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KKM barrels and plated bullets - issues?


wk5h

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I have a weird one here... I bought a box of 180gr X-Treme FN bullets on recommendation that they were great for the range.

I have a G20sf with the 6" KKM barrel, and so far have only reloaded with Hornady's XTM bullets with no problems.

But ever since I've been loading the X-Treme bullets, I can't hit the broadside of a barn. Even stranger, I get better grouping with the factory barrel with the X-Treme bullets than with the KKM; grouping is still pretty bad with the factory, but, it's noticeably better. I say horrible as in from 30ft, with the KKM barrel, I can't put but maybe 1 shot on a 8.5x11" target downrange out of 20. The factory, I can get maybe 3-4 out of 20 on target. Shooting longer distances today on the rifle range, shooting at the 100yrd targets, I'd have some go completely over the target backer, and some would dive into the dirt halfway to the target.

I've tried with several different powders (Power Pistol, Longshot, WS231, Titegroup, 800-x) and they all perform equally as horrible, so I'm not thinking it's a powder issue at this point.

Is there anything with plated bullets and the KKM barrels?

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There a lot of factors that can be in play, from the loads you use, to the gun to you.

If you have a chrono you can see how consistent a velocity you are getting.

If velocity is consistent then look at the gun... Shoot from a rest or supported.

Xtremes are good bullets. Have used many thousands of them.

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Plated bullets can be crimp sensitive, what is your crimp? Pull a bullet and check for a groove around the bullet from the case mouth; if you have one, you most likely have too much crimp. What crimp die are you using? The Lee Factory Crimp die can swage the bullet when used improperly and that can cause accuracy issues like you are experiencing. I use a crimp of .421 in .40 cal.

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When shooting the 30ft targets, I was shooting supported and happened to have my chronograph setup. I'm not the best of shot, I'll admit... But, I'm a better shot than the results I had today.

Power Pistol - 7.6gr

Avg 1,131 with a 60fps spread.

Longshot - 7.3gr

Avg 1,124.8 with a 25fps spread

WS231 - 5.2gr

Avg 959.6 with a 36fps spread

Titegroup - 5.4gr

Avg 1046.9 with a 41fps spread

800-X - 8.4gr

Avg 1184.8 with 70fps spread

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Plated bullets can be crimp sensitive, what is your crimp? Pull a bullet and check for a groove around the bullet from the case mouth; if you have one, you most likely have too much crimp. What crimp die are you using? The Lee Factory Crimp die can swage the bullet when used improperly and that can cause accuracy issues like you are experiencing. I use a crimp of .421 in .40 cal.

I'm using the LFCD, but, I don't have the measurements of the crimp at the moment. I'll load a few in the morning (I haven't changed my dies), get you a measurement on the crimp, pull the bullet and see what it looks like.

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i don't think you are the first to have this issue:

http://www.brianenos.com/forums/index.php?showtopic=212491&hl=%2Bxtreme+%2Bcrimp#entry2364378

i would lose the Lee Crimp die and go with the lightest taper crimp you can get to pass a chamber gauge.

Yup. Xtremes seem to use a softer lead alloy than Berrys or coated - my seating stem leaves mark on the noses of Xtremes. The FCD is swaging them down. Pop on a regular crimp die set to just remove the bell and you'll see a good amount of improvement.

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I checked a new bullet this morning before I ran a new cartridge through the dies, and the bullet .400

After running it through, then pulling the bullet, the bullet was .399 and there was a very faint line around the top, which you really have to squint to see, but, I'm not seeing any bullet deformation or mushrooming?

Would the .001" be enough to cause my issues?

Sent from my iPhone using Tapatalk

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Crimp is likely the issue.

Here is how you test. Get 5 of your normal loads. Then remove the crimp die completely and load 5. Shoot those two versions slowly hand clambering all rounds (of both versions). If your group is better with the un-crimped, you have proven to yourself that it is the crimp.

After that, you will have to slowly add in crimp until you see fall off of accuracy. When you find that, do some testing to make sure you will not reduce the COAL by clambering the same round 5 or 6 times from slide lock.

Hope that works out for you.

Edited by MarkCO
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  • 2 weeks later...

I also use a Lee fcd and I also get inconsistent larger groups than I think I ought to be getting. Question- I notice lots of die sets don't even include the crimp die. I've always assumed I had to crimp, but is that really true? If it is essential, what crimp die should I try out instead of the Lee?

MarkCO- the above advice you gave is great. I'm going to try it.

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  • 3 weeks later...

I'm a bit late on getting back to this... Crimp was definitely my issue. I changed up my process a bit, used less bell, less crimp, and had much better luck with the xtreme bullets. Thanks for the help!

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