Track Cases - Belt Mountain - Bowen
Classic Arms - Buffalo Bore -
Cosby Custom Guns
Revolver Muzzles and Forcing Cones
by Charles Graff
My bad experiences with professional gunsmiths could fill a small book. More times than not I have been disappointed with the quality of their work. I have used some of the biggest names in the industry with the same result. Some of the stories are almost comical. I have had some good experiences. For me, the good experiences seem to be the exception rather than the rule. Perhaps my standards are higher than the general public. That must be the case or many of the gunsmiths would have gone belly up.
At any rate I adopted two rules for working on guns. Rule One: Don't work on guns unless it is necessary. Rule Two: Do the work myself if at all possible. I care about my guns and will spend the time and care needed to get it right.
Working on guns does not require high mechanical ability. It does require knowledge, the right tools, and patience. The knowledge is available in books, articles and handbooks. The tools come from Brownells. Most gun work can be done quite well with hand tools. In my youth I knew German gunsmith who had spent years learning his trade in Austria. He could do wonderful work. The only power tools in his stop was a drill press, and a bench grinder. The patience? Well, that is up to you.
My first love, as far as guns go, are Smith & Wesson revolvers. They are fascinating little machines. Quite frequently when one comes into my house, the barrel needs attention at both the muzzle and breech.
Muzzles are frequently dinged with nicks and flat spots on the crown. Sometimes metal has been moved into the bore itself. A revolver with a damaged muzzle will not deliver good accuracy. When a bullet exits the barrel, the gases push against the muzzle. If the muzzle and crown are not smooth and concentric, the gases will not push evenly on the bullet base and accuracy will suffer.
The breech end of the barrel needs a smooth tapered forcing cone to center the bullet in the barrel. Older Smith & Wessons have very little in the way of forcing cones, sometimes amounting to little more than a chamfer at the breech. Frequently the forcing cones on Smith & Wessons, Colts, and Rugers display rough tool marks. These tool marks act like files against the bullet as it enters the barrel. This can play hob with accuracy.
Squaring the muzzle and recuting the crown and forcing cone can accomplish wonders in the accuracy department. All tools, supplies and gages to do both jobs are available from Brownells. These tools will pay for themselves in several jobs, and you know the job will be done right.
Step one is knowing whether your revolver needs work. Examine the muzzle through a magnifying glass under a strong light. If there are nicks, dings and flat spots, go for it. If not leave it alone.
Shine a light through the muzzle and look at the forcing cone. If it has a smooth adequate taper leave it alone. If it is shallow or rough, think about recuting it.
Before you make that decision get one of Brownells forcing cone plug gauges in the proper caliber. This is a simple drop in gauge with two steps. The bottom step is for the minimum forcing cone breech diameter and the top step is for the maximum diameter. Make certain the barrel is clean. Power fouling and/or leading with give false reading with the gauge.
Insert the gauge into the breech. If the gauge does not go in as far as the first (minimum) step, you have a shallow forcing cone. Recut it.
If the gauge goes as far as or beyond the second (maximum) step, then the forcing cone diameter is already maximum. Leave it alone and live with what you have. A forcing cone which is too large in diameter can destroy fine accuracy.
If the gauge goes in between the first and second step, then the decision to recut or not is determined by the presence or absence of tool marks. It there are tool marks present, recut. If not, leave it alone.
For the muzzle work you will need a Brownells 90 degree muzzle facing cutter, a 45 degree muzzle chamfering cutter and a muzzle pilot in the right caliber. The pilot works with both cutters.
For the forcing cone work, you will need Brownells .38-.45 basic chamfering kit with the 11 degree cutter. A chamfer tool pilot in the correct caliber. An 11 degree brass lap and a barrel chamfering plug gauge also in the correct caliber. I use an 11 degree forcing cone for all calibers, cast or jacket bullets. One word of warning. Late production Smith & Wesson revolver in .38/.357 calibers have a factory 9 1/2 degree forcing cone. If you try and recut one of these with an 11 degree cutter, you will have a two step forcing cone. Not good! Brownells suggest that you set the barrel back one thread before recuting. Thus far, I have not found any of these 9 1/2 degree Smiths that needed work so I have no experience with them.
