303 Barrel Dimensions

[Bad Ass Wallace]

I have several 303's that I have managed to get shooting with cast bullets

The shooters always take me to task, when they say "slug" the bore to determine the correct size cast bullet to use. I say, all that determines is the size of the tightest spot in the barrel, better to start a boolit into the muzzle and make sure the rifling at that point (the last point of contact before exiting) contacts both the top and bottom of the lands. Then size your projectile to that dimension.

The barrel of a No.4 will be either a 2 groove or a 5 groove and measuring the "slug" of a 5 groove, the micrometer will be on top of the land on one side and between 2 lands on the other 0(i.e. inaccurate).

According to the Small Arms Identification Series by Ian Skennerton "Magazine Lee-Enfield Rifle" Page 29

1) Lee Metford and Lee-Enfield Mk1:
Barrel Specification:
Barrel Length - 30.5"
Rifling Metford - 7 groove L.H. 1 turn on 10"
Rifling Enfield - 5 groove L.H. 1 turn in 10"
Bore Dia - 0.303"
Metford Rifling Depth - 0.004"
Enfield Rifling Depth - 0.0055
Metford Land Width - 0.023"
Enfield Land Width - 0.0936

From book "The British Service Lee" by Ian Skennerton Page 86
2) Short Magazine Lee Enfield Mk 3:
Barrel Specification:
Barrel Length 25.2"
Rifling Enfield - 5 groove L.H. 1 turn in 10"
Bore Dia - 0.303"
Enfield Rifling Depth at muzzle - 0.0065
Enfield Rifling Depth at breech and to within 14" of the muzzle - .005
Enfield Land Width - 0.0936

From book "The British Service Lee" by Ian Skennerton Page 158
3) Short Magazine Lee Enfield Mk 4 & 5:
Barrel Specification:
Barrel Length 25.2"
Rifling Enfield - 5 groove L.H. 1 turn in 10"
Bore Dia - 0.303"
Enfield Rifling Depth at breech - .005
Enfield Land Width - 0.0936

It would seem from this data that an Enfield 303 could be .303" over lands and a bore of up to 0.314" at the breech and up to 0.316 at the muzzle.

My Martini 303's shoot best with a .314 dia projectile which would seem to fit with the above specifications and bore diameter of .313"

A lot of folk don't realize there are two chamber specifications for the 303; Martini Enfields, LE & SMLE Mk1 all have a chamber suited to Mk6 ammo with a 215gn cupro-nickle, While the Latter No.1 Mk3*, No4's and No5's are chambered to suit Mk7 with a 174gn boolit.

When it comes to cast boolits, this is important to choose the right boolit to limit boolit jump into the rifling, normally about 0.010" - 0.020"

My starting load is 28gn 3031 and boolit are approx 14BNH. I am presently working on testing a powder coated boolit at higher velocities.

Start by tapping a boolit into the muzzle and see where the rifling bites into the boolit. If the barrel is in good condition that cast boolit should see rifling touching the nose.

This group fired with my 1896 Martini Enfield and the CBE 220gn boolit

[Outpost75]

Here are some drawings:

Attachment 269003Attachment 269004Attachment 269005Attachment 269006

[Der Gebirgsjager]

BA--I don't know if this will help you, but one technique for measuring slugs from bores with an odd number of grooves is to wrap it with one layer of paper, subtract the thickness of the paper, and you're awfully close.

[Adam Helmer]

Guys,

I have far too many SMLEs and all shoot cast bullets well. I SIZE My boolits by trying the boolits point down in the muzzle. If the boolit goes over half down, size it over down.

Webley

[MOC031]

I have several 303's that I have managed to get shooting with cast bullets

The shooters always take me to task, when they say "slug" the bore to determine the correct size cast bullet to use. I say, all that determines is the size of the tightest spot in the barrel, better to start a boolit into the muzzle and make sure the rifling at that point (the last point of contact before exiting) contacts both the top and bottom of the lands. Then size your projectile to that dimension.

As always, it's the caster's choice of how he wants to fit his bullets to his barrel. My preference is to design - and fit - a cast bullet that is almost an interference fit between the bullet and the bullet throat/leade at the point where (depending on bullet weight/length) you have the bullet loaded out to almost maximum length for the magazine while at the same time you're also just touching or almost touching the lands.

