necking up remington 7BR case or lapua 6br case which one

[bigrich954rr]

i built a 338 whisper which shoots a 338 Mk from a remington 7mm benchrest case. Can the 6mmBR lapua case be neck up that much. im looking for better cases

 

[Fiftydriver]

Yes but you will need a tapered expander from Redding and you will probably need to do it in two steps.

If it were me, I would neck it up to 7mm(just under half way) or to 308(just over half way) and then anneal the case necks before stepping them up to 338.

I would only anneal the case neck and avoid the shoulder to help prevent any collapsed shoulders.

You may be able to do both steps before annealing and if so great but make sure you anneal after you get to 338 or you will have some case neck splits upon firing.

Be sure to deburr the inside of the case mouth very well and use plenty of lube on that expander.

With the tapered expanders and the short case length of the BR you may run into some issues with clearance of the expander and case web. Watch for this so you do not pop a decapping stem by bottoming out in the case.

Let us know how it turns out.

Kirby Allen(50)

 

[bigrich954rr]

so the neck on the 6mm brass will still be thick enough. yes i will keep you guys updated i think this will be a fun project.

 

[Wild_Bill]

Hi i have gont through the process of necking various cases to form 338 Whisper type calibres and am going with a diferent case to try another approach. The Lapua cases are awsome and as stated neck them to 30 cal first then neck them to 338 anneal after fireforming. The cases neck up beautifuly and there is no trouble. The one thing you must watch with either is because you are necking the case up so far the neck gets longer than it used to be and the shoulder part is formed into the bottom 1/3 of the neck. If you have a good close fitting chamber you should neck turn the cases as their is a bulge of thick brass there. Just skim the neck so you keep the original brass thickness at the top of the neck and bring the neck down to a consistant thickness. I have not necked up Rem 7mm Cases but i believe they would have the same problems. You only have to neck turn a case once so it is worth the effort. Also make sure the Lapua cases fit the chamber the Rem cases are smaller than the Lapua cases in the web area. This also means if the Lapua cases fit the Rem cases will be small in the web and that will increase the chance that the head will expand with warm loads and the primers pockets will open and loosen earlier with the Rem case.

Cheers Bill
Australia