I'm still playing with my 308 loads...........

Is knocking down rams a function of energy directly, and if so what's the safest min ft/lb needed not to ring them?

I'm guessing approx 1000 ft/lbs would do, or can one go lower? Remember I'm still a B shooter, so my shot placement ain't perfect!

Keep on playing with your loads, it's fun.
However the longer I play this game, about 20yrs now, the less I think that there is a direct relationship between energy and score, I used to use maximum loads behind 180/190 gn bullets in the 308, tried game bullets & match bullets and kept hearing stories of rams being knocked down with light loads, shooters picking up their pig or turkey loads and shooting down the rams which went against popular theory that you needed fullhouse loads to get those heavy rams down.
I have been, for just over 2 years now, using starting loads ie. 10% down on the manuals max, with 168 gn bullets in both 7mm08 and 308 and have not been leaving any more rams stand than when I was using max loads, and they are a lot more comfortable to shoot.
I am a AAA shooter so get as many rams as most shooters do in competition and rarely have any stand at any other time either.

sobrbiker883

Good question but also one which is very hard to pin down. When first developing loads I had the same question and after reading a lot of posts I came to the conclusion that 1000 ft-lb (energy) or 1.0 lb-s (momentum) were good numbers to stay above at the rams. All my loads stay above both.

I prefer to look at momentum rather than energy for two reasons: 1.) Momentum works for large slow moving bullets like 45-70 where energy would say that it couldn't possibly knock over the rams when actually the rams go over all the time.; 2.) The 'energy' transfer is through momentum. Momentum = (bullet grains/7000)*(1/32.2)*velocity. Velocity in fps.

It would be interesting to compile a list of what everyone shoots to see what the consensus really is. I am willing to do the math if others provide their loads. I would need bullet weight (gr), bullet BC, caliber, muzzle velocity, and what load it is (CPT or ram). This is only worth doing if the response is high enough.

No, ram knockdown is NOT a direct function of kinetic energy. It is a direct function of momentum. Momentum is mass x velocity. The two variables are equally important.
Think of a 50 grain .223 and a 405 gr 45-70 with velocities adjusted so that they hit the ram with the same kinetic energy. The big, slow bullet will take the ram but the little, fast one won't. The big bullet has the same kinetic energy but more momentum.
While the relationship between ram takedown and momentum is "direct" there are other relevant factors and the experienced folks say that bullet construction/hardness is one of them. That puff of smoke you see when the HP bullet hits steel isn't paint. It's lead dust or, more likely, lead vapor. The deceleration of the bullet converts the kinetic energy to heat energy which vaporizes the bullet in a fairly short time. The idea is to impart some of that kinetic energy to the target before it is all converted to heat. I think. I'm not sure the jacket makes any difference but most say a harder core helps.
Nobody has perfect shot placement and the location of the hit matters. Lower hits require more momentum, presumably because the bullet has less leverage to tip the target.
There are other variables. The stand needs to be firm and not wobble as the target is hit. The condition of the target itself may matter. The wind is important. The target has a lot of surface area and a headwind absolutely tends to hold the target up.
Sometimes, the reason for a "ring" is just mysterious. Sometimes they just stand there and laugh at you after a good hit with a good load on a calm day. A few years ago, Jerry Tureau rang a PIG at Zwolle with a center hit from a hefty 7mm load. When I asked him how that was possible, he said: "'Cause he's a MAN."
Disclaimer: I am not a physicist, just a goober who talks too much. Somebody find Dan Theodore.
Edit: As Silo says, I've seen 1.0 pound/second used as the threshold number for reliable ram takedown.

Hello guys, after having shot HP rifle silhouette for almost 30 years I have to tell you that we as a whole with some exceptions like Phoenix and Raton rifle shooters do not pay as much attention to targets and stands as the Handgun shooters do.

I have been involved with running or shooting Cowboy matches at their ranges for over ten years and I can tell you that I am impressed to the extends they go through at their ranges so as not to ring any targets because they will have several shooters hit 40X40 at most of their matches and can

Those "stops" in front of the feet are a good idea. They make it easy to position the target and protect the feet, which are usually mild steel, from bullet damage.

Thank you gentlemen for your well thought out and expressed input.
I had overlooked the energy issue which I should have seen before, as I do load and used to shoot HP NM with a 223.......

The loads I'm using given the above formula for momentum are 1.21 for my 168 CPT load and 1.36 for my 180 R load.

I think I need to worry less about my loading and worry more about keeping my sight picture, stance, trigger pull and following through properly.....

Sobr,

You can't have the same momentum for CP&T, since they are at different ranges, you will have a different velocity at impact for each animal. You didn't do your calculation based on muzzle velocity did you?

No I didn't use MV, but I did use 500m Velocity........long day.
Here's the corrected version (I load my 308's for silhouette at 2525fps MV and shoot Hornady MBTHP's)

168's @ 200m=1.62, 300m=1.50, 385m=1.36
168's @500m=1.21
180's@ 500m=1.36

Looks like my 168's would do..............

I've mainly been thinking of different loading as I do shoot the discontinued Hornady 180 MBTHP for Rams and only have 400 or so left......

If the 1.21 figure is correct for the 168 at 500 meters, that's a pretty hefty safety margin. If you can feel the difference in recoil between that load and the 180's you might give the 168's a try. Remember, nothing you would want to shoot in a match takes them 100% of the time.

I did some calculations with this formula with some popular bullets. Interesting stuff.

Nice job. I'm kinda surprised the 6.5 120gr's aren't getting more uumph...

mordecai wrote:Nice job. I'm kinda surprised the 6.5 120gr's aren't getting more uumph...

The 6.5 120 has the second worst BC on the list. Only the 7mm 130 is lower. The affect of that really shows at 500 meters.

Nice graph Carl! It seems I have plenty of room to play with on my 308.

Now I can look for a different powder that will run my more case fill and may even go a little slower. I don't know how well my beloved IMR4895 will do loaded down to 2400fps......

I need to buy Quickload!!

My 243 with 107s at 3040 fps is taking the rams down quite well. Anything under 3000 fps does not to a good job. You are correct, it is the momentum that does it, not the energy. A slow heavy bullet works better than a light fast one.