converting '85 low wall from 32 rimfire to 32-20

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  • Last Post 29 March 2018
loophole posted this 20 March 2018

There are two sites with detailed instructions for converting a low wall 32 rimfire to 32-20--Larry Potterfield, owner of Midway, and Roy Bertalotto at RVB Precision.  Neither makes any mention of a problem which I am having doing this conversion.

Per the instructions on these websites I have reamed the chamber and extracter, modified the breach block and installed a centerfire firing pin.  As predicted by these gunsmiths the centerfire pin strikes the primer too low--about .040-.050 by my measurements.  Non the less, I chambered some primed Starline cases and it fired about a half dozen.  The tip of the pin strikes the very bottom of the primer but does not mark the case.  

My rifle is a 32 long rimfire, so marked on the bbl.  It has "32" stamped on the breachlock.  The spacing on the holes in the link is .428".  I carefully measured several times with dial calipers and made a new link with .478 hole spacing.  I installed this link and reassembled the rifle with new link.  The action will not close.  The link pushes the breachblock (and firing pin)  up in the mortices in the receiver at a slight angle to the face of the block so at a certain point the block cannot go any higher because the face of the breachblock presses against the rear of the bbl.  In my case the block cannot go any higher than it is positioned by the original  link.

Am I doing something wrong or forgetting something?  Did both these gunsmiths leave out somthing important in there instructions?  Any thoughts or suggestions greatly appreciated.

Steve K

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corerftech posted this 20 March 2018

how far does FP protrude when in fired position? Use a feeler gauge when it's fully depressed out of the gun.

How did you measure what your depth of cut should be?

How did you determine headspace in the current chamber (rim recess)? (when you chambered, what was your index for depth of cut)

How did you set headspace? (What control did you use to control depth of cut and hold your above figure)

How did you CHECK headspace after reaming?

 

Mike

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Ken Campbell Iowa posted this 20 March 2018

i would first take a day off .... it is really your sub-conscious mind that solves problems ( g ) .

then i would consider the scenario of just unscrew the barrel until the block just misses the rim of the cartridge about 0.0005 and cut that much off barrel, if the sights will still clock close enough.  ( if you can't easily tell they are canted, they are close enough . )     each 0.001 will take about 6 to 10 degrees.  if only a little relief works, you might not have to recut the chamber deeper .

just a suggestion, consider carefully all possible side effects.

ken

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loophole posted this 27 March 2018

Mike, I used a new case to check headspace and carefully measured firing pin protrusion but with the longer link the breachblock will not close on an empty chamber so these have nothing to do with the problem.

Ken, with the old link installed the firing pin seems to fire the primer every time, so I am going to try using the gun with the pin slightly off center from the primer before doing anything more drastic. DZ arms makes a few low wall parts, including links, breechblocks, and firing pins.  They tell me these all will fit an original low wall, so this possibly is a solution if what I have doesn't work correctly.

Thanks for your suggestions.  I still have no idea why I have this problem which is not even suggested by two gunsmiths who have websiteson the conversion?

Steve K

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RicinYakima posted this 28 March 2018

I have no idea why you would need a new link. If you keep to black powder pressure the old one should be fine.

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frnkeore posted this 28 March 2018

The breech block on a low wall and high wall is at a angle of 5 degrees, to the vertical and as you have found, you can not raise the BB with a longer link. The other thing about these actions, is the the geometry of the link to BB, causes the BB to raise and then lower, to the firing position, it goes over center, to do that. The common fix is to plug and bush the firing pin hole, to the higher setting or replace the BB. Personally, I don't like bushing them that way and would suggest replacing the BB.

Frank

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corerftech posted this 28 March 2018

I do believe that your link is wrong length, meaning since link is at an angle, the actual hole spacing will be more or less than the .050 you measure as your correction distance.

Are you sure the firing pin is staying retracted fully? I’ve had them hang the action identical to your description. On a rimfire to CF conversion too! Can you make a simple link ( like a 1911) like a dog bone, omitting the knob and test? Manually you’ll have to move the FP back to retracted. You made a part and it’s not geometrically correct. Either the FP is hanging because of it or the length is wrong and that’s binding the action.

My free .02 cents. The added data to your OP is helpful.

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loophole posted this 29 March 2018

Firing pin is fully retracted retracted--you can watch this when you open or close the action.  Both the conversions shown on the net use new links with about .045--.050 hole spacing and a centerfire pin--the tip is centered in the larger part of the pin so it strikes higher than the rimfire pin.   Take a look at the websites and tell me how the longer link functions.  I hope to get to the range Sat to see how my low wall shoots.

Steve K

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