I've noticed on some of the break top revolvers there is a mark on the frame screw with a corresponding mark on the frame. (as in pic below) What are the marks for and are they supposed to line up? Can there be issues of over tightening if the lines don't match up? Is this a possible indicator that someone has tried to tighten the frame by compressing the two sides and when they tightened the screw the marks don't align? Trying to figure out if this in an indicator that someone "tinkered" with one of these revolvers and should I stay away from it. Thanks in advance!

Later!

Simi

Frame screw.jpg

When you drive the joint pivot out of the frame toward the right side, make a note of the witness mark on the joint pivot and its corresponding mark on the frame. These must be aligned for reassembly. The barrel is now loose and can be lifted up out of its joint with the frame. The extractor cam is located between the ears of the barrel hinge and can now be pulled down and out of the barrel. Make note of the extractor cam's position for reassembly. Hope this helps.

Nick

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NRA Instructor\GCA Gunsmith

So this is actually a pin and not a screw? I always thought it was a screw since it has a slotted head on one side. Thanks for the info.

Later!

Simi

Under the pin, you will see a small slot in the frame, which corresponds to a small lug (or key) on the pin. The witness marks are so you can align the slot and lug. If they are not aligned correctly, the lug can be damaged if the screw on the left side of the frame is tightened. The lug is there to prevent the pin from spinning while tightening the screw. Hope that helps.

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Gary
SWCA 2515

It's a case of semantics. The pivot "pin" is actually two pieces threaded together, when assembled. Some call it a screw. As said above, the witness marks must line up on reassembly to have everything work properly. If you see guns w/o the marks lining up, you know Bubba has been aboard! Ed.

The slotted part is a cap , disassembly instructions say " remove cap screw on left side, push barrel hinge pin out to the right"

The Gun Digest Assembly/Disassembly Guide for Revolvers by J. B. Wood comes in real handy when getting these old top breaks apart and back together.
Don't take it apart unless you at least have a exploaded parts diagram.
Gary

Ed answered the first half of this question in post number 5.

I would be interested in the answer to the second half. Does mis alignment mean that the gun is toast??????????

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James Redfield
LM #497

As I stated in post #4, if the assembly is put together wrong, the lug on the pin will be damaged or ruined. If the gun is put together incorrectly, the witness marks will not line up and that is a gun to stay away from. The lug prevents the pin from turning when tightening the screw and if missing or damaged, one cannot tighten the pivot and the barrel will not have any resistance to dropping open.

We have all seen many where the pin and screw are turned around, but this does not always damage the small lug and simply turning it around will solve the problem

. . . best way to tell if the assembly is damaged is to pull the pin and inspect the lug, if there fine, if damaged, either find another pin or find another gun.

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Gary
SWCA 2515

So, you could actually replace the pin and install the new one correctly and the gun should be ok...is this what I'm understanding?

Later!

Simi

Yes, as long as you can find one for sale. Parts are out there, but some are tough to find.

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Gary
SWCA 2515

Thanks for all the information! I'm totally enjoying this new place and getting acquainted with all these people with such a wealth of knowledge.

Later!

Simi

Let's call a spade a spade! The "pin" is a nut. Once it has been properly installed---witness mark to witness mark, the screw can be properly installed. Once the screw is properly installed---and you want to call the nut a pin---or a hinge pin, you won't get any more sass from me---until the next time.

Ralph Tremaine

And if you want to get picky about it (like I should have), it's a "joint pivot"-----after it's been used as a NUT!!

It is actually a closed-end or dead-end "barrel nut" as it has threads inside it is a nut or even a rivet as it has no head to be held with a wrench or screwdriver.

While S&W's have a guide or line up tab, most common types of these have scored bases at the bottom most part of the tubular section of it that it would press fit to seat that it will not rotate once seated.

When the "score" line of the barrel nut and score line on the frame align perfectly, it is installed correctly.

A few more mechanical terms could be; Inside threaded blind rivets / nuts or Closed End blind threaded nut.

Either way it's that PIN / NUT / GIZMO / THINGAMABOB or just a barrel axis / hinge nut.

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ANTIQUESMITHS
LM1300 SWHF425