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Discussion Starter · #1 ·
I shoot cowboy action and was told that my loads had to be powerful enough to reseat the primer when fired. The primer backs out and is reseated when the cartridge goes off. In a sub load that is not loaded heavy enough, the primer will come out and not reseat causeing a lock up. Is there anything to that information. I myself have loaded everything for over 40 years and not heard of such a statement.
 

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Quick answer, yes. It all happens in a microsecond. The firing pin hits the primer, the primer ignites and at this time all the pressure is in the primer trying to get out through the flash hole. It is at this point that the primer can back out. When the main powder charge ignites the case will be pushed back against the faceplate of the revolver and the primer will be reseated.

Variables that effect it are; how tight the primer fits; how light your load is; how light the bullet is; what powder you are using; what primers you are using; the size of the flash hole and the gun.

I have used Speer plastic bullets as well as Renner’s X-ring rubber bullets, both of which are shot with just a primer to propel them, no powder what-so-ever. With theses you need to enlarge the primer flash hole to prevent primer setback. If you do that it is important that you mark the cases and only use them for these bullets. http://www.midwayusa.com/Product/71...lets-38-caliber-357-to-358-diameter-box-of-50


On the other hand I have 38 special loads that are so light that they will not reliably clear the muzzle of a 6” revolver. I use them for training new shooters how to use a snubnose, where they work fine. I’ve never had a primer back out with theses loads. But this brass has only ever been used in shooting light 38 loads.
If the brass has previously been used with very heavy loads, I can see primer setback happening. I’ve seen brass that, as a result of being used with heavy loads, had the primer pocket so stretched out that a new primer would just fall out of it.

If you aren’t having a problem, don’t worry about it. It is just nice to know about primer setback in case you do run into it. Then you will be able to recognize it and know what is happening.

I'm a cowboy shooter myself.
 

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Discussion Starter · #3 ·
Thank you so much Ranger, I tell ya one never quits learning, do they. All my brass, thus far, hasbeen loaded light. The fella that twisted my arm and got me into Cowboy, gave me a couple hundred cases. For events he uses nothing that has been fired more than twice. He told me of the primer thing and I was puzzled to hear it. Most guys are looking to get the fastest load they can, out of a cartridge. With Cowboy you are looking only for that DING on the steel and as little as it takes to do it and not be left with lots of fouling. I used up the last of a can of Bulleye that I bought in late 1970's and now I'm looking at going to Alliants PROMO powder. It's very inexspensive and somewhat available in these times. There are some Cowboys shooten it and seem t do well with it, in the .38's of coarse.
 

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Sliver, if you have ANY doubt, fire an primed but empty case in your revolver. It will normally back out a bit.
 

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What you say is correct

Primer hole too large IS another cause of primer set back.

One doesn't hear much about primer set back in a semi-automatic or single shot pistol or rifle. My theory is the revolver is the only device with a bit extra space behind the cartridge head - for the cylinder to turn freely. The non-revolver type actions hold the cartridge head more firmly against the breech face and prevent movement.

Which I suppose gives us grounds for thanks there are no .30-06 revolvers...
 

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Discussion Starter · #7 ·
Yes this was a new one for me. I didn't think it to be try till a Cowboy Shooter had a squib load barely push the bullet out the barreland drop in fron of him and his revolver was jammed from the primer pushed back that very small amount.
 

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The "primer back-out problem" is a well-known phenomenon with home-made blanks. The solution is as Ranger Z says - have some dedicated "blank cases" with enlarged flash-holes. Just don't get them mixed up and use them with regular loads, or you'll get primer back-out due to the second cause - i.e. back-pressure from the main charge ....
 
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