PC gives me 30% keyhole while shooting

[philproulx]

hello

i have started to do PC dry tumbling with PBTP graphite black
my bullet passes the smash test on both axis

but when i'm shooting 10 shot sroup at 10 yards , i have 7 shot touching each other and at lest 3 flyers
and at least 2 are doing keyhole

i'm shooting a glock 35
bullet are lee tumble lube 175 gr
5'0 gr UNIQUE @ 1,130 oal

i'm starting to wonder if the micro-groove from lee is not suited fo PC
they are sized to .401

should i go .402 or swith to a conventional 1 grease grove mold

thanks

phil

[Love Life]

Are you getting severe leading? What you are describing is usually caused by severe leading.

[BadCarp]

The Lee tumble lube boolets work fine for me in .45 when powder coated, but I'm putting them thru 1911's or my XDs. I thought Glocks didn't like cast boolets at all? I know I've heard that before, but as I'm not a Glock fan, I've never had to deal with it.

Are you getting far better results with the same exact setup and just tumble lubed with no powder coating?

[ipijohn]

I shoot 9 MM, 38 Spec, 40 s&w, 45 ACP, 41 Mag and 44 Mag Lee TL boolits that are ESPC coated with zero leading. I am using many different powders and size B4 and after coating to the same size I was using when I was tumble lubing.

[Love Life]

I have shot a whole bunch of cast through a couple 9mm Glocks and 45 acp Glocks with factory barrels. Please do no perpetuate a rumor here.

[HATCH]

for the OP, are you having those issues when you tumble lube or regular lube those exact boolits?

[popper]

ESPC both of the Lee boolits with no problems in my XDm, not a glock. I suspect leading from seating shaving, sometimes hard to notice. You get 7 good then 3 bad? IIRC 5 gr is midrange so your alloy may also have an effect. TLPC you have to inspect to make sure the coating is complete on the bands, a little tougher for the TL boolit. If you don't have complete fillout on the TL Lee, even PC will give small boolits = tumbling. Oh, 402 in mine produces leading due to chamber shaving.

[jmort]

Glock says no cast Boolits, but they are the manufacturer and it is a CYA to avoid liability for a kaboom. Lot of owners shooting cast Boolits from stock Glock barrels. Like everything use common sense and check for leading. Polygonal rifling is not ideal for accuracy and especially for cast Boolits, but many use Glocks for cast Boolits, just be careful and watch for leading.

[BT8850]

i'm starting to wonder if the micro-groove from lee is not suited fo PC
they are sized to .401

should i go .402 or swith to a conventional 1 grease grove mold


phil

Don't have any experience with the micro groove bullets but if you do switch to a one groove style the Lee .401 175tc mold has been working great for me when tumble powder coated and sized back to .401. Im running book starting loads using longshot. Accuracy is the same as shooting jacketed with zero leading. As for the no-cast-in-glocks myth, I can say that the bullets I've mentioned have been fired in a gen 2 glock 22 and gen 3 glock 20 with factory barrels with ZERO problems. Take it for what its worth Good luck!

[philproulx]

well
i only did 1 coat and i do have spots where paint is missing on the groove
i might have to do 2 coat

[philproulx]

well
i only did 1 coat and i do have spots where paint is missing on the groove
i might have to do 2 coat
and yea it gave me lots of paint flake in the barrel

[Boogieman]

Are you over crimping? a too tight crimp will scrape the PC off when fired. using a Lee FCD can cause this also. Pull one of your boolits to see if the coating is damaged. Seating & crimping in one step can cause that too. I had this problem with my first PC'ed boolits it was from using a Lee FCD die. went to their old style taper crimp die, pro blem solved. that was in a Colt 45ACP Lee 158gr.TL PC'ed tumbled when shot out of a 357 mag. untill I put a gas check on it. I think it was gas cutting through the narrow base band at higher pressure. 40 cal. run hot that could be your problem.

