As it's a fairly well-accepted rule in silhouette that momentum (m*v) is the best measurement of a bullet's ability to knock a steel target off its stand. Recoil is energy (m*v^2). In the never-ending quest to minimize recoil and maximize target knockdown reliability, it seems logical that a heavier bullet will attain the required momentum with a lower recoil than a lighter bullet as they scale up in velocity. Since it's off-season for HP silhouette, I want to play around and do some experimenting. We've all heard this debate over and over again for rams, but this time I'm thinking more about my CPT load. I'm not particularly recoil-sensitive, but I have noticed that the more recoil a load has the more critical it is for me to have a very consistent position, especially on pressure from my trigger hand pulling the rifle back into my shoulder and placement on my shoulder. Hearing a couple guys talking about slow loads with ~120 grain bullets and seeing a pig or two get rung,at the WA state match got me to thinking. Just how much momentum is required to reliably take chickens, pigs and turkeys? Based on the shape and weight of the pigs, I believe that they should be the hardest to reliably knock over so my math here is based on that assumption.

Using rough calculations of 30lbs for a highpower pig and 50lbs for a highpower ram, that leads me to propose that the necessary momentum to reliably topple a highpower pig is 3/5 of the necessary momentum to reliably topple a highpower ram. (Does that actually scale linearly?) There is debate that we have all read/heard, but the most often quoted required momentum for rams is at least 1.0 ft-sec of momentum at 500 meters, which gives a requirement of 0.6 ft-sec of momentum for pigs. With the two bullets below as examples, how fast would each need to go at the muzzle to achieve the required momentum at 300 meters for pigs?

Hornady 6.5MM 100GR A-Max
http://www.hornady.com/store/6.5MM-.264-100-GR-A-MAX/
Advertised Ballistic Coefficient: .390

Hornady 6.5MM 123GR A-Max
http://www.hornady.com/store/6.5mm-.264 ... LBC-Lapua/
Advertised Ballistic Coefficient: .510

At the required muzzle velocities, what would the recoil for each be? Would the higher ballistic coefficient of the heavier bullet make up for the longer flight time in wind deflection calculation? What would be a powder that could achieve the target muzzle velocity with >90% load density? How sensitive would that powder be to temperature differences? I'm about out of pontificating (read as "lunch) time, so I'll have to get to the actual calculations later. Feel free to throw in calculations and opinions of your own.

Jason,

Don't forget bullet toughness in your estimations. Also, hits on rams are much higher, in general, so there is more "leverage" to knock over a ram than a pig. And, a heavy, slow bullet will do a better job of knocking down rams and pigs than a lighter, higher velocity bullet even when their terminal momentums are the same.

After years of shooting pigs with 108 Scenars out of my 6.5mm TKS, launched at 2,750 fps, I only had one rung pig, to the best of my memory. That pig was hit center-of-mass at a range where the pigs could not slide straight back and fall off the stand due to the pads being below the top of the grader blades they were welded to.

A quick terminal, 300-meter, momentum simulation shows a terminal momentum of 1.0 ft-sec for the 108 Scenar load. I've also shot 140-gr, 6.5mm bullets at 1,760 fps at CPT. They produce a 300-meter, terminal momentum of about 0.870 ft-sec. However, those slow 140's whack the pigs with more authority than the higher terminal momentum 108 Scenars.

Jason,
I shoot c-p-t with a 123 Scenar at 2550 and have never lost a pig with that bullet at that velocity. Momentum is around 1.1. Mark

Jason,
I don't have the answer but the feet are narrower on the pigs than on the ram which would skew the comarison based on weight difference only.
One could take a baby scale and push it against different areas of a pig to see what lbs of force is required to push it over (probably low shoulder).
Then try some different loads concentrating the impact on that area.

w30wcf

Jason, We've been shooting reduced loads in 7-08's and 260's back East for years. I wouldn't go lighter than a 120 in 6.5. Knockdown will not be your only issue. You will need a firm understanding of your wind age knob.
We use IMR SR 4759, and accuracy with this powder is really good. A 7-08 will work best reduced with 150's. I use this powder for reduced loads in my 30-30 out to the turkeys. Al

I've been working on a load using the new CFE223 powder pushing the 6.5mm Lapua Scenar 123gr bullets at 2350fps muzzle velocity. This results in a terminal momentum of about 1.04 lb-sec for pigs and 0.97 lb-sec for turkeys. The felt recoil on this load is surprisingly light even after looking at the calculated recoil energy value, which I think was around 6.2 ft-lb or so. The data for the 123 Hornady A-Max bullets will be similar, but I did the actual testing with the Scenars as they are moly-coated and the A-Max bullets that I haven't aren't. Until I get around to cleaning that barrel thoroughly, only moly bullets will be shot through it.

Jason,

The projected 7-04 CPT load will have 4.3 ft-lbs of recoil when launching the 139 SST to 2,000 fps with 20-gr of H4198. Pigmentum should be about 0.94 lb-s. Hey, what's not to like.