Re: SMK 155 VS 155 SMK palma?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">So I remember from collage physics (so long ago) that inertia <span style="color: #FF0000">momentum </span>which is what the wind would be fighting is a function of mass and speed <span style="color: #FF0000">p=m*v or e=m*v**2</span>. So in order for a lighter bullet to have the same inertia i.e. the same ability to fight wind, it will have to go faster <span style="color: #FF0000">or have a lower drag coefficient</span>. My understanding is that you have to push the 155 grain bullets pretty hot and fast to compete with the heavier bullets and sometimes this causes them to disintegrate (I am talking competition) which would be a bad thing. However, some people shoot the lighter bullets because for them it provides a means to challenge themselves in terms of being able to read the wind. </div></div>
In essence this comes down to how much energy a bullet carries, and how much of that energy is being disipated into the air as the bullet passes through. You can do the math in momentum terms or in energy terms and get the same answer.
Unless the rifle has an absurdly high twist rate, bullet disintegration rarely happens. Down in the 223 range shooting 35gr-40gr light jacketed varmit bullets at 3500+ fps and a 1:7 twist may see some disintegration.
For example:
Consider:: {punching in some data to JBM)
155 gr bullet {<span style="color: #3366FF">Scenar</span>, FullBore, 2156} MV = 2950 fps, zeroed at 100 yards.
It will take MV= 2800 fps for a 175 SMK in order to have the same windage performance at 1000 yards as the 155 has at 1000 yards (9.4 MoA). And, even here, it will have another 2.6 MoA of drop over the 155.
It will take a MV=2892 fps for a 175 SMK in order to ahve the same drop at 1000 yards as the 155 has at 1000 yards (31.6 MoA). Here, the 175 windage is better by 5.3 MoA.
Can a 308 push a 155 to 2950 fps--quite a few of us do; at least one of us has over 30 reload cycles on a set of cases. A stiff load to be sure, over the top--sort of depends where one draws the line--caution is always warrented.
Can a 308 push a 175 SMK to 2800 fps? I really don't know, but my intuition says difficult at best, close to the edge at least.
Can a 308 push a 175 SMK to 2892 fps? Please warn the rest of the shooting range before attempting this with a 308.
Prior to the advent of the modern 155s, the 175 was king, and still is in many areas. Modern powders (Varget,...) have had some influence on this overall process.
