243 or 6mm reminton

Powerful enough for what? A whitetail? Definitely. A mule deer? Probably with a heavy bullet. A 6mm Remington shouldn't have any trouble getting a 115gr VLD to 800yds above 1800fps. It would probably kill deer just fine below 1800fps.

There's a guy on another forum that claims 87gr VLD's are excellent mule deer killers. I like to hit mule deer with more than 87gr, but that doesn't mean it won't work just fine. I killed my first mule deer with an 85gr solid base at 475yds.

Believe it or not, the BC on that bullet is so bad that it has the same energy at 500yds that a 115VLD from the same cartridge would have at 1000yds. So yeah, I think 6mm's have enough "power" for deer. I personally would recommend 105gr or more for large deer, and might not recommend a 6mm for elk, but a 243Win, 6mm Creedmore, or 6mm Rem should all be excellent deer cartridges, even at long range.

I've got a bolt action 6mm ARC that's 1800 FPS out to 600 yards with the 103 ELDX
 
I've got a bolt action 6mm ARC that's 1800 FPS out to 600 yards with the 103 ELDX
Read all the reviews and no one has mentioned 6XC! Have an AX AI with 3 barrels (260, 6XC and 6.5 CM in a proof CF). All three are headspaced to screw on and shoot, easy peasy. Longest shot on pig with 6XC was 425', one and done, using 115DTACS.
 
I love the .243. I have a cooper custom classic and I had it put together with a 24" bbl. I use a 85 grain Sierra BTHP Gameking in mine in 42 grains of IMR 4350. The little Sierra is absolutely deadly on groundhogs and deer out to 260 yards. I have used 95 grain Noslers in it too but honestly, the Sierra seems to kill better.
 
It is really up to you. If you want something that is mainstream with readily available ammo and brass then go with the 243. If you want something uncommon, and shoots faster/flatter but ammo/brass is harder to find then the 6mmRem is your choice. Plenty of 6mm Remington ammo is still out there, you just have to look a little and it will be a bit more expensive. You will generally have more COAL to use with the 243 over the 6mmRem but varies by rifle.

I tend to want the uncommon round so I would go with the 6mm Remington.
 
A thought just popped into my head...How hard is it to make 6mmRem brass from 7x57 brass?
 
A thought just popped into my head...How hard is it to make 6mmRem brass from 7x57 brass?
1) Run it through a full length die with a good lube. If you get dents in the shoulder, that's too much lube. If it chatters, your lube isn't good enough. Imperial Die Wax works. Too much will cause dents.

2) Know the neck diameter of your chamber via measuring a fired, but not sized case neck, or asking your gunsmith. Seat a bullet in a 7x57 case that you sized down to 6mm Remington. If it's not at least .001" smaller than your chamber neck, then you'll have to turn necks thinner, or ream them. I honestly prefer turning necks, so I don't mind if they're a little thick after sizing down.


3) Anneal your neck or you'll get very few firings before splitting case necks after sizing down. Because I have usually done a fair bit of trimming, turning and sorting, I want maximum case life after all that work, so annealing is a must for me if I size a neck up or down for a different caliber.
 
In addition to what ImBillT advises, as you neck down, the length of the case grows, be aware of this issue.

Necks will thicken as you neck down, and this may or may not be an issue, depending on the dia of the neck in your chamber.

For the win in a project like this, Neck turn at 7mm, then neck down. K&M's neck turner and mandrels make neck turning easy. When neck turning at 7mm, I cut all the way to the shoulder, then neck down. When the case is formed, part of the very end of the cut at the shoulder/ neck junction, becomes part of the shoulder which impedes the formation of doughnuts at the shoulder/ neck junction.

Accuracy on cases that are prepared this way is supurb, to say the least.

To make the neck turning simple and quick, I use a variable speed 1/2" drill, the type with the speed adjustment that is a small wheel on the trigger. I simply grip the small amount of the mandrel that is sticking out of the neck turner with the drill. I put the drill in a bench vise, leave it running at the desired speed. You can turn 5-6 cases per minute with .0001 run out. Put some lube in the case mouth prior to neck turning.

For those that have not ever tried the 6 Remington AI, it is one heck of a cartridge, extremely accurate and fast. Add 200 fps to the std 6 Remington. 95g Nosler Ballistic tips with their solid base will take the rotational torque at 3500 fps+ with extreme accuracy. If you want to use a 105g Berger VLD hunting bullet, use a barrel with 5R land design, 3350 fps will be your approximate accuracy node on a 26" barrel.

Here in the South, I have two friends shooting the 6 Gibbs with 26" barrels. They shoot the 70g Nosler ballistic tips at 4300 fps+, and the 55g Nosler ballistic tips at 4500+ on deer. I was shocked, and they were reluctant to tell me of what they were using, but I had extra bullets they were desperate to get their hands on, I have known them for years. These two guys kill a LOT of deer, and they said, with a smile, deer never took a step after being hit. By their account, the solid base Nosler bullet allows great penetration on deer.
 
