Criterion barrels and .314" diameter bullets

[Musgrave]

Hi Folks,

I'm not a very frequent contributor to this forum but I thought I'd share some findings.

I bought a 1953 vintage No.4 a few years ago which was fitted with a new Criterion barrel machined to 0.303x0.314" internal dims. Slugging the barrel would suggest the .314 groove was a bit optimistic and I have struggled to achieve anything better than 4moa with boat tailed bullets and 2 moa with flat based 180gn Sierras (or my dwindling supply of Dutch 174gr Mk7 flat based bullets). Careful measurements of these bullets suggested that biggest measured only 0.31145" and the skinniest (Hornady 174gn FMJ) 0.31005". Recovery of some of the spent bullets indicated rifling engraving depth was not equal but very much eccentric causing substantial in-bore yaw and a corkscrew flight pattern to the target. So the I set about trying to find a solution. I'm not much interested in cast bullets but wanted something I could use on the ranges out to 600 yards and maybe even 900 or 1000x. It had to have a jacketed construction. I settled on trying to reduce the diameters of larger bullets and picked the .322" PPU 196gn bullet.

I bought a 7.95mm reamer off eBay and set about making a die. This would in theory give me a bullet of 0.313" but it proved too hard a shove to pass through the die with my Redding BigBoss press. So I set about making a die to reduce the bullet to 0.319 (an 8.1mm reamer) and spent more time getting a nice finish on the inside with a soft wood dowel and metal polish. This gave me consistent and concentric bullets measuring 0.31935 to 0.31955 (measuring for ovality). Around about this time I realised LEE offered a 0.314" Swaging die (#90044) and I bought one of these. The net result is very good. Passing my 0.319" bullet through the LEE die give me very nice bullets measuring 0.31445 after 48hr spring back and less than 0.00040 run out of ovality which is on parr with a jacket made by Sierra.

The spigot I made to shove the bullet through the die has a nipple on the top which ensures the bullet is pushed by lead core and not the jacket, the theory being core is seated into the jacket again and there won't be any jacket/core separation.

These bullets shoot well and I have expended a few hundred of them. It has transformed the rifle into a capable machine. Although it's hard to shoot a consistent 1MOA group with my No32 scope, the rifle will do it reliably with a better high mag scope with decent parallax adjustment.

The bullet has a length of 1.340" after sizing and the nose profile is marginally less pointy than a Sierra SMK or such. In the standard CIP/SAAMI chamber you end up with a round of 2.950" COAL and about a 0.020" jump to the rifling. The round still feeds. I have tried several types of brass but PPU seems best. HXP does not work as it is too thick at the neck to provide enough clearance and it can get stuck in the chamber neck area. PPU brass is gives about 0.003 clearance in this zone which is fine.

I attach a pic of the groups shot a 100 yards off a rest with my No.32 scope (an original William Watson MK2 which I refurbed). PPU brass, 196gn PPU bullet sized to 0.3145". 40gn of RS50 and a S&B LR primer. MV is 2385fps. The rifle is blatant T replica, made of spare non matching numbered bits, the only original "T" bit is the scope! I have an unmolested Longbranch when I need to feel less dirty.

Ron

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.