Keyholing then not keyholing

[nemesisenforcer]

Bought a Zastava M70 (Tokarev platform) 9mm that I was putting cast boolits through (Lee 124 grain round nose tumble lube).

They were keyholing something severe 9/10 times. Figured something was off with the mold so I put it aside and just shot cheap factory ammo through it until I got around to fixing it.

Fast forward to last week. I had several dozen boolits left that I didn't shoot up. I decided to try and experiment. I loaded up some sized and and left some as cast .5cc of Unique and CCI primers (same recipe as before I believe.)

My dad has a nice little Walther P1 and we took both out and ran both kinds of boolits through them.

Results: no keyholing out of either pistol with either variation.

Literally nothing changed. Same batch of bullets, same recipe, same barrel, just some fresh lube (Lee Alox) for good measure.

FWIW, as cast they were coming out about .360, sized .356-7 straight WW alloy.

Thoughts?

[runfiverun]

Time.
things happen over time.
1 they reached their final BHN.
2 antimonial alloys can grow larger slightly over time.

the other possibility is the tumble coating was just enough increase to make them work.

[GhostHawk]

Age hardened? Firmer alloy = better grip.

[6bg6ga]

My opinion here.... If they are keyholing they are undersized for the barrel. Another opinion... hardness has nothing to do with keyholing. I've shot everything from straight lead to lead with a hardness of 20 and as long as it was sized correctly for the barrel it worked for me. I've had keyholing with undersized bullets and leading associated with that.

[Traffer]

If you fresh lubed over old lube, it may be that the old lube dried well enough so that you ended up with a more sticky, thick coating. That is all I can think of.

[William Yanda]

"Literally nothing changed."

In addition to the alloy ageing, and fresh lube, a second change, you mention shooting other ammo. How much other ammo. I am not calling you a prevaricator, but I believe you meant "literally nothing except........".
With respect,
Bill

[6bg6ga]

I think its time to slug the barrel and go from there. I think your going to find that the M70 is going to be on the large side of the normal 9mm size.

[runfiverun]

key holing is a function of stability.
your either spinning the boolit fast enough to be stable or you ain't.
the grip on the rifling [and speed] will determine whether your spinning the boolit enough or not.
too small = skidding and non stabilization. [usually accompanied by smoke and leading]
too soft= skidding and non stabilization. [usually accompanied by leading]

[tazman]

My opinion here.... If they are keyholing they are undersized for the barrel. Another opinion... hardness has nothing to do with keyholing.

My experience and testing directly contradicts those statements. My test was to air cool some boolits from the same pot of metal that I water dropped the rest. I was wanting to check on expansion.
What I found, was the air cooled(softer) boolits keyholed 50% of the time while the water dropped(hardened) boolits shot fine. As it happened, I didn't get leading from either batch of boolits.
All the boolits were shot as cast and tumble lubed. Both batches measured the same diameter(.002 over groove). What few boolits I was able to recover displayed skidding with the softer boolits and none with the harder ones.

[6bg6ga]

Well I guess we will have to agree to disagree. I've kept track of a number of bullet casting runs. I've air cooled a batch of bullets and I've also water dropped a batch and when properly sized saw absolutely no difference. Tazman I'd be more than happy to meet up with you some time and do some experiments. Like I said I've shot everything from 5 brinnel hardness to about 20 as verified by my cabine tree hardness tester. I've keyholed nothing when properly sized to the barrel. If there is some printed research you cn point me to tht I can read I would appreciate it. Note* everything I load with lead is kept below 1000fps.

[Victor N TN]

How has the weather changed? If the temperature has changed... Maybe they reached a higher muzzle velocity and were able to stabilize. With rifle jacketed bullets sometimes they have to reach a higher speed to "calm down."

[tazman]

Well I guess we will have to agree to disagree. I've kept track of a number of bullet casting runs. I've air cooled a batch of bullets and I've also water dropped a batch and when properly sized saw absolutely no difference. Tazman I'd be more than happy to meet up with you some time and do some experiments. Like I said I've shot everything from 5 brinnel hardness to about 20 as verified by my cabine tree hardness tester. I've keyholed nothing when properly sized to the barrel. If there is some printed research you cn point me to tht I can read I would appreciate it. Note* everything I load with lead is kept below 1000fps.

The ones I tested were all 38 special. I was using an NOE 360-150-SWC mold. The Revolver was a S&W model 15 4 inch and a model 14 6 inch. Loads were Bullseye 3.5 grains and CFE pistol 5.0 grains. Both of those are standard velocity loads. CFE gave me about 925fps the Bullseye load was a bit slower.

Where about do you live? I am about 40 miles south of the quad cities.

I can't say that I have ever seen any research on this topic. My own tests were done by accident more than a formal process since I was trying to test for expansion and had the keyholing issue. The alloy was range scrap which is hard to say exactly what it contained. I did use the same pot of alloy for both sets of boolits. I have no means of testing the BHN of any of this. The water dropped set cannot be scratched with my fingernail.
This all took place a couple of years ago. The boolits have all been recast since they didn't work for me. They may have worked just fine with lighter loads. I didn't try that since I was trying for a serious self defense boolit at the time..

