Just happened to finish reloading and testing my first batch of 45/70 cartridges ...

Hornady 300 gr HP with 53 grains of IMR3031 to be shot from a MArlin 1895SS ...

Accuracy is outstanding (using an IOR 4x32), but my concern started when measuring its velocity ...
I have an Oehler chronograph (rather used or better say bad used !) which make me doubt about its performance ...

The fact is that for that reload, IMR states I should be achieving something around 1900fps, but my chronograph "said" it was only 1650 ...

Powder in excellent conditions, and no, I don´t have any other chronograph available !!

BTW, no signs of over pressure at this stage ...

Comments ?? I don´t want to stress too much the brasses, since in my country they are quite difficult to find nowadays ... but will like to achieve a velocity of 1900/1950 fps .... Hogs are waiting for this combo !!

regards

The 45/70, at least in my marlins, like plenty of neck tension and crimp on the bullet. My accuracy and vel suffer when I dont have the proper amount of either. I'm not a Lee die fan, but their factory crimp die is a winner in this caliber.

Thanks, Catboat !
Your suggestions have a lot of sense ... the fact is that before taking my reloads to hunt I wanted to know what to expect from them, at least from a theorical point of view ...

My IOR? just excellent !! I am so pleased with these optics that I have just bought myself another scope (6x42) an a bino (10x50) from jim Maloney (qoptics@ott.net) ... Most reccomendable guy !

I found this web site looking for advice on the difference between measured and "book" velocities. The difference you see with a specific rifle is not that unusual, it's quite common. Try searching my posts to find that thread - it has some good comments.

The rest of this is just my opinion:

Barrel length is a factor; my rough allowance is 50-75 fps per inch. If the test barrel was 26" and mine is 22", I expect to lose 200-300 fps.

The real limit for a given rifle is any sign of excessive pressure. This is true whether you're below, at, or above the maximum powder weight given in a manual.

I consider the "book" velocity to be a better indicator of pressure than "book" powder wt.

So I will increase a load, in small increments, above the published maximum, until the load approaches book velocity or there is some sign of excessive pressure.

My IMR manual (from the Lee Shooter CD) lists 54 grains as max so you might gain a little speed with more powder.

You can rule out that the Oehler is a fault if it records accurate speed with other known calibers.

I can never seem to match ANY listed speed from a powder manual. 250fps slow is not out of the question if the load recipe is not followed exactly, such as different brand brass or primers.

Consider also that the reloading data was likely developed using a test barrel with a tighter chamber than your rifle. That would also account for the higher velocity of the published load.

You will never see 50-75 fps per inch of barrel difference in the 45-70. 20-25fps is more like it.

Exceeding the charge or velocity of a published load is not wise.

quote:

I consider the "book" velocity to be a better indicator of pressure than "book" powder wt.

Hornhunter
That was very well said!

quote:

Originally posted by Afrikaander:
Just happened to finish reloading and testing my first batch of 45/70 cartridges ...

Hornady 300 gr HP with 53 grains of IMR3031 to be shot from a MArlin 1895SS ...

Accuracy is outstanding (using an IOR 4x32), but my concern started when measuring its velocity ...
I have an Oehler chronograph (rather used or better say bad used !) which make me doubt about its performance ...

The fact is that for that reload, IMR states I should be achieving something around 1900fps, but my chronograph "said" it was only 1650 ...

Powder in excellent conditions, and no, I don´t have any other chronograph available !!

BTW, no signs of over pressure at this stage ...

Comments ?? I don´t want to stress too much the brasses, since in my country they are quite difficult to find nowadays ... but will like to achieve a velocity of 1900/1950 fps .... Hogs are waiting for this combo !!

regards

This sounds about right to me. I don't think your chronogragh is bad. The 300 gr. bullet likes a different powder than the 405 gr. For a 405 gr. bullet 3031 is THE powder, but not with the lighter bullet. I think the lighter bullet and shorter barrel doesn't let the pressure get high enough for 3031 to burn properly.

If you look closely I think you'll find a lot of unburned (3031) powder in the barrel/fired case. In my guide gun (also a 1895SS) I get around 1450 FPS with 48 gr. of IMR3031 using 300 gr. Rem. HP bullets. I'm only trying for basic 45/70 pressure loads as I have several much more powerfull rifles if I feel I need more velocity.

I tried RL7 and things didn't get much better.

Then I was loooking at an older reloading book and saw a load using Hercules (Alliant now) 2400 powder.

So, I'm currently using 30 gr. of A2400 and get 1755 FPS (avg.) out of the same gun which I think is about right for a standard pressure load for our barrel length of 18 ins.

BTW, according to that same manual 34 gr. of A2400 is a max. load for a 300 gr. bullet in the Marlin 1895.

Hope that helps, and good luck with the Hogs...

Roi

Oh, one more thing, I'd be careful with pressure signs in a 45/70 as I seem to remember that straight walled cases don't show "over pressure" signs until you are WAY over. And of course your brass will last longer the lower the pressure.