Do some CBs lead more than others?

I am wondering if someone can point me to a solution to a problem I'm having with my CBs. I am casting bullets from range scrap, adding a couple of ounces of tin to a 10lb pot so that I am casting bullets with an approximate BHN of 12. My CBs are cast from RCBS 38-148WC and RCBS 38-158CM molds. I shoot them out of a GP100, the chamber throats have been reamed (thanks DougGuy) and measure .358, and this is what I size the CBs to. The forcing cone has been given an 11deg bevel.

I load these bullets over 3.5, 4 or 5 grains of Red Dot in either 38 special or .357 brass. They are tumble lubed with 45-45-10. It is inevitably the case that the wadcutters lead very little, but the RNFP leads my barrel a lot. In addition, the area around the forcing cone gets painted with lead and I even get leading on the outside of the cylinder. (I have no pics at the moment but will have to remedy this soon). The velocity of the loads do not exceed 1000fps, so we are not talking hot loads here and the BHN of the bullet should be well within tolerances for such light loads without requiring a gas check. What would be the cause of this? I find it odd that similarly sized bullets would have such different results. Does the shape of the bullet make a difference? I've tried sizing the bullets up to .359 and down to .357, but get similar results.

Try a differant lube, I have been using 50/50 moly- beeswax.

What does the bore measure? When you had the throats reamed was it done based on the barrel dimension or were they just reamed for consistency? if the bore is the same size or larger than the throats that could be part of the problem. Ideally you don't want the throats to size the bullet but it is OK for the barrel to do so. In other words a slip fit in the throats and a push fit in the barrel. Shape of the bullet and number and width of driving bands can effect the amount of resistance it provides as it goes down the barrel.

dakotashooter2,

I've never measured the bore. I had the throats reamed for consistency. I've heard that the throat measurements are most important in comparison to bore measurements when shooting cast. Perhaps I have been given the wrong information.

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Originally Posted by dakotashooter2

What does the bore measure? When you had the throats reamed was it done based on the barrel dimension or were they just reamed for consistency? if the bore is the same size or larger than the throats that could be part of the problem. Ideally you don't want the throats to size the bullet but it is OK for the barrel to do so. In other words a slip fit in the throats and a push fit in the barrel. Shape of the bullet and number and width of driving bands can effect the amount of resistance it provides as it goes down the barrel.

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Not wrong, just incomplete. It is both. You need consistent throats but if the throats are smaller than your bore you will get leading and poor accuracy because your boolit is smaller than your bore.

Wayne nailed it. ^.
odds are on, when you see leading, boolit fit is usually off somewhere.
stubert brings a good point too. Lube failure also can be the culprit. Remember, only change one thing at a time so you understand what the solution was.

It has been suggested that I may not have given enough information about the loads I use in my GP100 -- that the 3.5, 4 and 5 grains of Red Dot represent quite a spread and might even seem arbitrary. It was perhaps also unclear in the original post as to what bullets I was using with these charges. So, just to clarify:

I have used Red Dot powder exclusively in my reloads because that is all that I have. Starting loads in 38 spcl according to the 49th edition of the Lyman manual for 158 gr bullets is around 2.8 as I recall. It may be .1 grain less for the 148 gr DEWC. I have shot loads from these starting charges with both bullets in 38 spcl cases up to and including the highest charge of 5 grains. The gun is accurate with all of these but the leading problem I mentioned in the original post is such that I can tell little difference between the lower charges and the higher ones.

The 3.5 grain load in the 148 grain DEWC is considered by Ed Harris a "full charge wadcutter" that yields velocities in the 850-870 fps range. Not having a Chrony, I can only take his word for it, but this seems fairly consistent with the data in the Lyman Manual.

The 4 grain load is a +P loading in 38 spcl yielding velocities somewhere between 900-950 fps. This load is derived from reading Glen Fryxell's stuff on the 38. The Lyman and Alliant sites say 3.8 grains of Red Dot is max for this load in +P. Having read that the DEWC can be pushed to over 1000fps without a problem, I shoot this and the RNFP in this load with good accuracy. Accuracy could always be better in any load I shoot, but the problem is mine rather than the gun or the load I am shooting.

The 5 grain load is a mild .357 Skeeter Skelton load that pushes the bullets at approx. 1000 fps. Sharpes' Complete Guide to Handloading shows that this load in a 146 grain DEWC yields a CUP of 17,000 and a velocity of 1085 out of an 8" barrel. I'm getting less than that in my 4", to be sure. I load these in either 38 or .357 cases. They are accurate loads as well.


The latter two loads cannot be found in the 49th Lyman. But since Red Dot's formulation has not changed, I think it is OK to use these older loadings. Shooting these out of my GP 100 is no problem. Neither the gun nor the spent rounds show any kind of stress or pressure warnings from these loads.

It was also suggested that I mic the bullets after sizing as the problem is most likely a combination of proper size and the need to use a softer lube. I will have to provide that data in the future.

