Leading and Boolit Sizing

[HoosierShooter]

Have a S&W Model 19 with a Python barrel that leads heavy at the forcing cone and first couple inches of the barrel. Cylinder bore slugs at 0.3575. Barrel bore at 0.354 at the muzzle with no tight spots the rest of the way. Rifling at 0.347

Have been shooting LSWC sized to 0.358 from Missouri Bullet, so about 18BHN.

From what I have read, my cylinder bore would indicate a 0.358 boolit diameter. But is that too large for the barrel? Would fire-lapping be a good idea to open up the barrel?

I am trying some other LSWC at 12 BHN, but in the mean time, thinking about next steps. Thanks in advance for your comments.

[cbrick]

Welcome to CastBoolits HoosierShooter,

Permanently altering the firearm is the last thing you should consider at this time. It's obvious your new to cast bullets and that is where your solution will most likely be found.

If what you mean by "Cylinder bore slugs at 0.3575" is the throats measure .3575" and your store bought bullets measure .358" and they chamber that should be good. Revolver bullets should be sized to the throats, not the bore. The only reason to even slug a revolver bore is to know that it is at or a tick under the throat diameter.

You didn't mention your load and that could well be where the problem is with 18 BHN bullets. Also, if your loaded rounds lie at an angle in the chamber and then the front driving band strikes the edge of the throat when fired that will shave off lead, the next round blows this lead ahead of it's bullet and deposits it on the forcing cone and then on into the barrel with continued shooting. This has caused many revolver shooters to believe they have a barrel thread constriction when they don't. A proper throat fit will either eliminate or greatly reduce this.

Don't alter the gun, it's probably not the problem.

Rick

[noylj]

I find that the bullets need to be a snug fit in the cylinder's throats and swaging the bullet down in the throat is not an accuracy enhancing action.
Back when I was shooting revolvers (and I was shooting a very special Smolt revolver of limited production), I only sized bullets for the revolver(s) to match the throats.
Pretty much gave up PPC, revolvers, and sizing bullets at the same time.

[Nora]

Something else that may or may not help..... Make sure the barrel is completely cleaned. If you have run a lot of jacketed bullets thew it, copper fouling may be in play. I've got a Taurus old model 66 that likes to play that game. I like Butches Bore Cleaner to take care of anything left behind. For lead clean up Kroil and 0000 steel wool on a worn out bore brush keeps things looking real shiny. When the barrel has been cleaned this way I have no leading at all. After shooting a box or two of the factory stuff, even if it looks good, but not cleaned with Butches the first 2" of the (6") barrel are a mess again when I go back to cast.

Nora

[44man]

Bet it is the powder! Try something slower.
Personally I would drop to a .357" boolit. No sense in using the gun as a double swage die.
The throats are removing any surface hardness.

[cbrick]

Nora, I took the statement of the OP as a clue as to the leading he is experiencing. On the forcing cone and first couple of inches of barrel is a different animal than "bore leading". A bore clean of any copper fouling is of course a good thing but per se "bore leading" isn't what he described.

The only way I have ever been able to get leading like that is when the chambered round front driving band doesn't reach the throat when fully chambered. Then when fired the front edge of the driving band strikes the edge of the throat and shaves lead, further shooting blows this lead out onto the forcing cone. Continued shooting moves the lead into the first part of the barrel and then continued shooting will continue to move lead on down the barrel. Where leading begins is a big clue to what is causing it. The OP should also see if the throats themselves are leading.

The OP didn't give a lot of info but he did say this . . .

Have a S&W Model 19 with a Python barrel that leads heavy at the forcing cone and first couple inches of the barrel.

Rick

[geargnasher]

My thinking is in line with the comments about trying a slower powder. If you have leading, you have a gas leak or a rough (or copper-fouled) spot somewhere.

Using a revolver as a "double swage die" like 44Man mentioned can, in some instances, shave or rub off lead debris that will travel and deposit in the barrel. In other instances using a boolit that has a front band just a frog's hair larger than the cylinder throats and having it swage through them when fired can increase the gas sealing as the boolit is breaking the crimp and reduce some leading issues there. Some revolvers like just under throat, some like a reduced-nose design with oversized front band that nestles in the CYLINDER forcing cone when chambered.

If your forcing cone is rough, it can abrade lead that will get ironed on the barrel and work it's way down the more you shoot. "Thread choke", or a constriction where the barrel screws into the frame and the threads are slightly crushed under the torque load is a huge problem with cast boolits in many revolvers. You can check for that using soft lead slugs, one pounded all the way through the barrel from the muzzle, the other pounded in from the muzzle but stopped within an inch of the frame and pounded back out with short pieces of brass rod inserted through the cylinder opening in the frame and stacked one after another as the slug is tapped back out the muzzle.

Sometimes, if you seat and crimp in one operation, or if you don't bellmouth the cases enough, you can shave a little lead when seating the boolit. This can both make the boolit undersized, AND create lead debris that gets deposited in the barrel when the load is fired.

Lots of stuff to check, but I'd measure for thread choke and look at getting a slower powder before anything else.

Gear

[HoosierShooter]

Thanks to all for input. I use 5 g Unique in 38 and 12 g 2400 in 357 mag. Lead pattern same for both. Yes the front of the cylinder throat gets lead also. From your comments, I will try to the longest bullet, 358429 in 357 mag case to seat closer to the lead edge of the cylinder throat. Mod 19 has long cylinder so even 358429 has plenty of room.

