What would cause leading inside of forcing cone only?

[Bruce H.]

I have searched the forum for an answer and have not found it. I have a .357 Magnum caliber 4 5/8" Cimarron colt clone. I have always shot jacketed or plated bullets in it because I don't want to deal with leading. A couple of months ago I bought 500-158 grain lead bullets from Missouri bullet company. The bullets are 0.358" dia. lead round nose. The Brinell hardness is 12. I loaded them with 3.8 grains of Windchester 231. with an OAL of 1.460". I chronographed these rounds at 769 ft./sec. out of the Cimarron. I shot 6 rounds through the chronograph and then 18 rounds at a target. I got a really good tight group at 10 yards. The best that I have ever done with this revolver. When I got home and got ready to clean the gun I found heavy leading inside the forcing cone and up to about 1/4 of an inch in the grooves beyond the focing cone. The remainder of the barrel was completely lead-free. I use Hoppes #9 and a 40 S&W bronze brush to remove the leading. I had to push the brush through the barrel about 40 times to get all of the lead out. It was a real pain in the butt. This is exactly why I have always avoided lead bullets. What would cause me to only have leading inside the forcing cone and beyond it about 1/4" and not in the rest of the barrel? I slugged the barrel about a month ago and measured 0.3554" grooves with 0.3464" lands. I also slugged the cylinder throats and found them to be 0.3591"-0.3595". Should I give up on lead bullets and stick with only plated and jacketed?

 

[Mark whiz]

Lead pushed at magnum load speeds are almost always gonna leave some lead in the bore - that's what lead does..............it's a maleable metal that displaces and sheds itself to fit in a bore. That said, since the fouling is just in the throat basically, your cylinder might not be lining up perfectly with the bore opening and causing the deposits - or maybe the forcing cone could just use a little polishing to ease the bullets entrance into the barrel.
A quicker way to remove that lead is to get a Lewis Lead remover - which is basically a brass screen that is extended over a proper-sized rubber cone that you spin in the cone to scrub it clean - then the screen can be pulled thru the bore to get the lead out of the bore too. Also for cleaning the bore, take a few strands from a Chore Boy brass dish scrubber (standard Wally World or Dollar General supply) and wrap in an older brass bore brush and work that thru the bore.................it'll peel the lead right out of the bore grooves.

 

[Steve C]

Your 3.8gr load of W231 is a nice light load. Usually leading at the forcing cone end is due to the bullet not filling the bore. Even though this sounds a bit counter intuitive you may want to try increasing your charge of W231 to increase the pressure to a range where the base will obdurate enough to fill the barrel and prevent gas blow by. 4.5grs of W231 will duplicate factory standard velocity and 4.7grs will do the same for +P, this is from the older Winchester data and the resulting velocities have duplicated published balistics by Winchester for their factory ammo in my 4" revolvers. Since your pistol is a .357 mag there's no pressure issue with either of these.38 spl loads safety wise or wear on your pistol.

The other reason for the leading could be your cylinder throats are smaller than the bore and are reducing the bullet diameter too much. You can slug both. The Cylinder throats should be 1-2/1000" over bore diameter if I remember correctly. Remember to slug all the cylinders as the leading could be the result of only one under sized throat. If you find the throats smaller you can have a gunsmith cut them to a correct size or buy the tool from Brownells and do it yourself.

Sometimes the addition of more lube will eliminate leading You can try a light coating on the bullets in additon to the commercial lube with some Lee's Liquid Alox.

I'm sure other cast bullet shooters can add other solutions.

 

[Walkalong]

Steve C is right......

 

[fourdollarbill]

plus 2 on Steve C, load em alittle hotter or get a softer lead.

Also if it only took 40 pushes of the brush that sounds pretty mild.

 

[fractal7]

627 with MBC Wadcutters

I have had a similar problem with Missouri Bullet Wadcutters in a 627 Pro series, I need to check my logs but I'm pretty sure I used the standard 2.7 gr of bullseye. Since the MBC wadcutters aren't hollow base should I load them a little hotter, or maybe a few extra tenths of a grain since I'm not seating them flush (I'm seating to the crimp groove with a light roll crimp)?

 

[243winxb]

I got a really good tight group at 10 yards. The best that I have ever done with this revolver.

If you loose accuracy after many rounds then you have real leading. Shoot a couple hundred rounds, accuracy should remain the same. No cleaning needed in between weekly sessions. Clean good before long term storage. Edit >

I use Hoppes #9 and a 40 S&W bronze brush to remove the leading.

I use Hoppes also, let it soak in the barrel for a day or 2, does make a difference.

 

[Jumping Frog]

Lead pushed at magnum load speeds are almost always gonna leave some lead in the bore

He said they were 769 fps -- hardly magnum load speed.

To elaborate slightly on Steve C's comments, leading on the front part of the barrel usually means a bullet fit problem (either too small for bore or not obdurating) whereas leading in the muzzle end of the barrel usually means a lube problem (running out of lube). Note, this is a rough rule of thumb, not gospel for every case.

 

[GP100man]

If useing 38 cases the boolit could be tilting & hittin the cone canted a wee bit .

Is the build up in a particular spot or all around the cone???

If 1 spot I`d say a line up issue if all around it`s a gas cuttin issue when the boolit makes the "jump".

 

[Red Cent]

I have shot thousands of light loads using lead bullets though the same single action revolvers and have never incurred leading. I have never had to clean forcing cone or bore over the last six years. My pistols were set up as I described in another post. The cylinder throats must be correctly sized. As mentioned above, an easy fix for slight misalignment of bore/cylinder is the forcing cone. Anywhere between 8 degrees and 11 degrees.
The only other reasons would be oversized cylinder throats or incorrect size bullet.

 

[918v]

The OP said he slugged his gun and the cylinder throats mike .004" larger than his barrel groove diameter. His bullets are .358" and are medium hard. His load is very light. I believe the pressure is not high enough to bump the bullets up enough to fill the cylinder throat. This causes gas cutting and leading of the forcing cone area. I vote to increase the powder charge and pressure to allow the bullets to bump up inside the cylinder throats.

ETA- or use .359" bullets.

 

[GP100man]

Agree with 918v, besides it`s the easiest & cheapest to try first!

 

[Arkansas Paul]

The other reason for the leading could be your cylinder throats are smaller than the bore and are reducing the bullet diameter too much

This is what I was thinking, but it was just a guess on my part. Glad to see I may have been on track. Hope you get it figured out.

 

[Tallinar]

Sounds like Steve C hit it pretty well.

I had a terrible leading problem with a Super Blackhawk last year. After trying several solutions (smaller bullets, harder bullets, softer bullets, different powders, crimps, etc), I finally gave up and sold the damn thing. Was probably the most accurate handgun I've owned, but I can't stand excessive leading.

One thing I learned though; when it comes to cleaning out excessive leading, I found the easiest cleaning method to be simply running a cylinder full of jacketed rounds through the gun after you're done shooting lead for the day. The copper scrapes all the lead out very well. This saves you a lot of the endless brush stroking when you get home.