243Win. vs 6mm Rem.

6mm REM is a necked down x57 Mauser case. It can hold more powder.

I am looking at Hogdon's website right now and it shows max loads for the 6mm Remington at least 1-3 grains more than .243, in some cases over 5 grains more. Obviously using the same powder for comparisons on both

51 grains of what? With what bullet?
Where is that in relation to book maximum?
I guess you can shop for data and read the numbers as you like, but MY Lyman and Speer data give the 6mm about a 200 fps lead over .243 with top loads of the best powders and 100 grain bullets. Nosler "only" a 100 fps advantage.

Jim Watson said:

51 grains of what? With what bullet?
Where is that in relation to book maximum?
I guess you can shop for data and read the numbers as you like, but MY Lyman and Speer data give the 6mm about a 200 fps lead over .243 with top loads of the best powders and 100 grain bullets. Nosler "only" a 100 fps advantage.

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Looking at Hogdon's site right now

100 grain bullet
Varget
.243 MAXIMUM load 33.7 grains
6 mm Remington MINIMUM load 36 grains

Well I am no reloader but having owned both the 6mm and two 243's the deer and hogs felled by all three would probably plead no contest as we are all quite dead.
At the end of the day as far as factory ammo is concerned I prefer the 243 because of easy availibility and cost.

What weight bullet, Sam? What powder?
Hodgdon does not go to 51 grains of anything in .243 except with bullets 70 grains and lighter, three listings total; unless I have missed something on their www.

They have five 51 grain loads of one powder or another in 6mm, also with those fleaweight bullets (that don't interest me at all.)

There was a guy here who thought how much powder the case would hold was what was important. He liked to fill them up. He blew up a gun every now and then.


I tend to agree, Heeler, the .243 won the advertising battle long ago; Remington made some mistakes with the .244/6mm and their rifles were not as pretty as the Model 70.

the added case capasity allows you to shoot the same weight bullet a tad faster without increasing the pressure. Ive used both alot and the 6mm will buy you an honest 100 fps maybe 150. Does that make it a better killer? I dont know. Both have given simular results on deer sized game for me. The 243 might hold 51 grains of powder but smash that down with a bullet and pull the trigger and see what happens.

Case capacity is measured in grains of water...not grains of powder

grains is a measure of mass. Different powders have different mass per volume. You cannot say "cartridge X will hold X grains of powder" You have to specify WHAT powder.

That is why it is easier to just measure case capacity by grains of water. Water always has the same volume per mass


Case capacity of the .243 Winchester 52.8 grains of water
Case capacity of the 6mm Remington 54.6 grains of water

Sam the 6mm will hold more powder and is faster. Your manuals are examples of a modern fear of liability and are not giving you the whole story. The 6mm Rem can be loaded so that it's velocities and performance are closer to 25-06 than 243. The heavier the bullet the more the 6mm shines. It also produces much more uniform pressure from round to round and lot to lot than 243 especially with 100 gr bullets. 243 can exhibit strange pressure spikes with heavy bullets in some guns. 6mm does not. The 6mm is a superior cartridge in every respect except for the fact that it is a little longer. If they made an action designed to fit it, there would be no comparison. Also a problem you run into with 6mm and standard reamers (standard throat) is that when you load the bullets out long enough to touch the lands, you probably are too long for the magazine. Early 6mms had slow twist barrels and even late guns with a 1:10 twist may not stabilize an ultra long bullet like a swift scirroco. If you want to be sure to stabilize everything I would go 1/9. To get the best accuracy fireform your brass and then neck size.

Fifty one grains of Win780 with a seventy grain Sierra. Did you find that load published somewhere? If not, what made you think it was safe to use?
15 grains of powder in a 218bee with a 52 grain Sierra bullet. What powder is that?

With some other powders, that 51 gr charge might cause bad things to happen quickly.

What is the difference, from what I can find they are about the same...........

For field use, it's pretty much six of one, half-dozen of the other.

In the FWIW department, Charles Whitman used a 6mm Rem...

Bullet diameter being the same and powder capacity solidly in 6mm Rem favor, it's a no brainer which one is faster.

