Awhile back, I reported on a low wall that had been rebuilt & rebarreled to .25-20 Repeater.  Last week I had my first opportunity to spend a whole day at a range, just me & the .25-20, with no interruptions for some hours.  So that's the rifle to which I refer.  Now about the ammunition.  A couple of years ago, my friend died and his widow gave me a very large batch of cast bullets. Probably a couple of hundred pounds of them, all sized & lubed and put away into dozens of small metal containers that formerly held shoe polish or leather dressing or some such. My friend had a .257 Roberts and a large # of moulds and cast a lot of bullets.  So I sorted through the containers and found most of the .25 caliber bullets, hundreds of them.  Then I got 100 new R-P .25-20 Repeater cases and a batch of CCI small pistol primers.  I have RCBS dies, etc., but I also have an old Ideal tong tool marked 25-20 R.  In the course of my employment, I spend 2 or 3 nights a week on the road and motels are a drag.  Loading 25-20 repeater cartridges beats the heck out of watching TV or hanging out in the local bar. So I put the tong tool, an old RCBS powder scale (the simple kind) and all the rest of the stuff I'd need into my travelling kit.  The first night out, I cleaned several batches of bullets, wiping off excess lube, sorted the good ones by weight and picked out 10 of each kind in the 80 to 90 grain range to try.  Then I expanded the mouths of the cases.  After that, I primed all the cases with the tong tool and picked out a starting load.  I read all the manuals I had and decided to start with 8.7 grains of IMR-4227 and to use that load for 10 different categories of bullets.   

The procedure was the same for each load.  Powder went into a shallow dish.  From there it was trickled into the pan on the scale with a spoon.  The scale was levelled & zeroed before each loading session, motel tables being what they are.  When the scale indicated 8.7 grains, I fit a powder funnel over the mouth of the empty case and poured the powder into the funnel.  Then I checked the depth of powder in each case with a flashlight, started the bullet into the case by hand, and finished seating with the tong tool.  All cases are kept in loading blocks when not being used.  By the end of the second night, I had loaded all 100 new cases and had 10 load & bullet combinations to try.

I had time last Tuesday and off I went to the range.  The first 60 + shots went OK.  Nothing to rave about, but I progressed from 50 yards to 100 and got the sights adjusted and was keeping the bullets in the black.  Then one went off with a real crack and a lot of smoke shot out of the bottom of the action.  I dropped the lever and the case came out with a big scorch mark on the primer pocket.  I'd blown a primer.  Not propitious, given the past history of this rifle as reported in the SSR Journal.  Then I looked down the bore.  No stuck bullet and all the powder had burned.  Checking the target showed a new hole right in the middle of the group I was shooting.  A patch on the cleaning rod showed a dirty bore, but no buildup of lube and no leading.  I scrubbed the bore and the chamber with a bronze bore brush.  No leading.  I blew into the fired case, but it seemed not to have a hole anywhere.  The bullet was a Loverin type gas check, 85 grains, cast very hard, lubed with Red Rooster and seated so that the entire base was within the cartridge neck.  No gas checks hanging down into the powder space.

This past Thursday, I was on the road again.  I weighted all the fired cases with the primers in place.  The spread was 65.7 grains to 60.4 grains.  The case with the blown primer weighed 60 grains.  I checked all the case lengths.  All within 0.005 and all within spec.  I measured all the case head diameters.  All had expanded, but the case with the blown primer was right in the middle of the range, 0.3450.  Other case heads had expanded to as much as 0.3455.  Nothing indicates an overload to me, but what happened?  The most likely culprit seems to be an overload from the old powder scale.  How reliable and accurate are they?  And I suppose the primers could be suspect.  Next week I'll take a magnifying glass and look at the primer pockets.

While I don't think your scale is the source of you problem with the 25, I do have to say that it is suspect of contributing to error. Some time ago I noticed erratic behavior with my similar Lyman scale. It was gettting a little age on it so I replaced it with a similarly aged but less used scale belonging to my brother.Same erratic behaviors. I'd challenge you to test the scale against itself. I found I could weigh the same series of powder charges or bullets and get different weights. Evidently they do wear and can become less than reliable.

This thread caught my attention because I had a blown primer in an 1875 45-70 Sharps replica, and got a face full of powder and bits of the primer. Not a pretty sight, but thankfully I had my glasses on, so no permanent harm done. At any rate, a friend of mine just bought a replica Hi Wall, and I noticed that the rear of the firing pin appears to protrude out the rear of the breechblock, which is necessary of course so the hammer can hit it, but wouldnt that allow gas to flow directly into the shooter's face? I had a gas block installed on both of my Sharps rifles after the incident, but you cant do that on a Hi-Wall or Low Wall. Apparently, Waterman didnt have the gasses come back at him, why not?  Thanks,Joe S

This week, I remembered all the reloading stuff for my business travel kit.  I looked at all the fired pistol primers in the .25-20 Repeater cases under the magnifying glass (old eyes, as I am sure some will understand).  Yep.  All of them had been pushed back against the breechblock.  The one blown primer was backed out of the primer pocket a bit.  So that is the end of small pistol primers in the .25-20 Repeater.  I note that in 1937, Sharpe wrote "In order to shorten the case and still have a semblance of power, the case has an abrupt bottle-neck, thus creating high pressures without achieving reasonable results."  I have used small pistol primers in my .32-20 low wall for years and never experienced anything like this.  Also tried them in my .25-20 SS.  The Stevens 44 will not reliably ignite rifle primers.