Winchester Short Magnum (WSM) CartridgesPromoted as a performance upgrade for short frame bolt action rifles, the 300 WSM provides about the same velocity as the original 300 Winchester Magnum... only it's chambered on .308 sized bolt action (short actions). The WSM is now also available in .270 and 7mm chamberings with similar high performance in short action bolt guns.
Why No WSMs (or WSSMs) on the Encore or Ruger?: "How Much Pressure Can That Action Take?" When customers ask that question, they're usually considering one of the New Magnums: WSM, WSSM, Short Ultramag, etc. The gun magazines and magnum bolt action rifle makers are promoting the heck out of these cartridges. And, as any business appreciates free promotion, we would have liked to get on the bandwagon. But these huge new cartridges are obviously unsuited to the small framed TC Contender and Model 97D. In factory ammunition, they've proven themselves problematic for the TC Encore... And even the Ruger #1, in our experience, seems to have some issues with at least the factory 270 WSM ammunition. I don't believe this is universal. These cartridges might work fine for one gun only to have problems with another. And in all cases, handloading ammunition to suit the gun produces excellent accuracy and gun function. But TC and Ruger aren't chambering the Short Magnums so, what gives?
Well first of all, it isn't only a pressure thing. What is happening (I think) is a higher than optimal level of bolt thrust for the design and size of the gun. This can cause difficulty in achieving accuracy and may also cause problems with gun function. My personal experience with developing high performance cartridges for our small framed Model 97D rifles and BF Pistols has taught me a lot on this subject. Generally speaking, the less bolt thrust a cartridge generates, the greater its accuracy potential will be and also, the more reliable and easy will be its function in a particular gun. Single shots with break open and/or falling block actions seem to be less forgiving of heavy bolt thrust than turn-bolt actions. And, turn-bolts may not show function problems as clearly. But I think even turn-bolts are going to have less accuracy potential as the level of bolt thrust goes up. (Update 11/30/05 - Apparently there ARE problems with some of the original turn-bolt guns. Some manufacturers have now introduced special guns or revised designs for the short magnums... Savage, CZ, and Browning, to name three).
A look at accuracy handload data that's published in the new Sierra reloading manuals shows maximum velocities (at least for 300 WSM) that are 100-200 fps slower than the published velocities of factory loaded ammunition. Handloading makes the WSMs potentially workable and superbly accurate in many non-bolt guns including Encore and Ruger #1. BUT, we sell precision and accuracy... And because of their potential for greater bolt thrust (and therefore less precision and accuracy), we do not offer the short magnums... or other chamberings with similar bolt thrust characteristics.
* Greater Bolt Thrust hurts accuracy potential *
* Greater Bolt Thrust reduces functionality *
So... what kinds of cartridges deliver high velocity
with match accuracy and the least amount of bolt thrust?
Long and Skinny with Very Little Taper -
P.O. Ackley did pressure tests with "Improved" cartridges (Vol I) and dry (not oily) chambers. These cartridges had very little body taper and gripped the chamber so well that they did not drive rearward even when the barrel was unscrewed a turn. A good example is the 300 Win Mag vs. the 300 WSM. They have pretty similar velocities but the 300 Win Mag will work more reliably in the TC Encore while the 300 WSM may have bolt thrust issues. The 300 Win Mag is longer and skinnier...
Size Matters at Least as Much as Pressure -
Big guns can handle big cartridges. Small guns can handle small cartridges... that seems obvious but the question, "How much pressure can that action handle?" still begs for an answer: A few years back we built a BF Pistol in 270 Max (a necked down 357 Maximum with very little body taper). The customer reported back some extremely fast velocities we didn't think were possible with good gun function in that particular cartridge. About a year ago the gun came back for re-barreling... apparently still with no problems, he just wanted to try a different cartridge. Upon disassembly however, inspection of the block face showed deep gas cutting from around the primer pocket. We have no idea how many shots were fired at such extreme pressures and velocities, but that relatively small cartridge had to have been working in that gun at pressures way beyond what would not have worked in a larger cartridge. So... merely asking "How Much Pressure..." doesn't tell you whether a gun will work right with a particular cartridge. Ackley's Vol I explains it much more eloquently... Unfortunately, it's out-of-print.
* Recommendations - Choose the smallest cartridge that will fit your needs, and go with as straight a body taper as you can find. Those features will give the best combination of velocity, accuracy, and shootability for hunting:
EABCO Model 97D and TC Contender -
17 Ackley Hornet, 22 K-Hornet, 218 Mashburn Bee, 223 Remington Improved, 224 BRM,
6mm BRM, 25-35 Ackley Improved, 6.5mm BRM, 7-30 Waters Improved, 7mm BRM, 30-30 Ackley Improved, 300 BRM, 30-40 Krag. - EABCO HOME PAGE -
TC Encore -
17 Ackley Hornet, 22 K-Hornet, 218 Mashburn Bee, 223 Remington Improved, 224 BRM, 22-250 Ackley Improved, 6mm BRM, 243 Win Improved, 25-35 Ackley Improved, 257 Roberts Improved, 6.5mm BRM, 260 Remington Improved, 7-30 Waters Improved, 7mm BRM, 7mm-08 Improved, 7X57 Improved, 280 Rem Improved, 30-30 Ackley Improved, 300 BRM, 30-40 Ackley Improved, 308 Win Improved, 30-06 Improved. - EABCO Thompson Center Products - EABCO Ruger #1 Products -
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