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michaelburns
Hello.
I’m working on designing a bullet to replicate as far as possible the old heeled & paper patched 7.5 GP90, and would like to gauge interest. What I have come up with so far.
Basically, this is the original cartridge and bullet:
There’s an iron cap to the bullet which we can forget about. For the rest, apparently the bare bullet measures as follows (will confirm once I’ve got hold of one myself:
Body: .315″
Heel: .302″
Length of heel: .233″
Length of bullet: 1.167″Small hollow base in the heel. Consider that a “(very) nice to have” rather than a necessity.
2 wraps of paper to add .006″.
Yes, the bores run about .308″ groove and under .300″ lands. No, they are not .304″ (that figure comes from people measuring a groove to the opposite land – they’re 3-groove). The bullet is vastly oversized and is swaged by a long tapered throat. I’ll measure one, but I’d be surprised if the hardness of the originals was over 11 or 12 BHN. As for the size, that’s just how they were in the original.
Right. So I was thinking: make the bearing section Loverin-style, with lots of grooves.
But, how many people want to load heeled PP for an obscure cartridge? Not that many.
But how many people have a fat .303 with a long throat? Plenty. It just so happens that the heel is basically the same diameter as a .32/8mm gas check shank (.3015″, or correct me if I am wrong). So, here we have a bullet with a long parallel section, to nicely fill a cordite-wrecked Enfield, with a gas check. The long shank will act as another (shallow) lube groove.
Am I crazy? Perhaps.
Or I may have solved 2 problems with 1 bullet.
Thoughts?
michaelburns
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Replies
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SwedeNelson
Hi Al,
Thanks for your kind words. I’ve cross-posted to a Swiss rifles forum and also to Cast Boolits.
Some further thoughts:
– If you’re prepared to do hollow base, I guess that would make it a nose pour bullet that could be cut into either conventional blocks or blocks with cavity pins?
– A cavity cut 0.006″ wider would replicate the original all-up measurement, but without the patch, as a conventional grease groove bullet. However, at anything over moderate velocity, I suppose that would lead like a mad thing, even with a hollow base.williamdunphy
lawrencethibeault
I’m also in for a mold, and also a neck expander plug to go along with it.
I’ve got a nice 1889 Schmidt-Rubin that I bought years ago from a guy in Switzerland and because it was antique was able to have it shipped here directly ! I’ve never fired it yet, need to trim down some of the 7.5×5 brass, etc…
lwatson
Having taken one apart, it is clear that the heels are formed at swaging, together with the hollow base. It also looks like the iron nosecap was fitted at the same time – I reckon they put the cap in the die with a good burr or rim on it, and then simply swaged the lot in a single operation. But I’ve not yet melted the lead out of one to see how it was constructed.
Having just had a superb result at 300m with an FMJ, I would certainly be in for an original profile bullet (without the nosecap, of course), either grooved or not, with the hollow base. There’s mileage to recreate the original round just because, and not for any particular accuracy improvement
Alloy should probably be pure lead (the original measured at 6 BHN when I tested it, even though the documentation of the era claimed “hard lead”), or 50:1 to make casting easier.
If Al could also make a metal paperpatch template to go with it, that would be even better!
I’m sure we can organise someone on the swiss rifles forum who’s in the US to mail Al an original bullet to look at the measurements of the bullet and the patch in detail.
SwedeNelson
edpindro
adamsutherland
williamdunphy
lawrencethibeault
lwatson
lylemcelrath
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