I have an old Forehand pin type .32S&W revolver. No matter what I try and shoot the primers back out against the breech and jam the cylinder tight. I've tried from 4 to nearly 9 gr. of 3F black, 1 to 1.5 gr. Bullseye and 1.5 to 2 gr. Unique. There's really no rifling left so accuracy isn't a concern, I just want to be able to shoot it. I know it's not worth a hoot, but I respect it for it's age and history. Really odd thing is: when I first got it, I fired around 15 to 20 rds. without a hitch, now every shot jams up with a blown back primer! It even blows'em back when I fire Just a primer with no powder or bullet. I can't find anything wrong, broken or out of place, what's the problem guys?
From your description, the headspace is likely grossly excessive. On firing the case walls grip the chamber before the head can press against the recoil shield of the frame. Thus the primers move back, under the pressure, to close this excess gap. If you cannot correct the headspace, you may have a case head separate (tear off) on firing, releasing high pressure gases that can cause injury.
For Hammerslagger, hope he sees it. Yes, the headspace was awful when I first got it but all that was a problem was a misfire now and then. I 'cured' the headspace with a well placed wee tiny washer, made the whole mechanism work smoother. As to the primers backing out, that only started when I tried making black powder loads, after just the first two shots I had this primer problem, even with smokeless loads afterward; however, I hadn't cleaned the gun after the BP fiasco. Your answer about the cases grabbing the chamber walls and not hitting the recoil plate got me wondering why?? Could it be that black powder fouling? I dropped the whole gun in a bucked of hot soapy water and scrubbed it down, then put it in the oven at 100 degrees (+ or -) for a couple hours to dry; then sprayed the bejeepers outta' it with WD40, wiped it clean and it works just fine now, no primer back up or hangup of any kind, single or double action. Did they have different cases and or primers way back then?? I have never had any luck with loading black powder cartridges, rifle or handgun; they always lock up, jam up or foul up. I should'a remembered, I had the same kinda problem with a S&W .44 American decades ago. Finally just shot 3 gr. Bullseye behind 240 bullet. Weak, but neat to shoot (damn, wish I would'nt have sold that!)
Old, inexpensive, caliber .32 S&W revolvers are not my strong field of expertise. Based on your last post, it would appear that the residue from the BP significantly increased the coefficient of friction between the case and chamber walls. You still likely have some excessive headspace.
When a cartridge fires and headspace is correct, the primers cannot back out because they are very close to the breech-face, The expanding gases can push the case backward against the breech-face before the case walls expand and seize against the chamber walls. If the chamber walls and cases are clean and/or oiled there is a lower coefficient of friction and the case is freer to slip rearward to close up excessive headspace as the pressure expands the case walls against the chamber.
When headspace is excessive two things can and usually happen. The pressure will often start an uncrimped primer out of the case; and the pressure (if high enough) will stretch the case head area rearward tending to cause a case head separation if the headspace is grossly excessive.
From your description you were not getting enough pressure to really stretch the modern cases; so the primers were backing out. When you thoroughly cleaned and lubed the gun the cases were better able to slip rearward when fired with likely still excessive headspace.
As to cases, yes old cases were made differently than modern ones. They would stretch easier than modern so called solid head cases.
Hope this helps.
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