forcing cone questions

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woodperson

Single-Sixer
Joined
Sep 27, 2004
Messages
407
I received my 11 degree forcing cone reamer and gauge from Brownells today. I sat and read the directions for a while. I am still undecided on this project. I will probably have a lot of questions before this is over. One thing the directions stress and that I have seen from other reading is not to do the re ream if you do not have enough room to completely remove the original cone. Do not end up with a 2 angle cone. I cannot see why this would be bad or a problem? Could someone explain a slight decrease in the angle near the end of the cone would be a problem? You would have a little more room near the cylinder for mis alignment. You would not have any more constriction in the cone than you do with the shallower angle one. What is the downside that I am missing?

Update: I slipped the gauge into the forcing cone and it goes in all the way and is a perfect seeming fit. Looks like some one already did the rework on this gun. It is a OM that I got in a very used, somewhat abused, condition.
 

Hondo44

Hawkeye
Joined
Apr 3, 2009
Messages
7,716
The importance of not having a two angle forcing cone is not a deal killer or as important as it's touted to be. The difference in accuracy, if any, certainly not to the average shooter.

To test if the forcing cone is already cut to 11 degrees, paint it with a black felt tip pen. Place the cutter in the forcing cone and turn it one turn with slight pressure. If it cleans out all the black ink, it's already been cut.
 

woodperson

Single-Sixer
Joined
Sep 27, 2004
Messages
407
Thanks for the reply. I will try the magic marker and check the angle. The cone is not double beveled now. I was looking ahead in case I tried the job.
 

Hondo44

Hawkeye
Joined
Apr 3, 2009
Messages
7,716
woodperson said:
Thanks for the reply. I will try the magic marker and check the angle. The cone is not double beveled now. I was looking ahead in case I tried the job.

Yes, that's what I understood, just that you thought it might have already been cut properly to 11°
 

snakeeyes4445

Single-Sixer
Joined
Mar 2, 2004
Messages
107
The value in recutting might be to get better alignment of the cone with the bore axis if you use a bushing pilot that is both snug to the rod and snug inside your barrel.
Two Dogs here can help you with that maybe. His .32 pilots are very precise, as is his thinking and fabrication. I am sending him that kind of work this week.

To determine that an eleven degree slope (shorter and fatter) is better than a recut to center a five degree forcing cone (longer and thinner), I had Pacifiic Tool make me a five degree cutter small enough to do a .32. It is also big enough to do a .38, but I just found out that the cutter is too long by about a quarter inch of going in any of my .32 frames.
I will have to talk to them about a remedy, as this one can only be used if you take the barrel off. A shorter one would work fine, but might not have the diameter for a .38.

It would be nice to run an experiment like that to prove or disprove some of the well intended conjecture that we hear about forcing cones and slope....shooting as I go.

To answer your question I would conjecture that if the short run of five degree cone is off axis, it would have little measurable effect after your work and could conceivably be fire lapped into alignment. If the five degree cone is already "on axis", I can only believe that there would be exactly zero problems created. Going too deep though will cause you all kinds of problems.....use your gauge, light touch and only half of what you think you need.
You can use a brass lap after cutting.
 

DougGuy

Single-Sixer
Joined
Jul 21, 2014
Messages
171
The purpose of the forcing cone is not to "funnel" the bullet into the barrel, it is there so if the bullet hits it on one side more than the other, it will cause the cylinder to rotate to be in better alignment with the centerline of the bore so the bullet enters the barrel concentric. The longer more gradual forcing cones can lessen distortion of the bullet more than a shorter one, i.e. 5 or 7 degrees as compared to 11 degrees.

On the other hand if you fire a relatively short bullet into a 5 degree forcing cone, then the bullet is often clear of the cylinder before it fully engraves itself into the rifling so you have this section where the taper in the forcing cone is larger than the bullet, and the bullet is not supported and it can cant and become off center and enter the barrel crooked and it will stay crooked once it gets crammed into the rifling.

I do favor an 11 degree forcing cone matched with the RF style of bullets where the ogive of the bullet is much more parallel with the forcing cone than say a Keith type LSWC would be. This way any misalignment would distort the ogive of the bullet and not the driving bands so damage should be lessened and accuracy would not be affected. Even though plenty of revolvers perform very well with Keith type LSWC.

S&W Mountain Guns have an 8.5 degree forcing cone angle I think, it's nowhere near 11 degrees, and I had PT&G make me a 9 degree cutter which would approximate the angle of the Mountain Gun, this worked quite well in a Ruger 45 caliber Vaquero.

My only regret is not going to Clymer for the cutter, since the PT&G cutter was made so thin it shattered on the second barrel I cut with it. Toss $55 down the drain. I ordered another 9 degree cutter to replace it, complete with photos, with dimensions added in red on the photos, basically a blueprint for dummies, and they sent back a cutter that was 9 degrees on EACH SIDE, 18 degrees totally useless, after waiting months and months and months. Toss another $55 down the drain. They never returned my calls, I think they did this on purpose to drive off a customer who only needed a few tools per year and non-standard items at that. Piss poor way of doing business if you ask me.
 

jgt

Blackhawk
Joined
Jul 30, 2008
Messages
773
I have purchased reamers from Clymer. From my past dealings with them, they do not seem open to feed back no matter how diplomatic you try to be. When I asked, they said they are open to feed back, but that was not the idea I got when I gave it.
 

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