9mm bore vs cast size limitations

[oley55]

looking for some input on what my options are in regards to just how much over bore size a cast bullet can be in 9mm. I have read where folks say it's ok to have a bullet as much as 4 thou over bore size, but in those discussions they were talking about larger diameter calibers. I presume in a larger bore there's more room to accommodate the displacement of lead and they operate at lower pressures than a 9mm.

I am/will be loading for (6) 9mm auto pistols and one AR-9 pistol (10.5" barrel).

For the normal pistols (6) the bores slug as follows: .356, .3555, .355, .3545. The AR9 pistol is: .3531"

I think I can push .357" bullets through all of the normal pistols (with appropriate load work-ups), but have doubts about the AR-9.

These will be for general blasting purposes and am not overly concerned about great accuracy. Obviously life would be simpler if I were about to develop a single load that would be suitable in everything, but.....(?)

[sigep1764]

Oley, I would reslug that AR9 barrel to be sure it is truly that small. If it is that small, Id think that even 357 would be ok in it. I agree it is easier to have one load for all the guns. I have been lucky and 358 runs in all my pistols. I load it for the shortest leade or throat. If I buy a new pistol and it doesn't like the load, down the road it goes.

[jim147]

I would plunk test to find the shortest tightest one of the seven. Pick that one to work the load up on.

You will still need to work the same load up on the others for safety but if accuracy is not a biggy the first one might work in all of them.

[Outpost75]

Chamber diameter and brass wall thickness variation matters more than anything. Exactly same conditions as with .32 ACP.

Using mixed brass oversized bullets in which seating depth exceeds that of factory FMJ the bullet base will impinge against the case wall where it begins to thicken, below where the base of a factory FMJ would be. This causes a bulge which prevents rounds from chambering.

IGNORE the groove diameter of your barrel. Instead sort brass and don't use the thick-walled stuff for cast. Experiment to find the correct diameter of cast bullet which will "plunk" test in your pistol, such that loaded rounds will drop all the way in of their own weight, the slide will close and lock and unfired rounds will extract freely without resistance.

AVOID having to deep-seat bullets in the 9mm to pass "plunk test" as this dangerously increases pressure and can set you up for a KaBoom~!

Accurate has a variety of 9mm bullets which approximate the same seating depth as factory rounds. I use 36-142H of my design with 3.5 grains of Bullseye sized to .357 for the majority of 9mm pistols AND REVOLVERS!

[Larry Gibson]

What can be okay sizing (up to .004 over groove size) in revolvers is not usually applicable to semi auto, carbines and single shots simply because they do not have cylinder throats. In non-cylinder firearms of pistol cartridges the diameter should not be larger than the throat at the case mouth. The bullets should be sized to fit that.

However, for 9mm ammo to be used in a multiple of guns I suggest sizing to .356.

I used that sizing for thousands of 9mm rounds shot in numerous handguns and subguns, old and new, for years before I read on the internet about sizing must "fit". Alost all of those were cast of COWWs [older with sufficient tin content, with newer add 2% tin] and lubed with Javelina (NRA 50/50 lube). They were loaded in mixed cases over 4 gr Bullseye and functioned every single firearm giving very good if not excellent accuracy w/o any leading problems.

Having helped numerous individuals with "leading" and keyholing problems with 9mms I've found the problems were usually due to a poor alloy, poor quality bullets and/or improper lube. Functioning problems are usually caused by improper seating depth, improper sizing to remove case mouth flair and/or over sized bullets.

[onelight]

What Larry said works for me to .
I just shot a bunch of .356 Hi-Tek 125 grain over BE-86 in a p365 and p210 no leading . They also work in 2 cz pistols a Ruger another sig p290rs Beretta nano ,S&W shield , Browning HP and HK p30sk and a sub2000.

[fcvan]

However, for 9mm ammo to be used in a multiple of guns I suggest sizing to .356.

Larry, I take most things written by you as Gospel as you are a wealth of knowledge mostly developed through meticulous experimentation. I learned to reload from my Dad and a close family friend of Dad's. We mostly shot 38 and 41 Mag and some 30 Carbine from a RSBH, basically straight wall cases. When I bought my first pistol it was a S&W 459, largely because my brother talked it up so much. He eventually got a 659 as he was working for City Harbor Patrol and wanted stainless.