[tomme boy]

My opinion here.... If they are keyholing they are undersized for the barrel. Another opinion... hardness has nothing to do with keyholing. I've shot everything from straight lead to lead with a hardness of 20 and as long as it was sized correctly for the barrel it worked for me. I've had keyholing with undersized bullets and leading associated with that.

Try shooting air cooled WW alloy in a 9mm TL design and come back and tell us what happened. Size and shoot them the same day.

9mm Lee TL molds are complete garbage. The lead hardened up as they sat. That was why they did not tumble the second time. Lee specs their molds with Linotype. You can make lube and shoot a TL in 9mm with lino the same day. Otherwise you need to water drop the WW alloy or whatever lead you have needs to be adjusted for a harder alloy. There is not enough bearing surface on the 9mm so the bullet is stripped going down the barrel.

[runfiverun]

Note* everything I load with lead is kept below 1000fps.

that could be where we differ in the opinion.
generally diameter and shape are king of how things work, but it depends on the launch.
I don't shoot much of my lead below 1,000 fps except the target type 38sp. rounds or the 45 acp stuff.
when you start working towards 23-2400+ fps fitment and flow [mechanical fitment and static fitment] mean a whole ton but you have to be able to hang on to the rifling too.

long bore rider boolits are the ones that really need the alloy strength and nose diameter to get them where you want them.
they rely on that nose that barely engraves the rifling to get things turning and aligned with the barrel.

there are other way's and parts of other designs that do most of the work such as in the AR rifles.

pistol designs are closer to Revolver caliber lever gun designs than most realize [I generally use lever gun or near lever gun designs in the pistols]
they rely on the nose for alignment AGAINST the rifling not IN the rifling and really rely on drive band engagement to stop the barrel up and get things spinning.

you can't really directly compare one system against another.

[nemesisenforcer]

"Literally nothing changed."

In addition to the alloy ageing, and fresh lube, a second change, you mention shooting other ammo. How much other ammo. I am not calling you a prevaricator, but I believe you meant "literally nothing except........".
With respect,
Bill

ntothing changed with respect to the recipe i was using. I shot a couple hundred factory jacketed rounds, true. Maybe the bore smoothed out or got more uniform?

[runfiverun]

possible.
you might have just scraped some 'bad' out of the throat.

[nemesisenforcer]

My experience and testing directly contradicts those statements. My test was to air cool some boolits from the same pot of metal that I water dropped the rest. I was wanting to check on expansion.
What I found, was the air cooled(softer) boolits keyholed 50% of the time while the water dropped(hardened) boolits shot fine. As it happened, I didn't get leading from either batch of boolits.
All the boolits were shot as cast and tumble lubed. Both batches measured the same diameter(.002 over groove). What few boolits I was able to recover displayed skidding with the softer boolits and none with the harder ones.

Good to know some things never change

[Lloyd Smale]

never saw the barrel quality, hardness level or even finished size of a cast bullet cause tumbling. Ive seen them all cause poor accuracy though. Tumbling is a sign of instability. Instibility is 99 percent of the time running a bullet to slow through a barrel that is twisted to slow. I guess its possible your barrel smoothed out and was shooting faster but I doubt you gained much speed and if you like you claimed saw bullets tumbling BADLY I doubt a few fps would make a difference. Ive also NEVER saw alox change a thing other then accuracy. If velocity changes between it and a conventional lube its a very small change. Now if you were going from coated bullets (that tend to be a bit slower then lubed bullets) to a lubed bullet I might concede 50 fps. Ive have two guesses. First is those first bullets that had alox contaminated your powder charge in some of those shells. I would have been great if you could have chronographed some of them to see if there was a swing in velocity in them. that or your powder drop wasn't doing a consistant job of putting out powder charges or was set lower and you didn't remember or realize it.

[Ballistics in Scotland]

Keyholing is also a function of concentricity, and hardness can have a lot to do with that. In a different context, I tested a .303 barrel with .308 Sierra softpoints, and I found that some would shoot rather accurately, with the rifling engraved shallow but even all around. (There would undoubtedly be gas escape, most harmful to a good barrel, but this was one I was about to discard.) But around twice as many would engrave to normal depth on one side, with little or no traces on the other. That extremely fast rotation had been enough to crush them against one side of the bore, and those were the ones that keyholed. More moderate eccentricity of the bullet mass would in theory produce regular straight-line deviation, but above a certain limit it turns into a wobble or corkscrew, or deteriorates into tumbling.

[Lloyd Smale]

I will concede that to soft of a bullet through to fast of a twist can cause instability due to the bullet stripping through the rifling and not getting the spin it needs or deforming the bullet. But that would be in the case of a lot more pressure and velocity then a 9mm developes.