243 or 243 ai

Discussion in 'Gunsmithing' started by etisll40, May 28, 2013.

  1. etisll40

    etisll40 Well-Known Member

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    If I had a 243 chambered as an ai, how well would factory ammunition shoot out of it? What Improvement would I see in the ai ?

    I'm thinking a 24" barrel

    ED
     
  2. westcliffe01

    westcliffe01 Well-Known Member

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    I fireform my brass by shooting a maximum load of H100V in the standard 243 Win case. With the 95gr Bergers in my 1:8 Shilen x26" I get excellent velocity too. The fireforming loads shoot 1/2MOA and I use them for hunting.

    If you are going to the effort of dealing with an ackley chamber and fireforming brass so that it can hold more powder, you really need to use a longer tube to get the full benefit. Otherwise I wouldn't see the point. If concerned about weight, go with a lighter contour, just reduce the firing rate. A 243 AI will burn out a barrel fast if the rate of fire is high.

    Perhaps you should state what you hope to gain ? A 6.5 may be more to your liking. FYI, you cannot re-chamber a "regular" 243 Win to an AI without setting back the barrel at least 1 turn on the threads. Otherwise there would be no cartridge interference for the fireforming operation.
     

  3. Trickymissfit

    Trickymissfit Well-Known Member

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    Ackley developed the .243 Ackley to help fix some of the issues with the .243 Winchester, and an increase in velocity was not in his mind. The only serious gain in powder capacity is from the 40 degree shoulder, and that's not all that much for the effort. But it still some. The .243's are well known barrel eaters do to their turbulance point and the short neck length (the TP is actually out in the throat). You'll gain roughly .006" in the case diameter at the shoulder at best. 150fps is a realistic gain (if your lucky), but most of the issues will still be there.

    A Savage action unlike a Remington is a little longer. I think it's either .150" or .187" longer. A 57mm case will cycle thru it with no problems (I have a mod 12), but will a 6mm case fit in your magazine is another story. A 6mm Remington is a far better round, and a 6mm Ackley is a true long distance call.

    What you could do, is to ream the chamber with a 6mm Ackley chamber reamer to headspace off a .243 Ackley gauge. Then either use 6mm brass or necked down 6.5 Sweed brass. Sounds hard to do, but is really very easy to do. With this round you get the best of it all. The desired longer neck length, and a much better TP point (Inside the neck). Barrel will last twice as long as a standard .243 and probably much longer than the .243AI. Ontop of this and the longer neck length is that the longer bullets like the 105 grain Amax will not be seated into the shoulder area. Then you gain even more powder capacity. Best of everything.
    gary
     
  4. J E Custom

    J E Custom Well-Known Member

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    The 243 AI is a good way to clean up an old 243 chamber.

    It will gain somewhere around 100 ft/sec+ and improve case life.

    The "Trick" to good accuracy while shooting standard 243 loads is to use a 243 Head space Gage
    and hold it to .0005 to .0000 head space. This will hold the brass in place and minimize case stretch .

    When set up this way you can expect 1/2 MOA or better while fire forming factory loads
    or full power 243 loads. This also makes fire forming cheep and easy and you don't waist powder
    and bullets because you can hunt while fire forming.

    The 243 AI can match the 6mm Remington and will fit nicely in a short action.

    Just my opinion

    J E CUSTOM
     
  5. westcliffe01

    westcliffe01 Well-Known Member

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    Here is a picture of a "virgin" and fireformed case for comparison.

    I recommend doing the right thing and using a true 243AI "go" gauge to set head space on your barrel. The 243 (in fact 308 Win case family) go gauge is not interchangeable with an Ackley gauge. MansonReamers.com carry all the popular Ackley gauges and can make customs, so no excuse to use the wrong gauge. Given the difference in shoulder angles, it should be obvious why you want to use the right gauge.

    You can tell a few things from the pic below. First of all, the height to the base of the neck difference can clearly be recognized. The AI chamber is shorter in this regard, deliberately, so that the base of the cartridge is forced tight against the bolt face. Second, the extra case volume can be recognized. The 243 case does not have a bunch of taper to begin with so it does not benefit from the "Ackleying" as much as others.

    Having said all that, I am not having any issues with my fireforming loads, they are just as good as shooting any ammo and given the reduced barrel life, I do not intend to waste my barrel life. My magazine allows the bullets to be seated to 2.9" overall length, which exceeds the throat dimension. But then that is what is advocated by David Tubb, that way the bullet is guaranteed to be jammed securely when it is loaded, as opposed to having a potentially variable jump.

    [​IMG]
     
  6. shortgrass

    shortgrass Well-Known Member

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    The only gauge I use is the "GO" gauge for the parent cartridge. When the barrel is torqued to the action, my chamber is deep enough that the bolt handle will close half way on the gauge. This allows for variances in brass, from lot to lot and maker to maker, but still allows the cartridge to be 'captured' solidly between the bolt face and the shoulder/neck junction of the chamber. The only times, when chambering an Ackley, that I follow a different procedure is with the new Nosler version of the .280A.I. , where I use both gauges, and the .257A.I. (I've found huge differences in .257 Roberts brass, over the years). My Ackley reamer list; .223AI, .22-250AI, .243AI, 6mmAI, .257AI, 260AI, .280AI (traditional), .280AI (Nolsler), .30-06AI, .338-06AI, 35 WhelenAI. As for barrel life,, think Melonite Black Nitride.
     

