7.62 hand loading for L42s

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?

44gr's of N140 under a 150 SMK was the "standard" during the transitional years when people were still using a lot of No.4 actions. Max load is quoted in the Hornady book for N140 & 150gr as 45.8gr.

I used 44gr & 150 SMK's in all of my No.4 conversions.

Here is some load data however it is probably for a Remington, think its the Load Data for the M118 round.

Thank you very much to both, of you! And apologies for the miss locating my original listing.

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Originally Posted by Micheal Doyne

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?

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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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Originally Posted by Micheal Doyne

. . . 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. . .

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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.

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Originally Posted by Lee Enfield

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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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 ----------

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Originally Posted by Parashooter

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.

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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!

Quote:

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Originally Posted by Micheal Doyne

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...

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

Keep in mind the 303 was developed before 1900 and slowly evolved subsequently. Almost unchanged since about 1914 I believe.

The 308/7,62 is a shortened 30-06 known in the USA as a 'wildcat' long before introduction as the 'new' military cartridge. Thus in theory a more 'efficient' cartridge but still developed within the constraints of ages old military shooting thinking. Actually broadly similar ballistics to most military cartridges in use in the preceding about 50 years.

Generalising, pressures, etc, would be similar for most of the WWI an WWII cartridges still in use today in rifles produced in huge quantities 70 and more years ago.

Not sure about the status of the 7.62x51 NATO as a "Wildcat" of the 30-06. Savage arms had a cartridge known as the 300 Savage in the 1920's that was supposed to duplicate 30-06 ballistics in a short action (99 lever action) rifle. It did so with 150 grain bullets. It is almost a clone of the 7.62x51 with the neck being slightly shorter. Winchester used it as a basis for the T65 round and then introduced the T65 as the 308 Winchester prior to the adoption of the 7.62x51 as the NATO standard round sometime around 1951. It was the advent of Ball powders that allowed smaller cases to duplicate the ballistics of larger cases. Anything the 7.62x51 can do, the 30-06 can do it better and faster. The downside is the less than 100% case fill with certain powders (medium burn rate like IMR 4895) and the long case. You can load the 30-06 up with slower powder but all the ammo produced by military arsenals around the world needed to consider the M1 Garand and stuck to 48-50 +/- grains of medium burn powder.

Dave

There were and still are many 'wildcat' cartridges based on the 30-06 case shortened, necked up and down. The same with many other cartridges, such as the 8x57 [Germany], 303 [Australia and Canada], 7,62x54 [Finland], propriety British big game cartridges on which many well known commercial cartridges are based, etc.

Many 'brand new' cartridges can be traced back almost to 1900. The book 'Cartridges of the World' by Frank Barnes provides hours of enjoyment when you read the detail and compare the dimensions of cartridges. Fascinating to see your pet 'wildcat' that you are developing for a specific use already existed decades ago. You will be astounded how many cartridges share the basic head dimensions of the 8x57 Mauser cartridge family from 1888 and British H&H cartridges from about 1925.

A colleague of mine spent a lot of time on wildcatting a family of cartridges based on the 9,3 Brenneke; wasn't impressed when I showed him it had been done in Europe about 50 years before he started.

Some useless information:
The 8x57 line up - all commercial - starts with 6x57 and goes to 10,75x57.
30-06 starts with 25-06 and ends with 400 Whelen.
The 6,5x57 predates the 257 Roberts and they are basically the same.
Etc.

Not disputing the status of any cartridge. You could say the 30-06 is a "wildcat" of the 30-03 as it has a shorter case length. If anything the 7.62x51/308 Winchester is a 'wildcat" of the 300 Savage, which is most likely a "wildcat" of the 30-06, at least the case head and rim are the same. For years "Magnums" had a belted case. This started due to the long low angle shoulder of the original 300 and 375 H&H magnums. They basically made a rimmed cartridge that would work in bolt action rifles without tricks and not have a real rim. When people started "wildcatting" these cases the belt just stuck around (7mm Rem, 300 Wby, etc.). Current Magnums and short Magnums have dispensed with the belt. Nothing new under the sun as they say. I believe that the 5.56x45 NATO/223 Remington were "wildcatted" from the 222 Remington Magnum. I love COTW. Great reading and more information than you can use in a lifetime.

Dave

So last weekend I made up 50 rounds of necksized once fired ggg cases, cci bench primers, 44grns N140, 150 gen SMK FMJ, with OAL 2.70”

I was zeroing a new sight to rifle and while I was at the range office I grabbed a few GGG 147grn. Down at the zero range I decide to dial it in with the GGG factory and then confirm where things were with my hand loads. The end point of the GGG was two rounds though a single hole (no great feat given the ~71’ range). Now for my confirmational shots with the hand loads, four holes a tad lower close but by no mains touching.

Rather disgusted I loaded a could more GGG and while the single hole enlarged or was still very much one round hole.

Upset I pulled out some 1980 144grn IMI, 4 rounds in a single hole a little lower and right.

So far when ever I've compared my 303 hand laods to PPU mine have very much proved superior. Is PPU 303 setting the bar for seasonal handlaoding low, is my 762 recipe way out, or do j really need to brush up my reloading game?

Any thoughts welcome!!!

I use 46 grains of RS50 over a 150grain SMK in my L42. I experimented with lesser charges but found the accuracy dropped off.

RS50 is almost identical in burn rate to N140. Might be worth trying a slightly higher charge.

Interest, I was also running a lee volume type.powder measure and the lee balance measure. I have just panic bought a second hand RCBS loadmaster lite, I'm in two minds as to whether it was a good idea but we will see.

Last time I looked at PPU .303 factory "ball" loads, they were using a 174gn BOAT-TAIL. This may have something to do with the results downrange. Because of the minimal contact with the "generous" dimensions of your average mil-spec .303 barrel, the bullets tend to "precess" a bit on launch.; describing an "orbit" around the nominal trajectory. This actually become proportionally smaller, the further down-range you get, because the spin rate stays pretty much the same whilst the bullet steadily loses forward speed.

Thus, it is not unknown for the groups at 300+ to be proportionally smaller than those shot at 50 or 100. Then there is "spin-drift" wherein the trajectory curves to the right or left of the anticipated flight-path. This stuff matters a LOT for those indulging in 1000 yard-plus shooting. My hunting rifle in .308 is zeroed to be "dead-on" at 200 yards with a 150gn bullet as hand-loaded. This means the bullet is roughly three inches high at 100 and about nine low at 300. In over fifty years of shooting, I have NEVER tried to take a shot at serious game at 300 yards with a .308 Win. If I can, I will happily walk as close as I can get before pulling the trigger. Sneaking up to rock-throwing distance on a hat-rack is at least as challenging as nailing one with a light field-piece at 400 yards.

In my wilder, younger, service days, I did my share of 600 to "zero" run-downs / 'fire and movement" shoots. On the trusty old L1A1, start with the rear-sight set for the first range to be fired and go with it. By the time you got to 300, the pace was picking up and thus, the rear-sight was pulled hard back to the 200 stop and hold-over / under applied as required for the rest of the ranges. Taking your eye off the targets popping up and down would lose valuable aiming time. The final rounds were snap-shots fired at briefly appearing "Hun's Head" and similar targets at ranges of under 25 yards. Not a relaxed day of bench-resting, by any means. KNOW YOUR RIFLE AND AMMO.