M1870/87 VV FPs are Longer, and fatter than those for the M70/87/15 Carcano 6,5 conversions. This is because the Bolt face ( '15) is recessed for the rimless case, and the old FP hole drilled out and sleeved for a smaller tip.

I don't know whether in 1915, they shortened and thinned down the original FPs, but I think it would have been easier and more efficient to make New Pins ( and of Better steel).

I found out that a proper '15 pin will fit in a 70/87, but is too short for proper firing pin protrusion, and sloppy fit in Larger FP hole of the Black-Powder Bolt.

Fudging an old FP for a newer rifle (so to speak) is not good practice.

Doc AV