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Very Hot Topic (More than 25 Replies) What primer for my Hepburn 40-70SS (Read 2930 times)
Bulseyetom
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What primer for my Hepburn 40-70SS
Apr 26th, 2020 at 12:57pm
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Some time back I had a thread on my Hepburn and primers backing out.  I wasn't sure if it was a headspace problem or a rebounding hammer problem and got lots of suggestions for fixes but along come Covid 19 and my range closed.  I have a chamber that was cut for full length 405 brass with a 0.073 rim and all of my Hornady brass was 0.068.  I bought some Baco brass to try that is the correct 0.073.  Not being able to shoot much as the range is closed I loaded a few of all of my brass types with a 330 grain bullet and smokeless for this go-around and shot a few each with Winchester WLR and Federal Match.  It didn't seem to make any difference which case was used but I had more problems with the Federal primers than Winchester.  I believe that the firing pin is sticking in the primer and not allowing ejection.  Firing a second time does not always work either.  I need to look at the end of the firing pin closer but I am not sure that I want to tackle taking a Hepburn apart.  My next thought was to try CCI primers and also magnum primers.  The lower pressure loads seemed to have more problems.  So my quick question is this, what is the toughest primer known to man so that the angled firing pin of the Hepburn with the force to penetrate the armor of a light tank does not stick in it so far as to pull the primer back out when it rebounds?  Thanks.  Tom
  
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JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #1 - Apr 26th, 2020 at 1:33pm
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I personally don't have any knowledge on anything regarding a Hepburn. But I do have a question is it possible to add a firing pin retraction spring. If not you can try stoning a back sloping radius to just the bottom half of the firing pin nose. This has always helped to start the firing pin to retract out of the primer indent. 
In regards to primer cup hardness I have found the CCI's to be the hardest that I have experienced over the years.
  
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Bulseyetom
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Re: What primer for my Hepburn 40-70SS
Reply #2 - Apr 26th, 2020 at 1:54pm
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John, I know one of the fixes suggested earlier was to put in a heavier extractor spring and to reshape the firing pin.  I have CCI LR and Magnum primers and am now going to experiment with black and paper patched bullets to see if I can find a reliable combination.  Most of the problems I had today were with Federal and I did not have any of the proper rim thickness cases loaded with anything but Federal.  Winchester worked 85% or so with the only problems with a light load of Buffalo Rifle.  When I used a heavier load of H4198 with a gas check bullet I had no problems except the recoil!  Tom
  
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hepburnman
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Re: What primer for my Hepburn 40-70SS
Reply #3 - Apr 26th, 2020 at 2:32pm
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I have a Jim Hamilton reproduction Hepburn. Here is a picture of how he profiles the tip of his firing pins. The tip of his is flattened at a down angle or, to say another way they would be flat to the breech block face. He says that this helps with retraction from the primer.

I use Fed 215 mag primers and never had an issue with these and several others i have tried.
  
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Re: What primer for my Hepburn 40-70SS
Reply #4 - Apr 27th, 2020 at 9:52pm
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You might try CCI  number 34 primers they are made for use in semi auto military rifles to prevent slam fires.
  
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Bulseyetom
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Re: What primer for my Hepburn 40-70SS
Reply #5 - Apr 28th, 2020 at 12:15am
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I was quite surprised to see a primer made especially for simi auto rifles.  I guess I have been shooting single shots way too long!  I will order some and see if they solve my problem.  I cleaned my firing pin good today (it was not dirty) and the spring looks good but will call DZ Arms to see what they have to say.  Thanks.  Tom
  
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Re: What primer for my Hepburn 40-70SS
Reply #6 - Apr 28th, 2020 at 9:43am
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I get my best results with a standard Winchester Large Rifle Primer.

40 Rod
  
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Re: What primer for my Hepburn 40-70SS
Reply #7 - Apr 28th, 2020 at 9:48am
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I've used both CCI and Winchester std. large rifle primers in all of my Hepburns, and never had a problem with any of them.
  

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JLouis
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Re: What primer for my Hepburn 40-70SS
Reply #8 - Apr 28th, 2020 at 12:37pm
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Hopefully you get the issue resolved primers shouldn't be creating the problem it has to be related to something else.
  
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Oldman1950
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Re: What primer for my Hepburn 40-70SS
Reply #9 - Apr 28th, 2020 at 6:36pm
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Some time back I had a thread on my Hepburn and primers backing out.  I wasn't sure if it was a headspace problem or a rebounding hammer problem

To me it sounds like it is a head space problem. As the  cartridge goes off the firing pin drives the cartridge forward into the chamber and brass case expands and grabs the wall of the chamber. With excess head space the primer now doesn't have anything to hold it in the primer pocket except friction. Chamber pressure pushes the primer backwards towards the face of the breach block until it contacts the block.
An easy way to check the head space is to take a piece of scotch tape and stick it over an unfired primer and try to close the breach block. if it closes over the tape add another layer of tape and try again. keep adding layers of tape until the breach block won't close. Add up the thickness of the layers of tape to get your head space.
On my 32-40 Hepburn using Winchester brass I can slip a .004" feeler gauge between the chambered brass and the face of the breach block.

