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Although it's not an AR 15, I think there is enough knowledge here to answer this one. Have a Tikka T3 in .223 and I mistakenly bought Hornady Match in 75grain weight sent via UPS, no return policy. The barrel twist is 1 in 9 and it had stuck in my head that you need at least a one in seven twist to shoot the heavy bullets. What performance can I expect from using the Hornady 75 grain match in this twist. Remember it is a bolt action rifle if that makes a difference.
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I have always thought bullet length made a differance more the weight, longer bullets need a faster twist. Of course if you keep dia the same and use like materials the bullet would get longer as weight was increased. You can't return them so you might as well use them. Consult the loading manuals. I have never seen this being such a concern until the .223 became popular, altho it was an issue with 22 Rimfire, altho not as critical.You can never go home again. -
1 in 8 twist would be the ticket but I've seen a 1 in 9 barrel shoot 77 gr bullets well. I've also seen them top out at 69 gr, too. Load up a few and see how they do. I took a quick look at Hornady's web site but didn't find anything about any barrel twist recommendations.Comment
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It is my experience that besides the proper twist rate, barrel length plays an important part in usable accuracy. For reference, look at Hornady's velocity for their 75 grain bullets. Since I do not, at the moment remember, I will not guess at that figure. My practice and tournament ammo was (I put down the mouse gun and picked the Garand back up)EL 9760. This round holds tighter groups than I can hold in my Colt HBAR with 1-7 twist and float tube. Never had a problem with the ammo's coated steel case either. People I know have tried heavy bullets in slow (8-9) twist carbines and the bullets key holed at short range, 50 yards. I am not certain if a change to 1-7 would help the short barrels with heavy bullets as the velocity may not be there to stabilize the bullet.
HTH. George in NHComment
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Sierra (i know you have hornady) states on their boxes of 77g USE ONLY IN 1:8 twist barrels or faster...
hornady at one time said that they recommended AT LEAST a 1:9 twist barrel for their 75s...
with that said ive seen some pretty good results with the 75s in a '9 twist barrel. youre going to have to do some testing and see if its what youre content with. if youre not happy im pretty sure youd be able to sell them off to another shooter, especially a HiPo shooter...Comment
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The barrel length will make a difference,you didn't mention thatComment
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use a Kreiger 1 in 7 here.be safe, enjoy life, journey well
da gimp
OFC, Mo. ChapterComment
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I used to own a 1 in 9 twist upper.
I sold it and used the proceeds to buy a 1 in 8 DPMS upper with target sights.
that said. my 1 in 9 would shoot 75 grain hornadys loaded with 24.5 grains of varget, LC Brass and small rifle winchester brand primers. BUT....depending on the LOT number of the projectiles I bought, sometimes they were LOUSY ...which is why I got rid of that upper. Forget about 77's in it. It (the 1 in 9) was reliable with 68 hornady's and 69 sierra match kings.
The 1 in 8 will handle 80 grain sierra match kings.... same load data.
HTHComment
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Bluesteel, I checked the Tikka web site and they list a 1 in 8 twist for that model in .223 cal. Are you sure you have a 1 in 9 Twist? They also list a 1 in 12 for this caliber.
JohnPeace is that brief glorious moment in history when everybody stands around reloading.
Author unkown.Comment
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I can not get 69 gr. to perform in my 1 in 9 twist 20" heavy barrel. I won't even try 77'sComment
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Rules are rules, but I would try a new bullet to check actual performance. Your combination may work fine---or not. Then you will know. Regards, ClarkComment
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I have 7 twist, 8 twist, 9 twist barrels on different 5.56 and .223 rifles. You just have work up some loads and test them in your gun to find out what will shoot.Comment
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The longer the bullet the more twist required to stabilize the bullet. Weight does not affect stbility, but length does.Comment
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