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Help me understand 9mm keyhole issue


MilkMyDuds

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I am loading with 147gr (.356 dia) plated Xtreme, 3.2gr Titegroup. Shooting out of my MP9 Pro 5''

I am noticing that at 10+ yard distances, some rounds would keyhole on the targets. It is true the range is very windy most of the times, with the targets swinging pretty widely. However, same swinging targets do not show much keyhole issues at 7 yards.

Is it safe to say that my reloads are having keyhole issues? Are there accuracy issues if the bullets keyhole, specifically for USPSA/IDPA distances (mostly 20 yards or shorter)?

What would cause the bullets to keyhole, e.g. tumble?

1. Crimping too much - this is certainly possible, as I am using mixed head stamp brass. Some are soft, and others are hard. The same crimp die setting leaves crimp line on hard (thick) brass and no crimp line on soft brass - this I have verified by pulling the bullets out of different head stamps reloads.

2. Seating too shallow - the bullets have to jump too far into the rifling causing it to tumble. Is this a valid theory?

3. ???

Thoughts?

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What kind of targets are you shooting? Are you sure that the targets aren't just ripped in a weird way that makes it look like a keyhole. Do you see a complete round grease ring, but the cardboard is ripped making it appear like it is key-holing?

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What Barrel are you using?

Crimp is a common issue for this.

what is the OAL you are loading to now? and what is the max your chamber can accept (have your measured this out)?

Is the barrel dirty (yep the standard 1:16 twist of the M&P when dirty can cause this).

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I am using standard IPSC cardboard targets. KKM barrel - not exactly sure what's the max. How do I go about measuring it?

OAL is generally in the 1.140 range, depending on different head stamps there are variations. (BTW - I load with Dillon SDB)

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What kind of targets are you shooting? Are you sure that the targets aren't just ripped in a weird way that makes it look like a keyhole. Do you see a complete round grease ring, but the cardboard is ripped making it appear like it is key-holing?

Most rounds have the grease rings on the target, even for the ones that keyhole. 1-2 out of 10 rounds would not leave any rings, but just a huge ragged line.

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KKM barrels have a 1:20 twist, and are best shot with 124gr projectiles.

You make a chamber gauge by taking a case, drill out the flash hole, get a fine thread bolt and a matching nut. glue the nut to the back of the case so that it does not interfere with the case being inserted into the chamber with barrel out of the gun. Thread the bolt the nut and into the case, glue a projectile to the bolt making sure that it is a straight as possible. Once that is all dry and secure, you can take this and measure the max depth of the chamber and back it off .002 or more and away you go.

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KKM barrels have a 1:20 twist, and are best shot with 124gr projectiles.

You make a chamber gauge by taking a case, drill out the flash hole, get a fine thread bolt and a matching nut. glue the nut to the back of the case so that it does not interfere with the case being inserted into the chamber with barrel out of the gun. Thread the bolt the nut and into the case, glue a projectile to the bolt making sure that it is a straight as possible. Once that is all dry and secure, you can take this and measure the max depth of the chamber and back it off .002 or more and away you go.

I see. I have one of those Hornady chamber gauges that I used on my 308 long distance rifle. Seems it should work for 9mm too (with the right shell).

Thanks for the info!

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By any chance, do you have a comp on the KKM barrel? Have you tried factory ammo as a baseline? What is the neck measurement of the rounds?

No comp. It's a production gun. I did shoot some factory ammo, mainly Winchester and Federal, but all in 115gr. Did not see keyholes with them.

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What about your neck sizing? Would you measure about 10 and tell us the size range?

Ranging from 0.377'' to 0.382' depending on brass thickness of different head stamps. I was targeting 0.378'' so this is expected.

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Sounds like excessive crimp like others have mentioned. I crimp my Xtreme's to .3775" - .378" in both my production 9 minor loads 147/165gr and open 9 major loads 115/124gr. This equates to just barely removing the bell. Try and get the caliper at the absolutely top of the brass to get a more accurate measurement of your crimp.

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I had the same issue with xtreme 147 RN and my Glock 34 (but none of my other Glocks). I tried adjusting the load but never figured out the issue. I stopped buying those bullets.

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What solved my problem is using a DAA Mr. Bulletfeeder powder funnel for my Dillon. This expanded and belled the case and the bullet would go in straighter. The Xtreme bullets are very soft and if the bullet didn't go in the case perfectly it would cause issues. Once I switched to the new powder funnel and the bullets would sit straight while seating, my accuracy improved to 3" offhand groups at 25 yards.

Same load. 3.2grs TG, Xtreme 147gr, 1.150 OAL, mixed headstamp brass.

For 38 bucks give it a try, may help.

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I'm in the "not crimped enough" camp.

I shoot the same round but a 16:1 twist.

My completed rounds have a shiny ring at the top. IMO it guards against "set back". One of the worst things that can happen. Most reloaders will not agree with this approach, but I have no tumbling issues and accuracy seems to not be affected.

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If the expander is made for jacketed bullets, it is probably .352 inches outside diameter. So the brass will swage the soft bullets down when seated. Pull a bullet and measure the O.D. To check for this. If this is the problem, you will be shooting an undersized bullet, guaranteed to lead barrels and key-hole. I use an oversized expander, .357 inch, to cure this. So, now the problem will be lack of tension, allowing set-back. What I do to prevent this, is adjust the expander to the seating depth of the bullet. This leaves a "shoulder" at the base of the bullet, to prevent set-back. May not be your problem, but it was mine. I shoot dead soft lead in mine, now.

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Xtreme supposedly has relatively thick plating, but are they using unusually soft lead? It occurred to me that I don't shoot my G34 a whole lot, so I wasn't entirely sure Bayou 147s weren't tumbling from it too. So, I took it to the range today and ran several full mags each of Bayou and Black and Blue (both nearly the same 147gr FP coated bullet), and none tumbled.

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I just tried some new crimping settings. These bullets do not keyhole in general, only maybe 1 out of 20 or so would keyhole. However, as the picture shows, I do see crimp line, though I don't think there is any deformation of the bullet due to that line.

The interesting thing is, with the crimp line, you can still see the brass has the bell. This is on Dillon SDB, and I was told the coke bottle shape of the loaded brass is normal. Is it normal?

I carefully measured a few dimensions:

1. Bullet base (after being pulled out) - 0.355''

2. Based of brass - 0.390''

3. Mouth of the brass - 0.378''

I am about to switch to FMJ bullets and try more.

post-56818-0-34609800-1427724440_thumb.j

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