I need some data!

[jameslovesjammie]

HELP!!! I loaned out my RCBS Cast Boolit Manual and my Lee Load book and need some data.

I have a 140 grain .358 diameter RNFPBB that is 91% Pb, 7% Sb, and 2% Sn. I need a load for .38 Special for use in a 6" GP100 for use in ICORE. To make power factor, I am going to need about 875 fps (856, but it's always better to have a little extra velocity, just incase.) The powders I have at my disposal that are handgun speed are 2400, SR 7625, SR 4756, Longshot, Bullseye, Unique, H110, Enforcer, and Reloader 7. I would like to use as light a charge as possible, to stretch the powder out a bit. This is for my uncle, who will be shooting a high volume of rounds quite frequently.

If there is a better powder than one I listed above, please let me know. I don't have a problem switching powders or trying something new.

Thanks ahead of time!

James

[felix]

Sounds like you do not have the gun in your possession. Needed is how much slop there is in the cylinder exit holes for the store bought boolits you have. If there is a press fit for the average boolit to go through the largest hole, then a provided load would be much cheaper to shoot. If there is any slop, then the powder speed will have to go way down. Your standard load would be 5.0-5.3 grains Unique for a press fitting boolit. James, the strike you have against you is the bevel base and hard boolit composition. ... felix

[JMax]

I shoot ICORE a lot and use Clays. I suggest 3.5 gr and chrono the loads. I use 3.3 gr with a 158 gr RN in long Colt cases and 3.6 gr in spl cases and a 125 gr TC for the Steel Challenge but that load does not make power factor. The 158 gr load PF's at 125k.

[jameslovesjammie]

Felix,

No, I do not have the gun in my posession, however, it is only about 5 miles away from me. So, what you're saying is that I need to measure the exit holes on the cylinder with a dial caliper and find the difference between all six cylinders? I agree about the bullet composition and style. I think he would have gotten better accuracy with a softer bullet and a flat base, but he bought them from a club member who makes them at home as a second business and wanted to support someone local.

JMax,
Thanks for the info. My uncle used to shoot Clays quite a bit when he shot skeet. He may still have some powder left.

[felix]

You want to force lead through the biggest hole and measure that. Fishing sinker, et al. That is the MINIMUM diameter to use with a boolit having a strong blow-by potential. Difference between cylinders won't be enough to worry about; just get the largest and go from there. ... felix

[jameslovesjammie]

So instead of slugging the barrel, I'll be slugging the cylinder, basically.

[slughammer]

Slug the barrel first. Clean the barrel 100% from all fouling and then lube it. Before you enter the bore all the way put an index mark on the slug at the 12:00 position. Then drive the slug through. You may feel a tight spot where the barrel is in the frame. If you didn't "feel" everything you wanted to on the first go through, feel free to re-index the slug and push it through again. I find that this second trip through gives me a better feel for what is happening in the barrel.

Ideally you feel a nice smooth flow through the barrel. Then you take the same slug and it slides through the 6 chamber mouths on the cylinder. This means the chamber mouths are larger than the groove diameter and this is what you want. Then measure the chamber mouths and pick your boolit size as Felix described.

[cbrick]

Slug the barrel first. Clean the barrel 100% from all fouling and then lube it. Before you enter the bore all the way put an index mark on the slug at the 12:00 position. Then drive the slug through. You may feel a tight spot where the barrel is in the frame. If you didn't "feel" everything you wanted to on the first go through, feel free to re-index the slug and push it through again. I find that this second trip through gives me a better feel for what is happening in the barrel.

Ideally you feel a nice smooth flow through the barrel. Then you take the same slug and it slides through the 6 chamber mouths on the cylinder. This means the chamber mouths are larger than the groove diameter and this is what you want. Then measure the chamber mouths and pick your boolit size as Felix described.

hhmmm . . . If done this way and the bore (groove diameter) is much smaller than throat diameter (and this does occur) you would never know how loose the bullets are in the throats. A mild snug fit in the throats is where it should shoot most accurately as long as the bore isn't larger than the throats.

Felix had it right, if you don't have available bullets soft enough (I cast bullets for slugging from stick-on WW) use fishing sinkers a bit larger than the throats. Use a new soft slug for each cylinder throat and slug them all. Size the bullets to a mild snug fit in the throats. If each throat holds a bullet and if they can be tapped out with the erasure end of a pencil (not a hammer and punch) your in business.

Next slug the bore with a new slug. With a good revolver the groove diameter will be at or just a tad under (never over) throat diameter.

Rick

[jameslovesjammie]

This is so cool! I've always heard of slugging the bore, but never the cylinders. It makes perfect sense! I've been shooting lead for about six years now (still in the process of gathering everything to start casting on my own) and it is such a neat hobby! I learn something every day.

Thanks for your help guys! I really do appreciate it!

[slughammer]

hhmmm . . . If done this way and the bore (groove diameter) is much smaller than throat diameter (and this does occur) you would never know how loose the bullets are in the throats.


I think that was the whole intent of my post. If you re-read you'll see the exercise is to check that we have that relationship where the groove dia is smaller than the cylinder throats. Then in the last line I stated to check the cylinder mouths and pick your boolit size as Felix had already discribed (his explanation was perfect, no need for me to find other words to say the same thing).

For guns like the 5 groove S&W you are going to have a heck of a time measuring the dia. of a barrel slug without a v-block. That is where this method really shines. (Use your chamber mouths as a ring gage.)

Truth be told I think you can establish the correct dia relationship for a revolver without having a caliper or micrometer. Barrel first, look for constrictions, then use that to check the groove relationship to the chamber mouths. Then size for that chamber mouth push through pencil eraser fit that you desire.

[cbrick]

slughammer,

Seems you are right. For some reason I didn't see the last sentence in your post, seems I started typing before finishing the reading :groner:.

My apologies to you.

Rick