MoNsTeR Posted August 13, 2012 Share Posted August 13, 2012 My Bedell full size 9mm open gun is about 15-20k rounds old, and just in the last few months it has lost accuracy and started tumbling bullets. It has a KKM 1/32 barrel which I know some people have tumbling problems with, but it has never given me trouble in 2+ years. The comp is titanium, if that matters. Other possibly helpful bits of info: My normal load is 7.3gr 7625 / MG 124gr JHP and I have not changed it in many months. The barrel doesn't look worn out to my (admittedly non-expert) eyes. There are no obvious-to-me signs that bullets are hitting the comp, but just in case what should I be looking for? This is not the kind of problem I want to be having with Nationals two months away Link to comment Share on other sites More sharing options...
eric nielsen Posted August 13, 2012 Share Posted August 13, 2012 First make sure your rounds are really tumbling. If you have nice round holes all over the target, that can be a scope/mount problem. If you can recover a bullet and check the rifling pattern, that might help. Best bet is find the nearest gunsmith with a comp reamer (most of them are 0.375 diameter). Take your gun there and run the reamer. Run a chamber reamer and a freebore/rifling reamer, if available (not related to your problem, but might as well while you're there). A lot of times you'll hit just one rough spot then the reamer spins freely, but it makes all the difference. If you shoot exposed-lead-base bullets, your comp/barrel alignment might look perfectly concentric when held up to a bright light but still be causing bullet strikes on a build-up of lead. If that doesn't fix it then the barrel is probably shot out. There's one famous/infamous brand in particular that's known to give up the ghost without warning; I've heard about national-champion shooters scrambling to replace this brand just prior to a big match & only 10,000 rounds on the barrel. Before you head out, make some ammo that is .010 too long, 0.020 too long, etc. Drop them into the chamber and see if the bullets hit the rifling - if it's a long jump with a short bullet that can be a problem. Bullets with a deep hollow base (like the 115 Remington FMJ) can sort of umbrella-out as they leave the crown, making a comp strike more likely. If it sounds like i've had your problem - yes, several times. Link to comment Share on other sites More sharing options...
ong45 Posted August 13, 2012 Share Posted August 13, 2012 Carbon fouling can build up over time and it doesn't take much to throw a bullet off, look for the faintest streaks in all your baffles. As far as reaming the comp holes for clearance a little bit more is safer than not enough. If you have it re-reamed all you might be doing is cleaning things up and putting it back to original condition. Link to comment Share on other sites More sharing options...
Sam Posted August 13, 2012 Share Posted August 13, 2012 If you haven't already done so, you might try really cleaning the copper fouling out of the barrel. I don't own an open blaster, but a good copper solvent is usually the first thing I try when a friend drops by with a rifle that suddenly stops grouping. The 25-'06 is famous for this little stunt. Hoppe's just don't cut it, even though the bore "looks" clean. That first turquoise colored patch is a beautiful thing! Link to comment Share on other sites More sharing options...
Steve_P Posted August 13, 2012 Share Posted August 13, 2012 I had the same problem with my supercomp bedell shorty. I was also using 124gr MG JHPs and did have a KKM barrel. I sent it back to Dan for a re-barrel. Came back with a scheumann and shoots just fine now. It was still fairly accurate, matter of fact I shot last years nationals with it cause I could not get it fixed in time. Good luck. Steve Link to comment Share on other sites More sharing options...
D__ Posted August 13, 2012 Share Posted August 13, 2012 Drill your comp out slightly. Look for easy stuff first. Link to comment Share on other sites More sharing options...
colt Posted August 14, 2012 Share Posted August 14, 2012 (edited) I have a Bedell with the same barrel and comp. About the same amount of rounds and mine did the samething. Didn't realize the comp was filling up with carbine. Took the barrel out and cleaned the comp and took care of it. Brent Edited August 15, 2012 by colt Link to comment Share on other sites More sharing options...
MoNsTeR Posted August 15, 2012 Author Share Posted August 15, 2012 I removed some hardened carbon fouling from the inside diameter of the comp baffles. I'll test it within the next few days and see if that helps. There's still some crud on the barrel crown which I dare not attempt to remove, and that I suspect may be the real issue. I suspect if the cleaning didn't cure it, reaming the comp and re-crowning the barrel will. I'll report back... Link to comment Share on other sites More sharing options...
CocoBolo Posted August 15, 2012 Share Posted August 15, 2012 Since no one chimed in. Look for a fine dust of shiny material in the comp, this be tiny flakes of copper jacket, and or fine lines in the baffel holes. Recenly I cleand a comp for a friend, he has been shooting forever, his comp was so cruded up I used a drimmel and about burned it down cleaning it. He had caca galore on the crown, I just carefully scraped it off, he is shooting fine now. For that occasional touch up on baffel walls I use an old cleaning rod with a little 200 grit sand paper wrapped around it, chuck it up in a drill and just turn it enough to get things nice and shiny again. Care is taken not to remove material just the debris. Link to comment Share on other sites More sharing options...
D__ Posted August 15, 2012 Share Posted August 15, 2012 How tight should the comp be in the location of where the bullet travels? Does it need to be tight to be effective? Link to comment Share on other sites More sharing options...
lcs Posted August 15, 2012 Share Posted August 15, 2012 I removed some hardened carbon fouling from the inside diameter of the comp baffles. I'll test it within the next few days and see if that helps. There's still some crud on the barrel crown which I dare not attempt to remove, and that I suspect may be the real issue. I suspect if the cleaning didn't cure it, reaming the comp and re-crowning the barrel will. I'll report back... After cleaning everything and your groups still sux-Don't know if I would waste money and time on reaming and re-crowning. Had the same thing happen twice around 20-25K and a new barrel cured the problem. I used the same comps. Link to comment Share on other sites More sharing options...
