Severe Barrel Leading

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sigman2

sigman2

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Guys, I'm fairly new to this site and would appreciate any help you can offer.

I recently purchased a new Cimarron Model "P" Pre-War SAA 5.5" barrel revolver in .44 Special. Yesterday I fired it for the first time and noticed accuracy deteriorated rather quickly. I fired about 50 rounds of my reloads. When I was cleaning it I found the first inch or two to be heavily leaded with some lighter leading through the first half of the barrel's length. I used a bronze brush with Hoppe's No. 9, patches, J-B Bore paste, then finally a Lewis Lead Remover but still have one spot I can't get out.

My first question is why the heavy leading? I am a fairly experienced hand loader and have fired cast bullets in handguns and rifles for years.

I was firing the following two different loads which are well within this caliber's specs.

.44 Special

Load #1
200 Gr. Missouri Bullet Co. #5
Medium Roll Crimp
7.5 Grs. Unique
WW WLP Primer
O.A.L. 1.450"

Load #2
240 Gr. Misspuri Bullet Co. Smasher
Medium Roll Crimp
6.5 Grs. Unique
WW WLP Primer
O.A.L. 1.450"


I was also firing a Browning B-92 rifle in .44 Mag. and experienced leading in it too. I was able to remove all the lead with the Lewis Lead Remover. I noticed that the Browning has rather shallow groves. I fired a number of the above handloads plus the following.

.44 Magnum

240 Cast SWC - I can't remember the manufacturer.
These bullets were also tumbled in Lee Liquid Alox in addition to the factory lube.
Medium-Heavy Roll Crimp
15.5 Grs. Blue Dot
WW WLP Primer
O.A.L. 1.620"


Any help you can offer will be greatly appreciated.
Thanks


Edited to correct bullet manufacturer.
 
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I recently purchased a new Cimarron Model "P" Pre-War SAA 5.5" barrel revolver in .44 Special.
Click to expand...

The barrel of a new gun is often a bit rough but smooths out with shooting, esp using jacketed bullets. One can use an abrasive like JB bore paste to smooth out the bore more quickly.

I found the first inch or two to be heavily leaded with some lighter leading through the first half of the barrel's length.
Click to expand...

Leading at the forcing cone end of the barrel usually indicates too hard a bullet for the pressure of the cartridge like the .44 spl or too small a bullet to fill the bore. Switching to a swaged bullet like the 240gr LSWC by Speer or other softer cast bullet like Missouri's 12 Brinell "Cowboy" bullets may help in that situation.

If the bullet is undersized the problem could be the cylinder throats are too small in which case changing to a softer bullet will not help. To eliminate leading one would then need to have the throats reamed out so the bullet enters the barrel at .001" larger diameter than the barrel. Slug your barrel and cylinder throats to check if that is your problem.
 
^^ +1 ^^

Check the cylinder throats by trying to push the bullets through the cylinder just using a pencil eraser.
If they won't go, having the right size bullets to start (e.g., 0.430") is destroyed by an undersized cylinder.

The #5 (Missouri?) bullets are BHN 12, so they should be OK [after cylinder throat size is confirmed as .430+]
On the other hand, the "Smashers" at BN 18 may be a bit too hard for anything less than full loads.
(Agin, after confirming the cylinder throat's OK)
 
The first item to address when dealing with leading is bullet diameter. Any hardness, any lube on a too small bullet will lead the barrel. I would suggest you slug the cylinder throats and the barrel, and measure the slugs with a micrometer. The groove diameter of the barrel should be smaller than the diameter of the cylinder throats. Purchase or size the bullets to the same diameter as the cylinder throats. This will eliminate leading prolly 90% of the time. All my revolvers are fed lead bullets the same diameter as the throats; .44 Magnums, .431" and .432". My 38 Specials are .357" and .358", same for my .357 Mags., depending on the measurements of the gun. Most of my bullets are cast of either my "Mystery Metal Alloy" (about 10 BHN) or my wheel weight alloy (about 12-14 BHN), plain based and often loaded to Magnum levels...
 
Thanks for the info. I was figuring it was a bullet diameter problem.

I'll slug the chamber throats.
 
Thanks again for the suggestions.

Ok, here's what I found.

Using an inexpensive micrometer, I measured the Missouri #5 and Smasher bullets and they are both right at .4305 - .431". Neither bullet would push through the cylinder throats under heavy thumb pressure.

I lightly oiled one #5 bullet and drove it through the bore using a piece of 3/8" round nylon stock... it measured .429".

The bullet used for slugging the bore will now easily drop through all six cylinder throats under its own weight. I would guestimate the throat diameters at .430".

This should prove that the cylinder throats, bore and bullets are the proper diameter for this individual revolver.

I guess my next steps will be to shoot some jacketed bullets through it to break in the bore. I'll follow this up with some polishing with JB Bore Paste.

Any other suggestions? Would a fine or extra fine lapping compound be better?


BTW, slugging the bore did remove the last sliver of lead.
 
Actually, if the .4305-0.4310 bullets wouldn't go through with eraser pressure, the cylinder throats are likely undersize for cast bullets. You want no reduction from that 0.431 starting point.

You want to be oversize by a coupla thousandths from groove diameter to get quick sealing and no gas blow-by even to start.
 
Ok, left field a bit, but... Since we're sorting out details that matter from those that dont...

You mentioned a "medium roll crimp".

Could you please measure the inside of a few fired rounds at the case mouth ?
 
Ok, left field a bit, but... Since we're sorting out details that matter from those that dont...

You mentioned a "medium roll crimp".

Could you please measure the inside of a few fired rounds at the case mouth ?
Click to expand...

I was going to reply to this post but when I saw lead bullets and leading I figured sooner or later Blarby would be along.