When I started loading for my 459 I bought a bunch of Lee gear as I could afford it. New on the job, our duty sidearm was a S&W M10 and we shot factory HBWC ammo, pretty soft stuff but free at work. I approached the 9mm like I was taught with 38 and such.

I read everything I could and noted that some folks experienced boolits being resized by the case. My Lee 356-125 2R dropped at .358 and so I figured if any resizing were to occur I had room so to speak. I began casting the soft lead, dip lubing with Javalina, and shooting as cast. I never experienced any leading. I also pulled and measured loaded rounds noting they were still .358 diameter. They plunked, they fired quite well.

When I finally bought a Lyman lube/sizer I didn't bother buying a sizing die smaller than .358, and by this time had a S&W M13 which loved the Lee 125 2R, particularly due to the RN and speed loaders. Many years and numerous 9mm pistols and carbines later, I did the unthinkable, I bought a .357 sizing die. Using a Glock 22 with a 9mm drop in barrel it patterned, not 1 hole groups as before. I got rid of the .357 sizing die like a bad habit. Someone here wanted it, it had only sized 500 boolits.

Stock Glock, S&W, Taurus, S&W pistols, a few AR 9mm carbines and 1 Marlin Camp 9, all prefer the boolit sized at .358, I don't know why I messed with a good thing. I still have the original dummy rounds made for every caliber I shoot, including the original 9mm for the S&W 459. Although I no longer have the 459, I do have a 639 single stack. I didn't buy it for me but couldn't pass on a $225 price tag.

Dad liked shooting my SA 1911 and has always been a S&W shooter, the 639 fit into that idea. Dad never did take the pistol, choosing to leave it with me for when he would visit us boys. Dad hasn't reloaded in quite some time as us boys always kept him stocked up. The folks are both 81, don't travel much, an hour's Sunday drive is about Mom's limit.

The last time they were up to see us, Dad helped load 15K 9mm as my Wife had picked up a large supply of once fired range. Dad would size to .358, load while I was at work, and get on me to cast a bunch more while Mom was cooking up a storm in the kitchen. This was before I started powder coating everything, and still size to .358 diameter. I know your results have been different than mine, I just wanted to share my experiences.

Pet load for the 9mm is 5 grains of Unique, same with 38 SP with the same boolit, and the Lee 401-175 TC. I have tried other powders, different charge weights, Unique was the powder Dad bought in 15 lb cardboard kegs, I just buy the 8 pound plastic jugs.

[gwpercle]

I worked up a load for 4 different 9 mm Luger pistols from new Springfield Compact , to WWII Walther P38 (1942) used .357" sized boolits in all .
Plunk Test them all and don't take anything for granted . The 9mm Luger with cast boolits is a Stinker with a capital "S" .
Had success with the following boolits : Lee 358-105-SWC , Lee 356-120-TC , Lee 356-125-2R and NOE 358-124-TC GC
All sized .357" and lubed with Lithi-Bee lube .
I found I had better results with a steel resizing die that resized with the taper... the Lee Carbide sizer resized the base too much and the mouth not enough . My old C-H steel resizing die did the job just right .

Good Luck,
Gary

[Larry Gibson]

Okay guys, What i posted was not "gospel" but was in answer to the OPs specific inquiry. He listed the groove diameters of the 9mm guns as; ".356, .3555, .355, .3545. The AR9 pistol is: .3531" He stated; "develop a single load that would be suitable in everything, but.....(?)" Since the majority of his post concerned the groove diameters of the firearms he was loading 9mm for I answered in relation to what sizing of my cast bullets has worked for me.

I merely suggested he use .356. I did not say other sizings would not work. I just gave reasons why .356 sized cast bullets [mostly with the Lyman 356242 and 356402 bullets and in the last 10 years the Lee 356-120-TC] worked for me in many different 9mm handguns and subguns.

Just a suggestion to the OP, not 'gospel" and that's all.

[243winxb]

My new Taurus G3C 9mm has a .3568" throat. If a larger diameter like .3575" bullet is loaded, the OAL has to be shorter. But where does all that extra lead go? Down the grooves to lead the barrel. :shock:

[fredj338]

I mostly run 0.356" coated. I have never needed to go larger than 0.357". I read a lot of stuff about 9mm needing 0.358" & I just haven't found that true, even in stick GLock. YMMV.

[Burnt Fingers]

The first thing I would do is check that AR9 again.

I've slugged five of them, from four different brands, and none of them were that small.