Hi all,
I'm looking for information on the practice of Breach seating. In particular the gap between the mouth of the Case and the Base of the bullet, and, the importance of Case length. Breach seating is not new to me, I have been shooting this way for 4 years, with several different calibers and with Smokeless and Black Powder, with some excellent results.
When I started out I was told that the Gap must be 1/16th (.062"). I have since learnt that the gap can vary considerably and with different rifles it has to change. 
If the idea of breach seating is to improve accuracy by creating the same back pressure, by pushing the cast projectile up into the Lands (rifling) and sealing the bore against gas leakage, what has the gap between case and bullet got to do with it and, if the gap is crucially important, then obviously case length must be important too. What happens with case length if the best load is not a full case of powder as in most smokeless loads, is it better to use a filler ?
I have a great book (The modern Schutzen rifle. by Schwartz and Dell) and a print off of "The Golden age of American Schutzenfest" which I re read now and again but some answers are missing.  I note that the gap was initially started by those who muzzle loaded, BPC Rifles, for no other reason (after testing) than to leave room for fouling to sit which was pushed down the barrel during muzzle loading. 
Do we need a gap when breach sesting ? Could I trim my cases longer to get more BP in them  and have no gap ? 
Let's hear what you've got gentlemen, I love the topic.  Cheers Dusty. 👍🇦🇺

So many combinations of seating depth, powder type and charge, position on the front rest, stock grip and  a few dozen more keep you coming back to the range with something new to try. I recently brought 3 of my breech seaters with me set to different depths.  I have one combination that works great with one bullet, but I found that two other slightly beaver bullets liked to be seated a few thousandths deeper.  Now if I could only figure out how to control the wind!  4 flags all showing different results. 

Jack

What have your targets been telling you about the depths that you have tried. Always analyze your targets…..and never stop asking them the “how”, “why”, and “what if's. I have found it to be very sound advice and that is what I also use for myself. It would also be your best approach to finding your own best seating depth.

I shot an Aydt 8.15 x 46R with a long throat.  I had to BS it 3/8" A ahead of the case shooting smokeless.  I did not have any problems.  I shot it offhand. The radical stock was not easy to shoot from the bench for accuracy testing.

Buffalo Arms sells a 38-55 Winchester 2.245" Basic Case.  I sized some to 32-40 when I wanted to try longer cases in my Ballard.

Jack

bpjack wrote on Jun 7^th, 2020 at 9:35pm:


True  would be great to get some but exporting to Australia is the issue.You guys have so much more choice than we do out here in the Antipodes.

If you're breechseating, the importance of case length is considerably less.  It just is the 'powder container', with as only variable capacity difference between cases.
No issues with neck tension, brass thickness or hardness,...

Schuetzenmiester wrote on Jun 8^th, 2020 at 4:41am:


Either a heeled or a stop ring bullet.

Dusty Rhodes. Star line has 38/55 long cases at I think 2.135"
Some times they are available for a price if that helps any.