Range Day .... Ruger GP100

[MtJerry]

Still searching for the elusive "most accurate load possible with cast boolits"

Got a bit closer today with a load of 12 grains of IMR 4227 and two boolits. Lyman 358439 and Lyman 358156 - both hollow point.

First out of the gate is the 358156 that I had hollow-pointed by our very own Buckshot. (He does GOOD work!) This had all the makings of a fantastic group but a few of the 18 rounds decided to go outside of the neat little hole the others. Must'a been the shooter!

http://i44.photobucket.com/albums/f17/MtJerry/DSCF0766.jpg

Next is a single cavity mold that I have had for a very long time. When I first got it the hollow-point pin was not fitting very well, so it too went off to Buckshot to have the hole opened a smidge and new pins made for it. The cool thing about this mold is that with the pins I have I can make the boolit be most any standard 357 mag weight I want. I have cast 148g, 158gr and 170gr boolits all with the same mold.

I also like the fact that I can focus on one single boolit at a time with the single cavity. Every single boolit will be the same diameter as the others. I just have to keep a consistent casting rate and they will all be within .5 gr of the each other.

http://i44.photobucket.com/albums/f17/MtJerry/DSCF0765.jpg

Next on the agenda is to do some water-testing to see how the 50/50 alloy expands at these speeds. I'm guessing about 1150 to 1200 fps. It's only a guess though as I do not have a chronograph.

All in all ... a good day :bigsmyl2:

[dale2242]

Try 5gr Red Dot with that boolit.
My 6" SS GP100 really likes it...dale

[MtJerry]

Thanks for the suggestion ... however, I think I am very close to something pretty good here.

I think the next step is to use segregated brass. I was using a mixed bag with these loads. Possibly the unequal neck tension may be causing the flyers seen in the 358156 load.

The first group of the 358439 loads is a sub 1" group without the flyer to the left.

The upside .. more range time :-)

[Grandpas50AE]

Years ago, before I started casting, I had a 4" Colt Trooper MkIII in .357 mag. The 140 Speer JHP SWC, Sierra 150gr. JHC, and the 160Gr. Speer SWC all did really, REALLY well with SR4756 loadings. My brothers and I had no chronograph back then, but those 140's and 150's hummed pretty good, and all three were tack-drivers at 25 yds. out of that little 4" Colt. Also shot some cast boolits back then that were cast by a friend of mine (that was before I started casting), and I have no idea what the alloy was, but they were SWC running 145 gr. We shot those with SR4756 as well, and had some really tight groups as well. About 15 years ago, one of my hunting buddies that owned a Colt Python 6" asked if I had any molds for .357 for deer hunting, and I told him I did. It is the Lyman 358429 with Javelina 50/50 lube loaded over 13.5 grs. of H110, and that is an extremely accurate load in his Python and my old Ruger BH. Just a couple of ideas thrown your way that you may like when you want to try something different.

[catboat]

You may want to take some accurate measurements of your gp100's throats. The revolver may have one tight throat, that is causing some of the wide shots.

I have a 4" barrel GP100, and it had two very tight throats at about .355", and it would group 4 out of 6 shots in a group, and two shots would be wide.

You can take a (or a couple) sized cast bullet (not cartridge) and see how it fits in each throat. Push them through the throat from the rear with a dowel/pencil. Measure the cast bullet diameter before/after. This, and the amount of pressure needed to push it through should give you an idea if there is a throat tightness/variability issue.

You can have the throats reamed by cylindersmith.com for ~ $30, and uniformed to .357" or .358" .

Your pictures state bullet is "...sized as cast." Check diameter, and make sure they are uniform. Are you pan lubing? Not sure what level of reloading/sizing experience you have, so I apologize up front if this following comment is "duh", but if you don't have a lubrisizer, you may want to try uniforming the bullet diameter with a simple Lee push through bullet sizer (~ $20). "Ranch Dog" (board vendor) sells one in .359" for ~ 20. Fits in a standard single stage press.

Good luck. Looks like you may have a nice shooting revolver, and even more accurate (less variable) if the throat diameters are an issue.

[MtJerry]

My throats are all .359 and the "as cast" boolits drop at .360.

I am "dip lubing" in which I heat the lube in a double boiler and then dip each boolit, wipe the base and then after the lube dries, I use a home-made cake-cutter to push off the extra lube.

I have two Lee style sizers - one .358 and one .359 (made by Buckshot!).

I also have two of Ranch Dog's moulds :-)

Thanks anyway!

[HangFireW8]

My throats are all .359 and the "as cast" boolits drop at .360.


Catboat is on the right track. Even without throat size differences, it may be time to start tracking each shot by what cylinder it was fired out of. Besides throat size, there can be timing (alignment differences) in the cylinder. One chamber may fall in high behind the barrel while the opposite may fall low. Positively identifying or eliminating different chambers as factors can help you to focus back on the loads again.

Also, like you said, if you are going for ultimate accuracy, you need to segregate cases. For casual practice or larger targets, mixed cases are OK. Once you find that ultimate load for your revolver, you may be able to go back to mixed cases with minimal loss of accuracy.

HF