Putting a .308 barrel on a 303 British rifle

[AbitNutz]

Due to many, many reasons I'm not going into, I'm putting a .308 barrel on one of my 303 British rifles. I have measured piles of empty brass from 1/2 dozen 303 British rifles and eight 308 rifles and have found the fired brass necks of the 308's and 303's were all about the same. In many cases, the fired 308 brass had larger case mouths than the 303 British. It just doesn't seem that that .003 makes much of a difference....however, it might.

My question is this. Do I need a custom reamer for this 30/303 British just to be safe? I'm not against it. This is going to have a Krieger barrel and the action and rifle are certainly unique but I'm not sure that any difference will be noticed in any way.

 

[boom boom]

Due to many, many reasons I'm not going into, I'm putting a .308 barrel on one of my 303 British rifles. I have measured piles of empty brass from 1/2 dozen 303 British rifles and eight 308 rifles and have found the fired brass necks of the 308's and 303's were all about the same. In many cases, the fired 308 brass had larger case mouths than the 303 British. It just doesn't seem that that .003 makes much of a difference....however, it might.

My question is this. Do I need a custom reamer for this 30/303 British just to be safe? I'm not against it. This is going to have a Krieger barrel and the action and rifle are certainly unique but I'm not sure that any difference will be noticed in any way.

The easiest is to convert it to a .30-40 Krag which is in .308--the Krag cartridge is very similar to that of the .303 British so much so that headspace rim gauges are basically identical. This would be especially important if you are using WWI era SMLE aka No. 1, Mk. 3 If you look it up, the Australians used a heavy barrel for the SMLE's which made them pretty accurate over longer strings of fire so you might want to have the Krieger barrel match that profile.

I believe that there are also some "improved" versions of Krags floating around out there that would be suitable for the No. 4 actions which are a bit stronger. The No. 4 was also used as the basis for some Brit sniper rifles in 7.62 Nato but that may have also involved re-heat treatment of the bolt/receiver or newly made receiver/bolts to spec. Ishapore arsenal also made some 7.62 No. 1 rifles but these do use a different bolt head and the receiver steel is different--I would not use a standard No. 1 for such a conversion as I do not believe the lug locking recesses would last that long and thus the rifle would out of headspace in short order--the bolt head might also peen under the load and lock up the rifle as these were case hardened if not proofed for 7.62 Nato.

 

[Slamfire]

It is a bad idea to chamber a No 4 to 308 Win. I have a British L39 conversion, standard 308 Win loads are at the proof pressure level in this action and you will encounter difficult bolt lift. You can chamber the thing, and fire it, if you use reduced pressure loads, equivalent to 303 British cartridge pressures.

Have you found a source for 308 Lee Enfield magazines?

Ten years ago the British NRA put out this warning about 308 Conversions. This action is so marginal that there are lots and lots of issues to take into account to keep from over loading the action, including not firing the rifle in the rain!. A dry case in a dry chamber will result in friction between the case and chamber, and that will lessen the load on the lugs and recesses, but controlling that friction is just about impossible. So this is a band aid fix that will failure more often than it will work. I mean, what if your fingers are greasy when you load the action, what if you sneeze on a cartridge? And then there are bullet diameters, throat diameters, warnings.

The 303 British cartridge is an accurate cartridge if used with a good barrel and you don't have any of the issues of an over pressure cartridge in this action.

http://www.milsurps.com/showthread.php?t=20339

This is the current stance of the British NRA safety warning which first appeared in the Summer 2009 NRA Journal:

Safety Notice
Enfield No 4 Rifle Conversions to 7.62mm


A safety warning concerning the use of Enfield No 4 Rifle actions converted to 7.62mm was published in the Summer Journal.

