45-70 Compression depth confusion....

[Dgunner]

My bullet is a 459530/m5 with a B.L of 1.45, Case length 2.09, cartridge chambered touching the lands 3.34. That gives me a .20 top-of-wad seating depth. However, when I load 66 grains and place a .060 wad on top my measurement is now .231 without compression. When I read a specific book a compression depth of .385 is suggested, which takes me to .615 which equals 10 .06 wads! I'm sure I am at fault somewhere in my calculations, Any suggestions? How do most of you come up with compression depth

[Kenny Wasserburger]

That much compression is for Fg and in a 45-110.

Definitely not for a 45-70.

KW

[semtav]

The 66 grains is your problem.
You don't start developing a load with weight.
You start with volume .
Since you already determined the volume you want is enough powder to bring the top of the .060 wad to .20 from the top of the case, put enough powder in the case to bring the wad up to that level.
That is your starting volume.
Now you can weigh that volume to get your starting weight. For that specific batch of powder.

Then you can add more powder or wads to increase Compression.

[Dgunner]

Thank you both!

[martinibelgian]

Fwiw, compression is a result, not a goal. And it might change with every different lot of powder.

[Don McDowell]

As Marini said compression is the result.
Start with what you have now with the seating depth you've chosen and then shoot some to see if they're grouping . Then you can add/subtract powder in 1 grain increments to achieve the group and velocity you're looking for. When you're satisfied with a load,that's the compression amount you have in your loads for your rifle.

[stevewhr]

Sounds like some confusion about compression and seating depth. For a couple reasons my compression might differ from yours. So ignore the actual compression and just shoot what shoots the best. Knowing the compression is interesting but not very important. You can compress till you bulge the case and the cartridge wont chamber. Anything short of that is fine and can be accurate. Only the target can tell you what compression to use. Hope this helps and doesn't offend should I have misunderstood your question.

[Dgunner]

Dang, you guys are great. I will reload mine reloads starting tomorrow. Thanks again

[semtav]

Another option you might consider.
Since your maximum compression with that bullet touching the lands is going to be .200. you could always just fill the case full of powder, add the wad. Compress it .200 and start working backward .
I like lots of compression so I very seldom follow my advice by starting with 0 compression.

[desert deuce]

April 7th is fast approaching.

[semtav]

I've got free reign til then