Fireforming

[maple_leaf_eh]

I have a French 7.5x54 rifle and started to convert .308Win commercial brass for it. The first step was to squeeze the shoulder in a full length die. Step two was to load salvaged .30 Carbine 110gr bullets over 12gr of the salvaged Carbine powder, and topped with Red River Cereal in some and white flour in others.

The firing tests proved three things. The extractor would not catch 90% of the rounds. Most if the time, I had to chamber the round then tap it back with a cleaning rod to snap under the extractor. Then close the chamber and fire. The Red River Cereal ones expanded well, but the white flour ones either didn't detonate or hardly blew out the new shoulder. I stopped trying after a few rounds.

My question to the collective wisdom: other than the flour and powder load which isn't igniting, am I doing anything wrong? Should I anneal the brass before or after fireforming? Still plenty of unfired cases to process and fairly few fired ones to ditch if I'm wrong. Is there a better spacefilling medium to use?

 

[thegunnut]

Try Kapok for a filler.
same stuff old lifejackets and pillows are made of'.
It is important to hold he powder against the primer for these types of efforts.
Thegunnut

 

[knockknock]

I use fast pistol powder like 231, fill the case with cornmeal full to the mouth of the casing, then use a dowel to push the cornmeal in, creating a compressed load, then a touch of hot glue to keep the cornmeal in place.
Start with a small charge and work up until you get the shoulders and necks the way you want them.
It makes as much if not more mess that the way you are doing it, but there is no chance of a blow up and you are not wearing the bore fireforming brass.
Be sure to clean the bore very thoroughly before using a bullet in it.
KK

 

[tiriaq]

According to Donnelly - The Handloader's manual of Cartridge Conversions - the head of the 7.5 French is .480, somewhat larger than the nominal .470 of .308. .308 is also on the short side. 6.5x55 is listed as .476 at the head, and is long enough to trim to length. From the dimensions given in Donnelly, I think that 6.5 brass could be FL sized in the 7.5 die, the neck expanded, and case trimmed to length. The amount of fireforming required would be minimal.

 

[maple_leaf_eh]

According to Donnelly - The Handloader's Manual of Cartridge Conversions - the head of the 7.5 French is .480, somewhat larger than the nominal .470 of .308. .308 is also on the short side. 6.5x55 is listed as .476 at the head, and is long enough to trim to length. From the dimensions given in Donnelly, I think that 6.5 brass could be FL sized in the 7.5 die, the neck expanded, and case trimmed to length. The amount of fireforming required would be minimal.

Yes, but the reality is I have hundreds or thousands of 7.62 NATO brass and negligible 6.5 Swedish and even less 7.5 French. I am ready to live with cases a few mm short. The other long way around would be to shorten some of my 30-06 cases. I have plenty of .30 carbine cartridges to salvage for powder and bullets, so I'm more inclined to work with .30 calibre cartridges than 6.5mm.

If I can get the shoulder out to hold the rim for the extractor and expand the body to seal the rest of the case, then I will be closer to having a shootable supply.

Kapok, cotton batting, faster powder, glue, compressed loads - great suggestions. Thanks. No one jumped in on annealing.

 

[tiriaq]

Its not so much the length as the diameter at the head. Before 6.5x55 brass became readily available, I formed cases from .270, 6mm Remington. The expansion ring near the head was pronounced. Never had a head failure, but I was a bit uneasy about it. 7.5 French is larger in diameter than 6.5. To set the shoulder, have you tried expanding the neck up and then FL sizing to create a bit of a shoulder, enough to set basic headspace for fireforming? After you have fired some formed cases with normal bulleted loads, you'll be able to inspect the cases for expansion near the head, and see if you are content.
If you have a large quantity of .30 M-1 carbine ammunition, you might want to consider selling it, rather than breaking it for salvage. .30 carbine ammunition isn't all that available at a good price; doubt you would have any problem selling it for more than its salvage value.

 

[aulrich]

I have been fire forming on a variation of above while fireforming 22khornet.

Detirmine the grains of water that the case can hold, use 25% of that value of 700x shotgun powder. fill with cream of wheat compact and fill again repeat as required. leave 1/4" or so and top with crisco (I have been using Muzzle loader bullet lube) if the case is malformed up the powder 1 grain.

I also lube the case lightly to ensure that the case gets right back against the breach.

 

[Mystic Precision]

I don't have the cartridge pic in front of me but assume from the comments the shoulder on the 7.5 is ahead of the 308.

If so, you must expand the neck then neck down to form a secondary shoulder on the neck. Set this shoulder so that there is firm pressure required to close the bolt. That case is now a crush fit to the chamber and will fireform without causing stress on the web area.

To fireform, I would use 10 to 12 grs of HP38/Win231/Titegroup lit by any LR primer. Dump the powder into primed cases, fill to the base of the neck with Cream or Wheat or Cornmeal (no instant stuff). Stuff some paper towel into the neck to hold this mess in place. Fire safely.

I get 100% ignition with this 'load' and it will move the shoulder forward or do that sharp shouldered AI thing to about 95% of perfect. The first full pressure load will form to the chamber.

With that much difference in head dimension, you will see a pronouced bulge in the case head area. If the brass is ductile enough, it is likely to hold at these moderate pressures. You cannot anneal that head area of the case for fear of catastrophic failure.

If you are using once fired commercial or western NATO brass, annealing the necks will not be necessary for fireforming. Only anneal when you absolutely have to (neck splits). Our methods are no where near as consistent as a factory and we can sometimes create more harm then good.

Higginson powders did have some Euro sizes of brass. Check with them as brass is the least expensive part of your equation. Case failure is much more expensive in the long run.

Good luck.

Jerry

 

[Hitzy]

buy the proper brass.....looking at $50/100 and 100 cases should last you years....well worth it.
The MAS is rear locking right?

 

[maple_leaf_eh]

Thanks guys!

I hear you on the .30 Carbine. The stuff is really dirty and a mixture of by-the-pound Caribbean dictatorship surplus that Marstar had a while back. It was hard to read the headstamps, never mind sort it to fire when I had a carbine.

I know what you guys are suggesting about the head diameter. I have been wrestling with that too. If my fireforming project falls a, I will get some of the right cases.

Part of the 7.62 NATO neck is within the 7.5 MAS neck profile. The French shoulder is about 3mm further forward. The NATO case length is 51mm vs 54mm, and the head diameter is about .470" vs .480".

I think I follow the suggestions you guys are using but is there enough resistence to hold the pressure high enough to blow out the neck with just a gob of Crisco, cotton balls or paper towel? I have been going on the principle that the pressure curve has to peak enough and push out the case before the bullet heads down the barrel.

This MAS is a tilt locking bolt that looks exactly like an FN49, FN FAL or SVT. There is a recoil shoulder on the receiver between the magazine housing and the hammer. The raw gas is fed off the bore through a tube into a recess on the top front of the bolt carrier. There are a couple of interference surfaces between the chamber and the outside, so any gas blowby on the cases is vented forward.

Keep the suggestions coming. I'm enjoying this conversation.