No4 enfield pressure limits

[Thundermaker]

I've been studying the enfield rifles lately. In my conversations with an old high power shooter, I've learned that the match load used by army marksmen in their M1As (back when they used them) fired a 175 grain bullet at 2500fps through a 1:10" twist barrel. It occured to me that this is very close to a standard .303 military load in a no4 enfield. However, the .303 does so with lower pressures. That got my wheels turning. I wonder if I can get 260 remington velocities (2700fps with a 142) on the .303 case with lower pressures? I'm interested in hearing about experiences in .303 wildcats and enfield rifle caliber conversions.

[Multigunner]

You might look into a powder called IMR 4007 SSC.
The SSC stands for "super short cut" the extruded granules being very short.
Loading data from Hogdons indicates good velocities with much lower pressures that other powders.
Pressures listed for a .303 load that equals the MkVII military ball load give much lower pressure than the AWP of the milspec loads. SSC gave less than 40,000 CUP while the listed pressure of the milspec load is 45,400 CUP.
No.4 rifles converted to 7.62 NATO are limited by the NRA UK to the 53,000 PSI pressure range unless re-proofed to CIP standards (75k psi Proof cartridge). That's several thousand PSI greater than the 49K PSI allowed for the .303 cartridge but far below the pressures of many 7.62/.308 long range match cartridges.

[Thundermaker]

BL-c(2) is a good one too. The starting load puts a 174 out at around 2450 with, IIRC, 36,000psi. Max load puts it at 2600fps with 39,000psi. All my logic tells me that pressures shouldn't get too high, given the lighter bullet. The round shouldn't produce as much back thrust as a .303 service load, but I could be wrong. I'm just wondering where to start with loads. I've read about a 6.5/303 cartridge, but no one has any load data. I could use 25/303 data as a starting point I guess.

[Outpost75]

In my experience the No.4 rifles converted to 7.62 NATO never held up very well and even if they had the extra stiffening rib welded to the receiver, bolt compression was still a problem and you were certain to have to fit a new bolt head to correct loosening headspace before the barrel was shot out. Even with the stronger Savage or Long Branch rifles I would not be inclined to exceed standard SAAMI or CIP pressures for the .303 British cartridge unless you have headspace gages and an assortment of bolt heads.

[Thundermaker]

I guess It's good I'm not converting one to .308 then. 308 is an aggrevating caliber to load for, properly anyway. Backthrust seems to be the limiting factor. The Austrailians convert a lot of no4 rifles to .223. Even though the pressure exceeds .303 limits, the actual thrust against the bolt is much less, so it causes no problems.

[303Guy]

Hodgdon shows H4350 driving a 180gr bullet to 2500 fps within the allowable pressures and it has the advantage of filling the case before max loads. I don't load to max because I want my cases to lase forever.

There are European powders that are claimed to produce 3000 fps with 150 gr bullets! They do not give the pressures though.

[Multigunner]

I guess It's good I'm not converting one to .308 then. 308 is an aggrevating caliber to load for, properly anyway. Backthrust seems to be the limiting factor.

The short COAL is a factor when using heavier bullets in the .308.
The heavier and longer bullets protrude into the powder space reducing effective case capacity.
The .303 doesn't have this problem because it was designed for the long heavy 215 gr bullets, and the long for its weight MkVII bullet. Solid lead core 175 gr bullets don't extend into the case as far as the MkVII bullet would, so lead core 175 gr bullets allow more effective case capacity.

So long as only 150 gr or lighter bullets are used with the .308 its a pretty mild cartridge with working pressures of around 48,000 CUP when using suitable powders.
The .303 when loaded using the 150 gr velopex got around 2600 fps, not much less than the original 7.62X51 test rounds which got about 2700 fps.
The 7.62X51 was never intended to be a hot cartridge, just a compact cartridge better suited to autoloaders than earlier main battle cartridges while maintaining similar power levels.
The sporting version, the .308 was intended as an updated .300 Savage, giving near .30-06 performance while being better suited to a wider range of action types than the .30-06, including the Savage Lever Action as it turned out.

[Thundermaker]

I may not have been clear in my original post. I'm thinking about necking the .303 down to 6.5mm.

[Multigunner]

I may not have been clear in my original post. I'm thinking about necking the .303 down to 6.5mm.
I think this has been done using 6.5 Japanese barrels fitted to Lithgow No.1 actions.
Since the .308 has been the highest pressure cartridge used in the No.4 it deserved some mention.

[Bret4207]

Seems like Ellwood Epps up in Ontario did a 6.5x303 back in the 50's or 60's. Might look into it.

[BruceB]

The experiments carried out in Canada, Australia and New Zealand over the years covered the modification of the .303 British case to virtually ALL of the common bore diameters, as well as some of the more-unusual ones.

Being a useful, moderate-capacity case (especially in its straight-body reincarnations) the .303 makes a very fine rimmed wildcat for single-shot actions, and if the 'smith is up to the challenge of getting it to feed from a magazine, it works well there, as well.

It's rather neat to see these old warhorse cartridges being adapted to peaceful pursuits.

[Multigunner]

First time I picked up a .303 cartridge I knew I had to get a .303 rifle.
The .303 MkVII cartridge looks and feels like you could throw it hard enough to kill something.

They say you can reform the .303 case to make 6.5 Manlicher cases. Some Dutch 6.5 Manlichers were rebored or re barreled to .303 , most apparently lost in a ship sinking but a few show up now and then.
Look into 6.5 Manlicher load data.

PS
That would be the Dutch 6.5X53R not the MS 6.5X54 .

[303Guy]

The 303 case has the same capacity as the 308 to the base of the neck (depending on case make) I have a 25/303 which lies right between the 257 Roberts and the 250 Savage. I've used an averaging of the two where powders and loads have similar pressures to find a guideline max load. The results bear out with actual loads in so far as case appearance compares with 303 loads. Being a 1942 Lithgow I am not scared of near max loads (43,500 CUP). Comparing two different sized cases is not reliable as sometimes the smaller case delivers nearly the same velocity and pressure as the bigger case but with less powder.

[Multigunner]

The 303 case has the same capacity as the 308 to the base of the neck (depending on case make) .
The difference between Case length and cartridge OAL for the .308 is .785. The difference for the .303 is .855. So when the heaviest bullets are used the base of a .308 bullet will extend into the powder space .070 further than the same length bullet in the .303. This reduces effective case capacity of the .308.
Pressures for the .308 when using the heaviest bullets will be a bit greater than with a equivalent .303 load of the same velocity. Lighter bullet loads, in the neighborhood of 150 gr, are closer in working pressure for the same velocity, unless you seat the lighter bullet further out when loading the .303, which I do when using the Hornady 150 gr .312, to reduce bullet jump to origin of rifling.

Some owners of .308 rifles have had the throat deepened to allow them to seat heavier bullets further out.

The working pressure of the .303 MkVII cartridge when expressed in CUP is 45,400. SAAMI rounds off pressures to the nearest thousand so their recommended limit is 45,000 CUP.

I considered having a 6.5X57R barrel made for a No.4 action, but quoted max pressure of this cartridge is a bit higher than I'd like and COAL is a hair too long for the magazine. It would have been a hand loading only proposition.

[Thundermaker]

It's just something I'm considering, given the number of bubbatized enfields I see for $100 or less. I would never modify my all-original No4 longbranch. I will be putting a parker hale 5c match rear sight on it and shooting high power with it. I've done no accurizing work to it, and It shoots 1.5" @ 100yards with PPU ammunition.

Has anyone here built a rifle from a nepalese martini?