45-70 three levels of pressure

11 October 2003, 09:04

I tend to load well within the limits of the manuals and the particular gun/cartridge combo, but I have seen pressure signs well before the max load.

So now for the really stupid questions:
Assume I was loading for a rifle in the low or medium pressure group. How would you know you were getting close to having a problem, before you actually have a problem?

11 October 2003, 10:05

NotRicochet

Great question! The short answer is, there's no easy or reliable way, without actual pressure measurement. There's a long thread about it in the "Wildcats and Handloading" forum over at: http://huntamerica.com/

[ 10-11-2003, 01:06: Message edited by: NotRicochet ]

11 October 2003, 10:59

ddunn

Thanks for answering the question.
I canï¿½t find the thread, but honestly it doesnï¿½t matter. I now know how to not hurt myself. I will stay witht he book loads.

Thanks again.

11 October 2003, 12:54

Hot Core

quote:
Originally posted by ddunn:
...but I have seen pressure signs well before the max load.

...loading for a rifle in the low or medium pressure group. How would you know you were getting close to having a problem, before you actually have a problem?

Hey ddunn, Once a person reloads for awhile and begins to understand Pressure Signs, it is not uncommon at all for them to see some Load combinations that show Pressure Indications before the SAFE MAX just as you said.

One SAFE thing you can do is shoot a box of Factory Ammo through your rifle and then measure the Pressure Ring Expansion(PRE) with a 0.0001" capable Micrometer. (A 0.001" Caliper just isn't accurate enough.)

Using your 45-70 as an example, simply measure the largest diameter forward of the Rim on a Fired Case that has not been Resized. Rotate the case between the anvils to locate the widest diameter "without" forcing the case to turn.

Use the value that will "hang" the case between the anvils where if you go an additional 0.0001" wider, thecase will not hang.

Write down the PRE for the entire box, average the value and use that number as your SAFE MAX PRE. Write that number on your box.

You will need to Full Length Resize the cases so the Pressure Ring is reformed(Neck Sizing will not do for this). when you Reload those cases, when you reach the Factory PRE value, STOP.

Most of the regular Factory Ammo is loaded to the Lowest Pressure. But, a few are loaded right up there and they will specify that on the Ammo.

...

PRE is the very best method to determine Pressure in cases like the old 30-30, 45-70, 38Spl, etc. The SAAMI Pressure is too low for Case Head Expansion to have any use at all.

Best of luck to you.

[ 10-11-2003, 03:57: Message edited by: Hot Core ]

11 October 2003, 15:57

Clark

http://www.nookhill.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=009116#000008

11 October 2003, 23:36

John Y Cannuck

Having worked with the 45-70, and other low pressure rounds for sometime now, I can say that I have seen pressure sign. However.... Pressure sign on some low pressure cartridges appears VERY VERY FAST. A tenth of a grain may be too much when working with smaller pistol type round for example. (Ringed chamber 38-40 [Eek!]

).
When looking at bolt action high pressure cartridges, flattened primers are considered a "first sign". Not so old low pressure guns. ANY (not just square corners) primer change should be regarded as an indication of fairly high pressure when working with older guns IMO.
I feel it is important to use as many pressure indicators as possible, as sometimes one will show what another does not. Some primers are rumoured to be harder, or thicker than others for example, and could negate pressure sign from the primer.
Same with case head measure. Lot to lot, or brand to brand variations could affect what you see here.
If you aren't sure, STOP!
Loose primers should NOT be happening AT ALL regardless of firings, with old guns.

All of the above is my opinion, based on what I have done so far.

12 October 2003, 01:46

arkypete

For the 45-70 get a copy of Ken Waters Pet Loads. He covers most everything you'll want to know, plus it's a good education in load developement.
Jim

12 October 2003, 02:10

<eldeguello>

quote:
How would you know you were getting close to having a problem, before you actually have a problem?

If loading for a rifle in the low pressure group, like a trapdoor Springfield, just stick with the known low pressure loads! Don't "work UP"!! Better yet, use B.P. or Pyrodex for these guns.

For the "medium strength" actions, like an old M1886 Winchester, start with the low loads, and quit when you get to the velocity range of 1600-1700 FPS, or your load is accurate enough to suit you. You'll need a chronograph if you use velocity as a gauge of when to stop increasing powder charges. One classic old load for the mediums is 53 grains of IMR 3031 and a 400 grain bullet for 1750-1800 FPS. This was Keith's load in the 1886 Winchester. It DOES NOT EXCEED 25,000 PSI, which is within the operating range of heavy BP loads with 500 grain bullets also. [Big Grin]

[ 10-11-2003, 17:15: Message edited by: eldeguello ]

12 October 2003, 05:17

John Y Cannuck

eldeguello

I always found it interesting that the 45-70 was not on Elmers hot loads list.
Maybe the old gentleman did feel recoil after all.
I have loaded considereably hotter loads in my custom 1886, but I finally came to the realization that those hot loads just are not worth the punishment they dish out. Elmers load, or it's equivilent is more than capable of dropping anything on the continent.