slugged the barrel and

[XDMinent45]

Slugged the barrel of my Sig .45 auto using a round ball starting diameter of .452 I pushed it through with a wooden dowel, the results were;
grooves are .451 and the lands are .442 so my question is lube/size my cb to .452 or .451?

[dondiego]

0.452 or 0.453 if it will chamber.

[mdi]

I'd suggest a larger slug, at least .460". Slugging a barrel with a slug only .001" larger than the groove diameter will often (prolly) give erroneous measurements. A slug .010" larger should be considered minimum (at least from an old machinist/mechanic's point of view). I like to see a good "donut" of lead shaved when I slug a barrel...

[mjwcaster]

While I haven't slugged a barrel before, I cringed when I read 'wooden dowel'.

Google 'removing broken wooden dowel from barrel', not the best thing to use.

[62chevy]

I'd suggest a larger slug, at least .460". Slugging a barrel with a slug only .001" larger than the groove diameter will often (prolly) give erroneous measurements. A slug .010" larger should be considered minimum (at least from an old machinist/mechanic's point of view). I like to see a good "donut" of lead shaved when I slug a barrel...

I'll second the .010 over for the slug.

[OuchHot!]

Just a suggestion, but I would get the slug into the area just ahead of the chamber and whack on it while restraining it from the opposite direction. You want to upset and flow the slug into the grooves. I have found a bit of violence gives a more reliable slug diameter.

[Larry Gibson]

Size .452 at max or you could be asking for chambering problems with some thicker brass. Also since the ACP headspaces on the case mouth larger sized may not go into the throat. That necessitates much deeper seating, can lead to feeding problems depending on bullet and the chamber can scrape of lead leaving it in the chamber and preventing the next round from seating all the way.

Sometimes "bigger" is not better.........

Larry Gibson

[DrCaveman]

Hate to say it, but you probably have to try both sizes to see which one is better for you. Sometimes the pre-calculations just dont work

You could get a 451 sizing die, see if you get accuracy and no leading, and if you dont, lap it out to 452 or larger, and try again. I lapped out my lee .452" to about .4525" for my sti 1911, it works great