GP-100 Sizing Question

[bdgackle]

I'm casting for a Ruger GP-100. I slugged the bore and chamber mouths. Grooves look to be about .357, chamber mouths are .358-.359. Boolits as cast are .361-.362.

From searching the forum, I've come to believe that the ideal situation would be to size down to .359 (to match the chamber mouths), but for the moment I don't have a sizing die at that size (or anything close for that matter). I can order a die, but I'm tempted to try to shoot as cast before I go through the trouble, just to see if I really need one.

I know chambering problems are a possibility, but I'll load a couple of dummies to check on that. If that pans out, can I get away with pan lubing and shooting as cast, given the measurements above? Any safety issues (for me or the gun)? If I experience leading, is this a likely cause?

Thanks!

[bdgackle]

Oh, I should have mentioned caliber -- it's in 357 mag. I'll be loading some light to mid range target loads.

[straightarrow]

That is the same weapon I began reloading and casting for about six months ago. I started by reloading 158 grain round nose bought at Scheels and they were very accurate but were about $47.00 for five hundred. Thought I would try pouring my own and ordered a Lee 158 grain tumble lube semi wadcutter and a sizer. Poured some up, lubed them, sized them and lubed again before loading. I went to shoot them and it was like I was shooting a different gun, no accuracy, no grouping and tumbling bullets. I was going to give up and just load the round nose when I read that some guys don't size the bullets. I poured up fifty, tumble lubed them and loaded them as is with 4.3 grains of Unique. They are very accurate and I would expect you would have the same results. The only other thing I can add is I switched to White Lable lube which is way cheaper. No fancy lead mixture just recycled range lead.

[ColColt]

You can get size dies up to .360" before they jump up to .363" from Lyman and probably RCBS as well and there not that expensive. If the throats are .359" I'd size to that or even .360".

[btroj]

I size at .359 for similar sized throats. Works well.