As far as practical effectiveness, other than than the undeniable 100 + fps & flatter trjectory that goes with 6mm Rem..

Well... I guess it is personal opinion...

The actions are the same

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Not really.

The 243 Win (introduced in 1955) has a case length of 2.045 inches. Being based upon the 308 Win (7.62x51mm case. And an overall loaded cartridge length of 2.710 inches.

The 6mm Remington (aka 244 Remington from 1955) has a case length of 2.233inches, being based upon the 7x57mm Mauser case. And an overall loaded cartridge length of 2.825.

The 6mm Remington / 244 Remington does not like true short actions. To be loaded for max performance it should be in a Model 48 Mauser length action or the longer M-98 action. This gives you more room for powder and takes advantage of the longer case neck of the 6mm Remington as compared to the 243 Win.

(The same story with the 257 Roberts which suffers from US makers trying to shove it into a short action by pushing the bullets back into the powder area of the case. )

The downfall of the original 244 Rem was supposedly the original twist rate of 1 in 12 which would not let it stabilize longer bullets. Thus the better twist rate of the 243 Win helped them make more sales. It was not until the mid 1960s that Remington went to a better twist rate, but by then they had lost marketing momentum.

A custom built 6mm Remington on a proper length action is hard to beat. If you want a factory rifle to shoot factory ammo, get a 243.

If you need that extra 5% and are willing to pay for it and work for it, the 6mm is superior.
A friend has a full house target rifle in 6mm Rem on a Tikka action that is a great shooter, but still a rarity.
There are a few people shooting .243 at Long Range to get into a short action.
Both have mostly been passed by for target shooting and the .243 definitely won the Ad Wars for hunting. I'd rather have the .257 for that.

The 243 uses the same barrel as a 6mm.The actions are the same.There is a tad different bolt face,maybe.

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As Float Pilot pointed out, they do not use the same action. 6mm Rem needs an intermediate or long action.

Bolt face is the same. Both are .47", and use the same #3 shell holder as all .308/.30-06/7x57 based cartridges.

The 6mm's advantage is slightly higher velocity and a longer case neck that allows one to play with seating depth more. If one handloads, the 6mm is a better choice. If you don't, .243 is the way to go, since there are all of about 3 fatory loads for 6mm.

Since I have both:

The two are so close in practice as to be practically identical.

Except:

The velocity that can be achieved does depend to a large extent on the action. For example, a 6mm Remington that is perfectly safe in a Remington Model 700 action is way over pressure in a Remington Model 788 (think perforated primers and sticking bolts). I found this out working through some of Ken Water's 6 mm "Pet Loads" (Note to the unwary: If Ken said it was MAXIMUM, I suggest that you stay well away from it).

How efficient the cartridges are is, in part, a function of case volume. A 243 has a smaller volume than a 6 mm Remington. With the same action, bullet, primer, and powder, the 243 can achieve the same working pressure as a 6mm Remington with less powder. Working pressure is one of the factors translates to velocity. BUT:

Some barrels are faster than others, and all chambers are different. (I know of two 270s that are "identical", except that one chronographs about 200 fps faster than the other WITH THE SAME LOAD).

So, we are essentially discussing something akin to how many angels can dance on the head of a pin.

Your Mileage may vary.

A final note to new handloaders that want to become old handloaders: Pay very close attention to the powder burn rate and adhere to the published data. Only put one type of powder on the bench at one time and triple check that you are using the correct type. Note that some pistol powders have labels very similar to labels on rifle powders. Just because the powder will fit in the case does not mean it is safe. If you find a load that is safe with, say, 50 grains of 4831, take it on faith that if you stuff 50 grains of, say Red Dot in the case, you have just created a very dangerous bomb that will destroy the firearm and who ever is shooting it.

There was a guy here who thought how much powder the case would hold was what was important. He liked to fill them up. He blew up a gun every now and then.

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That guy's user name was "Clark".

The OPs user name includes "clrk". I wonder if they're the same guy?


Anyway, just because you CAN stuff a case full of a given powder, doesn't mean that you SHOULD do it. Depending on the powder this can be dangerous!