I have a Savage 114, with a custom 26" 8-twist Shilen barrel, in 244 Rem, and I was just out at the range (temps 80-90F) and was getting some (to me) odd velocities.
With 2 different powders and 2 different bullets (Ramshot Hunter in 105 Bergers, and both Hunter and Win 760 in 88gr Bergers). I was getting about 50 fps less than listed velocity (for a 24" barrel, no less) for a minimum load, and around 125-150 fps less than listed for a max load, for all three combos tried.
Any ideas? Or just a slow-ass barrel... (it seems accurate enough that I'll keep it, either way)
There's several reasons why a given load shoots slower in ones rifle than what the source claims they got in theirs.
1. The powder and primer lots are different. Each one produces a given heat/flame output for a given amount. A 30 to 40 fps spread's common between lots.
2. Barrels have different bore, groove and chamber dimensions. Smaller diameters typically mean higher velocities. Most commercial factory barrels' bore and groove diameters are a bit bigger than SAAMI spec test barrels; they'll shoot a given load slower. A 100 fps difference across them can happen with the same load. Barrel length differences also has an effect.
3. Barrels were held differently. A test barrel in a universal receiver bolted to a fixed test stand will not recoil at all; it'll shoot a given load's bullet faster than if that same barrel was in a rifle held by a person who moves back in recoil while the bullet goes down the barrel; bullets from it will leave slower.
4. Two different people shooting the same rifle and load as its held against their shoulder testing from a bench can easily have 100 fps difference in muzzle velocity as chronographed. We all do not hold the rifle against our body with the same pressure and angle. Fixed, hard mounted test barrels give the most repeatable results and are best for getting good data and quality control.
5. Different chronographs and setups will also show different muzzle velocities for a given load. Is yours the same make, model and setup as what the load sources was?