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Win 94 Rebounding Hammer Fix (Read 1353 times)
mavt
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Win 94 Rebounding Hammer Fix
May 15th, 2020 at 7:42pm
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Back in 1998 I bought a new Win 94 AE Big Bore carbine for the 356 Win cartridge.  The 356 is the same case as the 358 Win except with a rim and a shorter loaded OAL to function in the M94.  It is loaded to the same pressure level as the 358 which gives considerable more firepower than the 30-30 class of cartridges. Like the 358 it can also be shot with any  38/357  handgun bullet and is a favorite diameter for cast bullet shooters.

This model has the crossbolt safety and rebounding hammer that replaced the traditional halfcock hammer position as the safety a few years earlier.  The Big Bore model has a beefed up receiver and substantially heavier barrel than the standard carbine which contribute to the accuracy level this model is noted for as well as cosmetic enhancements like checkering and nice blueing not usually found on the standard carbines. 

For a period of years there were no issues then at some point I began getting misfires from light primer strikes with about 5 to 10 per 100 shots requiring a second strike to go bang. Reloading equipment and techniques hadn't changed and looking around there was evidence of others experiencing it as well. So over the years since I have periodically researched for a solution  but had not taken any action except to shoot it less -.which is no fun.

Recently I again reviewed the topic looking for anything new but came away with a bit more of the same.  Many  have completely replaced the hammer spring mechanism with old model parts and disengaged or removed the crossbolt or tang safeties on even later models to revert back to the halfcock safety. But those used parts had dried up a while ago and new are not available probably for liability concerns. Others resort to using "soft primers" with Federal being mentioned most or even large pistol primers.  But I was looking for a permanent solution with 100% reliability using any primer and no special primer pocket condition - I have rarely cleaned them over the years.
  
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FredC
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Re: Win 94 Rebounding Hammer Fix
Reply #1 - May 15th, 2020 at 8:20pm
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Correct replacement springs not available? Is there a rebound spring that could be replaced with a softer one?

A light strike can produce a hang fire that will happen several seconds up to 30 seconds later, be careful till you find the solution. If you do get a misfire keep the gun aimed in a safe direction and do not open the breach for 1 minute.
  
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mavt
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Re: Win 94 Rebounding Hammer Fix
Reply #2 - May 15th, 2020 at 8:34pm
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And I didn't want to alter the crossbolt safety as it reliably serves the intended purpose. I wanted to leave the rifle as is except eliminate the misfire problem, if possible.

There were many references to an older Rifle Magazine article by Dave Scovill where he details a procedure to correct misfires with a M1886 which has a slightly different mechanism but works on the same rebound principle as the M94.  I remember reading the article and probably still have it in a box somewhere around here.  There are top and bottom prongs on the hammer spring strut that push the hammer forward and then start to pull it back before actually firing to the safe position after firing . He adjusted the balance of the push and pull by removing a bit of the bottom strut (about .030 inch ) which solved his misfire problem.

The M94 has two top and bottom fingers on the mainspring strut that contact upper and lower notches on the hammer.  Removing the tang screw and then the hammer retention screw allows the lower tang to be pulled out
exposing the the mainspring strut and hammer.  After removing the mainspring and hammer the strut and hammer should be checked for burrs that can impede the hammer force in addition to the imbalance of the strut fingers and stone smooth as necessary.  My strut was quite rough along the edges that would contact the mainspring.

There is a convenient shelf on the back of the strut that allows the lower finger length to be accurately measured with a caliper. Mine was .6235 and I stoned both evenly at the same time down to .600 keeping the ends rounded as they started out. Some had reported removing  .035 to .037 and not being able to push the crossbolt safety into place without thumbing the hammer back a bit - I stopped before that point and the crossbolt still works as intended.
  
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mavt
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Re: Win 94 Rebounding Hammer Fix
Reply #3 - May 15th, 2020 at 8:58pm
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The most difficult part of the exercise is getting the mainspring back on the strut. Someone may know a trick for this but I eventually had to place two 1/4 inch thick aluminum plates in a vise and use my gut to push the strut between the plates enough to allow a nail to be inserted into the spring retention hole barely sticking out the back of the plates

After reassembling I could tell by the sound that there was a difference in the forward hammer force. I have shot 100 rounds without  a misfire and the primer indentations look more normal.  It is said CCI primers have the hardest cups so I tested  with CCI 200s, without cleaning primer pockets,  and priming using my press rather than a handheld tool where you can feel  the seating depth. This should be worse case scenario which is what I wanted to test.

Hope pulling together and detailing the process will help others that may run into Winchester rebound hammer misfires to implement this relatively simple fix and not resort to the other more radical and potentially dangerous alternatives out there. I just needed to finally sit down and attempt it and I'm not what I would consider mechanically inclined.  All that is needed is two proper sized screwdrivers, a caliper, stone or fine file, and some time and patience.
  
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Re: Win 94 Rebounding Hammer Fix
Reply #4 - May 15th, 2020 at 9:08pm
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Fred,
Both the forward and rebound action are controlled by the same spring. Actually, some trying to lighten trigger pull have replaced the single mainspring with a lighter one which then created a misfire situation where there wasn't one. Apparently most rifles have the correct tolerence balance for the system to work as designed  while others need this simple tune up to get that balance.

Lightening trigger pull is another project. I was closely examining  those surfaces but at this time I'm happy with the reliability and haven't the courage to attempt the lightening...and may leave well enough alone and probably never do it.
  
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Re: Win 94 Rebounding Hammer Fix
Reply #5 - May 15th, 2020 at 10:36pm
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Glad to hear that you got it fixed. You might do some checking to see if the later style spring is available, since it may be a source of problems later. Get one now before it is obsolete in the future.
  
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