Gas check required for 1889 Schmidt Rubin? Which alloy is best?

[blabablab]

Hello All,
I have read a few forums on reloading GP90 for the 1889 SM, but they all say to use a gas checked bullet, though I believe the original bullet was a paper patched tapered .316-.307 hard cast lead bullet. My question is, do I need to use a gas check? If not, would using a .308 hard cast paper patched bullet work well? Also, what brinnell hardness, or alloy would you recommend for a load going about 1600fps with a 180grain .308 hard cast bullet?

Lastly, I realize this is probably a dumb question, but I origionaly thought that GP90 was a black powder round; my question is, is GP90 just a lower pressure smokeless round, and if so, why did they do this?

Thanks!

[runfiverun]

they had three different rounds one in x53 one in x54 and one the k-31 in x55.
some of the older [98/11's] rifles were re-chambered to the longer cartridge.
trying to recall here.
but I think the x53 round did have black powder loads that could have been tapered [just not quite that much]
B/P bullets would have been bore sized and then wrapped to groove then punched along when fired.
the load would have been fairly slow since the sharp shoulder alone would have increased pressure by 2,000+ psi.

what I would do [did for my 98/11] was/is to just use load data for the 308 and the rcbs 30-165 silhouette boolit for paper punching sized and checked to .310.
this also works very well in the K-31 rifles.

I have also used the magma engineering plain base 165gr rnfp on top of a light load of unique for 50 yd hole punching. [98/11 only]