Imr4198 minimum load, 45-70

[Obturation]

Hey all,
Hope everyone's feeling good.

Not really a question but more of a topic of interest concerning large case capacity and small charges in relation to published load data.

I'll start by saying that eventually I plan to get a 45 colt or 454 casull lever action rifle. I don't have such a gun at the moment and I do a good amount of plinking with a lever action 45-70. I typically use trailboss and have no complaint with accuracy , power or recoil. Works great for short range paper and soup can work.

For more powerful loads I use imr4198, no complaint. Does what I need and has all the oomph I care for. Trailboss is still difficult to put hands on and I'm down to 3 cans (1# size, they aren't a pound). So flipping through the manual I see that a minimum trapdoor load of imr4198 is 31.5 grains. That's considerably less than I use for a "full power" charge with a 405 grain bullet. Says it will produce in the neighborhood of 1300 fps. Sounds good for what I use trailboss for (typically getting about 950 fps).

So I made 10 cartridges, what's concerning is the amount of empty space. Not that I think I'll have an issue but wondering if I'll have position sensitivity. Almost seems like a filler could be helpful but I never used filler and the Lyman manual the load was sourced from doesn't mention it.

Just curious if anyone's used such a light load of imr4198 and what the results were like. I intend to test these loads in a couple weeks but won't be able to chronograph them anytime in the near future . if they shoot well I'll make 100 for range use to save the trail Boss for other things.

I've seen light loads in 45-70 using other powders that I do have on hand but I don't have a published manual in hand that has that data.

Just something bouncing around my brain and figured I'd throw it out there and see what the consensus is.

Thanks

 

[Charlie98]

I use IMR4198 almost exclusively for cast in rifle... it works very well, even with lower case fill.

For the 405grn cast, 30grn IMR4198 gives me 1375fps out of my Pedersoli 1885.
With the 350grn FN cast, 28grn gives 1430fps, 31grn 1500fps.

I'm going to guess 32grn IMR4198 and a 405grn cast will give me right at 1400fps, which is my target velocity, and be under 20K PSI. Hodgdon Trappy data starts at 30grn for the 405, but ratchets up a bit with lighter bullets.

30grn and a 405 give you about 65% case fill.

 

[ArchAngelCD]

Hodgdon has a min load for the 45-70 @27.0gr 4198. I see no reason not to use that as a light load.

You can also use Hodgdon's reduced load data. Its the 60% formula from the max charge of H4895.
They list 48.0gr H4895 so you would multiply 48 X .6 = 28.8gr H4895. Those loads are tested and proven safe. You can increase the charge as needed from the starting point of 28.8gr to adjust accuracy and velocity if needed. I have used this formula for the 30-30 and 30-06 for younger shooters to get then used to center fire rifles.

https://hodgdon.com/resources/data-sheets/ Look under "Reduced Recoil Rifle Load Data"

I hope this helps you.

 

[Roverguy]

In my experience, IMR 4198 is not position sensitive. I have used it, and H4198, successfully in a number of cast loads, the most relevant to your case being 444 Marlin. I agree that 31.5 grs in a 45-70 case must seem quite light, but as a published load, it is safe for use. You can mitigate concern by raising the barrel to push the powder back towards the primer before each shot if doing so is safe and permissible at your shooting range. I don’t think it’s necessary, but if it’s feasible and mitigates your concerns, why not?

 

[Edcnh]

I use IMR 4198 in my 45-70 and it works fine with the minimum loads listed in the manuals. I used the Lyman manual.