fireforming 303 British to 410 question

saskgunowner101

saskgunowner101

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So I decided to make up a few brass shells for the better half with 303 brass, for her 410. For no good reason really, just wanted to try as I'd read about it. Anyways, they all puffed out kinda goofy (as I've seen in other pics), so now I'm wondering how to blow the whole case out? Any ideas? I used 8.5 grains Herco/fill with COW/small piece of toilet paper for the initial forming.

I don't actually have components besides the brass and powder, so loading 'er up isn't an option.
 
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Many years ago I used .444 Marlin brass to make brass .410 shotshells. It worked just fine without having to do any fireforming. That being said, finding .303 British brass will be quite a lot easier than finding .444 Marlin.
 
Thanks for the replies guys. I did start off with a google search and the various links to making the 303 to 410 brass before posting. I filed off the back of the cartridge slightly (until the headstamp disappeared), I annealed the mouth and approx. half the body and all ten casings blew out nicely on the top half.

I used the same fireform load again to try and blow out the rest of the casing on a trial piece, and nothing. Then 6 grains Titegroup/COW and the same. Then 9 grains Titegroup and COW and the same. Just wondering how to pressure up the load without going overboard.

Side note: Does cream of wheat have impressive barrel cleaning qualities? After popping these off I ran two passes with a bronze brush and the bore looks immaculate...
 
Don't do it with the 44 cal. When I made my 458 brass from 338 I just took 338 factory loads and fired them in my 458 and whalla I had 458 brass. If the bullet on a full load has no resistance there is virtually no pressure. It sounded like a sick pellet gun when I fired them. If youre brave enough fire complete 303 rounds through your 410. The bullet will just fall out the end of the barrel and you will have 410 brass. There has to be resistance of the bullet touching the barrel to be a dangerous amount of pressure. If you had a winchester 9410 I wouldn't hesitate to do it.
 
I wish I had a way to neck down to .40 or .366 with my existing cases....I'd try it. Perhaps a detuned 303 cast load would work? I have a box of factory 303 ammo but saving it for the rifle.
 
When I tried it I had to fire each case 2-3 times before it fire formed to a nice, consistent shape. And even with 2/3 length annealing I had almost half of them split during the process.
 
Gentlemen

This thread peaked my curiosity so I did a quick examination of my tools at hand

The two examples on the left are what happen when you try to run a .303 British case into a .40cal pistol expander die (split neck) and a .416 rigby die (collapsed shoulder), however if you first gently flare the case in the .40 die then run it full length thru a .416 rigby die the results are quite close to perfect for a reloadable case and should "should" perfectly fireform.


 
Saw a fireform where they used a heeled bullet ie: turned tail end of a bullet from 45 down to 375 and fired in a 458, done
 
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Gentlemen

The above cases were loaded and fired today

CCI large pistol primer
30 grains by VOLUME FFg goex black
2x .125 cards
1/4" styrofoam wad
25 grain measure of #4 lead shot
.125 card
Roll crimped with a .308 seating die







Pattern was dismal at 25 yards but at 10-20 would be excellent for chickens
Minimal recoil and lots of smoke, an excellent novelty round for any reloader to play with.
 
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