Powder Coated Bullets are keyholing

[wv109323]

I loaded some 9mm powder coated boolits to test. I used an MP mold which is a 130g. round nose. With my alloy and powder coating they weighed 140-141g. I used 3.6 g. Of Titegroup.
The mold drops right at .356 and I powder coated them and sized them to .3560. I used the shake and bake method.
The group was 10-12 inches with 3 bullets keyholing that brought the group out to 15 inches. The pistol chamber will not take a larger bullet.
So what would you try to get a powder coated bullet to group well?

[BNE]

What gun are you shooting it out if?

[ioon44]

I size my 9 mm bullets to .358" to .359" but they have to pass the plunk test.

[charlie b]

First, what gun? Some of the mfgs ship barrels with no throat. My HK hates lead bullets because of that.

[Txcowboy52]

I’m no expert but I wouldn’t think the powder coating would be causing the keyholes. I would look at the barrel, the bullets and the barrel to bullet fit.

[mehavey]

As mentioned above -- size to at least 0.357, and adjust OAL to properly plunk

[kungfustyle]

Did you slugg your bbl? Boolits need to be .001 to .002 over and that includes PC'd ones. Charlieb is correct, some 9mm have no throat. However, you can fix that, Look in the vendor section there is a member that will ream out the throat if the bbl isn't hardened steel. It's only about $75 or so.

[JSnover]

The mold drops right at .356 and I powder coated them and sized them to .3560. I used the shake and bake method.
The pistol chamber will not take a larger bullet.
So what would you try to get a powder coated bullet to group well?
Slug the chamber/throat from the breech end. Then slug the bore from the muzzle end. Don't drive either of the slugs all the way through. I had leading in a rifle barrel once. Turned out the bore dimensions were slightly oversized and the throat/freebore was slightly under sized. Driving a slug all the way through, I was only getting half of the story. Your throat or chamber may need to be reamed.

[popper]

Size 357 and change oal to plunk OK. Make sure case isn't resizing bullet smaller. You're running 900+ fps but tumbling is due to small bullet.

[wv109323]

I forgot to mention the pistol. It is a Canik Rival. The pistol was returned because the original barrel would not "plunk" test 3 brands of factory ammo. Canik replaced the barrel which does have some leade.Per the returned documents the new barrel is generous enough to use 147g. bullets.
I have not slugged the barrel but Delta Precision 124g. HP bullets work fine. I thought PC .356 should be a "no brainer" to work.

[45DUDE]

I have a $400 Armscor that shoots 124 plated plenty good but lead keyholes and sized 357. My lead 9mm boolits shot perfect in my friends Fusion -so it's not the boolits. I have plenty of plated.

[243winxb]

Alloy to soft by looking at the bullets weight. Add linotype.

[Smoke4320]

I will say almost every PC customer I have shooting 9MM are sizing to 357 or even 358 to get them to shoot properly
If your chamber will not take bullets sized over .3560 you probably only have 2 choices. Have the chamber reamed and have a lead added or shoot jacketed bullets
But as directed slug chamber and bore first. confirm what you think the sizes are.

[dverna]

Alloy to soft by looking at the bullets weight. Add linotype.

Very astute observation.

If you are not getting leading, and shooting huge groups the bullets with keyholing, the bullets are too small. Likely being swaged down when seated/crimped.

Pull some bullets to check. Address that first.

If you have Linotype, cast some bullets and size them to .357". If they shoot well, and they should, you can move on from there. I run 92-2-6 hardball alloy in all my 9mm's.

[JimB..]

At the risk of putting the thread in the ditch, do you use a Lee factory crimp die?

I’d pull a loaded round and measure the bullet, I’m with the too soft/too small crowd.

[wv109323]

I use a Dillon taper crimp die that is set at .3795 which xaries some due to Brass OAL.
The .356 Boolits are Not being sized down. Pulled boolits are still .3560.
For giggles I seated the same bullet sized at .3582 and pulled it. It measured .3578 or sized down .0004"
I thought that with powder coating that lead hardness was not critical. Correct me if I am wrong. The alloy is COWW mixed with range lead from a Bullseye pistol range.
I will go with the largest bullet that will fit in the chamber. I have te following sizes, .3560, .3567, .3571 and .3582.

[mehavey]

...with powder coating ...lead hardness was not critical.Not as critical... :-?

But w/ the COWW and pure lead combo you mention, you're likely running 8-9 BHN
-- a bit soft for 9mm pressures twice that of the 45 auto.

