Just a bit of an experience question.

I have a CPA in .38-55. I’ve been breech seating an Accurate 
345-grain bullet in the 12” twist barrel using various smokeless powders. Our local match season is over at the end of August. Fall is a time to do some experimenting.

I have several pounds of Old E. 1 1/2 black powder. I’m guessing the .38-55 started its life in the BP era. So…

Is there an accuracy “gain” over smokeless in the use of BP in this rifle? If so, what charge weight of BP should be considered? I’m not interested in duplex loads.

I have 0.060” thick .38 veggie wads and a 24” drop tube. I think I probably need a powder compression die.

Thanks!

Black powder can be very accurate but you have to jump through a few more hoops to get there.  As far as a gain, no, my experience says not but, it can be very, very close.

I've been shooting BPC's with great success since the mid-80's and have never owned a compression die and the only wads I've ever used are .020 card wads punched from florist boxes or cereal boxes. 

As far as charge weight what I've done for decades is calculate the powder column height to the base of the bullet then add enough to bring it up 1/10 to 1/8 of an inch, add the card and seat the bullet.  With a .060 card you might want to deduct that  amount from the powder charge then add 1/10 to 1/8.

Olde Eyensford is a fine BP from my experience.

If you're wanting to continue breech seating I'm sorry I can't recommend anything as I've never breech seated.