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Key Holing in targets Why is it happening?


markmeone

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I was at the range yesterday shooting IPSC with my Tanfoglio HC custom 38 super. I found that a lot of the rounds on the paper cardboard targets looked as though they are key holed. I use 9mm 125 grain SWC with 7.6 grains of ADI AP100 powder and the speed is averaged at 1320 fps (over the chronograph).
Why does this happen? The barrel is compensated and when checked for leading was pretty clean and only needed 4 strokes with the brass cleaning rod.
One of the other shooters suggested that I use a bullet lube on the projectiles, I have just recently bought these, they are polymer coated and he says that they can leave leading in the barrel.
Being a 38 super pistol should I use a 38 projectile instead as I was told that the 9 mm is used by most shooters???
How can I check which is better? Does the size of or diameter of the bullet make that difference? I think we are only talking about 4 thou difference between the 9mm and the 38 cal.
When I load with Winchester 231 4.5 grains behind a 125 grain projectile it goes fine with 1040 fps for minor power factor and I have not seen any tumbling with this load.
I have been thinking a different powder may be better to use and a 130 grain conical projectile with the AP100 powder.
Or better yet try out another powder. I have heard that the Vihtavuori powder N38 is a good one to use.
Any help would be much appreciated.
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Keyholing is a sign of an unstabilized bullet, I would suspect either the bullet is not engaging the rifling enough because it's too small, or..... you could have too hot of a powder load and the bullet is scraping over the lands of the rifling and not spinning. .004 difference in diameter is quite a lot. Slugging your barrel would tell you if the size is correct.

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I have been told that the crimp for 38 super is straight walled type and I have done that.

Slugging the barrel with my 9mm 125 grain SWC before slugging, the measurement is 0.357 and after the measurement is at its widest 0.355 and at its smallest is 0.347.

After slugging the barrel with a 38 158 grain SWC the size before was 0.358 and after it is 0.355 at its widest point, smallest is 0.347 allowing for the inside shape of the barrel.

I presume that this tells me that the 9mm bullets are on the small size by only 1 thousand of an inch? By using the 38 cal bullets I hopefully would have a more accurate bullet and no tumbling? I have loaded some of the 125 grain SWC projectiles with bullet lube on them to see if that makes any difference. I will have to wait until next weekend to do so, I will post the results then.

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I shoot a CZ SP01 Shadowline and an 85 Combat 9mm. When I started developing loads, I had the same issue. The culprit: OAL. Load your desired amount of powder and adjust your OAL to the maximum your magazine and chamber can handle. Hope this helps.

Safe shooting!

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Ok I have made the bullets 1.260 long as per the loading books and will try them out this weekend as well.

The projectiles that I use are bought ones with a polymer coating on them, at minor power factor loads they behave great, at major loads they tumble. Would a different powder be any good, I know that some of the shooters are using the Vihtavuori N38 for their major loads, and some heavier projectiles maybe 130 or 135 grain ones might be better???

The barrel is clean as it only took 4 quick strokes of the brass brush to clean it.

Mark

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What is the ID of the comp holes? IF the bullet makes ANY contact with the comp, bullets go wild.

What is the bullet diameter AFTER seating and crimping? You may be swaging the bullet down, particularly if you are only flaring the case mouth and NOT expanding the case ID.

For myself, the two most common causes of "keyholing," where you can see the side-on silhouette of the bullet through the target, are (1) the bullet is slightly too small and (2) damage to the muzzle crown

Also, you really need to use a 0.360" or larger slug of lead to slug your barrel. Anything smaller can give a false reading as the bullet hasn't actually been squeezed down enough to completely fill the bore.

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Hi Noylj

the compensator holes are actually slots, the compensated barrel came from Tanfoglio, it has 3 slots going across the end. Also screws onto the end of the barrel. I could not see any wear on the inside of the comp and no shavings of lead either.

I did put in a previous post: After slugging the barrel with a 38 158 grain SWC the size before was 0.358 and after it is 0.355 at its widest point, smallest is 0.347 allowing for the inside shape of the barrel.

