9mm sizing

[Sailormilan2]

I just slugged a Rock Island 9mm & 38 Super barrel, since I was getting some keyholing at 10 yds with my 38 Super. My bullets are all sized at .356, but the barrels slugged at .356/.3555.
Fortunately, I have a .357 sizing die. If I PC the bullets would I still need to go to .357, or would .356 work?
Rocks tend to have tight chambers, and I'm not sure how they would handle the larger bullet.

[JeffG]

If keyholing you will need bigger. Load a dummy round sized at .357 and work with the seating depth till it will chamber with little to no interference when dropping the cartridge into the chamber (plunk test).

[reddog81]

I've had better luck sizing at .356 vs .357 for my 9mm's. I size then powder coat so the finally diameter is goon to be around .3565 or so.

[runfiverun]

key holing is only caused by two things.
either the bullet is too small to take the rifling or it isn't going fast enough.

P/C doesn't change that, it's just a coating.
I would size, coat, and size again.

[mdi]

FWIW, I treat/reload my PCed bullets just like lead bullets. So, I would suggest sizing any bullet you choose to at least .357", and 358" if necessary...

[Shiloh]

My 9's are sized to .358 and work wonderfully. Many 9mm bores are larger than the .355 they are marketed as.

Shiloh

[c1skout]

My RIA 38 super slugs .357. I've had the best luck with the Lee 125 rnfp sized .358. I gave up on the Lee 124rn from that gun, it always landed sideways.

[Sailormilan2]

Well, I finally got a chance to size some of the Lyman 356402, that I have been using, to .358. I loaded 5 into some unprimed 38 Super GFI cases and tried the plunk test. Well, they flunked the plunk test with my Midway loaded round guage, but passed the plunk test in my two RIA 38 Super barrels. The chamber test is more important than the gauge test, so I guess I am good to go using .358.
Now, I will have to do the same to some 9mm, as I have a RIA 9mm barrel too, and also slugs at .356
I did a bit of light research and found a couple of places that recommend .002 - .003 over bore size for lead bullets and .001 - .002 over bore size for jacketed bullets for best accuracy. Hopefully I can get out next week and try them out.