You will also need some cutting oil and a small brush. A worn out toothbrush works great.
If you are nervous about cutting on your pistol barrel, buy a junk barrel at a gun show and practice.
For purposes of this article, I am going to work on a Smith & Wesson 1917 that lives at my house. This one comes from the second Brazilian contract and was assembled by Smith & Wesson in 1946 from WWI era parts. It is in first rate conation and appears to have had little use. The muzzle does have some dings and flat spots and the forcing cone is shallow and rough. Some attention to both ends of the barrel will allow this old timer to do it's best work. Let's have a go at it!
Make certain the revolver is unloaded. Remove the cylinder and catch the barrel in a padded vice. We want to work on the muzzle first. Tilt the muzzle to an angle where you can turn the cutters by hand, with you arm in line with the bore. Assemble the 90 degree facing cutter, handle and pilot. Brush the muzzle and cutter cutting surfaces with cutting oil.
Insert the pilot into the muzzle and bring the cutter into contact with the muzzle. With firm and even pressure give the cutter a 1/2 turn clockwise. Remove the cutter. Brush away any metal chips from the cutter, pilot and muzzle. Clean off any oil. Examine the muzzle under a strong light. If any dings or flat spots remain repeat the process. Go slow, do not get in a hurry. Make certain metal chips are removed and re-oil every time. Use only enough pressure to get a good smooth cut. When the dings and flat spots are gone, quit!
Assemble the 45 degree muzzle chamfering cutter, handle and pilot. Do the same thing with it as you did with the facing cutter and you will get smooth 45 degree muzzle chamfer. Remember, take your time, clean and oil your work and inspect after every cut.
Clean any cutting oil out of the barrel with patches and solvent. That is all there is to it. Unless you got in a hurry, didn't clean your work, used too much pressure or didn't oil the work. In that case, the cuts will show scratches and/or tool chatter marks. I am tempted to let you stew in your own juice, but if that happens, there is a way out. Most of the time.
To remove minor boo-boos from the flat part of the muzzle, wrap 220 grit abrasive cloth around a smooth, flat metal bar and polish away the marks. Keep the abrasive cloth flat against the muzzle. Repeat with 320 or 400 grit abrasive cloth and consider it a lesson in patience.
To remove minor boo-boos from the 45 degree muzzle chamfer, buy a 45 degree bass lap from Brownells, coat it with lapping compound, and chuck it in variable speed hand drill. Keep the lap in line with the bore and use a slow speed on the drill. A good hand drill works fine. Again, go slow, clean and inspect your work frequently. Clean any lapping compound or abrasive cloth residue from the bore with soft patches and solvent.
The forcing cone project is very similar. Once again, make certain the revolver is not loader, remove the cylinder and place in a padded vice. Assemble the handle and cutter rod. Slide the conical muzzle bushing on the rod and insert the rod through the muzzle to the breech. Slip the brass bushing onto the breech end of the rod, thread the 11 degree cutter on the rod, tighten with the provided bar. Brush cutting oil on the cutter.
Hold the conical muzzle bushing in place with one hand and pull back on the rod handle with the other, bringing the cutter into contact with the forcing cone. Gently, we don't want to gouge the barrel. Continue holding the muzzle bushing in place, pull the rod back with firm and even pressure and turn the handle 1/2 turn clockwise. Dissemble and remove the entire tool assembly. Clean the forcing cone with solvent and clean patches. Drop in the plug gauge. You want the gauge to stick out between the two steps. Never cut so much that the second step goes into the barrel. Repeat the cutting and gauging until the part of the gauge that sticks out of the barrel is between the two steps. Remember, clean your work and cutter, inspect your work, oil the cutter and take you time.
If you left small chatter marks or scratches in the forcing cone, lap with the 11 degree brass lap and lapping compound as per the muzzle.
When you are through, you will have a revolver barrel that will deliver it's best, saved the gunsmith charges, and acquired the tools to do it again. Best of all, the work will have been done right because you did it.
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