When the flash goes off behind the bullet in the case... the bullet is going to end up eventually fitting the lands and grooves. Whether you cast and sized them over bore/land diameter, or under.

This is what I did for my Long Branch with two different moulds in one set of blocks from Accurate. I specified the slight dimensional changes after some cerrosafe casting and measuring changes. The result was that I got pretty darned close - bullets that jam in the throat/ball seate, just after touching the lands, and just before maximum length in the magazine.

Sounds like victory. And then I discovered powder coating. Meaning the two different designs have to be seated deeper now as they hit an interference fit in the throat/ball seat sooner than they did before. And my math skills suck to begin with anyways, so my math calculations might have been off a bit to begin with.

So, sometime next summer, I will probably make further adjustments to the two designs to account for powder coating, and have Accurate do it for me again. The cost for a custom mould to get the maximum out of a Lee Enfield (or similar rifle) is minimal when you think of how much you spend just driving back and forth to the range over the years, never mind the primers, powder, etc. The original mould design that I have decided is now a few thou too large in a few dimensions for use with powder coating will go up for sale.

The bottom line is I'm in the school that thinks you should think about obtaining the tightest fit possible at the point where the bullet first leaves the case mouth. I'm pretty sure that by the time the bullet is fully in the bore, it will find a way to fill the lands and grooves. The time between leaving the case mouth and being fully encapsulated inside the bore is where I think propellant gases have the most opportunity to work their mischief.

For Lee Enfields, the wide variations in size between rifles where land, groove, throat, and ball seate dimensions are concerned makes this more important in my view. My Long Branch's barrel pins at .3035" after a long day spent pouring and using lead laps until the barrel felt uniform from the start of the rifling to the bore. Immediately before the start of the rifling in the throat/leade, I get .316". I don't actually know what the groove diameter is because I haven't found anyone with the right V-blocks to accurately measure a cerrosafe casting from that five groove barrel. And I'm actually not all that concerned anyways; I'm not trying to chamber the bullet into the grooves. What I want to deal with is fitting that throat/leade diameter and nose/ogive diameters that won't touch the lands too soon.

In my Lee Enfield, this has worked very well for me and I'm incredibly happy to see how well it paid off in the accuracy I can get even with hunting velocity loads, not just scaled down loads for the range. As a bonus, the bullet designs also work very well in my grandfather's 1895 Winchester in 30 U.S. - which now has a bore with dimensions more properly found on something chambered in .303 British.

If accuracy is marginal when you're looking for improved accuracy/hunting ballistics... I think looking at how you're doing your sizing and how you're trying to fit the bullet to your rifle is worth a look and perhaps trying something different.

[MOC031]

BA--I don't know if this will help you, but one technique for measuring slugs from bores with an odd number of grooves is to wrap it with one layer of paper, subtract the thickness of the paper, and you're awfully close.

This is also supposed to work. But I couldn't see the faces of the micrometer well enough to do it precisely. Particularly while juggling the casting in one hand while manipulating the micrometer in the other. I wasn't worried enough about it to keep trying - maybe I should have put the casting in some soft jaws in the vice, grabbed a set of watchmakers magnifying spectacles, and given it another shot.

[john.k]

Far better result by simply measuring across one groove plus bore diameter.Deduct bore diameter ,and you have depth of one groove.....double this ,add to bore ,thats your overall groove dia.....As has been said countless times,if the bullet is larger than groove by around 002,happy shooter.......an undersize bullet will cause massive leading ,unless you use a wad,or some filler to block gas cutting.

[303Guy]

My thinking is to fill the throat and seat into an unsized neck. For a shorter and lighter boolit, simply shorten the nose. For paper patching that is simple because I can make smooth side molds with the dimensions and shape I want, plus I can make small diameter adjustments with paper thickness. I have made a plain cast smooth side to fit too.

I have a Martini Enfield carbine barrel on a MLE action with a very worn bore. The rifling is well rounded at the throat end but sharpens up some further down the bore then weakens a bit toward the muzzle. It shot well with paper patch so I'm ignoring the worn muzzle. In the middle, the bore is .307. I patch to .318 which seats firmly in the neck.

I'm hoping to shoot plain cast in it for lighter loads and range use.

Moco, I have a rifle that would probably suite your mold design. I like it. I do actually have a smooth side mold I made for it that I haven't tried yet. I've just developed a lube that's more of a lacquer that I want to try on it. So many projects and so many distractions!