Reduced 7.62x51 loads

[Otley]

Hello there - this is my first post on what looks like a most useful site. Thank you for having me! I live in the UK and have a question that I would appreciate some help with.

My local target range is limited to 100 yards and I shoot my .308 bolt action rifle there. I have a good supply of UK Radway Green military surplus 7.62 NATO ammunition going back to the 1970s and 80s. I've pulled a few rounds and they seem to be loaded with 43 grains of Nobel No 2 rifle powder. The Nobel manual lists a starting load for 150 grain bullets of 40 grains of No2.

I'd like to reduce the load to reduce wear on my barrel, shoulder and ears. I see no risk in pulling the bullets, dumping the powder and reassembling with 40 grains of powder, but I'd like to drop it further - to, say, 35 grains, or even 30. For economy, I want to use the powder that the round came with.

My question - do I risk detonation?

My understanding of how a cartridge works is that the primer flash envelopes each particle of powder, that then starts to burn at a rate that depends on the chemistry of the powder, its geometry (No2 is a chopped cylindrical powder) and the prevailing temperature and pressure in the case. The difference between a full case and a half full case is that some particles may start to burn later with a full case because the primer flash can't fully envelope them.

But I can't for the life of me see how a half filled case will allow any powder particle to burn instantaneously and cause this detonation phenomenon - I can see that the pressure may even be too low to sustain the combustion of each particle and I'll get unburned powder, but not detonation.

My question - is detonation a myth? Does anyone know of a case of detonation that is not hearsay?

Thank you.

[Otley]

I've just done what I should have done before posting - search the internet for light load detonations. It would appear that detonation of half full cases is a myth, but no one will commit to saying it will never happen. So my question might be better phrased as has anyone used 30 - 35 grains of a medium rifle powder behind a 147 grain FMJBT bullet in 7.62x51?

Thank you again!

[Thumbcocker]

There is data out there from old sources about using fast pistol powder with jacketed projectiles for small game and target loads. The U.S. had what was called a "Guard Cartridge" in .30-06 loaded with at 150 grain bullet and bullseye powder for around 1200 fps (IIRC). Not exactly what you are looking for but might be useful.

[castalott]

Hi Otley! Welcome I know it doesn't relate to your powder but I remember reading an article on reducing 4895 powder to 60 or 70% of maximum. I also 'think' the the latest Lee Loading Manual talks about and has data for very reduced loads in rifles. ( I am old and the memory fades.)

Like you, I don't want to use full power loads to shoot short distances. There is just little sense in it. We use the Lyman 311410 (Miha makes an improved version in hollow point) 130 grain plain base bullet with a few grains of some of the faster powders for a short range plinker. ( I don't give out data on the net) I get the best accuracy at just under the speed of sound.

I like other bullets too such as the ones for 32-20 and such. Short bullets can drive you crazy sometimes so a heavier (longer to suit the twist) one might be called for.

Not considering equipment cost, these loads are cheap to make and FUN to shoot. But one danger is too slow and sticking one in the barrel.

Sorry if my reply has drifted away from your question but I shoot so few jacketed bullets anymore that I wanted you to know another option.

By the way, my Sainted Mother was English, Irish, Scottish, French and American Indian. We are probably related... Have fun...Dale

[Outpost75]

If the original powder used in the RG ammunition is an extruded, tubular type, there is no issue reducing it to as low as 75% of the service charge.

If the powder used is a SPHEROIDAL propellant, do not reduce below 85%.

[williamwaco]

If you can get it. Try 8 or 9 grains of Unique. It will produce around 1200 fps with any bullet from 125 to 170 grains.?

[runfiverun]

if the burn rate is a medium speed powder then reducing it should pose no issue.
43 grs under a 150 sounds like it is in the 4064/varget area and a reduction to 70% would do nothing more than slow the bullet down.

a ball powder like Outpost mentions won't reduce that far but it can be lowered.

[Otley]

Thanks for the replies. 75% of 43 is about 32 grains, so I'll try that. Why should ball powder charges not be reduced, where stick powders can be?

[Outpost75]

Thanks for the replies. 75% of 43 is about 32 grains, so I'll try that. Why should ball powder charges not be reduced, where stick powders can be?

Ball powders behave erratically when reduced below their usual machine loading limits.

You can get hangfires, misfires, or ring a chamber.