Maximizing accuracy in semiauto 9mm

BHuij

Active Member
When first got into casting and reloading, I got the Lee 124gr TL RN mold for my 9mm and I'm still using it to this day.

I get reasonably good accuracy with W231, certainly better than anything I ever got with factory loads, but I'm curious what things I could do to increase accuracy at this point. I realize my M&P 9mm is not a target pistol, but I'd like to try and understand what things (other than my own skill) are limiting my accuracy at this stage.

I'm just using powder coated .358" bullets over 4 grains of W231. They're air-cooled COWW (BHN ~13), or sometimes air-cooled COWW mixed with 30% SOWW or so (BHN ~10-11). Seems like experimenting with different powders, changing my bullet design, or tinkering more with alloy composition would be the three things that might help me tighten up groups in addition to just practicing more.

Would a higher or lower BHN be more likely to help? Would adding 2% tin help any? I already get good fillout with no added tin. Is there any mold that has a reputation for good accuracy in 9mm? I've been eyeing the Lee 120-TC (non TL).

I should mention that I have tried Bullseye and Accurate #2, but kept coming back to W231/HP38, as it gives me noticeably better groups. Any other powders worth trying?
 
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popper

Well-Known Member
Heat treat! Might try 4gr of WST. Tin is for fillout, nothing else. I don't use it. Forget the number but I use a 130gr RNFP from accurate.
 

CZ93X62

Redlands, Kalifornistan
One feature that LAPD armorers insist upon for their match pistols is to GET RID OF the OEM barrels and replace them with aftermarket barrels having slower twists than the insanely-fast 1-10" or 4 turns/meter that has been "boiler-plate" for the 9mm since forever. Twist rates of 1-16" (like Colt and Springfield Armory use) to 1-20" are their stated preferences. The 2 most accurate 9mm pistols I have ever tried out I found during the same range session with some LAPD range rats. One was a moderately-modified Beretta 92 SB-F with a Bar-Sto barrel and 'tuned' locking block (GMBTA.....), the other was a box-stock Springfield Armory 1911A1-pattern/stainless/Loaded variant. Both used 1-16" twists in their barrels, both barrels had .355" groove diameters (rare in production service barrels, most run wider), and both had been shot A LOT with the ammo de jour of the times, the W-W 147 grain JHP sub-sonic loading pimped by FBI as Ammo Of The Future. Yeah, whatever. FWIW, my service load duplicator for these Crowd Pleaser 9mm Sub-Sonic Sub-Effective used the Winchester 147 JHPs seated at 1.135" OAL atop 4.1 grains of WW-231. 965 FPS from my SIG P-226, it sometimes required a follow-up shot to dispatch jackrabbits. I wouldn't use it on coyotes.

WW-231 has done good work for me in 9mm, as have the Lee 120 grain TC castings with the conventional lube groove. I size them to .357" and use 92/6/2 alloy to pour them. I can't see an advantage to using LSS Carnauba Red over 50/50 BW/Alox, at about 1100 FPS I get the best accuracy. Any faster than that (to 1225 FPS) and accuracy degrades a bit. I don't see evidence of stripping in the pistol barrels (both are fast-twists), maybe trans-sonic effects are kicking in. I lean toward this latter explanation because both Remington 125 grain JHP 357" bullets and Speer 124 grain .355" JHPs also start spreading groups once the speeds exceed 1100 FPS. This effect is not like "Improved Cylinder" patterning, but it is there and it is noticeable--about a 20%-25% radial expansion.

When I carry a 9mm, it is filled with Speer Lawman 124 grain +P ammo. My load for practice ammo using the Lee 120 TC bullet exceeds the "4.0 grains of WW-231" charge weight significantly. 4.0 grains of WW-231 will function the P-226, and barely functions the Ruger P-89. It IS quite accurate, but I have little use for the 9mm as a target caliber or hunting arm. I load the Lees for training & familiarization with a clone load of my carry ammo. 4" groups at 25 yards is adequate to the task, and my training reloads can meet and often surpass that standard.
 
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Cherokee

Well-Known Member
I use the Lee 356120TC lubed with CR and cast from 3/3/94 alloy @ 122 gr. sized to .357 for my XDm 5.25 9mm, XD9C, and other 9's. I use two loads, one light target load with WST ( apx 950 fps) and one service level load (1150 fps) with HS6. In over 50,000 rounds, never had a failure and accuracy is limited by my ability.
 

fiver

Well-Known Member
I run a bit harder than ww alloy in my 9's too.
like 8 parts to 1 part lino-type.
dunno the exact numbers but it's harder, probably 1.5% tin [since I have tin in my ww alloy] and around 4% antimony or little a bit less if I had to guess.
no water.

I'd probably try the little harder alloy first, then a bit more powder [unless I had another powder on hand] then another design starting where I left off with the last one.
 

BHuij

Active Member
I'm not finding anyone who makes an aftermarket barrel for the M&P platform with a twist any slower to 1:10, but the Apex barrels are highly rated. It's not in the budget right now, but down the road I was going to need a threaded barrel for a suppressor anyway, so I'll keep that in mind.
 

CZ93X62

Redlands, Kalifornistan
If you treat your9mm, 40 S&W, and 10mm Auto cast bullet loads like they are RIFLE cast bullet loads, you won't be straying from The One True Religion very far. These calibers mimic rifle environments closely--high pressures, fast twists, and velocities at the cusp of needing gas-checking (but generally don't use them). My recipe has been to use relatively hard alloys, relatively soft lubes, and STRICT adherence to throat diametric specs when sizing bullets.

