Why this insistence on Groove Sized bullets for Carcano??? The Original Design Parameters for the 162gn RN FMJ bullet was a Shank of 6,7mm (.2638",) base to the neck crimp cannelure, tapering to 6,5mm ( .2559") at the beginning of the Ogive.
The open base then Upset to fill the Grooves, whatever their diameter ( with the tolerances of the time, ) could be anything from .267" to .271" .
This is what is called " Base Upset Obturation", a principle first enunciated by Minie' ( France) and extended to the Rifled Muzzleloaders of Enfield ( Britain) and Springfield ( USA) by the 1850s.
The method was carried on into Breechloader Days, by Snider ( Enfield )
By the time of the Jacketed Bullet, a new problem arose...increased heat and pressure of Nitrocellulose powder, increased hardness of jacket material, and increased metal fouling of rifling from CuNi or GM jackets.
To alleviate all these problems, Double Based/ Cordite Powders were re- formulated to be "cooler" and less erosive
( Ballistite to Solenite-Italy; Cordite to Cordite MDT in Britain,
etc.) And the Bullet was designed to have a minimum engagement surface area, by only having the Base act as an artillery " driving band", the rest of the bullet barely being engraved by the rifling, hence effective obturation, effective spin generation, reduced pressure and friction, reduced fouling.( also reduced heating of barrel, and reduced felt recoil).
Changing to a Spitzer design, caused several changes...the shank went to Near Groove Diameter ( not enough Inertia in a lighter bullet to allow sufficient Base Upset, so Shank had to be larger)
BUT the Russians took a Belt and Braces approach with their 1908 LP projectile, they gave it a 45°
Divot in the Lead base, to allow Base Upset ( same as 1891 RN bullet). Thus any manufacturing variation in Mosin's rifling depth was allowed for ( .310"-.314").
The British MkVII ( Spitzer) projectile also used B.U.O., as Wartime SMLEs and Previous MLEs Rifling could go out to .314" from the nominal. 311" of the spec.
All Bullet-to-Rifling is a Compromise to get the best result over the longest time.
This note applies to open-base
Lead-core Jacketed bullets ( ie,
FMJ) ; Not Boat-Tails of any type, or Sporting Projectiles ( SP or HP).
Lead bullets are a Totally Different Ball Game....best left alone by Y.T.
Happy New Year all
Doc AV
Down under. ---- Rain, Rain and More Rain...Noah, what were those Measurements again?
The open base then Upset to fill the Grooves, whatever their diameter ( with the tolerances of the time, ) could be anything from .267" to .271" .
This is what is called " Base Upset Obturation", a principle first enunciated by Minie' ( France) and extended to the Rifled Muzzleloaders of Enfield ( Britain) and Springfield ( USA) by the 1850s.
The method was carried on into Breechloader Days, by Snider ( Enfield )
By the time of the Jacketed Bullet, a new problem arose...increased heat and pressure of Nitrocellulose powder, increased hardness of jacket material, and increased metal fouling of rifling from CuNi or GM jackets.
To alleviate all these problems, Double Based/ Cordite Powders were re- formulated to be "cooler" and less erosive
( Ballistite to Solenite-Italy; Cordite to Cordite MDT in Britain,
etc.) And the Bullet was designed to have a minimum engagement surface area, by only having the Base act as an artillery " driving band", the rest of the bullet barely being engraved by the rifling, hence effective obturation, effective spin generation, reduced pressure and friction, reduced fouling.( also reduced heating of barrel, and reduced felt recoil).
Changing to a Spitzer design, caused several changes...the shank went to Near Groove Diameter ( not enough Inertia in a lighter bullet to allow sufficient Base Upset, so Shank had to be larger)
BUT the Russians took a Belt and Braces approach with their 1908 LP projectile, they gave it a 45°
Divot in the Lead base, to allow Base Upset ( same as 1891 RN bullet). Thus any manufacturing variation in Mosin's rifling depth was allowed for ( .310"-.314").
The British MkVII ( Spitzer) projectile also used B.U.O., as Wartime SMLEs and Previous MLEs Rifling could go out to .314" from the nominal. 311" of the spec.
All Bullet-to-Rifling is a Compromise to get the best result over the longest time.
This note applies to open-base
Lead-core Jacketed bullets ( ie,
FMJ) ; Not Boat-Tails of any type, or Sporting Projectiles ( SP or HP).
Lead bullets are a Totally Different Ball Game....best left alone by Y.T.
Happy New Year all
Doc AV
Down under. ---- Rain, Rain and More Rain...Noah, what were those Measurements again?
ive never heard of blue collar. These might not be bad either
