elwoodm 0 Posted March 29, 2011 Report Share Posted March 29, 2011 my 2007 polish AK 74 just started to keyhole after 800 rounds.slugged the barrel to find out its a .223 grove.who can i send it to for new barrel and head space? Quote Link to post Share on other sites
MT Predator 2,294 Posted March 30, 2011 Report Share Posted March 30, 2011 (edited) I've personally seen two CAI 5.45s, different friend's keyhole at 25m. Subsequently, both were returned to CAI for a refund instead of a swap for a 5.45. It took you that many rounds to figure out it was keyholing? Both of these were discovered within on mag's worth. Edited for a typo. Edited March 30, 2011 by MT Predator Quote Link to post Share on other sites
elwoodm 0 Posted March 30, 2011 Author Report Share Posted March 30, 2011 had the gun since 07 and it was a tack driver up till now. had no reason to think it had a bad barrel so i did not check it. everything on the gun is fine. just need a new barrel Quote Link to post Share on other sites
MT Predator 2,294 Posted March 30, 2011 Report Share Posted March 30, 2011 Is it a 5.45 or. 223? 800 rounds should not wear out a barrel anyway. I've shot more than that in a five day class. If it is one of Century's infamous Tantals, you probably have a .223 barrel and for some reason, you didn't experience a keyholed round out of the 800 you have run through it. Quote Link to post Share on other sites
elwoodm 0 Posted March 30, 2011 Author Report Share Posted March 30, 2011 its a 5.45 the lands are at .2190 and grooves at .2230.its a century tantal mid 500s serial #. the gun had moa at 100 yards the first day at range.never had a problem with it until 3 weeks ago. had shot silver bear,military classic and bulg surplus only.the surplus is corrosive but cleaned it good soon as i got home Quote Link to post Share on other sites
MT Predator 2,294 Posted March 31, 2011 Report Share Posted March 31, 2011 Wierd! Quote Link to post Share on other sites
elwoodm 0 Posted March 31, 2011 Author Report Share Posted March 31, 2011 as old as the gun is century will not do anything for me not that i would want them to but i sure would like some help from all the smart gun people at this forum as to who can fix this tantal for less money than it would cost to buy another 5.45 Quote Link to post Share on other sites
YEL13 3 Posted March 31, 2011 Report Share Posted March 31, 2011 does the barrel have any weird pitting? I wouldn't think that corrosive ammo would take its toll on a barrel uniformly enough to do this....and you said you cleaned it every time as soon as you got home so I doubt corrosion is the case unless you live in a really high humidity/moisture enviroment, my best guess is its very rapid barrel erosion (probably could be attributed to poor metallurgy or the likes) OR, and I hope this is the case....an odd succession of bad ammo not quite to spec, if it really is the barrel and 100% not the ammo then I'm afraid the only thing you can do is replace it, but I'd try some more ammo first and another barrel inspection, 800 rounds definitely shouldn't be enough to wear out the rifling enough to make it keyhole Quote Link to post Share on other sites
YEL13 3 Posted March 31, 2011 Report Share Posted March 31, 2011 another possibility is that the twist rate on your barrel doesnt match up properly with the grain weight of your barrel, for example a 1/12 rate with say a 62grain might cause something like this, I know wolf 5.45 comes in 70, 60 and 53 grain varieties Quote Link to post Share on other sites
6500rpm 670 Posted March 31, 2011 Report Share Posted March 31, 2011 (edited) ^^^That was the question I was wondering about-any change in ammo? Century Tantal barrels spec'ing at .223 was on a lot of the boards. Probably no reason why you couldn't get a Bulgarian barrel from Copes or APEX and transplant-I've got a spare parts build in about 90% right now that I used a Tantal receiver, bolt, carrier and a Bulgarian trunion and front end that I haven't found to have any issues. http://www.copesdistributing.net/product_info.php?products_id=2265 http://whatacountry.com/aK-74-Bulgarian-5.45x39mm-16-Chrome-lined-Barrel.aspx Looks like KVAR and APEX are out of stock and I'd stay away from the US barrels unless you get a good confirmation. If your Polish is a Tantal the trunion should be the same diameter, but off the top of my head I'm not sure if all the pin locations for sight base,hg, gas block, ect are going to work. Bulgy barrels aren't threaded, and I'm fairly certain all I've seen recently have the pin cuts made and port drilled. Edited April 1, 2011 by 6500rpm Quote Link to post Share on other sites
elwoodm 0 Posted April 1, 2011 Author Report Share Posted April 1, 2011 sorry for not getting back till now but the tree rats chewed my power line up and it melted my cable just got going now. the ammo is the same i have shot for years high 50s to high 60s grain. the parts on the gun are tantal except the 922r stuff century put on. the only other issue is the tapco hammer being tall and causing the bolt to slam the barrel hard might have messed up headspace. is this something that would cause it to pinch the round and make the fps too fast to stabilize the bullet? Quote Link to post Share on other sites
elwoodm 0 Posted April 21, 2011 Author Report Share Posted April 21, 2011 went to range after grinding hammerand smoothing bolt and carrier in rails. Quote Link to post Share on other sites
elwoodm 0 Posted April 21, 2011 Author Report Share Posted April 21, 2011 found out that 60gr silver bear and military classic 70gr still keyholed but bulgy 53gr shot straight took bullets apart and measured diam to find bulgy at .2220 and 2930fps silver bear at.2215 and 2666fps military classic at .2210 and 2514fps. the barrel is close to 1 in 8 twist. i think these bullets are too small and slow for the barrel the only other test will be with or without brake on. Quote Link to post Share on other sites
elwoodm 0 Posted April 21, 2011 Author Report Share Posted April 21, 2011 these century barrels are picky about diam of ammo and fps Quote Link to post Share on other sites
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