Just spit balling here ymmv. Barrel constriction. My two RedHawks use to lead considerably with quality lube, with rather chunky diameter bullets, with powders up and down the burn and load scale. Good possibility I was using too soft lead at one time which may have skewed my results. Alloy aside, I used good American pin gauges and determined that I had significant barrel constrictions. Lapped the barrels, and both guns just can't seem to lead anymore. Worked well for me but it's a creepy feeling running abrasive down the tube.

You HAVE to slug the barrel. On both ends. That will tell you if you have a thread choke. Rugers are famous for this. The powder you are using is fine. It works. It's dirty but who cares.

One dumb question coming up: What am I looking for as far as a choke in the bore? Will I know from the "feel" when I slug the bore, will there be a noticeable difference in the measurement of the slug?

Also, I miced several bullets, both WC and RNFP. They measure .358, and move through the throats with a gentle push. .359 bullets do not and .357 bullets fall through. I think the first change I am going to make is to use a softer lube. But let's say the barrel slugs out at .357 -- would sizing the bullets at .357 work? I tend to think not given the fact that there would be an awful lot of blow by of gasses that would affect the bullet with some deformation and melting before it reaches the forcing cone. How wrong would I be about this assumption?

The thread choke will be right where the barrel threads into the frame of the gun. If going from the muzzle, it will be smaller when you push it out than the muzzle end.

I slugged the bore on my GP100 and it measures at .3555 as nearly as I can tell. That seems awfully narrow to me, but may not be a problem as the bore diameter is smaller than the throats. Some mentioned slugging both the front of the bore and the after part. It is not clear to me how one gets the slug out of the front of the bore. Do you use a screw and treat it like a BP bullet puller? It is also not clear to me how one gets the slug into the aft end. Suggestions would be welcome.

i have shot thousands of 38's in both colt and s&w. i have noticed that my lee 125rf and 158rf tend to lead the cone more than swc's or round nose. i am not sure why but the way i solved it was using carnuba red in the lube groove when sizing then a very light coat of 45-45-10. any that occurs now comes out with regular patch cleaning with Ed's Red. hope this helps, Tony

I put a long stick of hardwood through the frame and drop a brass rod down the bore to it. Leave enough room at the muzzle for a slug. Start the slug and upset it a little with another piece of brass rod. Then use the stick as handles and push the slug back out. A 3/4" thick length of oak works for me. You can set the muzzle on a board with a hole large enough for the slug to enter. You can even rap on on end of the stick with a mallet if the slug is tight while you hold the other end.
Then run another all the way through. Measure both to see what you have.
Make sure the bore is clean and oiled.
Now the fast powders, even though you say 17,000 CUP, will give you that pressure almost instantly. The soft boolit will slump and expand to the full dimensions of the cone and some will try to escape the gap. Then the pressure rise, being so fast will try and push your boolit straight into the turn of the twist, skidding and opening gas ports to cut lead.
Experiments with my .44 and all alloy hardness's has shown fast powders work better with very hard lead, my best accuracy with Unique and 231 came when I reached 28 to 30 BHN.
I don't like TL lubes at all but with your conditions, I don't see a better lube helping.
I also don't like your groove measurement of .3555, I suspect your slug has not reached the groove depth and is why I upset a slug. My best slugs are pure lead round balls just over groove diameter. Measure the wide parts of the slug, not between them because that is bore measurement.
A slug can be upset farther down the bore by using the stick and stacking a few short brass rods into the barrel, run another rod in the muzzle and give it a few raps to expand the slug. Pull the stick and pour out the short rods. They must be short enough to come out the frame window.

Cutting the cone 11* allows a smoother start to a boolit nose but they sell gauges so you don't open the entry too much. That will not hurt if lead is hard enough to not slump but softer lead will try to expand into a larger opening.
I don't like the idea of a Taylor throat because the boolit has to go too far to the rifling and is moving faster.
I have not found a problem with a long cylinder though and my most accurate gun is the BFR 45-70 with a long run to the cone. I do NOT believe the boolit has to be at the very end of a cylinder. Either way, long run or Taylor throat will work better with slow powders. Not much can be done with a 4" barrel where all of a slow powder can't burn but the start will still be easier.
The hardest thing to work with is having only one powder.

"In addition, the area around the forcing cone gets painted with lead and I even get leading on the outside of the cylinder."

I'm kind of new to this game but this sounds like something I've experienced. I also have noticed a light grayish build up around forcing cone, under the top strap and on the front of cylinder. I first noticed this when I first used 45-45-10 tumble lube. I don't think, in my case at least, that this is leading. It cleans off too easily with a light scrub with nylon brush and a touch of solvent. It seems to be a residue from the tumble lube. I get this on all three of my revolvers. On two, a Ruger and a Smith, both .357's, this is all the "leading" I get, not a problem. On the other hand, on a Ruger 44, I get the same plus a bit of "real" leading in the barrel. I think I've got some thread constriction and maybe some cylinder throat issues to work on, haven't slugged it yet.
I guess what I'm saying is, it's possible not all of what your seeing is really leading but lube residue. Has anyone else noticed this when using 45-45-10 tumble lube?