Leading: Forcing Cone and Beginning of Rifling...Cause??

[Southern Shooter]

What causes wide swaths of leading in the forcing cone and very beginning portion of the rifling but nowhere else in the bore?

40743
This is not my picture. I am displaying it as an example of what I am talking about.

Thanks.

[btroj]

You are not sealing the bore as the bullet enters the barrel.
could be bullet size, bullet hardness, lube hardness, pressure, and who knows what else.
First things I would ask are what bullet, load, revolver, and approx alloy composition.
A bullet smaller than throat diameter can easily give this kind of leading, especially if cast hard for the pressure. The throat diameter is important here too, not just bore diameter.

In the end you have things put of balance. Try a softer bullet, more pressure, a different lube.

[462]

Could be thread choke, where the barrel is threaded into the frame. Run a slug the from the muzzle to just before the threads, and another to the exit of the forcing cone. Any difference, between the two measurements, is thread choke.

You give too little information for any informative opinions, so at this point, they can be nothing more than idle speculation.

[geargnasher]

You are not sealing the bore as the bullet enters the barrel.
could be bullet size, bullet hardness, lube hardness, pressure, and who knows what else.
First things I would ask are what bullet, load, revolver, and approx alloy composition.
A bullet smaller than throat diameter can easily give this kind of leading, especially if cast hard for the pressure. The throat diameter is important here too, not just bore diameter.

In the end you have things put of balance. Try a softer bullet, more pressure, a different lube.

Bingo!

If you have a revolver, thread choke and undersized cylinder throats are the #1 culprit in my book, followed by a major embalance of alloy, powder, charge, lube, or something out-of-whack with your reloading technique.

Bottom line, if you have leading, you have either a loss of obturation (gas leak), a rough spot, or copper fouling.

Gear

[runfiverun]

that picture looks like skidding to me.
1. the bbl is bigger than the boolit, but down further it ain't.
2 the boolit is being shoved hard to start and is skidding. pressure is dropping off and the boolit has a hold.
3.you are shoving the boolit forward for a 1/4 inch then it hits the rifling and does it's best to start spinning.
any of them or a small combination will give you what you see in the picture....

[Three44s]

I agree with the above but don't change more than one thing at a time ...... you'll be chasing your own tail all over the place!!

Best regards

Three 44s

[geargnasher]

that picture looks like skidding to me.
1. the bbl is bigger than the boolit, but down further it ain't.
2 the boolit is being shoved hard to start and is skidding. pressure is dropping off and the boolit has a hold.
3.you are shoving the boolit forward for a 1/4 inch then it hits the rifling and does it's best to start spinning.
any of them or a small combination will give you what you see in the picture....

......skidding = gas leak = leading!

Gear

[Southern Shooter]

If skidding were the issue, would one of the cures be to reduce velocity?

[44man]

If skidding were the issue, would one of the cures be to reduce velocity?
No, won't do much if something is wrong. You must check the thread area and then make the boolit fit the gun. Make sure the throats are larger then the groove size.
If the gun is OK and the boolit fits, the only thing left is lead too soft for how you start it out and it can't take the rifling.
Leading is mechanical and even gas blow by is mostly mechanical and less thermal. Gas cuts the boolit like they cut steel with water jets. The lead does get hot, particles blown off might melt. The boolit itself will not melt. At times a skidding boolit can get lead peeled off like scraping it with a knife and that gets ironed onto the bore.
Step one is to check the gun first, get measurements.
Then post those figures for solutions.
If all is good, then you can change powders, velocity, alloy and lube.
It would have helped to have every detail of your gun, load, boolit, boolit diameter, caliber, etc. Most of us are guessing right now. The solution is here but you will also be guessing, picking the way to go.
Do a search on slugging your gun, it is easy. The gun is easy to fix too.

[Southern Shooter]

Again, the picture is not mine or one that I took. It is closest example I could find of what I saw in my barrel after a shooting session. It took about 3 minutes with some Hops 9 to clean it up...so, I guess that was not too bad??