I think that a new powder might be on order and a different weighted projectile, maybe a 130 or 135 grain conical should do it.

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With BBI 147 9mm I have witnessed keyholing. It was determined the keyholing was entirely caused by having too much crimp. Once the crimp was lightened just a bit, there was no more issue. Coated bullets (and lead) cannot handle a strong crimp like jacketed (and plated to some extent). Seems that would be an easy thing for you to test.

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The brand name of the projectiles is Hawksbury River from Australia, they are very popular here and have been fine before. As for the crimping I have let the crimp be a straight type of one. I did have a curved crimp but was told that the 38 super only needs a tapered crimp which I have done. Even with these rounds that key hole.

I have looked at the end of the compensator and see no leading or wear marks at all.

What powder do you think would be good for the 38 super? This powder I am using now I have nearly finished so I am going to try out another one. A different brand altogether maybe Vihtavuouri or any ideas??????

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I am currently using Vihtavuori 3N38 in my SVI but I am using Berrys projectiles.

Depending on where you are it may be hard to find any 3N38, I know there are some shops selling 500gm bottles around the $72 mark.

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I was thinking that maybe just doing the minor loads with the compensator and scope would be OK, may end up doing that as its just as easy to do rather than trying to find the perfect load for major. The old Vithavuori is expensive these days. I'll have a think on that after the weekend shoot and see what that brings.

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What is the ID of the comp holes? IF the bullet makes ANY contact with the comp, bullets go wild.

What is the bullet diameter AFTER seating and crimping? You may be swaging the bullet down, particularly if you are only flaring the case mouth and NOT expanding the case ID.

I would look at Noylj's suggested causes, first. My money is on the second one.

When you get it solved, let us know what it was.

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Bullets can hit a comp and not leave any evidence. It's sometimes very hard to tell. The only time my open gun ever key holed was when my comp had worked loose.

+1. Happened to me two years ago at Area 6, what a horrible day.

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Bullets can hit a comp and not leave any evidence. It's sometimes very hard to tell. The only time my open gun ever key holed was when my comp had worked loose.

+1. Happened to me two years ago at Area 6, what a horrible day.

Yeah, I forgot to mention that along with key holing it was patterning like a shotgun.

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Could the comp be gas cutting the polymer? Maybe a flap developing? Anyway you can recover a fired bullet (shoot into a barrel of water or wet phone books)?

From Precision's (coated bullet) website: "Can I use Precision Bullets in my 9mm / 38 Super "Open" pistol?

NO—we don’t recommend our bullets for compensated guns. When the bullet passes through the compensator, the gases are diverted and will cut the base of the bullet causing way too much smoke and leading. Stick with JHP’s."
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I tried out the major loads with the standard barrel and no keyholing what so ever. I tried out different loads (minor with the standard barrel) and no problems. I went back to the compensated barrel and the same thing happened with the major loads. So now I am going to try out polishing the inside the compensator and go from there??? This was told to me by another shooter, I will try out different loads again. I have some 38 cal 130 grain SWC and will try them out with the compensator and major loads again.

The lubed SWC made no difference, they still key holed. I lubed up some polymer 125 grain SWC to try out.

The AOL rounds (1.260 thou as per the loading book) were no good either as they keyholed as well.

I will keep trying.

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I tried out the major loads with the standard barrel and no keyholing what so ever. I tried out different loads (minor with the standard barrel) and no problems. I went back to the compensated barrel and the same thing happened with the major loads. So now I am going to try out polishing the inside the compensator and go from there??? This was told to me by another shooter, I will try out different loads again. I have some 38 cal 130 grain SWC and will try them out with the compensator and major loads again.

The lubed SWC made no difference, they still key holed. I lubed up some polymer 125 grain SWC to try out.

The AOL rounds (1.260 thou as per the loading book) were no good either as they keyholed as well.

I will keep trying.

I'd suspect the answer is in post 22, maybe the cutting action they describe only happens above a certain velocity.

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