(So I didn't to save myself from looking like a fool)

I have to be the worlds worst lead bullet user, but Blarby has been around so answer his questions so I can learn also.
 
Chapter 7 of Glen Fryxell's ebook is an excellent resource for the definition of leading, location of leading, cause of leading and prevention/removal of leading and is especially geared towards revolvers - http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm

After reading some of the chapters and his other articles, I no longer experience leading in my pistols using various brand/hardness lead bullets using low to high range load data - http://www.lasc.us/articlesfryxell.htm
 
I will measure some cases tomorrow.
What would the crimp have to do with leading?


After reading Glenn Fryxell's article I believe the following are correct on my revolver.
Cylinder throat diameter
Cylinder gap
Bore diameter
Bullet diameter
Bullet hardness

My interpretation of the article causes me to believe the problem may be one of two possibilities; perhaps a combination of both.
1. Rough bore - Needs breaking in or possibly lapping. I'll shoot some jacketed bullets and see if that helps any.
2. Hard commercial lube at low to moderate velocity. I could try tumbling some bullets in Lee Liquid Alox and see if it helps.


The leading in the Browning B-92 seems to be a different story. I may need to go to gas checked bullets or perhaps I'll just stick to jacketed bullets with the rifle.
 
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Ok, I think I see what you are getting at.

Are you saying that the crimped case may have cut or swaged the bullet down to a smaller diameter?
 
Perhaps !

Just one of the easier things to rule out, so might as well do it.

If you could load one of your rounds, disassemble it, and then measure the case and bullet as well, you could close a lot of "problem" doors with little effort.

The fact that you are having the problem in multiple platforms leads me to believe it may be a load problem, as your pistol seems to be within spec according to your measures.

When I first started experimenting with cast bullet hardness, I caused myself no end of grief with a far too aggressive crimp. Invalidated a bunch of (otherwise) good data !

Lets see where the measurements take us, and lemme see if I can get some folks far better than I at this involved in the discussion, too.

On a load by load basis, froma hardness standpoint :

.44 Special

Load #1
200 Gr. Missouri Bullet Co. #5
Medium Roll Crimp
7.5 Grs. Unique
WW WLP Primer
O.A.L. 1.450"
Click to expand...

7.5 grs of unique in this application would be about 12k CUP in pressure. Using the formula.... 12000/1279.8 = optimal BHN of 9.6 Your chosen bullet shows "too hard" based on the old standby table for optimum bullet hardness to reduce leading.

Load #2
240 Gr. Misspuri Bullet Co. Smasher
Medium Roll Crimp
6.5 Grs. Unique
WW WLP Primer
O.A.L. 1.450"
Click to expand...

6.5 grs of unique in this application would be about 12400 CUP in pressure. Using the formula.... 12000/1279.8 = Optimal BHN of 9.69 Your chosen bullet shows "too hard" based on the old standby table for optimum bullet hardness to reduce leading.

Leading at the forcing cone end of the barrel usually indicates too hard a bullet for the pressure of the cartridge like the .44 spl or too small a bullet to fill the bore. Switching to a swaged bullet like the 240gr LSWC by Speer or other softer cast bullet like Missouri's 12 Brinell "Cowboy" bullets may help in that situation.
Click to expand...
In this case, Steve looks like he's barking up the right tree. To make sure;

We need to eliminate the mechanical portions of the issue, then if nothing else persists, you can fall back on BHN. This is all we're doing !
 
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15.5 grains of Blue Dot is above max for a 240 grain jacketed bullet. Leading is caused by trying to drive a cast bullet too fast or excessively soft bullets. Too fast is likely your issue. And it's too long. Max OAL is 1.575" for a JHP.
The 240 .44 Special load is over max of 6.3 and short(1.475" is minimum) too. Not over by much though. Likely just a variation in data.
 
you might want to check your forcing cone and make sure it is cut right.

you can also slug your barrel and see if there is a restriction at the barrel threads.

these problems will cause leading no matter what the load.

murf
 
I'm still betting on the bullet being "cylinder-sized" to a
smaller-than-required 0.431 before it hits the forcing cone.

My 2¢ ;)
 
Sunray,

I checked with my Lyman 49th edition manual.
It has the following as a Max. Load for the .44 Magnum
240 Gr. Cast SWC
15.5 Grs. Blue Dot
R-P Cases
CCI #300 Primers
O.A.L. 1.645"
1159 fps


The only difference in my load is:
WW WLP Primer
O.A.L. 1.620"

However, I did run a few rounds through my S&W 629 8 3/8" over a PACT Model 1 XP Chronograph and got an average velocity of 1369 fps. That's 210 fps over Lyman's readings which was in a Universal Receiver 4" test barrel.
 
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One can use an abrasive like JB bore paste to smooth out the bore more quickly.
Click to expand...

Just an aside, but JB makes special note that it is non-imbedding, ameliorating the very mildly abrasive aspect. It does help with copper fouling reduction by removing existing powder and copper fouling, but it doesn't work on the barrel like some of the lapping compounds, which are up-front abrasives ( http://www.brownells.com/gunsmith-t...ing-compounds/lapping-compounds-prod1137.aspx ). The other more likely suspects have been pretty well covered here.
 
blarby,

I measured ten cases out of each of the two 50 round .44 Special loads.

The case mouths for each load ran from .430" to .432" however, each case was slightly out-of-round by .002" to .004". Some of this may have been from handling but I really don't think so.

I have some new, unfired R-P nickel plated brass that I can do another test with if necessary.


I have some Brownell's lapping compound. I'm not sure if it's 600 or 800 grit because the label fell off and is lost. Should I try lapping the bore some to smooth things out?
 
Fire a coupla-three dozen full power jacketed rounds.
That will smooth things out/remove minor constrictions
faster than you will believe. ;)
 
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