Just got my rifle slugged

[Gundogblue]

Hi All,
I just got my rifle back from the smith, I had the bore slugged. My rifle is a 2017 Miroku made Winchester model 1892 in .45 Colt. The smith didn’t pound an over sized slug down the bore but instead poured a lead like substance into the bore a couple of inches from the muzzle. When it hardened he tapped it out, he used a micrometer to measure the slug, it miked out at .4536, he said its more accurate than a caliper, but he said he doesn’t reload at all. When I got home I measured the slug with my calipers and it measured 0.4521, that seems more like it to me. I just got a new NOE MOULD 454-241-RF-AC3. I casted a bunch of boolits yesterday, so I grabbed 20 boolits at random, I measured them all then divided by 20 to get an average, it’s 0.4553. So I figure if I order a sizer bushing in 0.454 I should be good to go, am I right?
Thanks,
Paul

[mehavey]

If it (likely) was CerroSafe, it shrinks during the first 30 minutes of cooling and then starts expanding.
At the end of an hour, is EXACTLY as-cast size.

Timing is everything.

[Billwnr]

measure your bullets again after running them thru the sizer. The sizer may be off by a few .0001's.

[Conditor22]

If the bore is actually .4536 then .454 might not be big enough --- but it is easy to enlarge sizing dies.

[megasupermagnum]

A calipers is not accurate to .0001". A calipers is really only accurate to .001"-.002" if your technique is good, worse if you are not perfect. Both can also wear out over time, while the micrometer is adjustable for wear. As has been said, cerrosafe contracts, then expands. I would trust your gunsmith's measurements, but how relevant it is depends on the time he measured it. I'm sure his is familiar with it, if he uses it.