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Very Hot Topic (More than 25 Replies) What primer for my Hepburn 40-70SS (Read 2929 times)
JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #15 - Apr 29th, 2020 at 1:34pm
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I don't see any drag marks from the pin on the rims from not wanting to retract back which would be typical. If the pin where getting stuck in the primer indent the nose would tend to break off when opening the block.
  
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Bulseyetom
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Re: What primer for my Hepburn 40-70SS
Reply #16 - Apr 29th, 2020 at 3:40pm
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I just polished my firing pin to make sure there is no drag and also shortened it a tad as it looks like it is protruding a tad too far.  I also broke out my 310 tool and set the primer adjustment to seat 0.004 below flush.  I am changing lots of variables at once which I hate doing but am trying to figure out what is causing the primers to back out.  The problem occurs one the first firing so it is not like the primer pockets are enlarged. I thought for sure that the Baco brass with 0.005 thicker rims would solve the problem but it seems like the make of primer is contributing more to the problem.  Sunday will be my next test day!  Tom
  
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hepburnman
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Re: What primer for my Hepburn 40-70SS
Reply #17 - Apr 29th, 2020 at 4:18pm
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Bulseyetom wrote on Apr 29th, 2020 at 3:40pm:
I just polished my firing pin to make sure there is no drag and also shortened it a tad as it looks like it is protruding a tad too far.† I also broke out my 310 tool and set the primer adjustment to seat 0.004 below flush.† I am changing lots of variables at once which I hate doing but am trying to figure out what is causing the primers to back out.† The problem occurs one the first firing so it is not like the primer pockets are enlarged. I thought for sure that the Baco brass with 0.005 thicker rims would solve the problem but it seems like the make of primer is contributing more to the problem.† Sunday will be my next test day!† Tom

Are you seating your primers by pressure or by depth? Typically, pressure is the way to go as you want to be sure the anvil compresses the detonating material. Also, not seating the primer fully can lead to erratic ignition.

A light pressure-feel using a hand tool is (the best?) way to seat your primers. No flames please Wink!
  
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JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #18 - Apr 29th, 2020 at 4:19pm
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The primer indents appeared to be a bit on the deeper side. But even at that your Primers shouldn't be backing out. That is what is not making and sense if your head space is correct. Have you checked the primer pocket depths to see if they fall within specs. Here is the link to the specs. below.

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ballardhepburnmich
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Re: What primer for my Hepburn 40-70SS
Reply #19 - Apr 29th, 2020 at 10:58pm
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There has to be a little extra headspace or the primer could not back out, no way around it. I hope you noticed that I didn't say excessive headspace. A lot of firearms back primers out a little bit.
Lee Gibbs Pres.ASSRA
  
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Bulseyetom
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Re: What primer for my Hepburn 40-70SS
Reply #20 - Apr 29th, 2020 at 11:34pm
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The more that I see how the Hepburn works the question seems to be why is the action not opening easily after firing as the primer can only back out until it hits the breechblock.   It seems like if the firing pin is indeed retracting, which now that I see how it works after taking it apart I can easily tell the next time out, then the culprit has to be that the primer is pushing so hard against the block to lock things up.  Cocking and firing again drives the spent primer back in far enough to allow the action to work as normal.  I would think that the small area of a protruding primer would not be enough to completely lock up the action.  There is no in between, the action is either locked or opens easy.  I guess the next step is to try to measure the diameter of my primers and see if one brand is larger.  This is getting better than watching murder mysteries on tv and trying to solve the crime!  Tom
  
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oneatatime
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Re: What primer for my Hepburn 40-70SS
Reply #21 - Apr 30th, 2020 at 12:33am
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How smooth or not is the face of your breechblock?
  
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JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #22 - Apr 30th, 2020 at 11:48am
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Somebody could have used pistol primers in it. If so there might be an indent in the face of the block that the primer moves back into that is  locking it up.
  
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Bulseyetom
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Re: What primer for my Hepburn 40-70SS
Reply #23 - Apr 30th, 2020 at 1:10pm
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I did not notice any indentations but will pull the breechblock out and look it over.  I am most interested now in looking at the back of the firng pin when the action locks up to see if it is free or stuck.  That will either let me know that the firing pin is not retracting or if it is the primers pushing against the block.  Tom
  
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JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #24 - Apr 30th, 2020 at 2:49pm
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Run a straight edge across the area where the primer contacts the face of the block it should be flat and minus any indents.
  
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Re: What primer for my Hepburn 40-70SS
Reply #25 - Apr 30th, 2020 at 3:04pm
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Just for reference CCI primer cups are hardest in the industry and always have been. When I was in the business of building comp revolvers after some time working with several top smiths we set up our mainsprings at around 42oz for Fed and Winchester primers, and just a tad more for Remington. But CCIís needed about 50-52 oz for reliable ignition. Based on fully seated primers of course. If your firing pin is chasing the primer all bets are off.

Rick
  
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Re: What primer for my Hepburn 40-70SS
Reply #26 - Apr 30th, 2020 at 8:24pm
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hepburnman wrote on Apr 29th, 2020 at 4:18pm:
Bulseyetom wrote on Apr 29th, 2020 at 3:40pm:
I just polished my firing pin to make sure there is no drag and also shortened it a tad as it looks like it is protruding a tad too far.† I also broke out my 310 tool and set the primer adjustment to seat 0.004 below flush.† I am changing lots of variables at once which I hate doing but am trying to figure out what is causing the primers to back out.† The problem occurs one the first firing so it is not like the primer pockets are enlarged. I thought for sure that the Baco brass with 0.005 thicker rims would solve the problem but it seems like the make of primer is contributing more to the problem.† Sunday will be my next test day!† Tom

Are you seating your primers by pressure or by depth? Typically, pressure is the way to go as you want to be sure the anvil compresses the detonating material. Also, not seating the primer fully can lead to erratic ignition.

A light pressure-feel using a hand tool is (the best?) way to seat your primers. No flames please Wink!


Indeed. Pressure is the essence of primer seating as it relates to deformation of the metallic cup. Primer seating depth is pretty much a tough thing to measure but pressure relates directly to full seating and resistance.  A crushed or deformed cup will result in altering the primerís design sandwich consisting of explosive, retaining disc and flame anvil. A crushed primer will ignite but flame pattern will be disturbed resulting in uneven burn.
  
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