There was a recent thread, concerning the use of the Lee 7.62X39 mold (CTL 312-160-2R) mold in a 308 Winchester rifle. I have been testing that mold, in a 308 Win, at two boolit diameters. After firing 40 rounds, which generated two 10-shot groups for each boolit at 100 yards, I am not sure if there is a clear boolit diameter winner. But I am leaning to the 0.309 diameter boolit being more consistent. Would like to hear comments and suggestions. https://imgur.com/hnoDbG7
Barrel Preparation
The barrel had been shot with cast boolits prior to this test. It was dry scrubbed with Chore-Boy to remove any lead and then a dry patch was used. No chemical/solvent cleaning. Prior to the test, six rounds were fired to season the bore, if it was necessary.
Case Preparation
All cases, which are a mixture, had been previous trimmed to a minimum length. Since the cases had been previously fired in this rifle, the cases were neck sized, the length of the neck, only. The Lee neck expander plug has been turned from any oversize expander down to 0.311”. Looks like the brass springs back to 0.308”-0.309” internal diameter.
Boolit Preparation
The Lee 7.62X39 mold (CTL 312-160-2R) drops a boolit around 0.313” diameter. Previously cast boolits were sorted by weight. For this test, the sorted weights of 167.0 grains to 167.9 grains was used. A Hornady gas check was ultimately added to each boolit at the time of sizing. Boolits were run through 0.309” and 0.311” diameter sizing dies with the gas checks being attached. The boolits were then tumble lubed with the Lee Tumble Lube. No boolit culling was done. Boolits were fired as casted. May have been a mistake.
Round Preparation
Each round was charged with 16.0 grains of 2400. Rounds using 0.311” diameter boolits and 0.309” diameter boolits were assembled with the gas checks seated to the bottom of the neck. It was found that the chambered rounds may be pushing the gas checks below the bottom of the case neck. It is hard to tell if the gas checks are completely clear of the case neck. It was determined the COL of rounds loaded with 0.311” diameter boolits was 2.677” and 0.309” diameter boolits was 2.691”. These rounds have the boolits engaging the lands in both cases. It was found that the 0.309” diameter boolits could almost be seated using heavy finger pressure. Surely no swaging when these boolits are seated. A very light crimp was applied to each round in order to ensure the case mouth would enter the chamber easily and hold the boolits at the desired seating depth.
Boolits Tests
The boolits were group tested at a range of 100 yards. Two tests were performed on both boolit diameters. Each boolit test consisted of 10 rounds of each boolit diameter. The two boolit diameter rounds were fired in a round-robin manner to account for any barrel fouling during the test. Photo of the targets is attached.
|
   
   
|
|
Reply With Quote
Originally Posted by bluejay75
[/IMG]
[/IMG]
