Choosing the Best Cartridge for My Rifle – 6mm Options

To follow the entire series on my custom rifle build, click here.  (The most recent will at the top of the page.)

Choosing the cartridge is one critical step in building a rifle – and which one you choose depends on what type of shooting you plan on doing.  I have really been digging for info, weighing the pros and cons of various cartridges, and realized there is A LOT of debate on this issue.  What I have come to realize, is – there is no perfect round.  Otherwise, as one of my friends says, “Everyone would be using it.”  I have not decided which case I am going to use, I have not even decided if I am going to make it a 6mm.  So, this post will cover some of my 6mm options, and I will discuss 6.5mm and 7mm options in different future articles.

You will find the chart below, but click on the chart, or click HERE for a .pdf version.

I have included some 6mm rounds in my comparison that are not typically used for tactical long range shooting.  I did this for myself and for those who are learning about various cartridge sizes and types.  This way, if you hear someone talk about a 6BR, for instance, you will know what they are talking about.

I also added some cost info, take all of this with a grain of salt.  For instance, Lapua brass is very expensive, but people say you should be able to reload it twice as many times as any other brass, so maybe it all works out.

Some assumptions I am making for my rifle is that I will be using a short action and plan on using 105, 107 or 115 gr 6mm bullets.

I am sure that many of my comments in this spreadsheet are debatable, so let’s talk!  What are your experiences with these cartridges? Which ones do you recommend and why?

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5 thoughts on “Choosing the Best Cartridge for My Rifle – 6mm Options

  1. I agree there is no “perfect round”, but a lot of this work has been done for you. Take a look at some of the results of “Tactical matches” around the country, what are the predominate calibers in the winners circles? A few years ago the vast majority would have been .308, today things have changed. The last match I attended, out of 30 or teams there were two people shooting .308’s, not teams mind you, people. The match was won by a team where both members were shooting .260’s, and the second place team shot a .260 and a .284, 6.5mm cartridges seem to be the flavor of the day at tactical matches I’ve been to. But we all must pick our poison, to the best of my knowledge the heavy 6mm bullets give up nothing in the wind to a 6.5 and shoot flatter and with less recoil to boot! Barrel life being the only possible drawback, but if you’re shooting matches and practicing regularly you’re going to be replacing barrels on either at regular intervals, barrel life is an over exaggerated expense IMHO when compared to the big picture.
    Something else I’ve not seen you mention is, after you figure all this out who is going to build your “Dream Rifle”? Whoever it is, I suggest you ask them as many questions as possible, a reputable Gunsmith with experience building tactical rifles has more knowledge about what works (and what don’t) than most of us will learn in a lifetime. Make him your best buddy, send him Christmas cards cause you’ll want him working on your rifle down the road.
    But if you’re doing it this way just to learn as you go, well….carry-on Navy girl.

  2. The best way to find the perfect round is to get one that you can afford to practice with alot. each person seems to have a different idea of what “long distance” is. To me, it’s anything further than the 5.56 round will go (let’s say past 400 meters). A good highspeed low drag round will do that with the right equipment and skill. But to do it all the time, you have to practice.
    The CA NG state high power rifle team had match grade M14s with OPEN iron sights that shot up to 1,000 yards. that was using match grade 7.62 NATO ammo. The stock NATO ammo will almost do that.
    anyway, when you figure it out, write about it.

  3. If it was for me, Ide pick the 243 Winchester as Brass ,Bullets and Factory ammo is available every where. First off Ide either use a Remington 700 or a Winchester 70 Action. Then Ide give Shillen Barrel Co in Texas a call. If you are shooting the 100 – 115 grain bullets Ide ask Shillen for either a 1 in 8 1/2 or a 1 in 9″ inch twist Barrel. If you favor the 115 grain Bullets go with the slightly faster twist but either one will be fine. For Long range varmints its hard to beat the Berger Bullets. They put out a video a few years back about there Bullets and they were taking Coyotes at almost 800 yards. Thats impressive ! IMR 4350 seems to be the go to powder for that Ctg if you are reloading it although Ram Shot makes a powder that is just awesome and slightly cheaper than IMR. If you are looking for a hunting gun that will shoot Target grade accuracy, Its hard to beat a Thompson Center Icon ! Right out of the box I put a 4X16 scope on it, bore sighted it then proceeded to put 10 rounds in one little hole just a little bigger than the bullets diameter. They come fully aluminum bedded with an adjustable triger and the Weaver Bases are machined right on the receiver as an integral mount. I love, excuse me , LOVE That rifle so much I got four of them. One in 300 Win Mag, Two in 308 Winchester and one in 243 Winchester . If you are going to buy one of these rifles make sure it says Made in New Hasmpshire not Ma. The NH Guns are the original ones and the Quality is unsurpassed . Unfortunatly most of the people who made these Awesom Guns didn’t take the trip to Ma. When the company was sold to Smith n Wesson. Any way I could go on and on but I think ive given you a little info on my thoughts. Its entirely up to you on what you want to do. Oh I didn’t mention trigers Both Shillen and Timney make real nice triggers and depending on what action you decide on will depend on what one you use. What ever you do Don’t Cheap out on the Barrel as I went through and still am going through a nightmare with an Adams n Bennett Barrel on a Mauser action in 25-06. The Barrel was on sale and I should have known better . First n last AnB Barrel ill ever buy. What ever you decide,Good Luck and Happy Shooting ! John

  4. Tell her she forgot to mention the ultimate long range round the 6.5 284 Norma but it does require a long action all the other rounds she listed are based on a short action. George

  5. I agree closely with John’s posting on June 19th. with this caveate: I get the feeling you are leaning toward a tactical rifle? My experience has been the .243 is a round that performs far out of it’s class. It will perform decently with almost any load/powder combo you can throw together.
    That being said, as a reloader I haven’t had much sucess with the heavier bullets ( over 100 grains) which can most likely be attributed to my rifle, a lightweight sporter.
    I am primarily a hunter and the .243 is a decent round for many North American game animals. This same lightweight sporter is capable of shooting a 5-shot grouping of 3/16″ at 300 (yes 300!) yards with a pet-load. Oh, and I have the witnessed, signed target. This of course was in perfect conditions, from a bench, with a lead sled. I use this example to illustrate the accuracy available in the .243 round.

    PLUS ! It’s so danged fun to shot…..no recoil, minimal blast and low report….fun !! all three of my daughters began their hunting careers on the .243 and did very well with this round.

    If you want to shoot ammo off the shelf, it is readily available everywhere, at decent prices.

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