Hi,
How much should I expect to pay for a gunsmith to put a bushing in the firing pin hole?
How much should I expect to pay for a gunsmith to put a bushing in the firing pin hole?
:
Bushing Large Tip Firing Pins
Many early-day actions such as the Winchester High-Wall single shot, the Sharps-Borchardt, the Cadet Martini, and the model 1892 Winchester are of excellent design, but carry firing pins with large tip diameter. This was satisfactory for use with the low-pressure cartridges, but it isn't with modern high-pressure cartridges. The area of the tip is so great that high pressure can thrust that firing pin back and burst a primer through the hole. In order to convert such actions for use with modern cartridges, we must bush the firing-pin tip to small diameter and close tolerances.
Many methods have been tried, but the simplest and best is that which first drills the firing pin-hole with a #31 wire gauge drill and then taps a 6 by 48 threads in the hole. Drill a 6 by 48 screw lengthwise with a #50 wire gauge drill. This drill is .070 inch in diameter. Ream this hole larger at the tip of the screw, corresponding to the radius of the firing-pin tip. Then using soft solder, tin the screw threads and those in the face of the breech block. Heat the screw and the breech block just enough to melt the solder and turn the screw into place. Finally, face the screw off flush with the outer surface of the breech block. A file will serve to it off if care is used. This bushes the hole to a .070" diameter. Now you only have to grind the firing pin tip down to .068 inch, remembering that this diameter must be flowed into the body diameter with a smooth radius if breakage is to be avoided.
There is a better method of bushing firing pins on single shot actions such as the Winchester High-Wall. It calls for good equipment and considerable experience. On these actions the firing-pin hole is drilled entirely through the block., from the rear, to the full diameter of the body of the pin. In the Winchester this diameter would be .320 inch. Then 3/8 by 24 threads are tapped in the forward end of the hole. That hole is counter bored on the lathe to a diameter of .625 inch and a depth of .090 inch. A matching steel plug, threaded on the 3/8 inch section is forced in tightly. The forward extension is then faced off flush with the face of the breech block, and a new firing pin hole is drilled. Note the illustration.
Bush firing pin hole and turn pin $50.00
Bushing the firing pin hole and turning the firing pin sounds small but this one operation to the bolt has so
many benefits it's hard to believe. The biggie is it has to be done correctly to work as a total benefit. It took two
years to perfect my system to get all the good out of this operation.
What can it do for you? The most noticeable that you can see is for the cratering and or primer piercing
problem for PPC comp rifles, varmint rifles and the high performance 17's, 20's and 6mm's but not limited to
them. The part you can't see that took two years to finally figure out is to make the bushing long enough in side
the bolt to guide and support the firing pin.
Cratering and piercing is not a problem with firing pin fit to hole diameter fit. It has to do with pressure
control. The smaller the hole the more pressure it takes to blank out a washer from the same thickness and
hardness material. So when your 20 Tactical or any other cartridge craters bad and your load is 2 grains light,
the primer round and brass has barely formed the problem is not fixed by a larger firing pin! The correct course
of action is to reduce the firing pin hole diameter.
The reason you want Gre'-Tan Rifles to do the installation is because of the consistency of ignition by my
bushing. This is accomplished because of the longer bushing in the bolt. When you cock and load the firing pin
it stays encapsulated. This guides the firing pin back and forth. It keeps it centered in the bolt helping to prevent
the spring from rubbing on the interior bolt body. The pin doesn't drop down into the large ramp area behind
the firing pin hole in the bolt causing the tip to wear and have different initial vibrations started before the primer
ignites. This all adds up to consistent primer ignition and getting an accurate rifle consistently accurate.
So what size is needed? I always strongly recommend .062 for all comp, varmint, and hunting rifles. For the
guy that has to always take his gun apart in hunting camp it's an .068.
For the person looking for just the repair, all I need is the complete bolt. Turn around time is 2-3 days.
Dunlap says in his book on page 158:Tip diameters are always good for an argument-some intelligent people claiming that they should all be .075" for all center-fire rifles and large caliber handguns and .985" for all shotguns
For the small rifle primer, I believe that tip diameter of .062" is probably best, plus or minus .002" and a protrusion of .050" plus or minus .001", when pins are to be make for single shot rifles rebarreled to on of the high-pressured little cartridges such as the .22 Hornet, .218Bee, or .22/3000 Lovell. When bolt actions are adapted to the small primer cartridges, for best ignition it is wise to bush the firing pin hole and polish the pin down, if over .064" in diameter and the hole is enlarged. If the pin is of that dimension or slightly smaller, and it is a good fit in the face of the bolt, simply shorten it approximately .050" and use as is.
alf said:What methods do Gre-tan and Kampfield use?
Al.
You don't need to get insulting.