After further consideration of all factors influencing safety of these conversions and consultation with the Birmingham Proof Master, the following advice must be adhered to in respect of the use of Enfield No 4 conversions:

• Owners of Enfield No 4 actioned rifles converted to 7.62mm currently proofed to 19 tons per square inch are strongly advised to have them re-proofed to the current CIP standard (requiring a minimum mean proof pressure of 5190 bar) which allows the use of CIP approved ammunition with a Maximum Average Working Pressure (MAWP) of 4150 Bar.
• Conversions retaining their original Enfield barrel or a replacement barrel as manufactured by RSAF Enfield are safe to use with commercial CIP approved ammunition, which complies with a MAWP of 4150 bar, loaded with any weight of bullet, providing they carry a valid proof mark, and are still in the same condition as when submitted for proof.
• Conversions fitted with any other make of barrel (such as Ferlach, Maddco, Krieger etc) should be checked by a competent gunsmith to determine the throat diameter of the chamber/barrel fitted before use.
• Conversions where the throat diameter is less than the CIP specification of 0.311” but not smaller than 0.3085” must not be used with ammunition which exceeds 3650 Bar MAWP when fired in a SAAMI/CIP pressure barrel.
• Conversions which have been checked and found to comply with Rule 150 may safely be used with any ammunition supplied by the NRA including the 155 grain Radway Green Cartridge, 155 grain RUAG Cartridge or any other commercial CIP Approved cartridges loaded with bullets of any weight provided that the ammunition pressure does not exceed 3650 Bar when measured in a CIP standard barrel.
• Owners of Enfield No 4 actioned rifles converted to 7.62mm who are uncertain as to the proof status of the rifle should have it checked by a competent gunsmith.
• Owners of Enfield No 4 actioned rifles in any calibre are strongly advised not to use them in wet weather or without removing all traces of oil from action and chamber prior to shooting.
• Enfield No 4 rifles which are fitted with a barrel which has a throat diameter less than 0.3085” must not be used on Bisley Ranges.
• Ammunition loaded with bullets of any weight which are of greater diameter than the throat diameter of the barrel must not under any circumstances be used on Bisley Ranges in any rifle or barrel of any manufacture.

 

[AbitNutz]

I think you misunderstand in more than a couple of ways. I guess I didn't explain this well at all. First, it's not an Enfield. It's a Ross MkIIIB with a bad, bad bore. 2nd, I'm not re-barreling it to 308 Winchester. I'm using a .308 bore but the chamber will still be 303 British. There is no 308 Winchester involved at all. I'll be putting 308 bullets in 303 British cases and firing them down a 308 diameter barrel. This way I'll have a much greater choice of bullets. There are very few choices in .311-.312 bullets, if you can get them at all.

Also, I just talked to the folks and Clymer Tool, they make Clymer reamers and they set me straight. I'll need a 303 British reamer with a .308 pilot or bushing. They said that there is no way the pilot of the 303 British reamer, at .312, was going to fit in a .308 barrel, go figure. So there was little choice but to order a custom reamer with a custom bushing/pilot on it. That would run a whole $30 extra dollars. I said "Sold!" and ordered one. It will about a month to get here, which will beat the barrel from Krieger by about two months.

I thought about doing a wildcat based on the 303 British, like the 303 Gibbs but they won't feed right in the magazine. I hand load all the ammo for this rifle anyway and having a 30/303 British is just a better solution for me.

 

[#1buck]

I was going to suggest you use a .303 reamer with a .308 pilot. If you used something like a Pacific Reamer with their removable pilot you just get a .308 pilot with it and there is no special machining. The Pacific reamer like that is $150. I don't know what the Clymer will run you.

 

[Jim Watson]

Great, I think keeping a Ross shooting is an admirable project.
A Mk III you said in other thread. Got pictures?

 

[Slamfire]

I think you misunderstand in more than a couple of ways. I guess I didn't explain this well at all. First, it's not an Enfield. It's a Ross MkIIIB with a bad, bad bore. 2nd, I'm not re-barreling it to 308 Winchester. I'm using a .308 bore but the chamber will still be 303 British. There is no 308 Winchester involved at all. I'll be putting 308 bullets in 303 British cases and firing them down a 308 diameter barrel. This way I'll have a much greater choice of bullets. There are very few choices in .311-.312 bullets, if you can get them at all.

Wow! A Ross rifle. Those are rare!!