moparnut88 Posted August 23, 2015 Share Posted August 23, 2015 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. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
Solvability Posted August 23, 2015 Share Posted August 23, 2015 I would suspect the barrel or the see if there is a strike on the comp - tumbling is not coming from too little crimp. Link to comment Share on other sites More sharing options...
racnsoonr Posted August 23, 2015 Share Posted August 23, 2015 I've always thought it may be from too much crimp, not too little Link to comment Share on other sites More sharing options...
DougM Posted August 23, 2015 Share Posted August 23, 2015 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. Link to comment Share on other sites More sharing options...
Aircooled6racer Posted August 23, 2015 Share Posted August 23, 2015 Hello: I am voting for the barrel being worn out. You can also check your bullet diameter and try a larger bullet diameter. Thanks, Eric Link to comment Share on other sites More sharing options...
troupe Posted August 23, 2015 Share Posted August 23, 2015 Most common is carbon build up on the comp and the bullets hitting the baffles someplace. EGW sells a nice reamer that works great. Link to comment Share on other sites More sharing options...
mickd1 Posted August 23, 2015 Share Posted August 23, 2015 first try looking if you have too much crimp Check to be sure your crimp isn't damaging or deforming the bullet plating. Link to comment Share on other sites More sharing options...
theWacoKid Posted August 24, 2015 Share Posted August 24, 2015 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. Link to comment Share on other sites More sharing options...
a matt Posted August 25, 2015 Share Posted August 25, 2015 Double Check the crip, check for the bullet hitting the comp, Ream the comp and then look hard at the barrel? Link to comment Share on other sites More sharing options...
Pat Miles Posted August 25, 2015 Share Posted August 25, 2015 (edited) 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 August 25, 2015 by Pat Miles Link to comment Share on other sites More sharing options...
gunracer38 Posted August 25, 2015 Share Posted August 25, 2015 I have the same problem with the KKM barrel. This is now the second KKM barrel that key holed . One of my Open guns now has a new barrel. The other one I changed the bullet,checked the crimp and it worked fine. However I now have a new Schumann barrel if I need it. Link to comment Share on other sites More sharing options...
moparnut88 Posted August 26, 2015 Author Share Posted August 26, 2015 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. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
DougCarden Posted August 26, 2015 Share Posted August 26, 2015 Have someone look at the barrel with magnification. If it is shot out pushing the bullet harder will not stabilize properly. If you read all the posts here you see a pattern with the barrels...... DougC Link to comment Share on other sites More sharing options...
Dranoel Posted August 30, 2015 Share Posted August 30, 2015 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. Link to comment Share on other sites More sharing options...
racnsoonr Posted August 31, 2015 Share Posted August 31, 2015 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? Link to comment Share on other sites More sharing options...
Aircooled6racer Posted August 31, 2015 Share Posted August 31, 2015 Hello: The case wall can be different thicknesses and the overall length of the brass can be different. That will cause different crimp depths. I still say it's the barrel in this case. Thanks, Eric Link to comment Share on other sites More sharing options...
moparnut88 Posted August 31, 2015 Author Share Posted August 31, 2015 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. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
Solvability Posted August 31, 2015 Share Posted August 31, 2015 15 - 20K would be pretty normal for a Stainless cut rifle barrel - double that for Chrome Moly Poly barrels Link to comment Share on other sites More sharing options...
digi531 Posted September 1, 2015 Share Posted September 1, 2015 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. Link to comment Share on other sites More sharing options...
moparnut88 Posted September 1, 2015 Author Share Posted September 1, 2015 It's a 5" kkm barrel in a Caspian slide. I am unsure of the twist rate. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
adamge Posted September 1, 2015 Share Posted September 1, 2015 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. Link to comment Share on other sites More sharing options...
moparnut88 Posted September 2, 2015 Author Share Posted September 2, 2015 Ok did some checking. My mg 115 bullets measure .354 instead of .355. We r thinking that's the problem. Wat everybody's thoughts? Thnks. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
MilkMyDuds Posted September 2, 2015 Share Posted September 2, 2015 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. Link to comment Share on other sites More sharing options...
moparnut88 Posted September 2, 2015 Author Share Posted September 2, 2015 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. Sent from my SAMSUNG-SM-N910A using Tapatalk Link to comment Share on other sites More sharing options...
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