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

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[wesson357]

Very good idea too resized. 323 bullets!
I have a repro no.4T with a .314 barrel. It shoots quite well with hornady .312 but, as I have a bunch of .323 bullets I don't use, I'll sure try to resized them to .314. Can't be wrong I guess.

[browningautorifle]

Not the first time we've had this discussion here...what surprises me a bit is they spring back after swaging. I have done thousands of lead bullets over the years and never thought to check to see if they returned at all. Now, I'm only swaging a thou or two. But mine can sit two or more years sometimes.

[Bruce_in_Oz]

A couple of things:

.303 Brit runs some funny numbers for 'service" barrel dimensions.

On the original barrel drawings, of which I have seen a few, BORE diameter is .303" + a thou'.

Because there are FIVE grooves, (generally), the "groove diameter" is actually determined by individual groove depth relative to the bore diameter. (Assuming original production using indexed, single tooth cutters). Thus if you got a barrel with a "perfect" .304" bore with rifling, cut to "maximum" depth of .008", you would have a notional groove diameter of .320" and STILL be "in spec" / close enough for government work..

Mil-spec .303 bullet diameter is pretty tightly controlled at .311 (especially peace-time Commonwealth production) and standard BALL ammo for general use is FLAT BASED. Mk8Z is boat-tailed and was SPECIFICALLY developed to achieve extend-range performance in MACHINE_GUNS. The one big benefit of boat-tails is that they generate less base turbulence, and thus, drag and "deviation" at trans and subsonic velocities. This allows less "random" dispersion at ranges beyond 1200 yards.. At 196 gns, this bullet is not a "clone of a Mk8, which came in at 180gns. These heaver .322" PPU bullets are probably sS bullets for 7.92 x 57. .

Boat-tails are a REALLY bad thing to fire in a "pre-loved" mil-spec barrel.

The other thing about Lee Enfields is that as the ammo "developed", the rifle and machine gun designers had to "adapt" the design to work with the "new ammo. Hence, over a century of service the overall length of the loaded "issue" cartridge stayed pretty much the same. Change the overall length by changing bullets and EVERY box magazine and every belt and pan feed mechanism has to be changed. The old Mk6 220gn round-nosed bullet was fine, but the 174gn Mk7 was a LOT better. However, the adoption of the Mk7 required a total redesign of the rifle mags to achieve reliable cartridge retention and feed.

However, all that said; if you are obtaining 100yd groups like those posted, whatever you are doing is fine.If your groups at 600yds are proportionally larger AND more-or less in the same horizontal alignment, you have done really well.