Accuracy issue PC 9mm

[chris in va]

I've put thousands of the Lee LRN powder coated through my P01 with very little issue, sizing with the Lee 358 die. Now that I have a CGW Shadow 2, it flat doesn't like them. At least twice a mag I get one that sounds weird and it goes in sideways. Sounds like a 'thwack' instead of the usual SNAP.

It shoots like a laser with Hornady HAP, is theoretically possible the bullets are too fat? I slugged the barrel and it measures .355-.356.

[Mike / Tx]

That could be the issue. I've seen plenty of post in the past with 9's that have different diameter barrel causing numerous issues, usually excessive leading.

Lee dies are cheap enough if you can find one that is .357, ya might try it or the .356. Worst case get the smaller one and polish it out as needed.

Then of course you'll probably have to modify the sizing plug in your die set as well. With some I've just chucked up an old bolt, big enough to be filed down, in my drill press and made what I needed. Takes a little time but works for what's needed.

[Recycled bullet]

The loaded ammunition has to chamber easily.

Remove the barrel from your gun and take some loaded ammunition and drop it into the barrel and see that it plunks all the way down to headspace correctly ....then turn it up .....point the barrel up ....and does the cartridge fall out under its own weight?

If it falls all the way in then falls out freely under its own weight then it has passed the plunk test AKA the chambering fitment test.

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[JohnKSa]

...sounds weird and it goes in sideways. Sounds like a 'thwack' instead of the usual SNAP.

Does the recoil feel different on the ones that tumble?

[chris in va]

It feels a little different, recoil is roughly the same. I have a new Arsenal TC mold on order so hoping that will help.

I have to be extra careful with this barrel, it's a lot tighter than the P01. I have to manually plunk every round to be sure it chambers.

[243winxb]

When the .358" diameter is to large for the barrels .356" throat, the COL has to be made shorter so the action can fully close. https://www.thehighroad.org/index.ph...9mm-luger.317/

[reddog81]

What goes into where sideways? If .358 chambers it’s not too big. The barrel will size the bullet just as well as a sizing die does.

[chris in va]

The bullet goes into the target sideways, aka 'keyholing'. Accuracy is nonexistent when that happens.

[JohnKSa]

Would be interesting if you could run a mag over the chrono and see if the velocity is significantly different on the ones that sound different and don't stabilize.

[chris in va]

Good idea, I may have to try that.

[Recycled bullet]

Do you get barrel leading with the key holing bullets?

My Taurus gx4 has a sharp chamber mouth leade and shaves powder coat rings which then build up and prevent the slide from going into battery. The groups get larger and larger until I stop and clean the barrel grooves and chamber with the brass brush.

Is this the problem you're experiencing?

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[chris in va]

No it's just random, one in 10 will have this weird sound and be off several feet. I'm still waiting for the new mold to come in, taking a while.

[stagpanther]

Semi-auto's that "change their tune" in the middle of a mag always scare me--unless I see the shot actually land the first thing that pops into my mind is possible squib and strip the gun (mind you, I'm not a handgun guy so that's just my paranoia). My gut reaction would be something is causing the cartridge to not go into battery properly, low and keyhole I would suspect some movement/separation of the projectile and case on chambering. I've had a few handgun misfires with "odd sounds" but there was usually a noticeable delay in ignition. My less than 2 cents.

[Unclenick]

Stagpanther has a good thought. Next time you are shooting, after every shot, look at the back end of the slide to be sure it is all the way forward.

Other thoughts: Since the recoil feels the same, do the cases eject to the same landing zone as the proper firing ones? If so, it sounds like you have proper functioning up to the point the bullet clears the muzzle.

I am wondering, could the sound change be from the bullet diverting muzzle blast differently? In other words, has the bullet base deformed? This could change the sound and would also account for tumbling. You could intentionally file a slant on one side of a few bullet bases before coating them and see if that can make the funny sound on demand.

If the new gun's chamber or throat is a bit tighter than the old gun's, that could raise pressure some. You could try downloading 5% and see if that stops or reduces the rate of incidence of the problem.

[MarkCO]

I'd approach it the same way as stagpanther in post 13.

[rc]

Do you have standard or micro groove rifling??? Some rifling doesn't like cast lead.

[chris in va]

It's standard rifling, CZ Shadow 2. Short leade however.

[chris in va]

Update:

I finally got the Arsenal 130gr PC truncated cone mold and had a chance to try it. They are MUCH more consistent than the Lee 6-hole I have and if I do my part casting the right recipe they seem to me much more accurate. I did have a couple go in sideways out of 100 so not sure what happened.

[jetinteriorguy]

Sounds to me like you’re getting inconsistent powder drops. If you’re using a flake type faster powder this could be the problem. I’ve had this happen to me before and in my case just found that the best way to drop these powder types is the Lee Pro Disc. I load a ton of 9mm using both Clays and 700X and used to get these occasional soft shooting rounds, since switching to the Disc setup no more issues. I just find the cavity that throws a slightly short load then use a tapered reamer to slowly enlarge the cavity until it throws the right amount of powder for my usual load and it works absolutely wonderful.

[chris in va]

I'm using an RCBS Uniflow and check charges, they're super consistent with everything but stick powders. It's so weird, I'll be able to chew out a 2" hole at 10 yards then get this weird sounding CHOCK and it goes in sideways about 4" over.

Maybe I'll check every single case charge for the heck of it.

[Recycled bullet]

Can you describe your loading equipment dies and press and processes? What head stamp of brass are you using? Mixed brass or selected?

What are you using to expand the brass to accept the bullets?

From my personal experience for example CBC brass will squeeze the bullets and make them undersize, using the Lee 9mm factory crimp die can incorrectly apply the crimp with lead bullets leading to undersized, seating and crimping in the same step with flared casings and lead bullets will scrape the bullets and lead to undersize. Those are three examples off the top of my head where I know I have had issues with components or assembly processes leading to poor accuracy, barrel leading, and keyhole bullets on target.

Maybe pull a bullet and check for coating damage or bullet diameter change?

[chris in va]

I'm using mixed brass, Lee resizing die, just removing mouth flare with seating die. I used to do the FCD but quit doing that with this new mold. I pulled a loaded bullet and it measured .355, the top where the case mouth was set flush showed the PC had been scraped off when I used an inertia bullet puller.

[rc]

If your ammo shoots fine through your CZ I don't think it's your powder drop, bullet sizing etc. It sounds like the carbine has a different twist that doesn't agree with your cast bullets or shallow grooves that get leaded up causing your bullet to strip the rifling and not twist. That will give you keyholes like some old 22 revolvers do when they lead up.

[chris in va]

When I say PC I mean powder coated.

[chris in va]

UPDATE!

Thank you all for guiding me through this. I did a few 'variety pack' loads. I realized at 357, the bullet's powdercoat was getting hung up on the chamber face and stripping it off a bit. All the 355's were able to be seated fully into the leade at 1.09" and none keyholed!

For the heck of it I fired a few sized at 357 and a couple went in sideways. So there you have it, future reference for Shadow 2 owners.