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Discussion Starter · #1 ·
I wasn't sure where to put this or how to title it, so here is the puzzlement:

When "we three" were doing very up close and personal point shooting the other day, starting about 2 feet away and getting that first shot off "immediately" while moving at a diagonal away from the target and continuing to shoot for a total or 3 or 4 rounds only:

One friend's gun (9mm Taurus compact) left definite black pinwheels around each hole. Obviously the bullet was spinning (doh) but that amount of carbon or whatever black in that particular pattern is something I've not seen. It is also not what our other guns do in the same scenario. My P238 leaves very tiny specs all over the target which I think is probably normal for really up close shooting. The .22lr semi autos oftern leave black carbon around the hole, but it is a circle.

What can cause this pinwheel marking? She does keep her guns clean. That Taurus is one that her husband bought for her, not one she picked out, which should not have anything to do with the carbon pinwheel designs. No I did not take a picture. I can't find anything even close on a web search of gunpowder residue patterns or gunshot residue. Pictures of round carbon marks, mostly halo effect, yes and even one that looks like a calidoscope but nary a definied pinwheel.

Yes, that is a different kind of "carbon footprint"..........from the usual thing you will find in a web search. LOL

Any ideas? If this is a defect she needs to know.
 

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Interesting observation, SG, but it doesn't seem too surprising. If the twist in the barrel is sufficient to get the bullet spinning very quickly, I can see it happening. I guess I am more surprised that this isn't seen more often at very close ranges. Perhaps it has to do with a slower burning powder - I can see where that would make a difference as well, or a combination of the two.
 

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Discussion Starter · #3 ·
Interesting observation, SG, but it doesn't seem too surprising. If the twist in the barrel is sufficient to get the bullet spinning very quickly, I can see it happening. I guess I am more surprised that this isn't seen more often at very close ranges. Perhaps it has to do with a slower burning powder - I can see where that would make a difference as well, or a combination of the two.
Or could it be possible that with the shorter barrel the bullet is NOT spinning as quickly and therefore is slow enough to leave the pinwheel effect? I took one (hanging from twine) bottle but it was really hot and we were all getting exhausted, so I was the only one who chose to waste some expensive ammo putting holes in it while moving hither and yon. I wonder if that Taurus would also have left the pinwheel debris on the milk bottle plastic. ???

It really is an interesting puzzle. I wish I had asked her for her target or even better asked one of the other two to take a picture before the pinwheels go pasted over! I also notices a couple weeks ago that she had a few keyhole holes - at least I think it was her. But I have no idea which gun she was shooting that time. I've had my share of keyoles so didn't think much of it since there were just a few.
 

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Good point - not spinning as quickly might be the thing; centrifugal force is not enough to "throw" the particles our of the trajectory. Will be interesting to see your observations on the next outing.
 
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Discussion Starter · #5 ·
Good point - not spinning as quickly might be the thing; centrifugal force is not enough to "throw" the particles our of the trajectory. Will be interesting to see your observations on the next outing.
Unfortunately with the weather predicted to be way too hot for "we three" old ladies, we will be shooting at the indoor range for the rest of this month and maybe longer if we don't get a cool spell. My health issues prohibit me from getting to the range at 8:30 or 9 AM before it gets too beastly hot outside and my two friends defer to my needs. They are wonderful women!

Last year, with ShooterGramps in the hospital so much, and needing almost constant home care for more time, I didn't get out all that often. The two of them did continue to go every week, super early on hot days, and sent me detailed reports on what all they did. As said: they are wonderful women.
 

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I’d wonder what ammo the 9mm was using. I’d try different ammunition just as a thought.
Or have everyone use that same ammo and compare.
I know SG only shoots .380 and .22 now. Get Gramps to try different 9mm pistols. More fun investigation.

BTW praying for y’all’s health.
 

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Good point - not spinning as quickly might be the thing; centrifugal force is not enough to "throw" the particles our of the trajectory. Will be interesting to see your observations on the next outing.
A bullet is generally spinning 20,000-30,000 RPM. Sure it only spins 1 time per so many inches as per the rifling. 1:24 is optimum for the 9mm so it makes one revolution for every 24" it travels.
 

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my thoughts on this go toward what ammo she was using. I shoot some target grade 22 ammo that leaves a halo. I don't know if its a wax lube residew or the lead bullet that marks the target. I have had scorers use the halo as the bullet hole and lost a few points because of it.
I have never seen it with copper bullets. DR
 

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Discussion Starter · #10 ·
I’d wonder what ammo the 9mm was using. I’d try different ammunition just as a thought.
Or have everyone use that same ammo and compare.
I know SG only shoots .380 and .22 now. Get Gramps to try different 9mm pistols. More fun investigation.

BTW praying for y’all’s health.
Gramps shoots my former G19 and also his RIA 1911 9mm. He's finding (in his old age) that the lower calibers are more fun to shoot - but do not tell him I said that or I'm in deep doo doo! He's not about to give up his .40 cal or .45acp's - not now and most probably not ever.

I'll ask my friend what 9mm ammo she was using the other day in that Taurus. She might or might not remember.
 

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As others suggested, I think it is unburnt or partially burnt powder from slower burning powder. Slower burning powder combined with a shorter barrel?
 
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