7.62 hand loading for L42s

[Lee Enfield]

So I uber got my self into a little bit of a confusion on what is safe to hand load for my L42 clone, it is made from all original parts with a 20 tons proof. I can only find official load data for 308 Win, or people’s kids data for 7.62 NATO. I am aware that both 308 win and modern 7.62 are more powerful than L2A2 ball, and I am rather concerned that 20 Tons per square inch is only 44,800 psi and my published data likely being for SAAMI 308 at 62,000 psi.
So am I just being over sensitive or does any one have any pushed load data or personal that they can share?

Component wise I am happy to consider anything readily available in the uk, but I have on hand: N140, IWI and GGG cases, CCI BR primers, and Sierra 150 SMK or 155 TMK bullets.

Thoughts?

There is a lot of BS floated regarding 7.62 conversions of the Lee Enfield.

Simply put, be aware that .308Win and .303 British have identical case capacity of 56 grains of water.

If you are concerned with weakness of the No4 action when converted to .308/7.62 simply use .303British load data for that weight of projectile.

It may (or not) surprise you to know that the common fall back load 174-180grain bullets for .303 Brit of 41-42grains of IMR4895 - is the exact same load used for 7.62 NATO 175grain (and 168grain) match loadings....

As always, load data is specific to my firearms, primers, cases used, bullet seating ect play a role in creating pressure.

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[Micheal Doyne]

There is a lot of BS floated regarding 7.62 conversions of the Lee Enfield.

Simply put, be aware that .308Win and .303 British have identical case capacity of 56 grains of water.

If you are concerned with weakness of the No4 action when converted to .308/7.62 simply use .303British load data for that weight of projectile.

It may (or not) surprise you to know that the common fall back load 174-180grain bullets for .303 Brit of 41-42grains of IMR4895 - is the exact same load used for 7.62 NATO 175grain (and 168grain) match loadings....

As always, load data is specific to my firearms, primers, cases used, bullet seating ect play a role in creating pressure.

That is very interesting. I had not realised the case capacities where the same, looking at the them I would have always assumed .303 was greater.

Will a 7.62 round with the same mass bullet not develop more chamber pressure due to the bottle neck carriage and relatively smaller bullet diameter? That said will I would assume that to be the case, I have no idea if it is material or not? Any fluid dynamics experts please chime in now...

---------- Post added at 05:19 PM ---------- Previous post was at 05:15 PM ----------

You are comparing apples and pomegranates. The 20 ton (44800 lb.) figure is the archaic axial crusher measurement (normally some 10-15% below SAAMI radial crusher figures - expressed today as "CUP") and the SAAMI 62000 psi number is a piezo transducer result. SAAMI MAP for .308 Win. is 52000 CUP. Essentially, all these numbers represent the same pressure - it's the measuring systems that differ.

As a sanity check, consider the .303 British at -
41440 lb. (18.5 tons) axial crusher,
45000 CUP SAAMI crusher MAP,
49000 psi SAAMI transducer MAP.

Thank you I was really hoping some one would come in with this! I could remember reading this a while back (before I had a 7.62) but couldn’t find it so was hoping this would prove it without leading too much. Cheers!

[Parashooter]

Will a 7.62 round with the same mass bullet not develop more chamber pressure due to the bottle neck carriage and relatively smaller bullet diameter? That said will I would assume that to be the case, I have no idea if it is material or not? Any fluid dynamics experts please chime in now...

The practical effect of either or both of these factors is negligible in this case.