Gunsmithing 6mm Rem AI questions

jeffbird

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This round has caught my eye for a potential match round as it appears that it will add 250 - 300 fps over a 243 with the heavier 6mm bullets.

Would appreciate some input on a few questions.

Will this knock over a steel reliably at longer ranges?

Will this round feed out of an AI AW mag and function reliably in the AW rifle?

Can I buy an AI 243 barrel and just have it reamed to this round?

Any downsides to this round over a 243 other than using up the barrel faster?

TIA.
 

JCH

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Re: 6mm Rem AI questions

You might want to consider doing it on a long action. Otherwise you may have to load your bullets short and down to magazine length.

Other than that, yes it is a great cartridge. I have hit steel consistently at 1000 yards with my 243AI that I had at the time. My 243AI fed fine out of CDI bottom metal using AI mags.

The downside is fireforming. To take full advantage of the case capacity and steep shoulder you will have to fireform the case. By doing so you are taking away life from the barrel. There are ways to fireform without using bullets. (PM me and I can tell you several ways if you decide to go Ackley)
 

jeffbird

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Re: 6mm Rem AI questions

I have an AW rifle and was considering buying a 243 barrel for it. While looking at the Sierra manual for 243 load data, I noticed this one. So I really want to see if it is possible to do it easily in the AW rifle rather than building another rifle. Swapping to the 243 is just a quick barrel change.

Is the 243 AI was worth doing over a 243? How much velocity did you gain, and was it as accurate as the 243?
 

JCH

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Re: 6mm Rem AI questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jeffbird</div><div class="ubbcode-body">I have an AW rifle and was considering buying a 243 barrel for it. While looking at the Sierra manual for 243 load data, I noticed this one. So I really want to see if it is possible to do it easily in the AW rifle rather than building another rifle. Swapping to the 243 is just a quick barrel change.

Is the 243 AI was worth doing over a 243? How much velocity did you gain, and was it as accurate as the 243?

</div></div>

The gain is 10% (roughly) in case capacity. I was able to push a 105 amax at 3300 +/- using R17. I however chose to run the 105 at 3050fps because my rifle shot crazy accurate at long range using that load.

The ackley lets you run higher pressures more safely than with the vanilla 243. To me it was worth it. To others it isn't. I can say that a bullet with a BC of .50 at 3300fps is ridiculously good.
 

jeffbird

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Re: 6mm Rem AI questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JCH</div><div class="ubbcode-body">I can say that a bullet with a BC of .50 at 3300fps is ridiculously good. </div></div>

Yep, that looks easy to like.
 

DAVETOOLEY

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Re: 6mm Rem AI questions



[/quote]


The ackley lets you run higher pressures more safely than with the vanilla 243. [/quote]

I disagree and that statement might get someone hurt.

Changing the shoulder angle has nothing to do with increasing safe operating pressures. It just gives more powder capacity. You can't fool mother nature by just changing the shoulder angle. Pressure is pressure. Regardless of the headstamp or shoulder angle brass starts to flow in a narrow range of pressure.
 

rth1800

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    Re: 6mm Rem AI questions

    As one of the posters mentioned, case capacity is increased by a MAX of 10%. Very few if any AI's will actualy do this well. This will provide 2-4% more velocity at equal pressure. Any gain over that is due to overloading. A standard cartridge can be overloaded as well. For some reason it seems unsafe loads are not as fun with a 20 degree shoulder. The Ackley cartridges are and always have been a bit of a gimmick. The 40 deg shoulder is a nuscence and feeds poorly. Fire forming and more expensive dies, less barrel life, brass loss etc. I would just reccomend getting a bigger case if you want one. 6x284 comes to mind. I have and have had many wildcats. (k hornet, 22 varminter prior to standardazation, 275 H&H, 375 improved etc. Most are not worth the effort today, as there are no gaps to be filled.