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Posted: 12/26/2011 4:33:00 PM EDT
| Ok I know you guys are sick and tired of this!!! But I just picked up a ak 74 from a local dealer and from what I been seeing the good ones start with y and have a 1/8 twist barrel well my has a 1/9 twist and starts with y im praying that it doesnt keyhole anybody ever hear about the ones with 1/9 keyholeing thanks for any info |
| As you know this is a hugely controversial topic on all the sites that discuss '74's and especially Tantals...all I can say is that I have done ALOT of research on this topic, and am wishing to give you advice that might put you somewhat at ease. Keyholing can happen for a number of reasons, but the two most common are the oversized bbl and the quality of the ammo...my guess with your rifle is the ammo. Surplus ammo has incredably uneven QC...NONE of it (Russian or Bulgarian) was found to be acceptable by the Finnish Army when they tested it extensively...not to THEIR standards anyway. So they made their own Lapua match ammo and put excellent bbls on their test '74s, and it was better...but still not good enough for them, for various reasons, so they rejected the round and rifle. The S&W bbls on their AR's made for the 5.45 do not keyhole at all, from what I hear so far, and they are way undersized, very tight and they are chrome lined. They got it right. The thing is; is that 5.45 rounds are SUPPOSED to keyhole at the "slighest resistence" according to their design specs. Were your keyholed rounds on the paper target in a "good" group? If they all made it on the paper in a reasonably good grouping this would seem to say they they are flying STABLE untill contacting the target, which is what to expect from these rounds, I think. A truly keyholing round, generally has such an erratic flight path as to miss the paper altogether! They don't "spiral" they spin end for end...think about it. This whole issue is extremely complicated, and tough to get a handle on, but it might be something just as simple as the fact that the bore on your rifle isn't chromed, which is just enough to make that bore "big" enough so that when it is HOT that occasional poorly manufactured round might destablize just a little more than the rest...or a particular round may have the steel core inserted a little crooked in the lead jacket...or your compensator might be a little loose...get the picture? I don't even know 100% WHY my own Tantal refuses to keyhole, bit it never has keyholed once with everything I've put through it, even overheated TRYING to make it keyhole! I personally never saw a chrome lined bore that keyholed. Other "experts" may disagree with me, but this is honestly what I have found out, hope it helps...PS: I love shoot'in my Tantal! |
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Quoted:
that 5.45 rounds are SUPPOSED to keyhole at the "slighest resistence" according to their design specs. Were your keyholed rounds on the paper target in a "good" group? If they all made it on the paper in a reasonably good grouping this would seem to say they they are flying STABLE untill contacting the target, which is what to expect from these rounds, A sheet of paper will not offer enough resistance to cause bullet to tumble. Plus the bullet was well through the paper before any tumbling would occur. If it made a key hole shape hole, the bullet was tumbling before it reached the target paper. |
| According to data collected while testing in several countries, with respect, you are wrong, especially if the round is incorrectly manufactured...but just for the sake of argument, say you are right, how do you explain the round hitting the target at all??? Have you ever seen an M-16 or M-60 or Garand with a shot out bbl or bad chamber keyholing??? Rounds are all over creation, not on the paper. In fact rounds spinning end for end sometimes tend to head at arched right angles. Many of these keyholed targets actually have some reasonably good groups...the Finns found 7N6 rounds that began to deflect after hitting only the slightest resistence, like twigs and paper...remember the round is designed from the git-go to be super tail heavy, add an incorrect HOT bbl, a steel core off center, and maybe a little cross wind... "On paper" the early 5.56 bbl's Century used SHOULD have worked in theory, but the cartridge and QC are so far out of spec that it was never gonna happen. S&W learned from this and did their bbl's right. The true bullet diameter of the 5.45 Russian is .2146...but the European CIP which is the equivilent of SAMMI specs here list the rounds actual bullet diameter as 5.68mm (.2236) 5.56 NATO and .223 Rem. is spec'd at .224 caliber even though 5.56 NATO is REALLY spec'd out at .2188....This is WELL within govt. specs with only FOUR ten thousanths differencs so essentially they SHOULD shoot the same through the same size bore....IF everything is scientifically correct. So ON PAPER all Century guns should have worked, but they didn't!!! Why? Because the Russians, Bulgarians, Ukrainians and others do not even follow CIP specs and never have! The commercial Russian made ammo is different, and may follow specs for other reasons, such as liability and to follow customers requests, or their own QC just might be better. Check it yourself the actual diameter of surplus 5.45 from any country mikes at .2215/.2220 on up...each batch can be different, some of it is way larger...so in theory if you shoot this stuff in a Century Tantal or '74 with a SAMMI spec bbl made for a 5.56 the surplus round will be WAY too small most of the time. Add in all the other variables...heat...no chrome lining...poor QC...getting the picture? That is why I'm convinced that if the bores would have been chrome lined, the rifles would have worked much better. As an anti-personel round doing what it was designed to do, it was OK, but the Finns rejected it because it penetrated objects and cover no better, was more unstable, than a 5.56 and had no advantage in lethality over the 5.56...now that doesn't mean it isnt good, just not better enough than the NATO round to warrant the changeover. Oh yea and I was told that no two European reloading manuals agree on the actual civilian specs for the 5.45 . The bore specs for the S&W 5.45 bbls are unique, the rifleing being four grooves with a 1:8 right hand twist, the bore diameter is .217 and the groove diameter is .222, plus a chrome lining, that is nice and snug. I'm not trying to stir things up here, maybe i'm dead wrong, but I doubt it, because I have researched this as thouroughly as I could from good sources. Why? Cos it bugged me. |
| I have a TT serial numbered Tantal from Century with a 9 stamped on the bottom of the barrel near the front trunion. The tag from Century stated it was made in 08 with a 1/9 twist. I have not had the time to take it out and test it to see if it keyholes or not. Im keeping my fingers crossed. It did however pass the bullet test with flying colors so I am trying to be optimistic. The barrel almost appears to be chrome lined looking at the crown. One problem I did notice is when I cycle it by hand with live ammo every once in a while a round would be hard to extract. I thought it was the chamber but one time a round got stuck and I yanked on the charging handle and it pulled the bullet from the case letting powder fly everywhere. The bullet tapped out without problem using a brass cleaning rod. All this was obviously done in the safest of conditions. (I love me alot) |
| As I said earlier, I have a "Y" 1/9 CAI Tantal from about '08 and it does not keyhole and never has with any ammo I've tried whatsoever...and I can't figure that out, BUT I'll bet that either the twist rate or bbl inside dimensions are the reason. IF I slugged the bbl I'll bet I'd find that it was manufactured just a tad tighter than the early "loose" 5.56 bbls...just a guess. Just a couple of last thoughts...most of us when we set up a paper target, have some sort of backing that makes it stiffer that could cause the round to yaw...and... though I have seen numerous non chrome lined bbl '74's that keyhole alot or occasionally at the range, I cannot remember a '74 of any type with a chrome lined bore that keyholed. |
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