Anyway, here are some details:

Bore: Measures at .452

Chambers Throats: Average is .456

360 grain PB RFN boolit cast at .457 and was sized to .454

260 grain PB RFN cast at .453-.454

Wheel weights

Lube was LLA and mineral spirits about 50/50

Loads fired were:
1) 260 grain, lite crimp, 10 grains Trail Boss, 5-shot string averaged 808 FPS.
2) 260 grain, moderate-heavy crimp, 10 grains Trail Boss, 5-shot string averaged 843 FPS
3) 260 grain, moderate-heavy crimp, 11 grains Unique, 4-shot string averaged 1004 FPS
4) 360 grain, heavy crimp, 22.5 grains W296, 8-shot string averaged 940 FPS

Does any of this help to create some theories?

BEFORE I change any thing with the loads, my plan is to take one particular load at a time and check after each string to see if there is any leading. Then I will make modifications to the load once the culprit is discovered.

Thanks

[youngda9]

And start your testing with a completly clean (lead and copper) barrel.

[btroj]

.456 throats are not going to work real well with a .453 bullet. You might get away with a much softer bullet, maybe 50/50 wheel weights to pure lead and kick them hard with a charge of fast burning powder. This might allow them to slug up enough to fill the throats and prevent the gas leakage.
Pu have exactly the situation I had in my SRH with .432 throats when I was shooting.429 bullets. Leading in the same spots. I went to a .432 bullet and no more leading.

Have you tried the bullet that drops at .457 unsized? Just wipe some lube in with our fingers if need be but try them unsized. I would be willing to bet they don't lead.

Size to fit the throats, not the barrel. Trust me, the bullet will fit the barrel just fine with the amount of pressure it will have behind it.

[Charlie Two Tracks]

I had a similar problem with my .357. The throats were .358 and the boolit was .358. I still got a bunch of leading. When one of the members told me to pull one of the loaded boolits and measure it, I found the problem. The boolit was being swagged down while loading. A Lyman "M" die fixed that. For my revolver, I need to have the boolit really close to the throat size.

[44man]

Again, the picture is not mine or one that I took. It is closest example I could find of what I saw in my barrel after a shooting session. It took about 3 minutes with some Hops 9 to clean it up...so, I guess that was not too bad??

Anyway, here are some details:

Bore: Measures at .452

Chambers Throats: Average is .456

360 grain PB RFN boolit cast at .457 and was sized to .454

260 grain PB RFN cast at .453-.454

Wheel weights

Lube was LLA and mineral spirits about 50/50

Loads fired were:
1) 260 grain, lite crimp, 10 grains Trail Boss, 5-shot string averaged 808 FPS.
2) 260 grain, moderate-heavy crimp, 10 grains Trail Boss, 5-shot string averaged 843 FPS
3) 260 grain, moderate-heavy crimp, 11 grains Unique, 4-shot string averaged 1004 FPS
4) 360 grain, heavy crimp, 22.5 grains W296, 8-shot string averaged 940 FPS

Does any of this help to create some theories?

BEFORE I change any thing with the loads, my plan is to take one particular load at a time and check after each string to see if there is any leading. Then I will make modifications to the load once the culprit is discovered.

Thanks
I see several things I would work with. Dump the Alox first.
11 gr of Unique with a 260 gr is too hot even if below max. It thumps the boolit too much.
A 360 with 22.5 gr of 296 is also too much. I don't understand your velocity readings, that should do near 1300 fps or more.
Sizing a .457" to .454" might take away too much of the grease grooves.
Crimp? Find case tension instead with a proper expander. Do not over crimp. Look at fired brass and see if you have any indication of crimp left. If you do, you are sizing the boolit again trying to get out of the brass. Too much crimp can also break case tension.
Try water dropping your WW boolits, size and let them age a week or so. That will allow case tension without sizing while seating.
Throats are kind of large but it should still shoot with .453" to .454". The gun would do better with .453" throats. You do not want a boolit to expand to .456" in the throats, that turns the barrel into a size die.
The Trail Boss loads should be OK (I never tried it) but I think the other loads are just too heavy and you are not getting good Chrono readings.
I use 21.5 gr of 296 with a 335 gr LBT and get 1316 fps. With a 347 gr Lyman I get a little MORE but lost the figures when the book fell apart. A 360 gr should max out with 19.5 to 20 gr of 296. I would never be over 21 gr.
Primers? If you are using magnum primers, try WLP or the Fed 150.
You might be pushing the boolit out of the brass before powder ignition and then it gets slammed all at once.

