Let me tell you a little story.....

by Glen, Friday, May 24, 2013, 17:47 (4145 days ago)

Back about 1990 I started corresponding with John Taffin. One of those early letters asked him about a new sixgun (a 6" S&W 686) I had that was giving me bizarre results with cast bullets. With jacketed bullets, it was exceptionally accurate (sub-inch at 25 yards). With .38 Special loads using the Keith SWC it was mediocre at best (2-5"), and similar with full-throttle .357 Mag loads (all bullets cast with WW alloy, sized .358" and lubed with Thompson's Cold Bear lube -- back in that timeframe, I was a firm believer in shooting cast bullets that were .001" over groove diameter). These bullets shot superbly in my 8 3/8" S&W 586, so the bullets were good. With .38 +P loads (~1000 fps), the 6" 686 was having a hard time keeping all the shots on the paper at 25 yards, and bullets were keyholing, and groups were ~12". With .38 +P+ loads (aka .38 Heavy Duty loads, ~1200 fps), it would group better (~2-3"), with all bullet holes on the paper, more or less centered and nice and round. John and I discussed this back and forth, and both of us were perplexed. He suggested that I try a softer lube (an insight that proved to be clairvoyant as I later stumbled across problems with commercial hard lubes in the ~1000 fps range, and I have been a staunch proponent of soft bullet lube ever since). This helped, but still this 686 wasn't shooting to the same level of accuracy that we all associate with S&W revolvers. GCs helped some, but not much. Eventually, I moved on to other projects and forgot about this sixgun and its quirky cast bullet behavior.

I stumbled across this 686 in the back of the gun safe a while back. I hadn't shot it in a while, so I took it plinking with a buddy of mine about a month ago. After shooting, I was recalling it's quirky behavior and discussing it with my buddy, and I realized that I had never measured the throats on this particular revolver. At home, I found out that all throats were indeed a VERY snug .357".

Since those early tests, I have learned (and re-learned) the importance of sizing cast bullets to fit the THROATS of whatever you're shooting them in.

I have sixguns that get very temperamental with over-sized cast bullets (and some that tolerate them quite nicely), so I had to wonder, did this 686 need to have smaller bullets? I put together test loads using a variety of cast bullets, loaded to ~800, ~1000 and ~1350 fps, all sized .357", and lubed with 50/50 moly lube/beeswax (all plain-based SWCs and SWC-HPs). The first load tested was the Cramer #11 HP (the Cramer version of the Keith HP, the Ideal 358439) over 14.0 grains of 2400. The first 10 shots went into 1 1/4" at 50 feet. The other loads also shot similarly. There were no groups over 2", there were no oblong bullet holes, no keyholes, no shots off the paper. Just like you would expect from a S&W 686.

Size DOES matter! And, in some sixguns, even .001" over throat diameter can completely ruin accuracy. And when coupled with poor lube performance, things can go sour pretty quickly!

Thank you for teaching me John!