[bangerjim]

I shoot both std and micro boolits from a 9mm S&W and 40 XDm.....no problems. All have been ESPC (matte black!!) up to now. No leading and decent accuracy......for a semi. Have not noticed any significant decrease in grouping with those vs FMJ commercial rounds.

I thing OP has other problems as mentioned above in several posts.

I seriously doubt it is the PC causing the grouping problems. (no rumors allowed!)

bangerjim

[philproulx]

i pulled out one boolit and there's no crimp groove and the coating still intack

might be my casting method maybe i was casting too cold

[popper]

Look at your naked sized boolits and see if they are sized all the way around. Inspect the ones that don't take much force to size. Yes, the FCD can size them smaller.

[oldpapps]

'Keyholeing' is a result of loss of stability. But just why is this loading loosing stability?

Bad barrel, leading of the barrel, improper twist for the load, rifling too shallow for the bullet at the velocity?
To the bullet/s. Improper fit, too long for the twist, to slow for the twist, too hard/soft to take the rotational motion from the rifling.

I'm going to by-pass the barrel being at fault for the time being. And look only at the bullet combination. Roughly 30% failure rate at the tested range.

Start by eliminating the 'flaking' of the coating. Check the cure time and make certain that the bullet surfaces are very clean and dry (no oils or grease).
Increase the velocity a little and re-test.
Check the bullet to bore fit (slug your barrel and compare, 1 to 3 thousands larger bullet to bore).

If the bullet fit is right and pushing a little faster doesn't reduce the failure rate, options are getting slim.

Here is a formula that may help determine the instability problem.

Just copy this and paste it into a spread sheet (block C1 is a good option).

=(30*+C5)/((+C7/+C4)^2*+C4^3*+C6/+C4*(1+(+C6/+C4)^2))*(+C8/2800)^(1/3)*((+C9+460)/(59+460)*29.92/+C10)

Then copy and paste this (to make it simple, put the 'Where' in block E2).

Where:
Sg - is the stability coefficient and should not be less than 1.4, but more is ok
C4 - Caliber in inches (.223 for both .222 and .223)
C5 - Bullet Weight in grains
C6 - Bullet Length in inches
C7 - Barrel Twist in inches per turn
C8 - Muzzle Velocity in fps
C9 - Temperature in degrees F (59F normally used)
C10 - Pressure in inches of mercury (29.92 normally used)

This will put the variables in the 'C' column from row 4 to 10. The numbers will have to be typed in to the 'C' column. The location that you put the formula will display the final calculation value.

It is not that hard.

I hope this helps a little.

OSOK

[popper]

lots of paint flake in the barrel

Caused by shaving when loading OR getting scraped by the chamber/throat edge OR sized too small.

[prickett]

hello

i have started to do PC dry tumbling with PBTP graphite black
my bullet passes the smash test on both axis

but when i'm shooting 10 shot sroup at 10 yards , i have 7 shot touching each other and at lest 3 flyers
and at least 2 are doing keyhole

i'm shooting a glock 35
bullet are lee tumble lube 175 gr
5'0 gr UNIQUE @ 1,130 oal

i'm starting to wonder if the micro-groove from lee is not suited fo PC
they are sized to .401

should i go .402 or swith to a conventional 1 grease grove mold

thanks

phil

I got keyholing twice:

once from too soft of lead (skidding down the barrel)
and once from being sized too small

[popper]

What Prickett says. Had a problem with some 9mm not chambering (HiTek coating). Instead of pulling them I ran them through the case sizer again. All tumbled @ 7 yds. Your load is not low pressure like a 45ACP. I also shot some 40SW with 20:1 tin. Nope, don't work. Too soft for the psi & get sized too small, no springback. Even with moderate leading (coating failure on my part), accuracy doesn't appear to degrade much. IMHO you need to QC your coated boolits better.

[philproulx]

i cast with wheel weight
so i need to discard the boolits that past too loose in the sizing die?

when you say QC you mean...?