[Southern Shooter]

Dump the Alox first.---Why dump the Alox?

11 gr of Unique with a 260 gr is too hot even if below max. It thumps the boolit too much.---What do you mean 'thumps' the bullet, too much?

A 360 with 22.5 gr of 296 is also too much. I don't understand your velocity readings, that should do near 1300 fps or more.---From a 2.58" barrel?

A 360 gr should max out with 19.5 to 20 gr of 296. I would never be over 21 gr---But, the Hodgdon load data says 21-24 grains for this weight bullet?

Primers? If you are using magnum primers, try WLP or the Fed /150---I am using CCI Large Pistol primers



Thanks

[geargnasher]

+1 on dump the Alox. I have zero luck with it or any of its iterations in revolvers, although Recluse lube made with liquid Alox has done very well in several of my automatics.

"Thumping" the boolit means that the powder burns too fast and builds pressure too fast for your alloy. You want a gentle launch, and a delay in peak pressure. If pressure peaks before the boolit is clear of the case or just as it clears (as it probably is with Unique), the boolit is exposed to peak pressure while it is most vulnerable to gas cutting, distortion, etc. crossing the cylinder gap. It is also going full-speed and slamming into the rifling. The rifling has to yank the boolit into a spin and that causes little skidding of the engraves. If the skidding widens the engrave all the way to the base band, you get gas leaks, gas cutting of the boolit, and the debris from that deposits in your barrel creating "leading". Slower powders peak pressure after the boolit begins to engrave the rifling, so the boolit is going a bit slower and the spin-up is less traumatic.

For a 2-1/2" barrel, either go back to about 8 grains of Unique, or if you want +P loads, try about 10 grains of HS6, a bit harder alloy, better lube that fills the grooves, and work the powder charge up from there. 2400 or Blue Dot wouldn't be a bad choice, either.

Gear

[geargnasher]

Here's a pic of two different boolits with "skid" issues. Note the engrave is wider at the front and narrower at the back. The one on the left didn't lead, but the one on the right did, notice the gas-cut groove on the trailing edge of the rifling engrave that's deeper than the engrave itself. The one on the left was fired with HS6, the one on the right is a different style boolit but was "thumped" with Titegroup at about the same pressure peak pressure, but way different pressure curve. You're looking at well-aged wheel-weight alloy shot in SAA-style .45s.


http://castboolits.gunloads.com/attachment.php?attachmentid=16190&d=1254713425

Gear

[Iron Mike Golf]

...
Bore: Measures at .452 I think you mean groove diameter.

Chambers Throats: Average is .456

360 grain PB RFN boolit cast at .457 and was sized to .454

260 grain PB RFN cast at .453-.454
...
As soon as your boolits break seal on the case, you are getting blow-by propellant gases. That's taking lead off the base of the boolit. The vaporized lead condenses pretty quickly, just ahead of the boolit. Once the forward drive band engraves, you seem to be getting a good seal.

If you had the skidding problem, I'd expect to see leading down the whole bore.

I'd really be interested in seeing the 360 gr boolit shot as cast.

+1 on thumping too hard. If you smack the boolit hard enough to skid, or even bump up, then the whole boolit can deform. Think smacking a boolit sitting on concrete with a hammer. It smooshes everywhere. That includes the nose that's unsupported by the bore. The nose can lose symmetry and that can affect accuracy.

