Thread: 243-06?

Retrieved: 08/22/2016
Last Post: 12/01/2011

So in my restlessness I have come up with my "hairbrained idear of the day" and have started wondering about wildcatting a heavier (100-110gr) 243 bullet into a 30-06 casing. has anyone ever done this? Would it offer any real advantage over a 243 or 308 or would just be a colossal waste of time and money?

taylorce1
November 30, 2011

It has been done several times over and even smaller than 6mm/.243. But the performance over the .243 would be minimal and then only with long barrels and slow powders. The trade of for minimal boost would be an increased throat wear as you force the hot gasses down a smaller bore. The .257 bullet is about as over bore as you would want to go with the 06 case.

tahunua001
November 30, 2011

Yes I just read a short article about 6mm 06 which was basically the wildcat of choice after the 243 was released since 06 components were cheap and everywhere. however with a lot of the ballistics meantioned it looks like they are getting almost identical results as modern factory 243 ammo.

PawPaw
November 30, 2011

6mm-06? Sure, why not. You won't be the first and it seems that there is enough data for you to get started. If you want to use heavier bullets, like the 105-107 grain bullets, or if you want to jump to the 115 class, you're going to need a faster twist barrel. My 243 will just barely stabilize 105 grain bullets, but it does fine with 100 grain. Many of the guys who use the long bullets have changed over to a 1:7 or 1:8 twist barrel.

We've got to remember that Weatherby makes the .240 Weatherby Magmum and some folks use a 6mm-284, so there's lots of starting places when you get ready to reload. Start low, be safe.

Sierra recommends a 1:7 or 1:8 twist barrel for their 107 grain Matchking bulelts.

Linky Here from Rifleshooter Magazine on one such wildcat. rifleshootermag

FrankenMauser
November 30, 2011

When you get into the world of wildcats, even a 6mm-06 may not be a 6mm-06. ...It all depends on what dimensions are settled upon by the cartridge designer, and how well those dimensions are translated to the chamber reamer.

Quote:
has anyone ever done this? would it offer any real advantage over a 243 or 308 or would just be a colossal waste of time and money?

It has been done, in many different ways. My vote: 'waste of time and money'.

Even .270 Winchester is over-bore and inefficient. Dropping to 6.5-06 gets you a little farther over-bore. Getting down to .25-06 is pretty nasty territory (complete waste of a good barrel, with no real benefit over .257 Roberts, .243 Win, or 6mm Rem). Arriving at 6mm-06 puts us in a place where we have a cartridge that is even more over-bore than .220 Swift!

Don't waste your time. A good rifle chambered in .243 Win is perfectly capable of incredible performance. It's just a matter of using that good rifle. Sloppy tolerances and poor fit don't get along well with high pressures.

taylorce1
November 30, 2011

Quote:
As has also been pointed out, it'd be a considerably overbore case, so you'd be using up powder for no special gain, PLUS the thing would probably eat barrels for breakfast.

I think I was the first person to say it is overbore, but it isn't as overbore as the .257 Weatherby. As long as you aren't putting hundreds of rounds a day through the barrel shooting prairie dogs, I'd bet the barrel will out last a guys normal hunting lifetime. Just keep the barrel at reasonable temps and you'll be fine.

kdog70
November 30, 2011

My first two 6mm were 6-06 and 6mmAI. I shot 115 Dtacs out of the 6-06 an amazing cartridge out of a 28 barrel with brake with minute of a deer accuracy. The 6mm AI was a coyote rig and was more accurate than I was. You crank those bullets up to 3300-3400 fps and great things happen. I have firearm ADD and end up buying and shooting 500 rounds or so and sell or stash and buy a new toy or the latest and greatest to play with so I have no clue about barrel life.

I can tell you from barrel eater experience the average shooter will not shoot enough or fast enough to burn out a barrel. If you are not a super accurate shooter with the set up for great groups you may never notice. My dad shoots a 243 for coyote and deer and it shoots 2 inch groups at 100 and he is happy as ever. Your mileage may vary but don't be afraid to try something different every now and then.

Scorch
December 1, 2011

6mm-06 is a heck of a round, comparing it to a 243 is ludicrous. It is like a 243 on steroids. It will launch a 6mm 115 gr bullet at 3300 fps, a 243 would be doing good to hit 2800 fps with that bullet. 6mm-06 is a well-established wildcat, in fact it is one of the most popular wildcats based on reloading dies sales. Reamers are available.

There are lots of different versions: AI versions, versions based on the 270 Win case, different shoulder angles, etc. There is even the 6mm Gibbs, using a 30-06 case with the shoulder moved .150" forward.

troopcom
December 1, 2011

My thoughts is that if I build a custom rifle it would be a 6.5-06 over a 6mm- 06. I've read that the 6.5s fly better.

GeauxTide
December 1, 2011

Extreme overbore. A 6.5-06 gives you 87-140gr bullets with extreme ballistic coefficients. Example, a 120gr Nosler can be pushed faster than the 24 could push a 100.

taylorce1
December 1, 2011

Quote:
It will launch a 6mm 115 gr bullet at 3300 fps, a 243 would be doing good to hit 2800 fps with that bullet.

Scorch while I have no reason to doubt you I have no experience with the 6mm- 06. I built a fast twist .243 Win last year and am able to break 3000 fps with the 105 A-Max and 107 SMK I have backed them down to a little below 3000 though. I haven't tried the DTAC or Berger 115's yet but my 1:7 twist barrel can shoot them.

Here is some sample load data that I used when I started building loads for my .243 win. I found some load data for the 6mm-06 as well. Work up to these loads if anyone is going to try the as they may not be safe in your rifles.