“New to Me” 9mm sizing

[Krh1326]

I don’t do alot of 9mm casting. I had one 9mm ( P938 ) in the collection. I did NOT do my homework, and slug the barrel. I skimmed these forums , and took an educated guess at sizing to .357
This worked great in P938. My favorite boolit is a Hollow Pointed TC NOE version of Lee’s 124 gr TC.
Chambers flawlessly, and never leading of barrel ( I do powder coat, gas check and lube … I have the time and patience…. Why not? )

I recently acquired a Sig P229 9mm Emperor Scorpion… brandy spanking new, old stock.
I decided to sit down with it, and do my homework. I broke it down, casted up some beauty .359 HPTCs. I just tapped one thru the lubed barrel and I got a groove diameter of .3545-.355
Starting at .359 as cast, that slug didn’t show any real signs of heavy lead distortion or displacement, other than the obvious rifling grooves.
If I use the +.001 method , that would have me size at .356 Is that enough?
I would rather size for my, now two, 9mm’s , the same .357 , as well as load the same ( 4.2 gr HP-38 ) for both, just for simplicity, on my part.
As long as .357 chambers, and I don’t lead, would it make any functional difference being on the large size? For that matter, if I sized everything at .358 ( providing they both chamber and don’t lead ) would that make any functional difference?

[rbuck351]

Probably won't make any noticeable difference. I would just try some of your current .357 / 4.2 grs of hp38 and see how it works.

[Krh1326]

I thank you sir

[poppy42]

I’ve been loading 9 for years. Size all my boolets to .356 with out any issues so Sizing yours to .357 should be no problem. You could also try sizing to .356 and shoot some out of your p938. Either way I doubt you have any issues at all.

[hoodat]

If they pass the plunk test, I'd go burn a box and see if there's any leading. Your load is under listed max, if your bullets indeed weigh 125 or even 130, but you're close. Just pay attention to your brass and function when you get started. Technically you could have higher pressure with the tighter bullet, but it's not as critical with lead as with copper. jd

[Krh1326]

Thank you everyone!

[243winxb]

https://www.thehighroad.org/index.php?media/albums/taurus-g3c-9mm-luger.317/

A little over .356" does ok for me. Accuracy will depend on the gun.

This seems a bit much.
I do powder coat, gas check and lube If all on same bullet?

[fredj338]

I settled on 0.357” for all my 9mm pistols. Bullets are more accurate than i am.

[Krh1326]

https://www.thehighroad.org/index.php?media/albums/taurus-g3c-9mm-luger.317/

A little over .356" does ok for me. Accuracy will depend on the gun.

This seems a bit much. If all on same bullet?

Definitely overkill, but like I said, I have the time and patience. I’m retired, and if I’m tinkering in the barn, I’m not on wife’s radar, lmao. Plus it’s not so bad… the shake n bake is easy as you please, then I set and crimp GC and lube, in one shot , in lubrisizer. While I do agree it’s overkill, I’ve never had to scrub out lead, even running hot, with soft lead for hollow points… plus I think by taking the steps, and time, gives me some more consistency.