoot the first firing with that only. I then do the primer pockets after the first firing. I've never had to trim lapua brass with my 308. I would back my load off a bit since your changing from win to lapua the thicker lapua cases will give the same pressure with less powder.

I do flash-hole and primer pocket reaming on new brass, and expand the necks then size the neck before first firing, and chamfer the mouth. I would never length trim prior to first firing, maybe even wait till after the second, because it may take two firings for the brass to settle to length. There should be no harm in FL sizing new brass - it shouldn't touch the sides - so if you need to size the neck with it after expanding, then it shouldn't be a problem.

Jase, in the traditional context of the phrase, “fire-forming”, you will be most likely blowing the case shoulder and neck forward from a parent case to form a new case suited to a different chambering to that of the parent case. In that context, I would anneal and full length re-size after the fire-forming.

If the question relates to new brass, with the same chambering, similar processes post fire-forming are adopted because the new cases have necks in the annealed state. As such these cases are often shorter by up to .006” from a normalised state which may take up to 3 firings to obtain.

There are three important things to do.

Firstly, and most importantly you should use a lighter charge to break the case in. This sets up the hardening in the primer pocket, otherwise you will be tossing out cases before their time with loose pockets. Use these for club shoots and shoot with a lower velocity node.

Secondly, trim your cases, pockets after the second or third firing when the metal has stabilized unless you anneal after every shot like some do with induction annealers. If you are gas annealing, which is an imperfect process you have to anneal after about six shots like Denis says or when the seating pressures and dimensions tell you something has changed. After the case has stabilised in dimension, those that are pedantic about measuring to .1 grain know the internal volume of the case has stabilized as has the air gap between powder and projectile necessary for stable ignition. Also the spring back after sizing has settled. If you go about trimming too early, you may well have less cases of the same dimensions to choose from to batch them. You certainly go about load development with your best cases too.

Finally, and this is a different trick which assists the shoulder bump that Rod mentions in another post. It is not a case length trim but a case turn which thins the neck but only on new brass with a cleanup of 70% to 90% so you don’t decrease the size of the neck too much causing additional working of the brass. Cutting the neck back while the shoulder is setback (.006” because of its natural new annealed state) will cause the turning operation to even out the brass on that part of the neck closest to the shoulder. This last part of the neck becomes part of the shoulder on firing. For subsequent sizings, and this is the important bit, you only bump back .001” to max .002” and this will be consistent. This even thickness in the last part of the shoulder and the start of the neck will result in straighter brass coming out of the sizing operation.

Then run with Keith H, Peter S and JohnK’s sizing methodologies. David.

Yes David I was referring to fireforming in the wrong context sorry for the confusion, i will apply what i have read here to my loads. Thanks everyone for your responses and detailed answers i always take something positive from this forum when i have technical questions.