 Pressure signs in the Encore and Contender [message #16030] |
Thu, 15 November 2012 11:32  |
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Crubear
Messages: 1796
Registered: March 2010
Location: NW Georgia
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There's a thread going about problem with shooting a barrel and I thought we should have something up so new shooters can reference. When you talk excessive pressure signs most people are very familiar with the ones for a bolt action - Stiff extraction, extractor marks on the brass, cratered or flattened primers, etc....
In the Encore and Contender (depending on the barrel) you can blow the frame up before you see most of these signs.
Flattened primers can happen with the lightest loads, the process can go like this:
1) The firing pin strikes the primer and pushes the cartridge deeper into the chamber
2) The primer detonates, igniting the powder while pushing the primer out a little ways back against the breech face
3) As the pressure continues to build the case is forced back against the breech face and the extended primer.
4) The result is a flattened primer.
Cratered primers in an Encore/Contender usually occur because of a weak firing pin spring. I had a Contender that would crater 22LR. I don't think I ever fired a single center fire that the primer wasn't cratered, even in the rounds I had flattened primers in.
Stiff extraction means something else in the Encore/Contender. When you fire a round the brass expands to fill any open space around it, which pushes against the chamber walls and breech face. When you go above the max load of your barrel and cartridge bad things happen. In this case the steel of the barrel expands out and then contracts back down onto the case forming a tight friction bond. You'll know you've done this because the barrel won't drop down as easily as it normally does when you open it. In extreme cases you might even have to bang on the barrel. If you get to this point just stop shooting those rounds. You're flexing the frame and the barrel and it's just time to stop. Your loads are too hot and the barrel is trying to tell you something.
Keep in mind that this is mostly my view/opinion/experience. I no longer try to get to max and beyond because it shortens the life of the brass, which is too expensive in my view to waste just because of my ego.
Every barrel is different and you just have to get to know yours, just because certain signs don't mean anyting in my set up --- THEY CAN MEAN SOMETHING IN YOURS!!! It was signs of excessive pressure in the example above where I talked about cratered primers being flattened and I had to pull 199 loaded rounds apart (I used to think it was OK to start a Contender at max and work from there).
Honestly, I have all the barrels I want or could ever need..... wait, look, there's another!!
[Updated on: Thu, 15 November 2012 17:35] by Moderator Report message to a moderator |
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