7.5x55 from .284 Winchester?

[Kyle M.]

Has anyone here ever formed 7.5x55 from .284 Winchester? I recently picked up another 1889 Schmidt Rubin after selling my last one and my Prvi 7.5x55 brass. I managed to get ahold of 100 pieces of Peterson .284 Winchester brass and I have annealed it once. But about 50% of the cases are still springing back too much to chamber after sizing. Should I go through and try a second annealing or should I try something else? I’ve had no luck finding any boxer primed 7.5x55 brass. I suppose it could be my annealing process, I’ve just been heating the case necks with a MAPP gas torch while holding them at the base. Just before they get too hot to hold I drop them into water.

Thanks in advance for any advice.

[15meter]

Try F/L sizing using a shell holder with .010-.020 ground off the top, grind some, resize a couple and see if they will chamber, continue grinding and trying until you get them to chamber. I have a combination 9" disc/6x48" belt sander. Sanding by eye on the disc sander is all I have ever had to do.

Go slow on the sizing, I use Imperial lube, go into the die part way, back out, turn the case a 1/4 turn, back in the die again. Multiple passes before going fully into the die.

Remember, you are using a shell holder that isn't as strong as an un-ground shell holder. I have pulled the top lip off of shell holders I have ground down to do exactly this. Really, really annoying when you do it at 11 at night and you only have a handful left to do so you can pitch them into the polisher.

I've done this with several different case conversion problem children. First firing gets them to correct chamber dimensions.

After that, a standard shell holder(un-ground) will in all likelihood size them enough to chamber.

[Kyle M.]

Try F/L sizing using a shell holder with .010-.020 ground off the top, grind some, resize a couple and see if they will chamber, continue grinding and trying until you get them to chamber. I have a combination 9" disc/6x48" belt sander. Sanding by eye on the disc sander is all I have ever had to do.

Go slow on the sizing, I use Imperial lube, go into the die part way, back out, turn the case a 1/4 turn, back in the die again. Multiple passes before going fully into the die.

Remember, you are using a shell holder that isn't as strong as an un-ground shell holder. I have pulled the top lip off of shell holders I have ground down to do exactly this. Really, really annoying when you do it at 11 at night and you only have a handful left to do so you can pitch them into the polisher.

I've done this with several different case conversion problem children. First firing gets them to correct chamber dimensions.

After that, a standard shell holder(un-ground) will in all likelihood size them enough to chamber.


Thanks for the info, I’ll give that a try.

[DonHowe]

At this point I do no remember details I ls but 15+ years ago I used .284 Win brass in a K 31 and am sure I did not grind a shellholder. Guees you will have to try it and see.
Despite the smaller case head the .²84 brass worked fine.

[BK7saum]

Does the sizer and shellholder work (and bump the shoulder) on fireformed 7.5x55 brass? If so, a second anneal woupd likely help. Also, well lubed cases will size a bit more than some that are lacking in lube. A few second dwell time can help push the shoulder back that little bit further. Also, have you adjusted the die to touch the shellholder and then turned it in that additional ⅛ turn to account for press frame flex?

[green mountain boy]

i too have done the same thing as 15 meter has done. these were made for and shot in my K31, i see no differance between the accuracy of the 284 brass and NNY (privi) and i am sure i have fired them a couple dozen times now without a failure or case loss.

[Kyle M.]

Does the sizer and shellholder work (and bump the shoulder) on fireformed 7.5x55 brass? If so, a second anneal woupd likely help. Also, well lubed cases will size a bit more than some that are lacking in lube. A few second dwell time can help push the shoulder back that little bit further. Also, have you adjusted the die to touch the shellholder and then turned it in that additional ⅛ turn to account for press frame flex?


Yes on everything but the fire formed brass. I haven’t shot this particular rifle yet. I’m going to try a going slower and turning the cases sizing in steps. If that doesn’t work I’ll try a second annealing.

[Mk42gunner]

You may also need to pause at the top of the stroke, to give a little dwell time for the brass to flow where it needs to be, instead of springing back.

Robert

[725]

I've used that brass to make brass for the 7.5 Swiss. Works just fine. Go slow. One thing I have noticed is that the smaller base rim may sometimes make for a challenge for your extractor claw. I actually prefer the .284 brass to the regular stuff.

[Kraschenbirn]

I've formed quite a bit of .284 Win to 7.5x55 with no issues. Works just fine in my K31 but not so good in my G96/11. Nominal dia. of .284 rim is .470 and 7x55 is .496 - .026 larger - and extractor of the 96/11 often slips off the reformed .284s...leaving them to be popped out with a cleaning rod. Privi brass, on the other hand, works just dandy in the 96/11 so I keep a batch dedicated to that rifle.

Bill

[Kyle M.]

Success! I had to turn the die in a bit further and I paused for about 3 seconds at the end of the stroke. I only checked one in five cases but they all chamber and extract fine so far.

[green mountain boy]

glad to hear it !