6mm Cartridges.

BLUEROLL

Well-Known Member
Looking for opinions on 6mm cartridges that may be more efficient than 243 in a 20" barrel please . Bullet will be 85gr Sierra GK (1530) and make deer legal in England.
 
'Efficient' is an interesting question.
Perhaps the greatest amount of energy in the powder converted to energy in the bullet? Or financial: energy in bullet per cost of powder?
 
The list will be a short one. Maybe a list of... one.

6mm Creedmoor

Having studied 6 mm for a fair few years the Creedmoor is the only one that I would change to. But if I was limited to only your choice of bullet then I wouldn't bother changing.

There's not enough of an upgrade to bother going to 6mm Rem.
 
Define "efficient" pls, @BLUEROLL
Yes sorry maybe should have explained in more detail.
After finding that I can achieve the same MV (same bullet) with my 6.5x47 (18" Barrel) using 39.5gr of Varget as I can in my 260 (20" barrel) using 47gr of H4350, I was thinking along the lines of a smaller case in 6mm. The load of 45gr H4350 does not fill the Lapua 243 case, so I thought I might be able to get better load density in a smaller case and maybe even using a lower charge of Varget in a high pressure case, like the Lapua 47 case or the fact that Lapua now do a 6mm Creedmore case, both with small rifle primer.
 
You could do it with 6.5 Grendel and under 30 grains of powder. Seriously considering it, mainly as a target rifle, very similar ballistics to a .308 but much cheaper to feed.

If you are looking at sub-100 grain bullets they would only be legal in Scotland for roe, for which I'm sure the Grendel would do the job, and is actually optimised for 100 grains plus, and just about legal for all species, suitably loaded.

Here's a commercial example:



VELOCITY
(FPS)
ENERGY
(FT/LB)

2580
1818


It seems like a very efficient, and potentially accurate little cartridge.
 
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There are a couple (or six) 6mm versions of the Grendel. You're into wildcat territory though and also the Grendel has a smaller case-head than the 243 so your bolt wouldn't be a great match. Also, the Grendel case is actually a tad lower capacity than the 6mm BR so there is no benefit in a rebarrel to it rather than the BR except for magazine feed. The 6mm Grendels were mainly developed by Robert Whitley in the USA for AR shooters. They offer very efficient little sixes that fit the length constrained AR magazine and operate reliably in this design's action.

You only really have three or four readily available options - 6mmBR; 6mm Dasher using off the shelf Norma brass to avoid the hassle of fireforming the 6mm BR case; 6-6.5X47 Lapua; 6mm Creedmoor (using small primer brass if desired). The 6-6.5X47 whilst a 'wildcat' is an easy one - most accuracy orientated gunsmiths have the chamber reamer and dies are (or certainly used to be) widely available at not much more cost than the standard chamberings. Then simply resize the standard Lapua 6.5x47L case in the new die. You'd just have to specify a no-turn chamber.

The Creedmoor is the easiest and most likely the most practical way forward though, but when all's said and done, it's not that much smaller than the 243 and with the 85gn GameKing offers a relatively small efficiency improvement or powder charge reduction. With small primer brass it could be loaded rather hotter than the 243 though if maximum MV is desired within the package. (Small primer 243 is becoming available off the shelf now though, although with some slower burning powders, you are pushing the available ignition power to or beyond its limits especially in very cold conditions.)
 
6mm Remington is a better cartridge IMHO. Except that in most rifles the twist rate won't stabilise the modern bonded bullets or Partition bullets of 100 grain weight. But even if not that much better it is certainly a more elegant cartridge.
 
Thanks for the info Guys, all very interesting.
The rifle has only just arrived with Callum so will be waiting to hear his opinion, he has not let me down yet with the 2 re-barrels and his custom 6.5x47 (work of art in form and function). The results with the 6.5x47 is the prompt for this thread.
 
Looking for opinions on 6mm cartridges that may be more efficient than 243 in a 20" barrel please . Bullet will be 85gr Sierra GK (1530) and make deer legal in England.
My favourite is this one - 6XC Cartridge Guide within AccurateShooter.com
Regards
JCS
 

Yes, I forgot the 6XC. It is a very nice cartridge and it is significantly smaller than the 243. Easily deer act compliant with a 20-inch barrel. Good brass (Norma) and dies are readily available these days.

Here is how it stacks up against the competition in case capacity (grains water):

6-6.5X47 Lapua ......................... ~47gn
6XC .................................................. 49.7gn
6mm Creedmoor ..................... ~53gn
243 Win ......................................... 54gn

It'll be very interesting to see what Callum recommends. He's a great 6.5X47L fan in the 6.5s (and was for 260 Rem before the Lapua appeared), but I don't know what he favours in the sixes.
 
Yes, I forgot the 6XC. It is a very nice cartridge and it is significantly smaller than the 243. Easily deer act compliant with a 20-inch barrel. Good brass (Norma) and dies are readily available these days.

Here is how it stacks up against the competition in case capacity (grains water):

6-6.5X47 Lapua ......................... ~47gn
6XC .................................................. 49.7gn
6mm Creedmoor ..................... ~53gn
243 Win ......................................... 54gn

It'll be very interesting to see what Callum recommends. He's a great 6.5X47L fan in the 6.5s (and was for 260 Rem before the Lapua appeared), but I don't know what he favours in the sixes.
Hi Laurie.
Yes the 6XC has got my interest, but was thinking along the lines of Lapua manufatured cartride case determining my choice. Are Norma cases good/consistent quality please ?
I will let you know what Callum says.
 
Are Norma cases good/consistent quality please ?

Yes, very good. They're maybe not as strong as equivalent Lapuas, certainly not in the case-head as they are large primer whereas Lapua BR, 6.5X47L, and 6.5 Creedmoor are small primer / small flash-hole. A lot depends on how hot you want your loads - if you're running max pressure better to go small primer Lapua. On the other side, the Norma large primer XC case has ignition that copes with any powder grade and extreme cold-weather stalking temperatures.
 
Yes, very good. They're maybe not as strong as equivalent Lapuas, certainly not in the case-head as they are large primer whereas Lapua BR, 6.5X47L, and 6.5 Creedmoor are small primer / small flash-hole. A lot depends on how hot you want your loads - if you're running max pressure better to go small primer Lapua. On the other side, the Norma large primer XC case has ignition that copes with any powder grade and extreme cold-weather stalking temperatures.
Hi Laurie.
Thanks for the info.
I am looking to use a lower charge of faster powder than H4350 and have plenty of Varget, so hoping to use it for a 6mm cartridge along with 6.5x47 and 308.
 
My favourite is this one - 6XC Cartridge Guide within AccurateShooter.com
Regards
JCS

I'm definitely with JCS I have a 6XC and love it mine is a 20" barrelled rifle built on a defiance deviant action and sat in a PSE ETAC carbon fibre stock, I'm getting 2940fps with a 105 grain projectile.
 
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