Overthinking a low-pressure rifle load

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First: I'm loading for an antique black powder cartridge rifle that has no known "official" published data available, so let's get "stick to the books" out of the way.

This Swiss rifle was a 41 RF, now converted to centerfire. Cases are formed from 8mm Lebel. Google-fu tells me I should use a 300-ish grain bullet with light charges of Unique. It also tells me to NEVER use light charges of fast burning powder in large cases or detonation can happen, so I'm getting seriously mixed messages. http://www.reloadammo.com/liteload.htm

I don't wanna ka-boom a 134 yr old gun. My question for you experienced reloaders is this: What cautions, methods, techniques, etc can I use to more safely develop a load?

What if... I use a light charge of slower burning rifle powder with a bit of wadding and some grits to fill the case? Am I unwittingly treading on dangerous territory there?
 
You want the powder to burn from primer forward. Detonation happens when the powder lays low so the top of the charge ignites, more area = more pressure.

If in doubt, filler is good.

-R
 
Perhaps you could consider using Trail Boss instead? It's a very bulky powder typically used for filling the cases of large calibers when subsonic or light loads are desired.
 
Flashpoint;n52055 said:
Perhaps you could consider using Trail Boss instead? It's a very bulky powder typically used for filling the cases of large calibers when subsonic or light loads are desired.
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x2. I see trailboss mentioned a lot for this because it fills the case so well and is made for light loads like this
 
The Trail Boss people do explain a method for using that powder in about any chambering. Give it a look and see if that would work for you. I have actually started seeing Trail Boss for sale again.

edit: I use Trail Boss in most of my 45/70 loads.
 
I don't believe the kaboom/detonation claims from light charges in large cases. I don't have proof that it can't happen (proving the impossible always being a backwards approach) but have also seen no proof that it does happen. That said, I have a bunch of TrailBoss and I like it for light loads in 45-70.
 
This is great stuff... my problem is that while people use the term low density powder or light charges, they never actually define what is considered too low say in % or how light is too light.

i was going to start reloading light 454 casull loads(say 20gn of H110) and subsonic 300 blk but it seems i need to do some reading.
 
Zedhound said:
This is great stuff... my problem is that while people use the term low density powder or light charges, they never actually define what is considered too low say in % or how light is too light.

i was going to start reloading light 454 casull loads(say 20gn of H110) and subsonic 300 blk but it seems i need to do some reading.
Click to expand...
H110 is just a terrible powder for light loads... It's more about using the right powder for the job. Magnum powders like to be run in full power loads... Unique is possibly one of the most versatile powders out there and you can always use trailboss.
 
Zedhound said:
This is great stuff... my problem is that while people use the term low density powder or light charges, they never actually define what is considered too low say in % or how light is too light.

i was going to start reloading light 454 casull loads(say 20gn of H110) and subsonic 300 blk but it seems i need to do some reading.
Click to expand...
@mckenziedrums
do you know a place to find good reccomendations for light loads, all i ever is regular and people pushing the upper limit with hot loads.
 
Zedhound said:
This is great stuff... my problem is that while people use the term low density powder or light charges, they never actually define what is considered too low say in % or how light is too light.

i was going to start reloading light 454 casull loads(say 20gn of H110) and subsonic 300 blk but it seems i need to do some reading.
Click to expand...
I've had good success with H110 in my 300 BLK. AR or single shot. I run 9.6 gr H110 under a 220 gr round nose (usually hornady). For my single shot I might work up a slightly lighter load. But I need 9.6 gr to cycle the AR consistently. It still stays sub sonic too. Basically find a 300 BLK load for 220 gr bullet and start playing with it. I went down to the minimum load and worked my way up until I got a crack, the dropped down a tenth or two. Only load about 5-10 rds at a time to test. I loaded 4 different loads and took them to the range.

Unique is a good powder and Trailboss does come highly recommended for pistol/sub rounds.
 
Zedhound;n52073 said:
...and subsonic 300 blk but it seems i need to do some reading.
Click to expand...

I've been loading subsonic 300BLK. I use 8.6-8.8gn H110 under a 203gn Palmetto coated LRN with any brand SRP. I get ~1050-1075 FPS from a 10.5" barrel, suppressed.
 
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thanks, if anyone has advice running lighter loads woth those mentioned powders id love to hear it or read online where the info would be.

this may be a stupid question, but can you seat the bullet further on a 454 to reduce empty space in the cartridge while not over pressurizing it in the process for these mouse fart loads?
 
Zedhound;n52187 said:
this may be a stupid question, but can you seat the bullet further on a 454 to reduce empty space in the cartridge while not over pressurizing it in the process for these mouse fart loads?
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My experience with 38 special that may be relevant - I got a good deal on a bunch of wadcutters. I seat them just protruding from the case mouth, which means they reduce the case volume. I worked up a very light load of Titewad powder for these. You can even drop it below 2 grains.

On a revolver you can play with overall length a lot more because you don't have bullet feeding issues
 
Zedhound said:
thanks, if anyone has advice running lighter loads woth those mentioned powders id love to hear it or read online where the info would be.

this may be a stupid question, but can you seat the bullet further on a 454 to reduce empty space in the cartridge while not over pressurizing it in the process for these mouse fart loads?
Click to expand...
I wouldn't necessarily worry about seating the bullet deeper... part of the reason is most of the bullets you're going to want to use will likely have a crimp groove. (Assuming you're shooting lead... and if you're not... why the heck not?!) You really could run 45 colt loads in the 454 brass as a good starting point. I'd avoid any of the truly magnum powders though. The H110, 2400, etc are designed for full power loads and don't burn well in reduced loads. If you post on the Cast Boolit website I'm sure you'll get some specifics but I'd be looking at the 45 colt loads as a good starting point. Trailboss is obviously the clear winner for reduced velocity shooting.
 
I use a few grains of reddot in a 45-70 and a 190 collar button for reduced loads. I think you should start by determining your case water capacity, in CCs (cubic centimeters) Then you can determine a what other cartridges have a similar CC capacity and start figuring out some reduced loads. I have seen older loading manuals that did have much different loads than what are published today. With a fast burning powder that isnt position sensitive (reddot being one of those) you dont really have to worry about detonation, it all burns up too fast. I have gotten the 45-70 below 600FPS with reddot. Castboolits is a great site for finding help with odd ball stuff like this.
 
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