[Frozone]

.....A bullet smaller than throat diameter can easily give this kind of leading, especially if cast hard for the pressure. The throat diameter is important here too, not just bore diameter.......

This is the first place I'd look for the problem. Oversized throats / undersized (and/or a very hard) bullet.

If the problem was in the barrel you wouldn't have leading on the forcing cone.

[runfiverun]

look at the boolit on the right in gear's picture. look closely at the bottom half of it.
look at the pitting and the lube groove.
that's why changing a load up or down or switching powders works if you are close.
if you are way off on size nothin will help.

to the o.p.
if it come out with hoppe's and a couple of swipes it could be lube there and not lead, i'd however doubt it with alox.

[Southern Shooter]

runfiverun, I had not thought about this, but, about 2 weeks ago I shot about 20 rounds that I had lubed with Lyman's Super-Moly...and, I did not do much to clean the bore up. Maybe a few passes of the brass bore brush. Could that be what I was seeing in stead of lead?

This time, all I did to clean what was there was dip the end of my .45 caliber bore brush in Hoppe's 9 and work the bore. I repeated this about 3 or 4 times. Did that for a few minutes and then swabbed it dry. The bore looked brand new, then.

I think what I will do is leave every thing as is. Put each of the loads through in separate sessions and see what the results are after each load is completed. I should have done that this time.

THEN, if there is leading start making single changes whichever load was the culprit.

[runfiverun]

could be.
i have had carnuba red leave smears in my bbl before.
i was able to change the spot where the smears were just by changing powder speed.
keeping pressure behind the boolit longer [more powder slower burn rate] moved it down the bbl.

i have also had leading in the bbl of my 41 [from lazercast storeboughts] that i could see cleaning up from my soft [ww's and pure mixed- air cooled] boolits, even though they should have had gas checks installed and didn't, they still shot well, and was able to eliminate the leading.

[Southern Shooter]

The only other thing that comes to mind right off hand is the 11 grains of Unique with the 260 gr PB. It got the 1,000 FPS that I wanted and with a good grouping. But, maybe it was too much for the bullet and fit combo (the "thumping" that was mentioned, earlier?). However, I only fired 4 rounds...would that be enough to cause noticeable leading?

[44man]

Gear, great pictures. My camera is not that good.
I never had luck with LLA, get leading and accuracy drops off big time.
Some make it work, I never could. I swear it not only runs out but it burns in the bore.
Mixing it with ingredients to raise the flash point is better but in all my shooting years I never figured out why it was chosen for a boolit lube in the first place.
It was made to rust proof cars and I paid a lot of money through the years to have cars in Ohio's rust belt done but they rust out just as fast, some even faster then bare metal.
Then I bought a Chevy truck that had Rusty Jones on it and I sold it recently, it was a 1982, and it had zero under body rust.
Anyway I think those that use JPW do better.
Even PBCR guns have lube preferences and the worst and most expensive I ever tried was SPG. It left the last 10" of the barrel full of fouling so hard a patch could not be pushed through. I had a bunch left, tried to sell it at shoots and then tried to give it away with no luck. I left it on a table at every shoot with a "free" sign with no takers.
Then I bought some real expensive stuff with molly in it, can't remember the name but it was pure junk.
I started long ago to make my own lubes with success.

[44man]

The only other thing that comes to mind right off hand is the 11 grains of Unique with the 260 gr PB. It got the 1,000 FPS that I wanted and with a good grouping. But, maybe it was too much for the bullet and fit combo (the "thumping" that was mentioned, earlier?). However, I only fired 4 rounds...would that be enough to cause noticeable leading?
You should never get leading more then one patch will remove and it should be just a few pieces. Leading that does form should be shot out with every shot and never build up.
All removal of any fouling with every shot is the secret to accuracy and can let you shoot for years without cleaning. Anything found in the bore after one shot should be exactly the same after 1000 shots.

[Southern Shooter]

Well, folks. I have tried and tried to get the gun to lead up, again. But, it won't happen. I fired an even larger number of rounds this time and no leading. I don't know what to say.

