Velocity Question

[Catfur]

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-*** barrel... (it seems accurate enough that I'll keep it, either way)

 

[royinidaho]

I'm thinkin' a slow barrel. . . but if the pressure isn't there it may be a "fast" barrel.

More friction = more pressure, higher velocity.

Less frictiono = less pressure, lower velocity.

Pour some more coal in her and watch pressures as see what happens.

 

[Bullet bumper]

Are the bullets Moly coated ?

 

[Catfur]

With Hybrid 100V I've been able to get just under 3100, we'll see what more experimenting brings.

All my test loads have been .02 off the lands, or on the lands.

 

[venatic]

Not really unusual to see less than book velocities. Now if they are slower than previous chronograph results with same loads then might be reason to be concerned and I would recheck.

 

[Catfur]

I thought 125 fps less than book, with a 2" longer barrel (said book anticipates roughly 33 fps additional per inch) was odd, at least.

Not out of the question, but still.

Hybrid 100V seems to be performing well, I want to try Superperformance, as well (it's at least something I can lay hands on).

 

[Bart B]

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?

 

[Greyfox]

While I have seen barrels give velocities differences from published , or expected results, I am always suspect of the chronograph/conditions. When this had happened to me, a very high percentage of the time it turned out to be the chronograph readings being effected by lighting conditions. I almost always go their first when I'm suspect of the velocity is very efferent from expected. It appears this issue may be resolved with a Magnetospeed I have been using for the past few months. IMHO.