Pressure problems fom light loads?

08 April 2003, 09:29

I have read that you have to be careful not to start below minimum starting loads. [Eek!]

As in 45-70 those loads vary so much it is mind boggeling. [Confused]

Like a starting load for a ruger #1 may be 50grs of xxxx and for the 1895 48grs of xxxx and 45grs of xxxx for the rest of the guns. Why would it be dangerous to shoot 45grs of xxxx in a #1 when they can withstand higher pressure than the rest. Then these really light loads sound like fun [Smile]

yet they are way below this minimum starting load data. [Eek!]

I have shot 25grs H4198 behind 350gr FNs and liked them [Big Grin]

but am a little nervous to shoot them now. [Roll Eyes]

Has anyone ever had a problem with light loads? I also would love to find some light load for my 300 WSM that is safe.

08 April 2003, 11:07

Bob338

The main problem with light loads in large capacity cases occurs when using very slow powders. You can get a secondary detonation that will destroy the gun and maybe put you in a world of hurt. It can also occur when using fast powders that fill only a fraction of the case. This enables to powder to move forward and leave nothing but air near the flash hole. When using fast powders for light loads, a filler is helpful in keeping the powder back against the flash hole at primer ignition.

They make bulky powders for light loads in most any cartridge. IMR makes SR4756 for light loads in pistols and SR4759 for rifles. I've used the latter with great success.

As for the question relating to 45-70's specifically, you'll get at least three "maximum" loads for that cartridge. That is because of large numbers of old black powder guns of that caliber still in use. Were you to use high pressure loads for something like a modern Ruger #1 in an old Springfield, you'd have instant destruction, hence they will show light, medium and heavy loads, the latter for modern guns, medium for older smokeless powder guns, and light loads for some black powder weapons.

08 April 2003, 11:15

Tailgunner

A Trapdoor starting load in your #1 wouldn't be a problem.
Where the warning comes from (and who it affects) is people loading squibs (IE: 30carbine level plinking loads in a 300 (somthing)mag case) and the ocasional S.E.E. (secondary explosive effect) "KaBoom" that has occured while doing the same.

08 April 2003, 12:09

Clark

http://www.serveroptions.com/ubb/ultimatebb.php?ubb=get_topic;f=5;t=005878#000012
http://www.realguns.com/loads/4570.htm
http://www.realguns.com/article.htm

http://www.serveroptions.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=005976#000005

[ 04-08-2003, 03:16: Message edited by: Clark ]

09 April 2003, 18:17

JerryO

quote:
Originally posted by DickPal:
I also would love to find some light load for my 300 WSM that is safe.

But how light do you want?

IMR 4759 builds rather mild loads and would be as safe as any other load.

I shoot some very light loads in my 30-06. I got the starting load from a lyman cast bullet load and worked up. I have done the same for my .223.

Useing 55 grain .223 and 125 grain .308 bullets, I used 700x in both calibers and found that I ended up with about 1/4 the weight of a full case of a dense powder. It takes up about 1/2 the volume of the case.

As should be expected, 1/4 the powder gave 1/4 the energy (thats 1/2 the velocity) (OK, not exactly).

BTW. the very fast pistol powders are often suggested for these very light loads. ie. 12 grains in a 308 case, 14 grains in a 30-06 case.

The key to reduced loads seems to be avoiding pressures which are lower than the powder was designed for. The lower pressure implies lower temperatures which can heat the kernels of powder all the way thru. Then as the heat builds and some powder burns, the pressure (and heat) rise creating a very rapid burn (ie. explosion).

It has been suggested that slow ball powders have the most danger because the heavy deterrent coating requires high heat to ignite the kernels.

JerryO