Nobody sez the load books are cooking the books. Even if you matched their set-up as closely as possible there would be variances. You could take barrel 1 and 2 off the assembly line and one would undoubtedly shoot "faster" than the other. Sometimes by quite a bit.

One more...



My buddy and I were shooting some Federal 200gr GameKings, Factory fodder. His was a 24" Ruger 300 WM, mine a 24" 700 ADL. His was exactly 75 fps faster than mine, same box of ammo... I've been testing pressures long enough that I think the pressure on mine would have been much less though.



Considering barrel length, MV is a supurb indicator of pressure, just don't ignore the other pressure signs if you don't strictly adhere to the book charge weight.



You are likely to find that the closer to the lands you load, the less powder it takes, grain or two less is likely. Different bullets have different bearing lengths, lead and jacket hardness, so friction will change the load swapping them too. Generally, max speed will be "nearly" the same for a given bullet weight, at the same pressure. Much easier to see this with pressure equipment though, but it's charge weight and OAL that differs mainly.



It probably ain't what you want to hear, specially after getting the speed from it, but once you get a some good shinning ejector marks and bolt lift and extraction is obviously getting difficult, back off about 75-100 fps and you're more than likely down in the safe 60-65k psi range.

Dave R.

Barrel length will influence MV, but not peak pressure... to a point. Peak pressure is achieved in the first few inches of barrel length, generally in less than .8 milliseconds.

I spoke to Gary at Federal Cartridge Company about getting pressures for some ammo lot numbers I was working with, and while talking with him for a while about this sort of stuff he told me that all the various ammo MFG's send around all their ammo to everyone with SAAMI test barrels in the SAAMI member "loop", and the maximum pressure is defined by the combined data. In other words, the way I understood him was, Federal sends ammo to Winchester, then to the Hornady etc, and after that it is determined if it is safe and below SAAMI specs, if not it gets reworked until it is. I could be wrong about that, but that is the way I understood him.

Makes sense that the more damn tight ass SAAMI barrels the ammo is analysed in, it eventually will be too high in someones test barrel and be adjusted downward in charge and MV, but still remain "at SAMMI spec" for pressure.

A tight barrel may produce higher pressure, but generally produces higher MV as well. If Winchester had it producing 65k psi, but Federal had it at 58k psi, SAMMI will never allow that ammo to exceed the 58k psi in Federal's barrel, or load/pressure data, because it don't work in all the SAAMI tight test barrels and produce that same 58k psi, and in this example Winchester's test barrel set the limit on that ammo lot in the sequence of "SAAMI round robin testing".

I just tested some Winchester PowerPoints in the 300 WSM here the other day, MV averaged 2990 fps for 10, and Pressure on the Oehler M43 and PressureTrace was about 56k psi testing simultainiously. This is the lowest pressure factory load I've ever tested, or I should say, furthest from SAAMI specs for pressure. Everything else has been at, or about 2-3k psi lower than spec'd by SAAMI in several rifles.

This load very likely could have been simply downloaded for accuracy and not maximum pressure/MV, it did shoot 3 consecutive groups at 300 yards all under 2"...