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In addition to what ImBillT advises, as you neck down, the length of the case grows, be aware of this issue.

Necks will thicken as you neck down, and this may or may not be an issue, depending on the dia of the neck in your chamber.

For the win in a project like this, Neck turn at 7mm, then neck down. K&M's neck turner and mandrels make neck turning easy. When neck turning at 7mm, I cut all the way to the shoulder, then neck down. When the case is formed, part of the very end of the cut at the shoulder/ neck junction, becomes part of the shoulder which impedes the formation of doughnuts at the shoulder/ neck junction.

Accuracy on cases that are prepared this way is supurb, to say the least.

To make the neck turning simple and quick, I use a variable speed 1/2" drill, the type with the speed adjustment that is a small wheel on the trigger. I simply grip the small amount of the mandrel that is sticking out of the neck turner with the drill. I put the drill in a bench vise, leave it running at the desired speed. You can turn 5-6 cases per minute with .0001 run out. Put some lube in the case mouth prior to neck turning.

For those that have not ever tried the 6 Remington AI, it is one heck of a cartridge, extremely accurate and fast. Add 200 fps to the std 6 Remington. 95g Nosler Ballistic tips with their solid base will take the rotational torque at 3500 fps+ with extreme accuracy. If you want to use a 105g Berger VLD hunting bullet, use a barrel with 5R land design, 3350 fps will be your approximate accuracy node on a 26" barrel.

Here in the South, I have two friends shooting the 6 Gibbs with 26" barrels. They shoot the 70g Nosler ballistic tips at 4300 fps+, and the 55g Nosler ballistic tips at 4500+ on deer. I was shocked, and they were reluctant to tell me of what they were using, but I had extra bullets they were desperate to get their hands on, I have known them for years. These two guys kill a LOT of deer, and they said, with a smile, deer never took a step after being hit. By their account, the solid base Nosler bullet allows great penetration on deer.
After using a K&M for a few years, I have to say it sucks, and that's why I don't own one anymore. Too small a body. Too small a cutter. Their expander die sits too low and doesn't allow you to adjust it to hit the proper part of the ram's stroke. Their threaded rod for a stop bends too easily. There case holder for a drill may be the worst part of all. Their mandrels need more taper, and are a different size than most, so you can't even buy a good mandrel and circumvent that problem like you can with the expander die and case holder. I hate all of K&M's turning products, send will never go back. There was a time when turning equipment that was better on all other fronts had adjustments that were inferior to the K&M, but that time has passed.

Also, although popular wisdom seems to be that cases increase in length when necking down, unless I've made some very serious mistakes, they actually shorten. This makes sense geometrically. You're turning what had been neck into shoulder. It makes sense that it would shorten. My reloading room is being moved and I do not currently have access to a press or I would double check that. Perhaps I'm mistaken, but I'm fairly sure that necking down results in shorter cases with thicker necks,
 
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I ran a 6/06 for years, with the 55 and 70 and 95 NBT's it was a decisive killer on game from yotes to elk!
 
When I was young and into my middle years, I hunted Whitetail and Mule Deer with a 6mm Remington using 87 grain Hornady SP bullets. I harvested a lot of deer with it and all but one dropped in their tracks! However -- and it's a big however -- I 'placed' that bullet in the ribs for a lung shot with all the deer I shot! The 87 grain was considered a varmint bullet at the time and with every deer I gutted, the lungs were completely pulverized! If you're hunting the heavy woods and can't be as precise as I was with that bullet, use a 100 grain bullet. Also, if you're a handloader, the 6mm Remington is superior to the 243 Winchester! If you are not a handloader, the 243 will be far, far more common on the retail shelves. In fact, you might not find any 6mm ammo on the retail shelves - so you should opt for the 243!
 
87g Hornady flat base, I buy all that I find. I prefer the Speer 85g btsp vs the Sierra 85g bthp, it is tougher and has a bc of .401.
I shot cow elk with the 100g Norma Ornx bullet(factory) and the 100g Nosler partition, max load of 4350 in a 243 with shots never over 100 yards, never having to track one. Without a doubt, the 100g Norma always pleases you on penetration and vitals just blended, but I would not use this bullet on small deer.

With R#26, both the 243 and the 6Rem are transformed into exceptional cartridges. The 105g Berger VLD Hunting bullet is worth building a rifle around for deer/hogs, use a 5R barrel for the fastest speeds you want to attain.

BillT, sorry to hear of your woes with the K&M, I seemed to have worked around all those issues. On another issue, cases do grow in length when you neck down. I made my own case holder, vs k&M that I never owned. Bill, what neck turning tools are you using now to circumvent the problems you found with K&M?
 
My 6mm Remington Cooper mannlicher really likes 85 grain Speer boattails..
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