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Bullets tumble


moparnut88
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High I switched back from open minor for steel to open major and now am experiencing a few bullets tumbling. Could too little crimp be the issue? No problems with open minor. Load is 8.7grns of silhouette under a mg115 with federal srp. It's got a kkm barrel with a Bedell comp got around 30k on barrel but looks superb. Thnks for the input.

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Tumbling can be caused by a number of factors including damage to the barrel crown or too much crimp - especially on a plated bullet. Check to be sure your crimp isn't damaging or deforming the bullet plating. Also, look closely at your barrel crown to be sure there is no damage or deformity that can cause the bullet to leave with a slight difference in pressure where the damage might be.

Let us know what you find.

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My well used KKM tumbles too. Can't stop it. Reamed comp, played with crimp, changed bullet weights, changed bullet styles, changed bullet make, changed bullet diameter. Barrel is done. I'll be curious to hear if yours is ultimately done as well. G'luck.

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Tumbling can be caused by a number of factors including damage to the barrel crown or too much crimp - especially on a plated bullet. Check to be sure your crimp isn't damaging or deforming the bullet plating..

Let us know what you find.

Check to be sure your crimp isn't damaging or deforming the bullet plating.

Montana Gold bullets are jacketed, not plated.

Edited by Pat Miles
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It's not too much crimp. Definately ruled that out. Checking comp next. I would find it hard to believe it's worn out with only 30k er so on it. All the lands and grooves look true no rounded edges or nething. And shoots excellent with minor loads. Just tumbles with major.

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What kind of muzzle velocity are you getting and what distance are you seeing tumbling?

Reason I ask is I was just watching a video on long range shooting and they were talking about the loss of accuracy and stability as the bullet velocity dropped back through the sound barrier. Got me thinking that with 9mm rounds (and most auto pistols) being right around sonic speeds, over and under, Maybe your minor loads were sub-sonic and your majors are just slightly above and dropping back causing the tumble.

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I was discussing this with another competitor this weekend. I have had a few tumbling here and there recently. I have backed off crimp since I shooted plated xtremes. My question is how can I shoot 2-3k rounds with the same load/press and have one tumble every once in awhile

The thought he mentioned was that shooting mixed reloaded range brass might be part of the answer to my problem at least. Some case walls may be thicker and cause more crimp than the rest?

moparnut88, are all of yours tumbling or just intermittent?

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I don't believe it's barrel. And racnsoonr mine were just intermittent. My major load was around 1550fps. With 115 grn mg. I tried some coated bullets with same load but sized to .356 and havnt noticed issue yet. But cleaned comp as well. But it didn't appear bad dirty at all. Will continue to keep an eye on it and keep everybody posted. How long should a barrel last with 9mm major? It's a kkm that I have now. Thnks again.

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What is the barrel length and twist rate ? If the bullet is not hitting the comp baffles with minor it's not hitting with major either and I doubt your over crimping with MG bullets. Years ago I had a real shorty open gun with a commander length barrel with a 1/32 twist that wouldn't stabilize bullets ( I believe the barrel was to short for that twist rate ) It's very possible the barrel is shot out.

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An open shooter in these parts claimed he was always at a disadvantage on stages with long shots because his plated 124grn 9mm major ammo would have jacket separation, so at long distances it didn't fly straight. I imagine crimp would play into that as well by damaging the plating and allowing it to split open.

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My KKM 9mm shoots only minor, and it started tumbling recently. It has only gone through 10k. I shoot coated bullets, however.

So far I have isolated the cause to the FCD that is resizing finished rounds causing the bullets to be squeezed undersized. In some extreme cases with unusual thick brass walls (certain headstamps do have very thick walls), the finished rounds leave the last station (FCD) on my 650 with bullets separated from the case. It was said that when squeezed hard, brass spring back much more than lead. No wonder I pulled some of those squeezed bullets and measured -0.02 to -0.04 inch difference with the new bullets.

I am trying a taper crimp die in place of FCD.

If you are suing MG I don't know what may be causing it.

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I've shot about 4k of the mg 115s this season so far and have been having intermittent tumbling with major. But tried a few of my own coated and the grouping tightened up significantly and no noticeable tumbling. But they r sized a true

.356. So at this point I am leaning on believing that the undersized mg bullets are the culprit.

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