Aircooled6racer Posted August 15, 2012 Share Posted August 15, 2012 Hello: Take a real good look at the barrel just in front of the chamber. See if the lands are worn there. If they are it is time to rebarrel it. Check the comp to see if it tight on the barrel. Lastly, check your crimp is still good on the reloads. Thanks, Eric Link to comment Share on other sites More sharing options...
MoNsTeR Posted August 16, 2012 Author Share Posted August 16, 2012 (edited) I removed some hardened carbon fouling from the inside diameter of the comp baffles. I'll test it within the next few days and see if that helps. There's still some crud on the barrel crown which I dare not attempt to remove, and that I suspect may be the real issue. I suspect if the cleaning didn't cure it, reaming the comp and re-crowning the barrel will. I'll report back... After cleaning everything and your groups still sux-Don't know if I would waste money and time on reaming and re-crowning. Had the same thing happen twice around 20-25K and a new barrel cured the problem. I used the same comps. We'll see what it needs, but I will happily spend $50 to have it crowned & reamed if that has a chance of saving me $400 to have it re-barreled, plus the time to order a barrel, and then once it's fit the gun's reliability record is reset to zero. At any rate to my eyes the bore looks nearly new. Comp is on tight. Load hasn't changed. I appreciate all the input Edited August 16, 2012 by MoNsTeR Link to comment Share on other sites More sharing options...
MoNsTeR Posted August 26, 2012 Author Share Posted August 26, 2012 Cleaning it and scraping the gunk off the crown with a brass punch helped a little, but tumbling was still evident. I had it re-crowned, got it back today and shot a match. Accuracy is improved but tumbling is still frequent. The smith that did the crown for me suggested I try some Zero bullets, so I got some. I noticed that the MG bullets I have measure between .3543" and .3545" in diameter, and the Zeros measure between .3550" and .3552". I suspect what's happened is that my barrel has worn to the point where the undersized MG bullets are no longer adequately stabilized. I'm going to load some of the Zeros and shoot them tomorrow. Link to comment Share on other sites More sharing options...
superdude Posted August 26, 2012 Share Posted August 26, 2012 Then you could try some .356, maybe some Hornady HAPs, which have a good reputation for accuracy. Link to comment Share on other sites More sharing options...
MoNsTeR Posted August 27, 2012 Author Share Posted August 27, 2012 Today's shooting seems to have at least partially confirmed my hypothesis. The Zeros are tumbling much less frequently than the Montana Golds, and overall accuracy is, well, "acceptable". I shot a group off the bench at 25 yards or so and it was about 4 inches. I used to be able to shoot better groups than that freehand! That's going to have to be good enough for now, but it's distressing that this barrel has worn out so quickly. Link to comment Share on other sites More sharing options...
superdude Posted August 27, 2012 Share Posted August 27, 2012 The strategy for some shooters has been to increase the bullet diameter in these circumstances. The good news is that you have a way to go -- with .356, then .357 bullets available. And on a serious note, it might really work. You can try some .356 and perhaps a better test would be the .357 to confirm your suspicion. Link to comment Share on other sites More sharing options...
MoNsTeR Posted September 4, 2012 Author Share Posted September 4, 2012 If you haven't already done so, you might try really cleaning the copper fouling out of the barrel. I don't own an open blaster, but a good copper solvent is usually the first thing I try when a friend drops by with a rifle that suddenly stops grouping. The 25-'06 is famous for this little stunt. Hoppe's just don't cut it, even though the bore "looks" clean. That first turquoise colored patch is a beautiful thing! OK now I feel really stupid. I've been operating more or less according to the Wil Schuemann "nothing down the bore but bullets" philosophy for several years now. The idea that copper fouling could hurt accuracy to this degree never even entered my mind. But, for good measure, before testing some samples of Zero .356 and Hornady HAP, I decided to do a thorough cleaning including copper solvent. I did three full saturate->wait->wipe passes with M-Pro 7 Copper Remover. Then I took my gun to the range and bench tested it with Montana Gold 121gr .355 IFP's, Zero 125gr .355 conical JHP's, Precision Delta 124gr .355 JHP's, Zero 125gr .356 classic JHP's, and Hornady 125gr .356 HAP's. The MG's, which had previously been patterning more than grouping, handily won the accuracy test grouping about 2 inches at 20 yards. The PD's weren't quite as tight but just as consistent. Neither the MG's nor PD's tumbled at all. The HAPs and both types of Zeros suffered from unexplained flyers and occasional tumbling. None of those three even came close to the consistency of the MG's and PD's. So, yeah. After blowing $350+ on fancy-pants bullets I'm back to the Montana Golds that I started with. Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted September 4, 2012 Share Posted September 4, 2012 Thanks for all the info - I'll file that away until the time comes that my TruBor starts tumbling Link to comment Share on other sites More sharing options...
CocoBolo Posted September 7, 2012 Share Posted September 7, 2012 Darn interesting. I've been shooting mine and doing the Schueman cleaning method, shooting more bullets down the barrel. I think's I'm going to go back to swabbing some hops +9 down the barrel just for Insurance. I've been shooting the MTG's for a couple years since Zeros went extinct, or at least endangered species, hard to get and pricey. Accuracy of both seems to be about eqivalent, but as you noticed the MTG's are a bit smaller in diameter and take a tad more powder to push at the same speed, but getting them is much faster. Link to comment Share on other sites More sharing options...
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