Point of reference, I'm running PC'd Lyman#2/147gr bare-base* in my SIG at 1,015fps/32,000psi.
Very accurate/dependable/clean shooting w/ Power Pistol

But I'm pretty sure 30-1/BN~8 under the same conditions would start stripping out.



* Base is also PC'd via S&B. Baked upright on copper grill mats (great stuff)

[crackers]

I've never done well with the fastest powders in a 9mm and that load pretty hot for cast - a lot of pressure forcing a leak. Something like a Unique or BE86 might help.

[hades]

For what it's worth I'm using a BHN 9-10 alloy in my M&P 40 with a kkm conversion barrel, a RIA 9mm And a buddy's Canik and they all shoot great with 0.356 sized bullets.


WV do you have a lead hardness tester by chance?


I think the combination of a borderline to soft alloy and possibly undersized bullets is the issue here.

Both issues are easy enough to change.

Is there any noticable leading down the barrel?

Sounds like you should really just slug the bore and see where you're at. At least you'd be more comfortable with the bullets size and could move on to alloy if they still shoot as bad as they are now.

[D.Bullets]

Lower your charge, or your bullet weight, or both. Your mold is for 130 and you are getting 140.
Your mold should be throwing closer to 130gr bullets and you are getting 140gr w/PCing your % of lead is to high leaving them to soft.
At what distance are you getting Key holes? I thing you are getting severe gas cutting. Could be the size could be the hardness or both.

Bullet Obturation; is to slug up and fill the throat sealing the gasses. When fired the bullet obturates and seals the thoat. To hard of a bullet and it will not obturate and gases go by cutting , deforming bullet, leading the barrel. Bevel-base do not obturate well, especially as higher pressures increase, causing cutting , deforming bullet, leading the barrel, bad accuracy. PCing helps seal Bev..Bases also.

I shoot a 45 Auto 230gr at 800 fps = 13,700psi, The lead is arround 9.5 BHN with PCing.
You are using 3.6gr of Titegroup = about 27,600 psi (w 140gr bullet). That require a BHN of about 21 using non-coated lead.

Using PCing you will get away with using a much softer lead, somewhere around a BH of 15-16 is my guess. Lyman #2(5% tin, 5% antimony, and 90% lead) or Harball (2% tin, 6% antimony, and 92% lead).

If I have a soft lead say (BHN9) I would mix it 50/50 with Linotype Lead (BHN22) that will get you close.
The CUP pressure needs to match the Bullet Hardness.

[243winxb]

The mold drops right at .356 and I powder coated them and sized them to .3560"
Tap a oversize .360" bullet into the barrels throat. Measure. Size to .0005" smaller.

Looks like a different mold is needed that will produce a LARGER as cast diameter. Pure linotype can add as much as .002" to as cast diameters.

Fit is KING. (after adding some linotype.)https://www.thehighroad.org/index.php?media/free-bore-throat-diameters-in-9mm-luger.3612/full

[Thomas918]

Since you are getting a heavier bullet out of a mold made for 130gr is telling me you have a very high lead content. Probably close to pure. For example my 147gr mold out out 150gr bullets when using an almost pure lead mix but when using a hardball mix it puts out 145gr. Hardness is a larger factor in 9mm than alot of people say because 9mm is a fairly high pressure round. I had pretty bad keyholing before hardening my lead. Soft lead also leads to being sized down by the case when seated

[Thomas918]

I'm also using a Canik Rival.

[GregLaROCHE]

PCing shouldn’t be the problem. As mentioned, the hardness of the alloy or the boolit not large enough diameter, is most likely reason.

[hermans]

I have the same problem now with my 9mm keyholing after I started with a new powder for powder coating my 138gr MP bullets.
So I am sizing to .357 as I always have done. I am using COWW with a little lead added for stretch my alloy somewhat, the BHN measures 15 with my Cabine Tree Hardness Tester.
I have pulled a bullet and it still measures .357 exactly, measured with a micrometer, yet it keyholes when shot on a target at 10 meters.....
The only difference I could see is that with the new powder, the coating looks much thicker that with the old powder.....could too thick a coating cause this keyholing? When I switch back to my old coated bullets, I shoot a very tight group at the same distance.
I am looking forward to hearing your expert opinions, since I am at a dead end now with this problem.

[wv109323]

I did try a 124 Lee TC boolit. I powder coated and sized to .3570 and dropped the charge to 3.6g. of Titegroup. I only shot 10 rounds but no keyholes.

[243winxb]

9 mm 135gr LRN from Summit City with bad coating. Leaded the barrel on another forum. https://www.thehighroad.org/index.php?threads/barrel-leading-with-coated-bullets.920929/