fireforming oversized cases

damndirtyape

damndirtyape

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So I did something dumb and resized my 8mm mauser brass too much. I drop it in my cartridge headspace gauge and it's a little too short. I haven't measured it, but it's below the minimum by less than the difference between max and min.

Can I fireform these to get the headspace back up? I know a full pressure round with short headspace is a Very Bad Idea (TM), will fireforming be safe and effective? Is this even what fireforming does? I'm very new to rifle reloading, but I've been doing pistol for a while.

Anyone have a fireforming recipe for 8mm mauser with W231, Titegroup or Universal clays?

This is for a Yugo M48 btw.

Thanks.
 
You could use a normal starting load and seat the bullet into the lands to keep the case against the bolt. Thats how you fireform for AI rounds.
What type of press are you using, normally you just screw the die down to touch the shell holder and size, only exception I have seen is the Dillon progressive. This would make it very hard to size the case to much.

Andy
 
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Cartridges don't have headspace. Only firearms have headspace. Cartridges have dimensions. The length being the most important. Fireforming is making cases by firing another cases in a chamber made for another cases. As in the AI, that 765nato mentions. Shoot 'em and your cases will be fine.
 
sunray: Nope; you want to regain the length by moving the shoulder forward not by stretching the rear of the case back. Follow the instructions given for bullet to land contact to ensure the case is pushed back against the face of the bolt. Then the forward part of the case will move ahead.
 
762nato said:
You could use a normal starting load and seat the bullet into the lands to keep the case against the bolt.
Andy
Click to expand...

How do I load the bullet to this exact depth? Do I start long and slowly increase seating depth until the bolt only just closes? Maybe color the bullet with a felt pen and chamber to see where it's contacting the lands?

Thanks again.
 
dda: You are on the right track. Felt pen will work and do it by trial and error without really jamming it in. You should feel a slight "crush" fit when you close the bolt. The bullet doesen't have to be deep in the lands , just firm contact to force the case head against the bolt.. Set it up with a dummy round so you aren't playing with loaded rounds in the house.
 
Insert a cleaning rod into the gun with the bolt closed and nothing in the chamber, mark it some how. Take the bolt out, put the bullet you are using in the chamber(bullet only), tap it gently from the chamber end. Put the cleaning rod back in the muzzle and mark it where it stops this time. Tap the bullet out with the rod. The distance between the marks is the Collective Over All Length (C.O.A.L) of the cartridge with that specific bullet to have it seated in the lands. I would add .030" to that length and work on a dummy until the bolt closes with minor resistance. This is the length to load to to fire form.

Andy
 
Just a thought - the gauge you are using is based on SAAMI specs? What is the headspace situation in the rifle? If it is a used ex-military rifle, cases that gauge correctly could still be short.
Using the bullet to set the casehead against the boltface can help, but the firing pin strike can also push the case foreward, before pressure spikes and holds the casehead against the boltface.
There are mixed opinions about this, but a bit of lube on the case will help fireforming, although loads should be reduced, or fireforming blank loads used.
If absolutely necessary, the neck can be expanded, and the case then sized to create a false shoulder to position the case correctly in the chamber.
It shouldn't be necessary to move the shoulder foreward in an AI chamber if the chamber is cut correctly; the case should make contact at the neck/shoulder junction area. There are wildcats that require the shoulder to be blown foreward.
How many cases are involved? 8mm isn't that hard to get. Might be just as easy to replace them, if you are concerned.
 
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