6mm SLR vs 243 AI ??

Discussion in '6PPC, 6-6.5x47, 6XC, 6 Rem, 243' started by Stickler, Feb 21, 2019.

  1. Stickler

    Stickler Silver $$ Contributor

    Mar 8, 2015
    For those that load both, do you see enough difference in one or the other to warrant loading another caliber?
  2. XTR


    May 15, 2011
    There are some differences.

    1. fire forming. In an SLR you don't. You size new 243 brass in your 6SLR die, load, and shoot. With any AI you have to fire form to blow the shoulder out.

    2. case capacity. I've measured my fired 6SLR cases compared to brand new WW 243 cases and the water capacity is the same. In a 243 AI you will gain ~3% in case capacity, in round terms about 1.5-3gr.

    3. Velocity. The 6SLR can get the same velocities as the 243, with a long neck and a better shoulder angle. With the 243AI, in real world velocity, you can gain about 50 to 75 FPS for a given pressure. There will be those who may claim 150 FPS, and I'm sure they're getting it, but there is only about 150 FPS between a 308 and a 30-06 with a ~21% increase in case capacity, so if they are getting that much they are running higher pressures.

    4. brass. The easiest way to make SLR cases is with WW brass. It's what I run today. If you want to run more expensive brass you're going to have to turn necks because they (Lapua, Peterson, Alpha) have thicker brass in the shoulder that gets pushed into the neck when you make the SLR. Something to consider though, I have read that Alpha or Peterson is making 243 small primer brass. That may be worth turning necks.

    I think the SLR is better, you get the advantage of a 30* shoulder and a long neck. The AI gives the case a good shoulder but does nothing for the neck and adds a tad bit of capacity and velocity, but they can both get you north of 3100FPS with 105 class bullets in long barrels.

    I'm personally not a fan of AI's made from cartridges based off of the 308 (or pretty much any modern case). They are all already a pretty straight walled to begin with, so it buys you very little for your work. When PO Ackley was blowing out cases like the 30-40 Krag it went from a tapered case with a 308 capacity to a straight walled case with a 30-06, that's a big improvement.
    Raptor, 6MMsteve, bullzeyenj and 3 others like this.
  3. swd

    swd Silver $$ Contributor

    Nov 25, 2008
    For what application and bullet range??
  4. 1shot


    Feb 19, 2006
    Everything said here is spot on. I shoot the AI for varmints, but I compete with the SLR. The SLR is my go to rifle for mid range matches where there is money on the line.
    I hope this helps,

    6MMsteve likes this.
  5. germanlongbow

    germanlongbow Scott M Bainbridge

    Apr 24, 2011
    I've shooting the 243AI for 6 years. All of the above is true. Barrel burner, brass destroyer, feeding issues. I'm not a fan of jumping on the popularity band wagon of new cartridges every other month. The SLR does offer some better options. Brass and barrels are no different than buying tires or putting fuel in you dodge, chevy or ford. Good luck with choice, either way plenty of more to build in the future.
    bullzeyenj likes this.
  6. Geno C

    Geno C

    Aug 2, 2014
    The SLR is pretty much a 6 Creedmoor, if you can admit to shooting a creed... :) I’ve shot a 243ai for 12 years and love it. The little extra speed isn’t really needed for anything but it sure is fun!
    stacy likes this.

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