Swamp Donkey Magnum

Buckboy:

I have personally seen these Swamp Donkeys chronograph over 3000 fps in 24" barrels and that was with 2 or 3 different rifles. I am having one built as we speak and with 26" barrels I have seen velocities as high as 3150 fps. So with the stats from the .338 Mcdonald that you stated, I see at least 100 + fps advantage for the Swamp Dokey!!

And remember boys it burns less powder than the Lapua and the RUM!!!
 
8.6x72 Swamp Donkey Magnum

Yes ,but at what cost in regards to powder?. The 338 McDonald is on a regular magnum case. The SDM is on a longer case therefore more powder. The RUM"s are very ineffecent. I have shot the 7mm RUM,300RUM,300Weatherby,& 340Weatherby and find that the Rum's are not that more powerful. Just alot more powder. Just what does the SDM compare to?
 
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True, by the sounds of it the .338 McDonald is also a very efficient cartridge. But if you need a magnum bolt face , and a long action, why not the SDM!!! You get the extra velocities and you also don't need any of the mag box,feed rail mods as the RUM, etc. The same would be the same as the .338 McDonald!

Maybe HPBT can help here as I do not have lots of experiance with the cartridge as of yet. Maybe the SDM would have a better edge with the 300gr+ bullets, with the added case capacity???

As far as what it compares to.... I guess the .338 Edge, the 300 RUM necked up to .338 but with a lot less mods and less powder!!
 
The SDM compares to a 340 Wthby juiced up. With 87gr IMR7828 it will drive a 250gr SMK at 3100+fps, 90gr H1000 3100fps, 26" pipe with a 1-10" twist.
 
Can you guys explain to me why a case with less capacity can shoot faster than a case with more capacity? All things being equal, shouldn't the case with more capacity shoot faster given equal loading pressure.
 
Thats pretty awsome, you change the case shape slightly and get 200 fps. It must operate on the SWM principle. Sort of magical. I've had a 338-06 IMP several 338s, 3 340 WBYs a 338-8MM basically the same and a 338/378 and a chrono so don't bother telling me I don't know.
 
Troy G said:
Can you guys explain to me why a case with less capacity can shoot faster than a case with more capacity? All things being equal, shouldn't the case with more capacity shoot faster given equal loading pressure.
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The larger case will only increase velocity if all the powder can be effectively burnt within the barrel length of that rifle.

When some of the powder does not effectively burn within the barrel, it becomes part of the projectile weight and in some instances a smaller case and bullet combination will have a higher velocity than the larger case with the same bullet and barrel length. It is all about efficiency.
 
Troy G said:
Can you guys explain to me why a case with less capacity can shoot faster than a case with more capacity? All things being equal, shouldn't the case with more capacity shoot faster given equal loading pressure.
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That's elementary - much higher pressures.

P.S. all the powder is burned within 3" of the chamber. Longer barrels just allow for more time for the high pressure gases to accelerate the projectile.
 
I haven't fired a SDM but I know from the case specs it will be great performer. Having said that I also know larger cases than the SDM will produce higher velocities with equal pressures - SIZE DOES MATTER. I'm not picking on the SDM here as size matters with all other calibers. Size also matters if you are looking for efficiency - the smaller the case the more efficient it is for a given caliber. Remington developed their RUM line because they knew the belted magnum cases do not have the case capacity to deliver higher velocities - they were not looking for effeciency, just higher velocties. The boys looking for the fastest, meanest rifle in the valley don't give a rats a$$ about efficency.

Some of the belted magnum .338's can equal or better the velocities of larger cases as published in the loading manuals but the belted magnums are pushing the edge of the envelope with much higher, and probably dangerous, pressures. I have done it while experimenting with loads over a chronograph but quickly reduced the load when pressure signs & velocities told me I was treading in unknown territory. 60,000 psi is ok but 75,000 psi is way over the safety limit. Some of you may be pushing 80,000 psi :runaway:

The SDM is a great cartridge but it simply cannot equal the velocities of larger cases with the same pressures. Shoot lots and have fun, the high performance .338's really deliver.
 
guntech said:
The larger case will only increase velocity if all the powder can be effectively burnt within the barrel length of that rifle.

When some of the powder does not effectively burn within the barrel, it becomes part of the projectile weight and in some instances a smaller case and bullet combination will have a higher velocity than the larger case with the same bullet and barrel length. It is all about efficiency.
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Sorry Dennis, I can't swallow this. In fact most of the powder is burned in the first few inches of barrel and assuming you are talking similar pressures then the larger case capacity will have greater initial speed in those few inches. Efficiency (case capacity) comes into play if you would want to tailor the load to the barrel length for a given pressure/velocity, otherwise all things being equal the larger case with the same chamber pressure will have a greater speed. In short there are no substitutes for case capacity when looking for higher speeds with sensible pressure levels. A prime example of this is handgun calibers that all shoot from short similar length barrels. Take a 38 spl and the 357 mag both shooting the same bullets, in no way can the 38 spl come close to the 357 unless the pressures go through the roof, same goes for the 380 auto and the 9mm parabelum, 44 spl and 44 mag etc. Or in rifle cartridges take the 308 win and the 30-06, 7-08 and the 280 rem etc.
imho
bigbull
 
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