Had some time on my hands between jobs & had a brainstorm.  I had read where using large pistol primers in regular large rifle pockets could lead to peening of breech block face due to shorter pistol primers getting running start and slamming into block.  Now I don't know how much of a run they could get in only .008"..the height difference between the LR & LP primer, but I turned up some half-hard brass to .2105" dia. & drilled .062" hole thru.  Using thin part off tool made from tool bit, I parted off a dozen .008" shims.  Hardest part was catching those little suckers before they got lost in chip pan.
    Now then, do you think using these would be practicle..and worthwhile?..any thoughts on danger?  Thanks!

Superb! A classic enthusiasts solution to a problem that doesn't exist.
Fred

I didn't say, but the reason for the pistol primer was for gentler ingnition ..greater accuracy?  with black powder loads.   
Frnkeore..I have been thinking of turning up some stainless LR-SR bushings..have to come up with a .1745" dia. reamer...perhaps make up a half reamer?

I simply made a swage to reduce the Large Rifle Primer pocket depths to minimum Large Pistol Primer depth specs. I have also seen the damage to the breech block face that some would say does not exist. Kermit Hoke ( Kermittool ) now retired also used to make and sell the same type of primer pocket reducing depth tool for use on a reloading press.

.22-5-40 wrote on Mar 16^th, 2019 at 12:57pm:

The only way that I would make them, is with a CNC, screw machine or at the bare minimum, a small turret. There isn't much tolerance on the ID size so, the reamer would have to either float or be very close, on center, to work out.

Frank

I also had the non existance breechblock peened on my High Wall using large pistol primers in a 40-65 using black powder.  I took the shell holder and ground
a slot in it to accept paper strips of the required thickness.  When priming put paper in slot and ran primer thru it into case.  I now can use pistol primers and also paper in front of primer to lessen primer flash.  I sold my High Wall but now 
use the same technique on Stevens 32-40 with blackpowder.  It did improve accuracy for me.
Waiting for summer so I can shoot some bragging groups with black powder.

I too tried pistol primers last fall in my 40-85 Ballard.....the first 200 yd group showed a huge improvement. Was worried about denting the breech, but a dozen shots seemed ok. Considered paper under primer for a spacer but have not tried it yet. A top shooter we all know told me about trying the pistol primers. If money was no problem I would have a new custom made batch of brass for the small primers.

Primers do make a difference and all of them should be tried. I have been having great success with the Federal Large Pistol Magnum Match with 300MP and the powder used also comes into play. But I also highly recommend that you don't use Pistol Primers unless the primer pockets have been reduced to the LP minimum specs. I would never encourage anyone to do anything that would or could damage a breech block face and why I would never advocate their use if the primer pockets depth has not first been reduced. And this is what I do and use in my 32-40.