question about sizing

[rmatchell]

I have been casting up some boolits for my father in laws marlin 30-30 and I have been sizing them at .311. Looking in the Lyman cast bullet book they list size as .308 should I keep doing what im doing or follow the book.

[45-70 Chevroner]

Slug the bore, then size to .001 to .002 over that size. You should then be good to go.

[Maven]

You'll first need to slug the bore in order to determine the sizing diameter: http://www.castpics.net/subsite2/HowTo/Slugging%20the%20Bore.pdf However, until you do, I'd try the .311" CB's with mild loads as you may be pleased with the results. Btw, my ca. 1991 Marlin 336 shot CB's sized to .311" pretty well, but .310" CB's were outstanding.

[sundog]

If feed, function, and accuracy are good, I'd leave it alone. I'm not an advocate of hammering stuff down a bore just to get a measurement, unless all else fails.

Load a dummy cartridge or two or three and check for feed function and fit. I've shoot .314 thru a 30-06 barrel with no problem. That same bbl shoots .310 with great accuracy.

[captaint]

What Sundog said... If it works, why worry about it - as long as accuracy is good and it feeds and functions. enjoy Mike

[runfiverun]

marlin and 311 seem to go together quite well.
they have that rounded over micro-groove rifling that demands an oversized boolit to fill the bbl and grab hold.
i'm pretty sure the lyman book also shows 5/5/90 or linotype alloy too.

[MtGun44]

Sucess in a measured .308 bore is often found at .310 or .311, but you should try
.309 at least.

Bill

[44man]

Yeah, micro groove needs a little larger boolit. Rifling is only .003" deep and bore is usually larger.

[rmatchell]

sounds good guys thanks. It kinda through me off to see the lyman book say size different im still learning about loading boolits so I always assume that somebody else will know better than me.

[Maven]

"Looking in the Lyman cast bullet book they list size as .308 should I keep doing what im doing or follow the book?" ...rmatchell

I just looked at the 3rd Ed. of the Lyman CB book and, as I suspected, they did NOT use a Marlin [#336 Microgroove] rifle in their testing, but a universal receiver. Hence, I wouldn't put too much faith in their suggestion to size to .308".

[rmatchell]

I didn't think of that maven thanks for the reply