Anybody every heard of this practice - intentional dimpling of a bullet mold

[curioushooter]

I came across a nice mold on Ebay that appeared to have a pin hole dimple on one cavity. I asked the seller if that was a piece of debris or really a dimple. The reply was that it was intentional--to facilitate easy sorting bullets for accuracy loads.

I have a hard time believing this. It is a two-cavity Redding-SAECO mold, the best I've used, and each cavity cut from with the same cherry one at a time. They will be as nearly identical as possible. And if you were really that demanding of consistency then why not just pour only into the top or bottom cavity when you cast. Why damage one of the cavities?

Or is this some sort of weird practice that I am puzzled by?

It's a shame because it is fine mold otherwise.

[Larry Gibson]

Used to be a common practice for the reason mentioned.

[MT Chambers]

yes, you use it to orient the bullet in the case/bore, prolly used more for breach seating.

[country gent]

It was and is common practice to ID cavities of multi cavity moulds for several reasons. Mostly its done with rifle bullets. I used a O on the nose of one cavity and the other bare. But a dimple, X, 8, Z or other mark ( I preferred marks that were even around nose) works. The reasons for this were
1) it allowed for sorting by cavity into "lots" with each cavity shot as a individual. This lowered weight variations and variances in shape and form.

2) It allowed for orienting the bullet. Case bullet oriented when loading then oriented in chamber.

3) it helps when trouble shooting fliers, if a "lot" shoots good sorted but groups open when mixed its obvious.

[5Shot]

I use it on molds with different weights but the same nose profile. That way I can differentiate the loaded rounds.

[Bazoo]

In the art of bullet casting book, Mike Venturino, when he was younger, wrote an article where he tested the accuracy of each cavity of a multiple cavity mould. He did it with a revolver but using the same chamber for each. He tested several moulds and found that indeed the bullets from a single cavity can shoot better than their identical brethren. Some he found had no difference while some he found a pretty substantial difference in group size. He also found that the poi would change very slightly sometimes.

If anyone has any links to similar studies I'd love for you to share as it fascinates me.

Bazoo

[John Boy]

Mike Venturino, when he was younger, wrote an article where he tested the accuracy of each cavity of a multiple cavity mould. He did it with a revolver but using the same chamber for each. He tested several moulds and found that indeed the bullets from a single cavity can shoot better than their identical brethren. Some he found had no difference while some he found a pretty substantial difference in group size. He also found that the poi would change very slightly sometimes.

This was before molds were cut with CNC software & computer cutting of the molds. I shoot Accurate Mold 2x cavity bullets cut with a CNC computer program out to 1000yds and there is no difference which cavity they came from

[gwpercle]

Some used the resulting tiny bump to orient the location of the boolit/round in the chamber .

I've even heard you were supposed to use your thumb nail to remove the tiny bump prior to chambering and firing it so the bump would not cause any imbalance in the boolit thus damaging accuracy .

Seems like it was done mainly with cartridge loaded ammo but may have been used with muzzel loaders also .

Gary

[stubshaft]

I have dimpled a lot of my molds for the reasons stated above.

[Dusty Bannister]

I have purchased a few molds that have this feature. My abilities and my equipment fails to raise any concern about affecting the target groups.

[Bazoo]

One of these days when I'm in the notion I'll test my 31141 and see if I can detect any difference.

Is there any moulds that are not cut with CNC machines today?

[upnorthwis]

I loaned a SAECO mold out and when returned it had dimples. I did not ask him to do this. But since they were there I shot them separately and there was no difference. I do not do this to my other molds.

[curioushooter]

I still don't get the point. The bullet will rotate even in the slowest twist barrel for this caliber (.358). Why should the starting position of the bullet matter? Couldn't the sprue be used to do this as well? They have a single direction. This is a heavy handgun boolit design for silouette or perhaps 35 Rem. It's not some 1000 yard bench rest design.

And if one wants single cavity consistency (I sincerely doubt there is practical difference with a modern quality mold) just pour only in one cavity.

He could have at least dimpled on a driving band so it would be erased by the lube/sizing operation, but the ogive was dimpled, potentially effecting both geometric and aerodynamic balance adversly.