A. J. Palik
  
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Re: What primer for my Hepburn 40-70SS
Reply #10 - Apr 28th, 2020 at 7:34pm
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Oldman1950 wrote on Apr 28th, 2020 at 6:36pm:
Some time back I had a thread on my Hepburn and primers backing out.  I wasn't sure if it was a headspace problem or a rebounding hammer problem

To me it sounds like it is a head space problem. As the  cartridge goes off the firing pin drives the cartridge forward into the chamber and brass case expands and grabs the wall of the chamber. With excess head space the primer now doesn't have anything to hold it in the primer pocket except friction. Chamber pressure pushes the primer backwards towards the face of the breach block until it contacts the block.
An easy way to check the head space is to take a piece of scotch tape and stick it over an unfired primer and try to close the breach block. if it closes over the tape add another layer of tape and try again. keep adding layers of tape until the breach block won't close. Add up the thickness of the layers of tape to get your head space.
On my 32-40 Hepburn using Winchester brass I can slip a .004" feeler gauge between the chambered brass and the face of the breach block.

A. J. Palik


I have a Marlin 336, 30-30 that does this - primers backing out of the case. It is most prevalent with starting loads, although I have seen it with factory ammo, too.  Never had a case head separation in this rifle, due to case stretching.

Primers nearly always back out of the case due to chamber pressure.  With low pressure loads the, case does not stretch and the primers stay backed out of the case.  The amount that the primer backs out is the difference between the thickness of the rim and the total headspace.  High pressure loads stretch the case and reseat the primer.

One question, can you rechamber one of the cases with the primer backed out.  It would be interesting to measure the amount of primer protrusion, rechamber the case, eject it and measure the protrusion again.  I have a feeling that you will find there is no difference.

Mike
  
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Re: What primer for my Hepburn 40-70SS
Reply #11 - Apr 29th, 2020 at 9:30am
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After shooting 10K+ rds thru three original Hepburns (40-65, 38-50, 32-40) have never had a primer back out. I standardized on CCI 200 LR primers for my loads (as high as 70gr of 2F Swiss pushing a 439gr bullet in the 40-65).  I would suggest the easy start would be to take your Hepburn apart and give a good cleaning/lube and look for any broken/bent parts. They are as simple as all original single-shot rifles. The only 'trick' I can think of in taking apart and putting back together is the last step of installing the tang/trigger guard. Loosely install the front two screws first and use them as you pivot the back half of the lower tang into position. This lets you use the tang as a lever to easily compress the main-spring and install the rear-most tang screws. The other suggestion is to polish the tip of your firing pin. It may be a bit too long. You can purchase Hepburn spare parts from DZ Arms or C. Sharps.
  

Glenn
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Re: What primer for my Hepburn 40-70SS
Reply #12 - Apr 29th, 2020 at 9:35am
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I had this trouble when I used Remington 2 1/2 pistol primers in my .40-2 1/2 Rem. Hepburn (as I do with all of my other large primer calibers I deal with.)I changed to Remington Rifle primers and the problem was solved.
  
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Re: What primer for my Hepburn 40-70SS
Reply #13 - Apr 29th, 2020 at 9:41am
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Take a couple of pieces of brass and drill out the primer holes to oversize. Do a little increase in diameter at a time and the protrusion problem should go away. When and if the protrusion ceases drill the rest to the same diameter flash hole. This won't fix a headspace problem if any but will rebalance the primer/flashhole relationship.Good luck.
  
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Re: What primer for my Hepburn 40-70SS
Reply #14 - Apr 29th, 2020 at 1:18pm
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I believe that the problem is that he primer tip penetrates the softer primers so far that it sticks in the case as it is hitting on an angle and not inline with the bore.  The attached photo shows 10 cases fired with the identical load.  The cases on the left are 405 Winchester from Hornady and the rim thickness is such that there should be excessive headspace.  They were primed with WLR primers and did not experience any issues extracting.  The ones on the right were from BACO brass with the correct rim thickness to eliminate excess headspace.  Four out of five hung up with Federal Match primers.  You can see where the Federal primers have deeper craters.  I now have that same load with both types of cases loaded with CCI to see if the problem goes away.  If so, I might buy some CCI 34 primers to make sure that it stays away.  I have taken the firing pin out and cleaned everything and inspected the spring.  I would imagine a heavier return spring might lighten the pin impact and also give more effort to retract the pin.  Without better knowledge I was not able to see how the tip was shaped compared to the above pictured firing pin.  Tom
  
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