Whatzit?

[earlgo]

Yesterday I had to dig this tool out of the archives and apply it to the project I was working on. I thought perhaps some of you had never seen one, and most likely had never had the occasion to use one. It is sort of like 123 blocks or toolmakers clamps, in that if you need one there is no good substitute.

Whatzit END.jpg (29.18 KiB) Viewed 4389 times

The center pin slides and is clamped by the thumbscrew.
Any guesses?
--earlgo

[mcostello]

Depth gauge.

[wlw-19958]

Hi There,

It looks something like a firing pin protrusion gauge.

Good Luck!
-Blue Chips-
Webb

[pete]

Yep firing pin protusion gauge and likely bought from Brownells where mine came from. However there's more than one possible use for something like that so I won't be betting money Earl.

[earlgo]

Ha, you are correct. I did not know Brownells sold them. We had to make our own at the CST in 1970.
There is no better way (that I know of) to measure firing pin protrusion in a revolver, due to space limitations and closeness to the frame strap.
Still, I'd bet it is not found in a lot of toolboxes.
Incidentally, the firing pin protrusion for a 22rf is .043/.046 according to Roy F. Dunlap, just to complete the topic.
--earlgo

[pete]

Yep it's a simple but handy tool Earl. Brownells did sell them, I haven't checked if they still do. Most of the commercial versions are as far as I know properly hardened and ground on the ends. I highly doubt a well made home shop unhardened version would provide less accuracy so it's an easy tool to duplicate with a lathe and good reamer. Today I have much better metrology equipment and for something such as a bolt action where the bolt can be removed using a proper depth gauge might be the better option. My protusion gauge and a cheaper dial caliper lives in my range box probably more in case someone else needs there gun checked than mine. A good reminder though, I really should have the recommended dimensions handy for the average pistol, shotgun, rifle specifications.

A bit OT maybe. So why would you want one of these gauges? A lot of shooters besides Earl don't know there's an optimum protrusion for the firing pin. Very rare, but I guess possible in a highly worn gun you could get very dangerous pierced primers. A major miss by QC on a new gun might be barely possble as well. At the other end and while you may not quite be to the point of seeing missfires, the firing pin protrusion might be set a little too low. The primer due to very minor manufacturing changes from machine to machine may see slight changes in seated crush depth. Primer pockets also show even more changes in there diameter from case to case and more importantly there swaged depth again from changes from machine to machine at the factory. I found if your reloading then recutting the primer pockets to all the same depth with the proper tool designed for the task helps in consistent primer ignition and accuracy. Knowing your firing pin protrusion is correct is also just part of the chain. Even .001" changes in primer height affects the firing pin lock time. Seating primers by feel will always be far better than high volume primer seaters at the manufacturers. Those minor vibration changes because of primer height can and do transmit themselves as slightly different vibrations to the barrel even before the round fires. That at least with well shooting rifles does show up on paper. Adding titanium firing pins to help speed up those lock times against a steel one isn't uncommon either. High speed lock times and consistant travel on the firing pin is always considered to be a good thing.

As an extra bit of related information most or maybe all carrtridge primer flash holes are punched not drilled in the cases. Almost without fail that leaves a variable sized hole due to punch wear from machine to machine and even worse a serious inside burr inside the carrtridge head. Redrilling and deburring plus beveling the the internal exit side of the flash hole is also helpful for consistent accuracy. If you have an accurate enough gun all of this does show up on paper at 100 yds.

[earlgo]

Pete:
All of what you wrote regarding accuracy related to primers and protrusion is right, and Warren Page goes into this in quite a bit of detail in his book 'The Accurate Rifle'. Copyright 1973. Winchester Press. LCCCN 73-757665 ISBN 0-87691-102-5.
However, the students at the Colorado School of Trades made and replaced firing pins for any and all firearms, and this gage is an absolute necessity to be sure the protrusion is correct.
I hauled this gage out of the archives because of a make and replace scenario.

--earlgo

[pete]

I had the exact Warren Page book you mention Earl. Lent it out and that was the last I ever saw of it though. A bit hard to find today and it was a short soft cover when it was published is Stuart Otteson's Benchrest Actions and Triggers. Really good and informative although dated a bit now about what makes a top shooting rifle. I'd be surprised if you haven't heard of it or maybe even own a copy. Today it's probably much easier to start with a custom single shot action designed from the start to do the job than rework a Remington 700 and still have a much lighter built action after all the work. Stuarts book was a big influence when I bought my Hall action. But Stuart also did a top quality job detailing exactly why the 3 lever triggers are so good. That looks to be a bit time consumeing to repicate that firing pin. Not one I recoginse, what make of gun?

[earlgo]

Pete, I've not heard of Otteson's book, but that is mostly because I wasn't into one hole groups. Page's book convinced me it was too much trouble.

The fp is from a FI Regent 22 cal 8 shot revolver, which in my humble opinion is a POS in spades.
But the new fp came out nice. O-1, full hard and drawn back to a deep straw.
--earlgo

[pete]

Yeah it's a lot of trouble to be sure Earl. Today to be really competitive it's a rich mans sport. They may go through a dozen or more barrels per year trying to find one or two that shoot really well, 10k + practice rounds every year and the barrels those shoot out, complete new rifles every few years etc etc. I did learn a great deal about what's involved in the rifle, shooting technique and loads to get a combination to shoot those one hole groups.

Sounds like the best piece of that revolver is now the firing pin.

[SteveHGraham]

Firing pin protrusion? ANOTHER thing to worry about?

I picked up a .204 Ruger recently, and I was hoping to reload for it and see how well I could do here on the farm. I had no idea I had to think about the firing pin.

[earlgo]

Steve, if you know the fp is NOT factory original then it may be advantageous to check the protrusion. If you get intermittent misfires or pierced primers with factory loads, then it would indicate something is amiss and it would be good to check.
If it came from the factory then it is good. Too much liability, otherwise, and I assume you are familiar with liability?
--earlgo