[runfiverun]

try less crimp on the boolits.

[Nora]

Nora, I took the statement of the OP as a clue as to the leading he is experiencing. On the forcing cone and first couple of inches of barrel is a different animal than "bore leading". A bore clean of any copper fouling is of course a good thing but per se "bore leading" isn't what he described.


Rick

Never once did I say "bore leading" I did say "barrel " 3 times though. To me the barrel starts where the cylinder leaves off. This include both the forcing cone and the bore. I also started my post with "Something else that may or may not help.....". In my case it corrects the problem, your results may very.

Nora

[geargnasher]

Nora, Rick is right, and very clear in his explanation. There is a HUGE difference between general "barrel leading" and lead deposits only in the first part of the barrel. You might not make that distinction in your own purposes, but it's pretty important sometimes when a person is trying to isolate and eliminate the cause, or even try to determine the first step in the process of reducing or eliminating a significant leading problem.

An example would be thread choke or undersized cylinder throats that causes heavy lead deposits in the forcing cone and beginning of the barrel and sometimes a "wash" the rest of the way to the muzzle. The alloy, powder, powder charge weight, boolit, loading technique (especially case tension and crimp) might all be just right but the dimensional mismatch will screw it all up no matter what load you use. However, lead streaks the whole way down the barrel usually indicate an undersized boolit, poor lube, or a boolit that's too soft being fired with too much of too fast of a powder so it skids the rifling and has gas leaks on the trailing edge of the rifling no matter how well dimensioned the gun is. One is a problem with the gun that will require changes to the gun, the other is problems with the load that will require careful, scientific tweaks to eliminate.

Gear

[MtGun44]

How hard are the boolits? Too hard can be a problem. AC WWts would be a good
starting hardness. What lube? Start with LBT soft blue or NRA 50-50 as 'known good'.

Try 16+ gr of H110 or W296 under that 358429 at .358. My guess is that your Python has
a choked barrel, as is often reported. I would bet that the rear portion is larger than the
muzzle and possibly your boolit is not fitting tightly at the rear portion of the barrel, but
sealing up as the bore tapers down.



Bill

[Nora]

Ok let me see if I have this right????? The OP said "Have a S&W Model 19 with a Python barrel that leads heavy at the forcing cone and first couple inches of the barrel." I commiserated with him as I have the same problem of having heavy leading in the forcing cone and first inch or so of the rifling.

I didn't realize that my suggestion of make sure it is very well cleaned and have no deposits of any kind to start with was going to be so offensive. Perhaps then we souls make it a forum rule that a simple solution with a disclaimer that it may not even help be banned from the forum. As it will be discredited and cause to much controversy to just take at face value and be passed over if it has no merit to others on the forum.

I hole heartedly apologize to HoosierShooter that his first thread has run so far amuck by looking for help. Regardless of what the cause or solution I hope you are able to sort it out.

Nora

[geargnasher]

Hey Bill, not bad from a sitting position, always good to see the entire "weapon system" represented by the target. I can't shoot a pistol worth beans without a rest.

You know my stand on the subject and that I mostly agree with all you've said, BUT if you want to have similar groups a 100 yards (off a firm rest, obviously) you might need a 22-24 bhn boolit made from WDWW and a pinch of tin. I got to shoot a nice scoped S&W the other day with some water dropped WW and lots of H110, it was so boring at 25 yards we moved over to 100 and were getting 2-3 MOA with a 4 MOA red dot. Not bad I thought, never was able to do that with the softer boolits I normally shoot in my guns. You might remember my .44 magnum experiments where I was getting about the same groups with the harder boolits, and couln't hit squat with ACWW past 25 yards.

Gear

[cbrick]

There is only one person here offended Nora and he seems to be getting more so.

I only explained how I saw the the OP and I used the correct terminology to do so. You got offended, took it personal because you used the incorrect terminology. Gear tried to make it right and now you seem to be offended with him also.

Keep using your terminology of a revolver and you'll be a crowd of one that knows what your talking about.

Lighten up lifes too short and besides, we were both only trying to help out the OP.

Rick

[Mooseman]

Lets all stay on track here People...

[fredj338]

I also have a Smolt, no issues, but all guns are diff. I am betting too hard a bullet, maybe too much crimp. Have you pulled one to check after seating/crimping? If you are getting any undersizing & hard cast, it's gonna lead the cone & early in the bbl IME. LFCD? Always a likely culprit. It could be you just have a rough forcing cone & bbll, but Pythons were always among the smoothest of bbls if a bit tight. I know it sounds counter but try a softer bullet.

[HoosierShooter]

Thanks again for all your comments. My next steps are seating a 358429 18 BHN out so the front band is almost at the cylinder throat. Light crimp with 10 g 2400. So I have the boolit as close to the throat as possible and the slowest powder I have. I always start with clean but do appreciate the reminder.

I also have 12 BHN SWC at 158 g that I have loaded up. Will try both this week at the range and update results.

[sig2009]

I have had terrible results with Missouri Bullets. Will not buy then again.

[canyon-ghost]

I'm going to agree with 44 man, there are times when you can drop .001 or .002" and make it work really good. That seems to be true of plain based bullets.