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  7. etisll40

    etisll40 Well-Known Member

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    I'm really glad you all chime in on this, it's gonna make me think a little more on it. It's hard to believe such a small case would eat barrels up so fast? What kind of barrel life in rounds would a 243 vs a 243ai have? Any experience with that?
     
  8. westcliffe01

    westcliffe01 Well-Known Member

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    Many people who own "standard" 20" sporter barreled 243's shoot relatively mild factory loads in them, not too many a year and they last a long time. The exception would be guys shooting the light varmint loads at near 4000fps on prairie dogs, and barrels don't last long for that group either.

    But most of us who go with an Ackley chamber are looking for speed and run close to max (for an Ackley) or even slightly over loads. So it would be logical that the barrel life would be shorter than the case of someone shooting factory loads with 10-15% less powder in them.

    If I was not after the speed I certainly couldn't be bothered with all the work associated with fireforming brass.
     
  9. Trickymissfit

    Trickymissfit Well-Known Member

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    Dwight Scott did a couple of guns for friends of mine years back in .243AI. The rifles started out shooting in the mid twos, and by the time they reached the eight hundred round count they were .60" guns. Barrels were Shilen (I think). Neither gun hit the 1000 round count, and were rebarreled into something else. One rifle seemed to split necks during fire forming about 20% of the time. Yet both barrels had identical chambers and used brass from the same lot. Several years later one of the guys built another 700 Remington in .243AI, and cut a very short barrel for fire forming in another rifle. Chambers were very tight, and he also had the same neck splitting issues, but not during fire forming this time.
    gary
     
  10. Hired Gun

    Hired Gun Well-Known Member

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    Neck splits are common in any caliber when the brass is not annealed properly whether it be new brass or reloads. Anneal the necks and the issue will go away.

    An Ackley must be done with a proper Ackley gauge and I like it tight on it because new brass is commonly up to .010" short. The bolt halfway down on a go is not .004" It's more like .001"

    I prefer the 6mmAI. It no more of a barrel burner than any other gun of this performance level. in my opinion the plain 243 Win is a dog. I would set it back one turn and turn it into a 6mmAI if it was mine. A longer barrel like 26 or 28 will really make it run.
     
  11. Trickymissfit

    Trickymissfit Well-Known Member

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    Doug bought one of the first indexing machines to anneal brass. In my opinion he was overworking the brass in the sizing process, but the splits were even odd. They were never all the way down the neck, but in that last half of the neck. He had at least two different die sets with the same results. One set was made by Scott and the other was a Redding die set. (which I later got from him to modify)

    The other guy and a couple other buddies of his built 6/284's, and became a barrel maker's dream come true! They (at onetime) were going thru two or more barrels a year. Then one of them got the grand scheme to make the shoulder .100" shorter! Lost about 50 fps, and greatly increased his barrel life. Then one of the other guys went -.150" on the shoulder and saw a loss of about 75fps, and nearly doubled the life of his barrels; plus grouped tighter. (actually that advice came from Ferris Pindell). Looks like Ackley was right in his book.
    gary
     
  12. westcliffe01

    westcliffe01 Well-Known Member

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    I have had no neck splits and have fired PPU, Hornady, Remington and Winchester brass in mine. Agreed that a longer neck would have been better.

    Unless I am mistaken, 6mm Rem brass is harder to come buy and with a lot fewer vendors. Similar to the 375 Ruger wildcats. It makes a nice short magnum with no belt, but I believe only Hornady makes the brass and it is notoriously soft and for months now, not available.
     
  13. Hired Gun

    Hired Gun Well-Known Member

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    If you anneal the Remington brass it works pretty good. I have been really dissapoint with Hornady and Winchester brass in all calibers for the last couple years.
     
  14. Trickymissfit

    Trickymissfit Well-Known Member

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    you know I hear about Hornaday and even Norma brass being bad all the time, but I have been using both for a long while without an issue. I have some Hornaday .223 brass that I know has to be twelve years old with lots of firings. Just never had an issue with it. Most of the Norma brass I have is factory Weatherby stuff, and just never had an issue except for the cost. I also have .222 and .223 Norma brass and it just seems to perform well for me. On the otherhand I have a thousand Blackhills cases that were at least 40% junk from the start. The Weatherby stuff has to go thru a two step sizing process due to the expansion of the belt area, but even then it's not much and I just do it as a matter of fact. I did make up some brass out of once fired .300 Federal once for the Weatherby (DON"T!). The brass was hard to work with, and had to be annealed twice to get there. I use a lot of Remington brass, and just never saw much of a problem with it, yet I hear guys complaigning all the time about it. The only serious brass issue I ever had was with the 22-250. I was too lazy to anneal on the fourth firing and waited till the fifth or sixth firing. That's not Remington's fault!
    gary