doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Superposed firing pin drag again

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

Jack,

Perhaps a call to Jason at Midwest Gunworks is in order.

Phil

Could be Phil. I have one of their parts kits which was pretty well cannabalized by Kenny Eyster on another gun except for the pins and beads. Questions on pin measuring methods seem to me pretty generic altho the answers I'm sure, if there were any, would be individualistic. Maybe it's stack barrel aversion? Should have asked about Alkanet root.

jack

Brownells has a Firing pin protrusion gage - http://www.brownells.com/aspx/NS/store/P...ROTRUSION+GAUGE

You can probably make something similar out of a 1/4" threaded rod coupling and a smooth ended bolt, and measure the depth with your caliper. Hope that makes sense.

If you still have a wee bit of drag, and the pin is maximum length (.065"), try shortening it a wee bit more to say .060", or even to .055", if no misfires are happening. Big "IF".

As an alternative to heating and rebending the cocking lever, perhaps you could soft solder a piece of shim onto the right hammer's cocking face? Or perhaps a drop of steel tig welded to the face of the right side cocking lever?

I'd make a domed punch out of brass to start the pin out, then use a long pin punch with a piece of cut brass shim on the end to drive it out the rest of the way. A dab of grease will hold the brass shim on the end of the punch. You can perhaps find solid brass in 12" lengths at some hardware stores and hobby shops also to make a punch out of.

Best of luck with your pins. Joe

Gunsmither:

Thanks for the link. In the case of the lower barrel firing pin, the max protrusion recommended in the Arnold MO. bulletin is .056" and the minimum .051". .064" was the "as it comes" protrusion of the pin from the Midwest kit in this gun. Pretty long and the pin previously in the gun appeared to be a replacement which had not been shortened as it was pitted and the retaining pin shaved one side, probably from bad alignment of the retention slot when the pin was driven in. Primer drag from that one was noticable. The strike in the primer looks much better now and drag is very slight. I'm going to sleep on that cocking lever problem for awhile but appreciate you sharing your trick of padded undersize pin punch after starting the crosspin with a domed brass punch. Thankyou.

jack