45-70 rifle vs. pistol primers ...

[wquiles]

Definitely not "conclusive", but I got a fun/target load of 16gr of TrailBoss with a Ranch Dog 300gr boolit (about 1250fps), and it is generally accurate for me (at least at my current skill level). So I decided to try it, with just changing the primer from the Federal large rifle, to the Winchester large pistol. These are at 50 yards, from the bench, using a 4x scope in my H&R Handi Rifle.

Rifle primers:
http://m3coupe.com/Firearms/loads/shooting_range/Feb13_2015/20150213_160843.jpg


Pistol primers (note that I am aiming at the center of the target as above):
http://m3coupe.com/Firearms/loads/shooting_range/Feb13_2015/20150213_160845.jpg


I tried the load with the pistol primer at 100 yards, but it was again not as good. With the rifle primers, this was my best group at 100yds:
http://m3coupe.com/Firearms/loads/shooting_range/Feb13_2015/20150213_160757.jpg


I am not given up on experimenting with the large pistol primers, but with the "fast" TrailBoss it appears it is a no-go for me.

Will

[Duckiller]

Small rifle and small pistol primers are supposed to be the same height. Large pistol primers are supposed to be thinner than large rifle primers. This may effect ignition. Winchester large pistol primer are supposed to for both standard and magnum loads. You may have hot pistol primers.

[MT Chambers]

I think that playing with pistol primers is/was common in cals. like the 45/70 when using black powder because it is so easy to ignite and it is felt by some that the more powerful rifle primers just move things before powder ignition.

[Scharfschuetze]

I've never tried using pistol primers in the 45/70 as my thinking has always been that with that big volume, it needs all the help that it can get for uniform ignition. I use magnum primers in it when loading black powder for the best accuracy in my original Trapdoor Springfields.

Where I have had positive results using pistol primers in a rifle is with the 25/20, 32/20 and of course many of the pistol cartridges chambered in rifles like the 357 and 45 Colt. These are all small volume cases cases compared to the 45/70. Conversely though, rifle primers often produce the best results depending on the powder and boolit weight, so experimentation (as the OP is doing) is the key to refining any load to your satisfaction... and that all part of the fun of reloading and shooting.