Fireforming the Brit

[Kyrifleman]

Just picked up a No4 Mk1* and I'm starting to load for it. I've shot some surplus ammo and they have the shoulders blown out a noticeable amount so I'd like to use the cornmeal fireforming method on my small supply of currently ultra rare Winchester 303 Brit brass. My main question is with sizing and trimming. I have a Lee FL size die and an RCBS neck die. All of the cases fit freely in the chamber. I assume the best method to increase case life is to fireform with Bullseye under cornmeal, then neck size and trim. Is this correct or is it best to size and trim before fireforming?

[Jack Stanley]

I've never used cornmeal or Bullseye to form case so I don't know if this will help . With cases I've fired in my rifle it's easy , a small rubber "O"-ring in front of the rim with a medium cast bullet load works good . It's better if I can find a few cases that have been fired in a larger chamber and adjust my full length size die down just a little untill the bolt of my rifle will just close . The empties from my number four MkII won't fit my SMLE so I used them like this with the "O" ring when firing . Case life in the SMLE is then very good even when using a "full" length resizer . I did get a Redding Bushing die to cheat case death even a little more ..... it's almost unfair . With the new case annealing machine ... it might just be short of immortality for cases .

Jack

[Kyrifleman]

So do you size and trim before or after your light load forming?

[303Guy]

I'm in the O-ring camp. I go a step further - I lightly lube my cases before firing. Neck trimming should be used to square the cases but otherwise the longer the neck the better. Up to a point! The idea is to keep the gap between the case mouth and the chamber end to a minimum. I'm not sure it will make any difference to the POI whether the cases are 'new' or already fire-formed.

Why not load up some boolits with the 'fresh' cases using the O-ring trick, group them then reload them and group them again and see what differences there might be. Ummm .... please report back so's we know too.:drinks:

P.S. I've never needed to re-trim a case and those I trimmed too short stayed that way!

[curator]

+1 on the "O" ring trick. I see you have already bought dies but you should consider getting the Lee Colet die to resize your cases after the first firing.
http://leeprecision.com/reloading-dies/rifle-dies/lee-collet-dies/
In my experience this die not only works the brass the absolute minimum, but also loads the most accurate ammo with the least "run-out." Used a couple of times it will actually result in uniform neck thickness without resorting to neck turning. The case mouth is squeezed around a fixed mandril of correct diameter. Other neck sizing dies resize the neck more than necessary then have the expander plug pulled through to create the correct inside diameter, double working and stretching the brass. Using the colet die and dedicating the brass to the rifle, I have cases that have been loaded more than 40 times without a split. When you read about this incredible innovation on the internet the guys who are trashing it either don't have one or they aren't using it correctly. I don't work for Lee but am an NRA Metallic Cartridge Reloading instructor with 50+ years of handloading experience.

[303Guy]

I can't see why anyone would want to trash the collet die concept. I didn't realize it would actually help to uniform the neck thickness. I know how it works even though I have never seen one - well, up close that is.