And again like rifles--don't shoot yourself in the foot by using a too-small expander spud to process cases after sizing. The .352"-.353" expander spuds in 9mm Luger die sets WILL SIZE DOWN CAST BULLETS, and most 9mm throats are in the .357"-.358" ballpark. Better to have a relaxed case neck and set a taper crimp that digs in slightly to the bullet sidewall on that Lee TC casting. They won't "telescope" on feedramp contact, unless you run the same cartridge 7-10 times from the magazine into the chamber.
 
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Ian

Well-Known Member
When I first started loading cast bullets for the .40, I ran into all the usual problems everyone else was having, except the solutions seemed obvious enough to me as someone who had a decent amount of experience loading cast bullets for rifles and magnum handguns. A custom expanding spud was sourced from JimInPhx, WW alloy was water-quenched, lube was soft soap lube, bullets sized to just under throat entrance diameter, and an aggressive crimp applied. The sizing ring was knocked out of the Lee FCD, and no more issues. When people take the same tooling and technique approach to the hard, thick, high-pressure brass of the 9mm and .40 as they do to the .38 SPL or .45 ACP that they're used to, they run into problems.
 

fiver

Well-Known Member
I remember when the LEE T/L mold was the number one thread starter at boolits for like 2 years.
it seemed as though every new guy had that mold and was having all kinds of problems.
the two posts above me explain what they were facing and what they were doing wrong.

I do load my 9's and 40's like a 1911 would want but mostly in the speed department and not so much in the loading or alloy area.
as I have gone along I have noticed that alloy make-up and how it's treated does make a difference on the target.
a little more 'stuff' in the alloy usually doesn't hurt anything in that regard, but it can generally help
as long a you don't go too far.
 

358156 hp

Well-Known Member
To expand a bit on Als post above, the case mouth expander spuds for 9mm are pretty short. This is partly because 9mm bullets are pretty short to begin with, but also because of the case ID being limited because of the inside base diameter being so thick at the base. I have pulled some of my heavier 9mm bullets and found cast bullets were getting swaged down at the base because of the inner case taper. In the past I've considered making a custom expander that would allow me to maximize my seating depth to eliminate or at least minimize the potential for base swaging. I wonder how many 9mm leading problems in 9mm may be caused by this situation, even though the primary bullet diameter is still where we intended it to be. I had a thread going on "Boolits" about this years ago, and we found that of all 9mm expanders we had access to as a group, the Dillon was the shortest of all. We didn't get to measure every brand out there, so there's a lot of uncharted territory here. The inner case taper can also be dealt with by using bevel base or boat tail designs. I may rerun my tests using Lyman 356637, since I now have a 4 cav. version of it. As always, 9mm seating depths must be taken really seriously since pressures can skyrocket very quickly, but I wonder what sort of accuracy gains may be possible. Someday...
 

KeithB

Resident Half Fast Machinist
I made an expander spud for 9mm that has two diameters. The main section sizes the brass for a .002-.003' interference fit and the second section is slightly larger than the bullet OD. The length is such that the base of the bullet sits on a little "shelf" inside the case and the neck is expanded enough to stand the bullet straight in the case before seating. Unlike a flare you can't oversize the mouth and it is easy to put a taper crimp on the case (which I do in a separate step). It seems to work in my HiPower, I can't recall ever telescoping a cartridge.
 

popper

Well-Known Member
The general opinion of the amscor stepped case is it's done for cost but it does solve a lot of 9mm loading problems as long as the step is below the base. Still get a bulged case with oversized cast but loads like a straight walled 40SW.
 

CZ93X62

Redlands, Kalifornistan
358156 makes a GREAT point concerning 9mm case construction quirks, and I will pile on by saying that 9mm has some real wide tolerances between makes as well. Thankfully, both 40 S&W and 10mm are not so "poetic", and tend to have pretty consistent throat and groove specs in their barrels and chambers.

ETA--Armscor cases with internal step......another mote in the eye of God, on the same order as taper crimp seating dies. I "get" the idea behind the feature, but Life Is Good using Remington and Starline 9mm brass right now--so I leave well enough alone.

FWIW, the Win 147 grain JHPs I once used to clone my sub-sonic service loads had a boat-tail base. I presume this was "tuned" to the W-W cases they were being fitted into by the factory. Wasted largesse, though--I had free access to once-fired Winchester 9mm brass at the agency range, but I couldn't make that &^%$ cooperate for love or money. The primer pockets were VERY undersized, and had extreme resistance to being swaged by the RCBS tool so-designed and to reaming. It was easier to just pay for Remington new brass and call it "good".

9mm is just a PITA.
 
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BHuij

Active Member
I have to laugh at the replies here, because I went on a months-long wild goose chase trying to figure out what was causing my leading problems in my 9mm with the 124 TL RN mold...

...before I finally figured out that my bullets were too small, and the stock expander plug in the 9mm Lee die was causing my case to swage them upon seating to even smaller diameter. Some of the bullets I pulled were .353" at the base. Yikes!

I haven't measured my throat (and perhaps I should if I'm serious about improving accuracy), but my groove diameter is .357" - about average for an M&P OEM barrel from what I can tell. The .358" bullets have eliminated my leading entirely, but I think an easy first step would be to re-examine seating depth.

And honestly I think I may just swing for the 6 cavity 120 TC mold from Lee (non TL). Everything I have ever read says it's more accurate than the TL design. I would guess that's due to far superior bearing surface more than anything else. I generally seat out as far as I can get away with before causing FTFs, any reason not to do that with 9mm?
 

BHuij

Active Member
My alloy calculator tells me mixing roughly 3 parts COWW to 2 parts Lino will give me something very close to 92/2/6 - Pb/Sn/Sb. Will probably give that a shot.
 

Pistolero

Well-Known Member
Too small bullets and too big barrels is a huge chunk of the "why is my 9mm throwing bullets sideways
and leading" questions which were a regular on the other site.