My recent and perhaps badly articulated request for info regarding dressing new firing pins to spec'd length in a Superposed Lightning Trap got no replies. The underwhelming response suggested that either the technique involved is either so patently obvious and oldhat that mine was a very dumb question or . . .? Anyway, I called Mike Orlen and he said grind em down without heating and keep measuring. If anyone's interested, here's my progress so far and a further question.
When first replacing the pins, I removed both the hammer springs/struts and the hammers. I have since discovered that if the hammers are rolled well back under the sears, their removal is not necessary and the pins will clear on the way out. The Arnold MO service manual is not too clear on this.
The protrusion of pins past breech face with hammers down looked long cf. to those in another Browning Super. I was not sure how to measure so initially tried to use the depth gauge on a dial caliper. Altho I confirmed that the pin protrusion was over-spec I didn't feel I could manipulate the caliper to repeatedly get the measuring rod plumb to the breech face for a repeatable measurement. I decided to use a combination of feeler gauge leaves which gave the max spec'd measurement laid flat on the breech face adjacent to pin and a piece of key stock bearing on them and pushed back and forth as a sort of GONOGO. The key stock caught on and rode over both pins in both cases so I added feeler leaves by thousandths until the key stock cleared the dome of the pin. QUESTION: Is there a machinist or gunsmith-specific gauge which is most suited to picking up this measurement? Seems to me it would have to be something like a piston or rod in a cylinder of a diameter which would encircle the pin and measure plumb off the breech face.
I established that I needed to remove about 2 mils from the upper and 8 mils from the lower pin. I bonded 1/3 sheets of wet&dry paper in several grits to tempered Masonite sanding sticks with Spray 77. I began by doing the lower pin because I had a good bit of leeway for error on that one. Measured with caliper, scrubbed a flat on the dome with several strokes of 220 grt and measured. Didn't take much; only about 1/16" wide flat. Then I reshaped by chucking in drill motor and re-radiusing the dome with 400 and 1000 grt sanding blocks followed by polishing with Simichrome. For the upper pin I didn't create a flat but worked the existing dome briefly with 400 and 1000 until I got the .002" reduction and then polished.
Back in the gun and hammers down, the upper pin was on the max spec but bottom pin still .003" overlength (probably due to the fact that the housing of bottom pin is at an angle to breech and a reduction on centerline of pin does not adquately reduce effective length at the point on the radiused dome where the pin hits. So out of the gun again and back in the drill motor. Checked in the gun, lower pin now at .055" protrusion from breech face or 1 mil under max spec'd length.
Now to the QUESTION which concerns me most now. I'm still getting very slight pin drag mark in the primer of shell in lower barrel. Browning service manual says caused by bent or worn cocking lever and the telltale (aside from the drag mark) is smaller than .002" gap between hammer face and action wall with hammers down. I have no detectable gap on either hammer/action wall interface so believe that cocking lever is not pulling the hammers soon enuf when action opens. The service manual suggests removal of cocking lever and a bending procedure under torch heat. Has anyone here done this procedure? If you have, is there a particular type of domed punch for drifting out the cocking lever axle or did you make one? Obviously a bit more of a cosmetic issue on outside of action and I don't exactly have the tune in my head on this corrective procedure so would appreciate any and all advice.
jack