The mold left the SAECO factory identical twins, but that wasn't good enough so punching one in the nose hard enough to permanently disfigure one twin was deemed necessary so they won't be identical anymore...

In short, a rude thing to do to a fine mold IMO.

[Texas by God]

I have a Lee C309150F 2 cavity mould. I size them .309". The bullets from one cavity go thru the sizer easier than the other. If I marked one, I could separate them and see the difference. Or not. Unsorted, they shoot very well so I'll just shoot them.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[bedbugbilly]

Just because it's a double cavity - or multiple cavity - doesn't mean all cavities are created equal. I've seen lots of "dimpled molds" over the years. Personally, I'm not that worried - cast 'em and shoot 'em - but it's like anything else - to each their own and some are more OCD than others. If there were THAT much difference between two cavities - then I'd be shucking the mold away and going to a single cavity - where each one would be (in theory) "equal".

[KCSO]

Everything matters in the quest for accuracy. Case orientation bullet weight and orientation, flash hole size and chamfer and on and on in the quest for the most accurate round. I have never found a small dimple on the side of the bullet to cause a problem so I don't peel them off when loading.

[dverna]

I used a 10 cavity mold when shooting Bullseye. Imagine marking each of those cavities and sorting the bullets and reloads? Sometimes common sense is needed.

Most commercial bullets are coming from 16 cavities. Good enough for the shooting most people do....or are capable of. Sometimes good enough is good enough.

But for ultimate accuracy, consistency is paramount. Understand why molds would be dimpled to aid sorting. Goes against my grain to purposely add even a minor defect to a mold and bullet...but it must work. Just not my thing with cast.

[MT Gianni]

In general it would only matter at long ranges. Most of target accuracy is not how much powder you have in the case. It is the case itself, how little it expands to fit the chamber, how uniform the flash holes and neck tension. It does little or no good to orient the bullet in the case if the case is not marked so the bullet goes in the exact same position, the cartridge is loaded into the bore in the same position and the same technique, [elavating, or lowering the muzzle] is done every time. As it was found to make a difference the practice continues.
Consider a spark plug cap to be like our bullet. The car runs just fine if the gap varies by as much as 0.005". It might make all the difference in the world to a performance car where every part is balanced and the engine blueprinted if that gap difference was eliminated.
Many of the older schutzen matches were shot with only one case. You can be sure all items were indexed and it went on for decades. For the size of a pistol X ring if you think it makes a difference I won't argue but will when it comes to a 600+ yard target.
I think you could drill a 1/16" hole, 1/16" deep in the nose and it would not affect a 25 yard ppc target, don't worry about a pin prick. If however the "flaw" was at the base the mold is trash.

[Green Frog]

I still don't get the point. The bullet will rotate even in the slowest twist barrel for this caliber (.358). Why should the starting position of the bullet matter? Couldn't the sprue be used to do this as well? They have a single direction. This is a heavy handgun boolit design for silouette or perhaps 35 Rem. It's not some 1000 yard bench rest design.


And if one wants single cavity consistency (I sincerely doubt there is practical difference with a modern quality mold) just pour only in one cavity.

He could have at least dimpled on a driving band so it would be erased by the lube/sizing operation, but the ogive was dimpled, potentially effecting both geometric and aerodynamic balance adversly.

The mold left the SAECO factory identical twins, but that wasn't good enough so punching one in the nose hard enough to permanently disfigure one twin was deemed necessary so they won't be identical anymore...

In short, a rude thing to do to a fine mold IMO.

Back in my active SCHUETZEN days, especially at the ASSRA Nationals, it was common practice to put a dimple on the bullet so that each time a bullet was breech loaded into the single chamber, it was in the exact same orientation so each bullet started down the bore the exact same way each time. The more alike each shot can be, the more consistent your performance on the target... or so the story went! BTW, a chamber cut with a a cherry (or for that matter, with any method) is still a mechanical accomplishment, but then it will also be expected to have a mechanical variation.

Froggie

[cas]

This was before molds were cut with CNC software & computer cutting of the molds.

I've had at least two molds in recent years that were off (and I'm not a big caster who buys tons of molds) , so it can still happen.