????????????????????????????

[runfiverun]

i'm gonna go with the lube build up you removed.
it could also be explained by.....
not letting your boolits fully harden the first time and the little wait allowed them to harden up.

[noylj]

http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm
From Ingot to Target: A Cast Bullet Guide for Handgunners©

Index of Additional Glen E. Fryxell Shooting Articles

Most leading questions should be directed here.

"Location of the leading

Location, location, location! Perhaps the single most telling piece of evidence is the location of the leading in the gun....Throats...This is rare, but it does occasionally happen when the throats are rough or undersized...Another potential cause of leading in the throats is severely oversized throats or undersized bullets, but these extreme dimensional mismatches are rarely encountered today.

Cylinder gap/barrel face. Leading can also be found on the face of the cylinder or the rear face of the barrel...an oversized cylinder gap...oversized throats also can contribute to this form of leading as well.

Forcing cone. Leading found in the forcing cone proper can be the result of the cast bullet being significantly over-sized relative to groove diameter and being swaged down as it enters the forcing cone. It can also be due to the forcing cone being poorly or roughly cut, or cut off-center (it does happen...). Or it can be due to poor cylinder timing leaving the chamber(s) in poor alignment with the barrel at ignition. This last case will generally have an asymmetric build up on one side or the other, and the revolver will commonly "spit lead".
Immediately in front of the forcing cone. If the leading is observed immediately in front of the forcing cone, then it's almost always due to a constriction in the barrel caused by an overly tight barrel/frame thread..."

[geargnasher]

You should never get leading more then one patch will remove and it should be just a few pieces. Leading that does form should be shot out with every shot and never build up.
All removal of any fouling with every shot is the secret to accuracy and can let you shoot for years without cleaning. Anything found in the bore after one shot should be exactly the same after 1000 shots.

There's a nugget of wisdom! This is EXACTLY why I don't shoot anything containing any kind of Alox except for occasional small batches of 45/45/10 and one lot of 50/50 BAC/Carnauba Red that works really well in my .40 S&W. Alox contains way too much calcium soap and too much gummy gunk scraped off of the bottom of the distillation tower. In rifles, I've found the accuracy begins to degrade after as little as ten shots, and continue to degrade unless a quick cleaning with solvent and patch is done. I don't experience this with Felix lube, LBT Soft, or Speed Green.

Gear

[williamwaco]

The leading in that picture was caused by commercial hard cast bullets undersized and lubed with a commercial hard lube.

The load was 4.2 grains A#2 in a .38 Special case. Very slight roll crimp.
The barrel is a TCA Contender. Slugs .3565 at the leade and .3562 at the muzzle.
The bullets were "sold as" .357. They actually measured .3566-.3568.

That degree of leading was accomplished after only 20 rounds of that load.

Re-lubing the same bullets by tumbling in Lee Liquid Alox eliminated that particular load/bullets leading problem completely.

[Southern Shooter]

Thank you for the details. That helps to better understand what was happening.

[Jtarm]

Bingo!

If you have a revolver, thread choke and undersized cylinder throats are the #1 culprit in my book, followed by a major embalance of alloy, powder, charge, lube, or something out-of-whack with your reloading technique.

Bottom line, if you have leading, you have either a loss of obturation (gas leak), a rough spot, or copper fouling.

Gear

+1, especially revolver. Harder != better

[btroj]

In a revolver harder is not always better.
Better fit to the throat and barrel is better.
A poorly fit hard bullet will lead like no tomorrow. Been there, done that.
A soft bullet that is a bit undersized can be kicked by a faster burning powder hard enough to slug up and fill the bore. That isn't going to happen with a hard bullet in many cases.

Just saying, the rule of "harder is better" is a bunch of hooey.

[44man]

Slugging a boolit to fit with pressure just turns your cannon into a 20 yard spray machine! :kidding:

[williamwaco]

Slugging a boolit to fit with pressure just turns your cannon into a 20 yard spray machine! :kidding:


I own several of those!:Fire:


.