Wildcatting: Red Hot 6

Like the earlier 6mm Remington cartridge that offers better performance than the standard .243 Winchester, the newer .243 WSSM should have been an incredible hit but it seems to languish in the ‘also ran’ category. I really can`t see why, as the overall design and velocity potential with both light or heavy weight projectiles and associated rifling twists offers optimum performance in a .243 platform.

The WSSM started life as a shortened version of the original WSM (Winchester Short Magnum) series of calibres, which were shorter versions of the round they were to replace - 300 WSM for the 300 Win Mag. The 243 WSSM is designed as a short magnum 6mm, to achieve 15 % better velocities than a .243 Winchester, but it does burn more powder but has the oomph for heavier bullets for longer range use, so a balancing act is needed.

CASE

At first glance the 243 WSSM is a pretty impressive round, it has presence. Fat and chunky with a small projectile seated compared to the overall size of the case. The case uses magnum bolt face head size at 0.5311” and has a body diameter that only tapers from 0.556 to 0.544” along its length, so pretty straight and Ackley-esque! The shoulder though has a 28° angle, so really pretty shallow, but probably intended to allow better feeding through the magazine than increasing powder capacity.

Overall length is 1.670” and so an empty H20 capacity is 54-grains, so combined with the 0.278” neck length allows even the heaviest bullets to be seated well without impeding on the powder column and forcing a compressed load. Factory loads are light and heavy, 55-grain bullets are claimed at 4060 fps but in the short 22” barrel of the Browning A-Bolt I initially used for testing could only manage 3825 fps! The heavier 100-grain load shot at 2877 fps and not 3110 fps. But that’s the point, the WSSM case has a lot of potential and when tuned to the correct barrel length and rifling twist it soon becomes into its own.

The 243 WSSM seems to like medium to slow burning powders and due to the large and squat/dense powder column I like to use magnum primers to initiate full powder burn. Best velocities are gained therefore with a longer barrel.

IN THE FIELD

Again, having shot the .243 WSSM, albeit in a shorter barrelled A-Bolt I am still very impressed in the performance of the cartridge. But we shooters are fickle beasts and tend not to venture out of our comfort zone and stick to what we know. I think that’s a mistake, as the extra velocity from a longer 6mm barrel and correct rifling twist, say a 1in 9, or better 1 in 8 to stabilise the heavier streamline bullets and then you have a very good, flat shooting, energy-retaining game getter.

The older A-Bolt Medallion I was using is a really good rifle, I like this model, but 22” is too short for the .243 WSSM round. Despite this the Browning turned in really good groups with factory and reloads. Velocities were down, obviously but both the 55 and 100-grains loads turned in sub-inch groups at 100 yards, which from a lightweight sporter is very good in my book.

REFINING THE RELOADS

Reload wise, with the slow twist factory barrel rate, there was a sweet spot at around 70/95-grains. The Berger 70-grain bullets were excellent to be honest, 48-grains of Alliant RL17 powder and a CCI magnum primer launched this bullet to 3632 fps for 2050 ft/lbs energy. Groups were equally good from these ‘target pedigree’ pills, with three shots under 0.5” at 100 yards.

Equally good were the Nosler 95-grain Ballistic Tips, which have that fox and deer potential, so a good all-rounder in my view. Here a load of 43-grains of H4350 yielded 3028 fps for 1934 ft/lbs and keyhole groups, which is amazing from a factory sporter weight rifle.

Going up the bullet weights, which for me are the best 243 WSSM loads, is where you have a conflict of not enough or fast enough rifling twist to really stabilise the heavier 6mmm bullets that elongate as the weight increase and thus need a tighter pitch to optimise stability. I shot the heavier and ballistically superior Berger bullets from 105 and actually up to 115-grains. But and although the velocity figures were of interest, accuracy tailed off, which is not surprising.

SWEET 105

However, the 105-grain Bergers with a load of 42-grains of 2984 fps for 2076 ft/lbs would certainly increase in performance from a longer barrel but still interesting in the 22” Browning tube.

The Sierra Game King 100-grain on the other hand did stabilise and produced 0.75 to 0.85” groups at 100 yards, again very good for a lightweight sporter rifle. Velocities too were good at 2948 fps and 1930 ft/lbs energy, with a load of 46.0 grains of Hodgdon H4831SC powder.

Having sorted a good load I ran it through the ballistic program Quickload/ QuickTarget to determine an accurate down range performance chart. I then sighted in the Browning and shot some familiarising groups and headed out to actually hunt with the rifle.

I had great longer range foxes with the Browning, one a memorable 250 yard + shot across a stubble field with the Nosler 95-grain Ballistic Tip load and those 55-grain factory loads were great on foxes too. The heavier loads were deadly on crows as well, with better abilities to buck the wind than lighter weight .22 centrefire projectiles. You do notice the extra muzzle blast from the shorter barrel, but this is negated by fitting a sound moderator and the newer rifles with longer barrels and varmint profiles allow the true potential of this round to be obtained. However, I would caution you on going too hot and fast, as chamber pressures can run high and you can get primary extraction problems. This was more prevalent in the sister cartridge the 223 WSSM.

CONCLUSIONS

I have only shot the 243 WSSM in a shorter barrelled Browning A-Bolt and although the rifle is really good I think a faster twist 1 in 8 or 9” barrel of 26 inches is where you want to be with this short and fat 6mm. Barrel life will be reduced compared to a standard 243 Win but every time you pull the trigger you are getting more bang for your buck and on a stalking rifle I doubt if you will wear a tube out any time soon, however on long range Varmint, that could be a different matter entirely.

CONTACTS

BWM (Browning UK) Browning rifle, Winchester ammo 01235 514550
JMS Arms Quickload/QuickTarget www.quickload.co.uk 07771 962121
Henry Krank Sierra bullets 0113 256 9163
Norman Clark Reloading supplies 01788 579651
Edgar Brothers Hornady, Reloder powders, Hornady 01625 613177