What sizer die for 40S&W polygon barrel?

[a.squibload]

I have a Kahr PM40 with a polygon barrel, have been using
.400 store-bought (J-word) bullets,
and swaged .400 bullets from 9mm cases. Both work fine.
Have not slugged the barrel as I wouldn't know what to measure
(points or flats?).
I just did my first batch of powdercoated boolits, did some 40s,
they came out at .402, might be too big.
Not sure what sizer to use, .400, .401, ....
Powdercoat is not as stiff as a jaxket, it's more like a lube.

Anyone have experience with casting for polygon barrels?
I figure normal rifling would want .001 over at least, but
this barrel ain't normal! Thanks.

Edit: did some searching on CB,
looks like Kahr barrel is not like a Glock barrel,
I count 12 lands.
Also can't find twist rate.
Will try slugging it, couldn't hurt.

[AggieEE]

I've had good luck with 401 in a stock glock barrel. No experiance with Kahrs but its a starting point.

[a.squibload]

Thanks, been searching, in general it looks like polygons like
an oversized boolit. I'll keep reading.

Hey, remember which building at A&M has the Liberty Bell replica?
I have a pic somewhere of a guy standing in the bell.
All you can see are his feet.
It was a very small town back then...

[NSP64]

slug it, measure the widest points, shoot 0.001=0.003" larger.

[a.squibload]

Thanks I'll give that a shot.
Dangit, think I used up all my 40s, will cast a few soft ones.

[Lloyd Smale]

my .40 and 10mm glock do just as well at either .40 or .401 in actuallity my .40 sizer does .405 so that could be why theres little differnce.

[AggieEE]

a.squibload, its been 36 years since I was up there. I don't remember seeing the Liberty Bell rep. Could have been in the Admin bld. As an eng. student I spent most of my time in the Old Accademic bld, Zackery and a few others. When did you graduate?

[Garyshome]

This should be the first step: slug it, measure the widest points, shoot 0.001=0.003" larger. Not really hard to do either.

[a.squibload]

a.squibload, its been 36 years ...

Looks like I was there 5 years earlier. I think it was in the Admin building.
One of the dorms I was in was torn down between semesters it was so old.

Sorry, off-topic...

[a.squibload]

Had some soft slugs for swaging 44s, they measured .402,
I smacked a couple with a hammer to .405.

Slug max dia. measured .3985 to .399 with some real good calipers,
verified that with a micrometer.
The Kahr has 6 "lands" and 6 "grooves", meaning half the flats are smaller dia.
and half are larger dia.
Actually they seem a little curved, not flat, but I don't know what to call 'em.

.399 grooves for standard .400 j-word bullets is about right I guess.
Suppose a .401 sizer would be out of line for cast? That's only .002 over.

Dang polygons!

PS: I tried holding a loupe in front of the lens on the iphone, seems to work OK.

https://lh5.googleusercontent.com/-xsdD62-JNRo/UmcGc8kRNEI/AAAAAAAAAoQ/4b_Uj5yLI2M/w640-h480-no/40+004+%2528%2529.jpg

[Mk42gunner]

.401" sounds like the diameter to try first, at least to me.

Robert

[bobthenailer]

although not a Kahr 40 S&W I have 3 Kahrs , PM9 uses .357 dia bullets , the CW45 & TP45 both use .452 dia cast bullet with excellent accuracy and no leading.