Newbie question about slugging the barrel

[SKYPHI]

Hi guys, I am new to casting but not new to reloading. I always used berrys FMJ and never even heard of slugging the barrel. Heres what I got. I bought a lee 6 bullet mold, 125 gn 9mm. This drops them about .360. I bought a .356 resizer and went to work resizing. Then i loaded up a hundred 9 mm's and was ready to go, or so I thought. I then read about slugging the barrel. My glock 9mm was about .353, my M&P 9mm is also .353, for fun I checked my S&W 585 357 was also .353. So my question is, will my boolits, which are actually closer to .354 be ok in these guns, even though they are tad big. I still had some berrys laying around and they were also .354, anyone know what the deal is. The thought did occur to me that maybe my caliper is off, but IDK. Thanks for sharing your wisdom.

[stubshaft]

You need to get yourself a good micrometer!

[BACKTOSHOOTING]

You need to get yourself a good micrometer!
This

[Sir Castalot]

I was wondering if lube was involved in the sizing process, cuz that's important the cast boolits as well. CB are usually .001 larger than fmjs to seal the bore better, thus slugging for exact fit plus .001. Also your lead recipe is a factor, 9 mm are moving right along and alloy should be @ 15 bhn. Or gas checked. Depends on how hot of a load you're looking for, watch for leading. Read,read,read.... Good luck

[ssnow]

There is a problem with your measurements somewhere. The bullets should come out of the sizing die at .356, or whatever you sizing die is. Your gun probably slugs in the range of .356-.358. .356 is "standard" sizing die for the 9mm in cast bullets, and many guns would benefit from sizing them at .357 or even .358.

You need a good set of calipers, and a micrometer is a much better tool for measuring the "slug" from the bore.

[runfiverun]

yes.... see post number 5 again.
your numbers are waaay off.
back it down and start over.

[SKYPHI]

Good advice on the micrometer, I've just been using my hornady digital calipers. I thought that would be good enough but maybe not for thousandths of an inch. Yes I did lube it before I slugged it, and I get my lead from the range, I melt down the old bullets out of the trap

[williamwaco]

Another consideration:

.353 may be the bore diameter but it is NOT the groove diameter.

Note that the lands and grooves on the slug are a reverse image of the inside of the barrel.
The high spots on the slug correspond to the grooves in the barrel.

And yes. A caliper is not accurate enough for this measurement.

See:

http://3.bp.blogspot.com/_59GYpEVAu0U/S_NyVDPVw7I/AAAAAAAAAFI/bnE9unBLDZw/s1600/boredia.jpg