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View Full Version : Excellent to Hmmm results with new 140 grain RNFP COWW .38 Special loads



Tallbald
06-12-2015, 03:19 PM
First, I'm very very happy with my new RCBS .38-140-CM mold. Very well made, excellent fit and finish and flawless in operation. It throws consistent 137-139 grain slugs from straight WW lead. I'd buy an RCBS mold again without hesitation. Also, I'm a dedicated Trail Boss powder shooter. I have no reason right now to change to anything else, unless one day I can't find TB and have to use the 15 year old bottle of Clays I have languishing in the back of the cabinet. I know from experience that my Ruger 77/357 carbine prefers the heavier end of the recommended Trail Boss loads with 125 grain slugs, and expected the same with the new 140s and Trail Boss.
This morning was the first chance I had to shoot some loads with the new 140 grain COWW round nose flat points and once again, as with the 125s made of pure lead/WW alloy, my groups began quickly deteriorating after the 10 round mark. I had hoped to avoid this by switching to straight COWW lead but it didn't happen. I cleaned the barrel after 20 rounds and began getting good tight 50 yard groups again. There was no indication of leading I could find in the barrel. Just powder residue.
Below is a photo I took of two targets. Please no comments about my cigarette in the ashtray on our kitchen table. Our tobacco crop helped put food on our table and clothing on my back.
The group at the right is ten shots starting with a clean barrel. The target at the left was a series of several rounds approaching the 20th shots.
I'm thinking that 1) I may have a rough bore that's gumming up, but I cannot feel it. It only has 400 or so shots through it and most of those were cast. 2) The Trail Boss is fouling up the bore more than I realize. 3) I just have to get used to cleaning the bore after every ten shots or 4) I need to shoot jacketed slugs to smooth the bore or blast it out each 10 rounds after shooting cast. I don't like jacketed slugs. I can't make them, they are pricey, and they have no soul.
productive thoughts sure appreciated. Thanks. Don.
141931

dubber123
06-12-2015, 05:29 PM
I have never had a negative result from firelapping, but have had very positive results. I'd lap it in a second if you are even vaguely worried the bore has issues.

runfiverun
06-12-2015, 06:21 PM
try the clay's it burns clean and will tell you if it's the trail boss or not.
they both produce high initial pressure and a small gas volume so the comparison would be valid.