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Minimum Loads Safe ?

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Kurt
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Minimum Loads Safe ?

#1 Post by Kurt » Fri Jul 21, 2017 10:50 am

I am working with a 1916 Spanish Mauser 308 and so I have been reading about minimum loads a little bit. My reading indicates a strong concern from writers to avoid going below the minimum listed in the manuals for fear of detonation. I also want to load for low pressure[/band I believe going to low would actually increase pressure? So my concern is this; My Lyman book list 40 grains IMR3031 as minimum, Hornady lists 36.3 and I have read that for the Spanish '93 7.62, to use 300 Savage data which lists 34 grains? What do you gentlemen think? Lyman's 40 grains show a pressure of 36000 CUP.
Last edited by Kurt on Fri Jul 21, 2017 3:30 pm, edited 2 times in total.

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Re: Minimum Loads Safe ?

#2 Post by dezzertrat » Fri Jul 21, 2017 11:08 am

I believe going below minimum is very dangerous for certain slow burning powders and some ball powders. If you want a mild load, Hodgdon H4895 is good for that. Their website has information on reduced loads for less recoil using that powder.

It's called the 60% rule. Find the maximum load (not the starting load) for a particular caliber and bullet, and multiply that by 0.6. That is the lowest safe load.

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Re: Minimum Loads Safe ?

#3 Post by Tommy Atkins » Fri Jul 21, 2017 2:17 pm

FWIW I check several different manuals & us e the lowest high through the highest low as my working range.

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Re: Minimum Loads Safe ?

#4 Post by Rapidrob » Fri Jul 21, 2017 6:11 pm

The loads you list will work fine. Before your rifle "blows up" from too light a load, you will get a lot of blow back into your face as the case will not seal the chamber. This will be serious to your face and folks close to you.
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Kurt
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Re: Minimum Loads Safe ?

#5 Post by Kurt » Fri Jul 21, 2017 11:30 pm

I assume both Lyman and Hornady know what they are doing. Actually I'm certain after thinking about it but it is puzzling how one has a 40 grain minimum load and the other 36 but I guess that is not that much. I am going to the range tomorrow, if the rain is tolerable. Thanks to all for your replies and advice.

I will watch for pressure signs.

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Re: Minimum Loads Safe ?

#6 Post by ammolab » Sat Jul 22, 2017 7:19 pm

:mrgreen: You will be fine with any conservative .308 load. All Spanish GI ammo, both 7.62 CETME and 7.62 NATO has THE SAME chamber pressure listed on the Spanish Arsenal ammo data sheets. There never was a low pressure load for converted rifles. The CETME round was designed for low recoil in auto fire, not low chamber pressures.

The 36,000 psi load is well below the original 7x57 pressures the gun was used to.

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Re: Minimum Loads Safe ?

#7 Post by Kurt » Sat Jul 22, 2017 9:16 pm

I went to the range today and fired the ten rounds i had loaded. Unfortunately there was a minor problem in that the firing pin marks seemed to punch through slightly and show a bit of gas escape. No primer protrusion and the smoke appeared only on the case neck not the body, that I could see. Bolt opened easily too. Not sure what the problem was as I loaded 36 grains IMR3031 with 143 grain bullet, FMJ. This is just a shooting load, nothing special intended. Could it be that the firing pin is just hitting hard? Your thoughts appreciated. Thank you.

7/27/2017 After some thought I think I know what was going on. To size these cases I had turned the die in to touch the ram at the top of the stroke but the cartridges would not chamber. I reset the die a quarter turn deeper and still no good, so I went a quarter turn more. I think this may have been a bit too much and head space became excessive. I will be loading more today and backing off a bit. This stuff is fun! I wish the range was closer to home.

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Re: Minimum Loads Safe ?

#8 Post by noylj » Fri Jul 28, 2017 5:51 pm

Do you have a manual that calls out MINIMUM loads, or just STARTING loads. Starting loads are generally only a 10% reduction in charge weight from the MAX loads and don't represent any sort of minimum load.
Richard Lee is the only one I know who has ever called the starting loads "minimum loads," and he hasn't even developed any data himself.
If you really want to go lower, you move to faster powders. You can look up Red Dot and "The Load."
Detonation: IF it happens, it happens in LARGE capacity cases with relatively SMALL quantities of powder, where about half the powder is against the primer and the other half is against the bullet. This was found NOT to have any relationship to what any shooter will find. So, unless you are well under about 30% of case capacity, the mythological Detonation is not an issue.
What is an issue are reloaders who NEVER look into the case and observe the charge height in the case and miss problems.

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Re: Minimum Loads Safe ?

#9 Post by les1234 » Fri Jul 28, 2017 6:13 pm

Kurt: you may have a problem with excessive firing pin protrusion, or a rough tip on the firing pin. As to case lengths, once the shellholder contacts the die, that's as short as it gets. Turning the die in farther will just stop the ram sooner, but not make the case any shorter.

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Re: Minimum Loads Safe ?

#10 Post by Kurt » Fri Jul 28, 2017 8:34 pm

les, I see what you are saying and understand. I discovered the case body, just above the head, was not getting sized so I fixed that. I will be testing more rounds next week and will look at the pin if deep hits continue. Thank you for the guidance.

noyji, thanks for taking the time.

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