I greet you from Argentina, problems with keyhole

[Ballester molina]

Hello, I am reloading for a bersa bp9cc pistol and I do not stop doing keyhole. I am using a bullet of rcbs # 9mm-124-CN, w231 3.9grains with an oal of 1.080 ".
If someone can give me some advice, I would be very happy and grateful!

[onelight]

Welcome to the forum .
You might tell us what size your are sizing to and lube you use and the over all length you load to , the more information these guys have the better they can answer .

[Ballester molina]

It It is dimensioned at 356 and the lubricant I do not know its composition.

[skeettx]

Hello Ballester molina
Welcome to the site
Two things,

First, what is the diameter of the bullet
after you seat it? You will have to use an inertial
puller and measure the bullet

Second, have you tried .357 diameter bullets?

Mike

p.s. I assume the barrel has rifling and is clean

[dverna]

Sometimes the brass case will reduce the bullet diameter during the seating process. Either starting with a larger sized bullet and/or a harder alloy will be helpful. Adding antimony is the least expensive way to get hardness. Your ratio of antimony to tin should be about 3 to 1....My alloy is 92 parts lead, 6 parts antimony and 2 parts tin. It is what commercial cast bullet makers typically use.

Welcome to the forum. My load is also 3.9 gr of 231 with a 122 gr bullet.

[wv109323]

I suspect that the bullet is too small for the bore.
That can be caused by three problems;
1.) The actual bore is over .355" and the bullet is not getting the correct rotation. This should be associated with lead in the bore after firing several rounds. This is where bullet hardness may matter. The harder the bullet the less likely it will strip the rifling and be more likely to rotate.
2.) While the bullet is being seated in the brass, it is being reduced in diameter. This is common because die manufacturers dimension their necking stems for jacketed bullets. Necking stems may be as small .352. Make sure you are belling the cases where lead is not being shaved during seating.
3.) You may be crimping the rounds so much that you are reducing the bullet diameter.
You may oil the bore and drive a bullet through the bore. If you do not have micrometers you can observe the depth of the rifling into the bullet.

[Ballester molina]

the size of the bullet is .356 and once extracted with the inertia hammer it measures 355.5
the inside diameter of the barrel is .353.5 "measured with a bullet through the barrel

[onelight]

That should be okay
Are you getting any lead build up in you barrel ?
I have had certain bullets that tear a target (looks like a keyhole ) that are not key holing particularly when fried at a bit of an angle to the paper but they shot good groups . They were almost always Semi wadcutters at low velocity.
How do you loads group compared to factory loads ? In that gun.

[Eddie17]

I size my 9mm cast boolits to .357. They work with good results in my 9mm hand guns!

[Petrol & Powder]

There's a possibility that .353" is not the groove diameter. I think the OP may be providing us with the bore diameter.

[nueces5]

Hello Ballester, I m from Buenos Aires, I have the same mould and also the same problems, I have already solved them. I am going to send you a private message, you can click on the top right.

[Ballester molina]

I just measured with a micrometer and it gives me a diameter of .354 "
Is it normal that in the place where the bullet struck the side, there was lubricant on the target paper?

[Petrol & Powder]

I can't say that .354" is wrong but it seems a bit small for most 9mm barrels.

Technically they should measure .355" but in reality, most measure a bit closer to .356"-.357"

Your bullet weight is in the right range for a 9mm. The keyhole effect (bullet tumbling when striking the target) suggests the bullet isn't being stabilized.
I would suggest you clean the barrel and try sizing your bullets slightly larger, like say .356".

[Ballester molina]

I can't say that .354" is wrong but it seems a bit small for most 9mm barrels.

Technically they should measure .355" but in reality, most measure a bit closer to .356"-.357"

Your bullet weight is in the right range for a 9mm. The keyhole effect (bullet tumbling when striking the target) suggests the bullet isn't being stabilized.
I would suggest you clean the barrel and try sizing your bullets slightly larger, like say .356".

thanks for your advice, the cannon is like a mirror! Something happens with the bullet because when I use a jacketed bullet of the same diameter as the cast, the keyhole disappears. Could it be the lubricant?

[Petrol & Powder]

Some guns with large bores will shoot jacketed bullets well even when the jacketed bullets are undersized. But those same guns will not stabilize an undersized cast bullet.

[Ballester molina]

unfortunately I have no elements to get a bullet with a larger diameter than .356 "
that same cartridge configuration but with another lubricant I have used a glock 17 with sactifactory results.
I no longer have this gun for testing

[Ballester molina]

can I use liquid allox lee lubricant for a bullet with a traditional lubrication groove?

[Ballester molina]

LLA as they call it on their payments

[skeettx]

Yes, you can

Cast the bullet, and if you can, use harder alloy
Then do not size, shoot as cast, and use the LLA
to lubricate the bullets.

https://www.youtube.com/watch?v=STfJ3qCi5tY

Mike

[Dusty Bannister]

thanks for your advice, the cannon is like a mirror! Something happens with the bullet because when I use a jacketed bullet of the same diameter as the cast, the keyhole disappears. Could it be the lubricant?

rcbs # 9mm-124-CN, w231 3.9grains with an oal of 1.080 ".
----------------
It is usually a good idea to have the cast bullet larger than the groove diameter. Key hole bullet impact is usually due to the bullet not filling the grooves of the barrel. Often this results in leading after several shots are fired. So several questions come to mind.
If you are somewhat experienced with cast bullets, you will know that most times, the bullet diameter must be larger than the factory jacketed bullet. The jacketed bullet shoots well, the cast bullet of the same diameter does not.

The bullet alloy needs to be sufficiently hard, but perhaps not too hard. Can the bullet be marked with a thumb nail? Easy to do or hard to do?

The bullet lube might be too hard and while it helps seal the bore, might not be sufficient for the 9MM . Not knowing what the bullet lube is, does seem to leave unanswered questions.

The RCBS cast bullet manual does not give a cartridge OAL, but it does show the following load data. Cast 09-124-CN 231 powder Start 4.5 grains, Max 5.0 grains. Your load is 3.9 Grains and that seems a bit low given the data for the RCBS manual. This is complicated by the data shown in the Lyman Cast Bullet Handbook for the same bullet giving 3.9 to 4.3 grains as the starting and max loads. The data was developed in different types of test apparatus and with a different bullet alloy. The Lyman data shows the cartridge oal of 1.050" and your oal is 1.080" so is making less pressure in the small case.

If you have fired factory rounds, then you know the ejector pattern and most likely the cast loads are not ejecting the cases as briskly as the factory. With a clean bore, after 50 shots, you are probably not that much undersized, and may just need to increase the powder charge in very small increments and watch for case ejection, primer cratering or other pressure signs.

It is always good to be conservative and always, always, always work up your load to reliable functioning and no more.