velocity

[44 AMP]

I would expect they would be using magnum primer for those heavily compressed loads with the high pressures.

magnum primer in 9mm Luger? AA No.7?? no need. And likely no benefit. Magnum primers aren't about how compressed the load is they're about igniting difficult to ignite (slow) powders. AA No. 7 isn't a slow pistol powder.

And, my personal feeling is that anyone who is providing loading data without providing the primer, and case used or the gun it was tested in isn't telling us enough.

 

[74A95]

magnum primer in 9mm Luger? AA No.7?? no need. And likely no benefit. Magnum primers aren't about how compressed the load is they're about igniting difficult to ignite (slow) powders. AA No. 7 isn't a slow pistol powder.

Some 9 Major and 38 Super IPSC/USPSA shooters use magnum or small rifle primers to reduce primer flow - for their thicker cups. I have with my Major loads.

And, my personal feeling is that anyone who is providing loading data without providing the primer, and case used or the gun it was tested in isn't telling us enough.

That link provides the primer used.

 

[Unclenick]

The effect of a muzzle brake on velocity depends on how it is implemented. A radar engineer once shared a Doppler Radar trace with me of a 40 S&W round from a pistol, and it picked up about 3.5% of its peak velocity (about another 35 fps) from the muzzle blast after it cleared the muzzle. That agrees well with Harold Vaughn's magnetometer measurements of about 2.7% (82 fps) for a rifle in 270 Winchester (Rifle Accuracy Facts, last paragraph p. 165). Since a muzzle brake vents the muzzle blast pressure, you can expect to lose that 3-3.5% of so if the vents are located behind the muzzle, as with Magna-porting or other brakes that drill into the barrel. But if your brake extends forward from the muzzle, since the main effect of muzzle blast on a projectile is within a very short distance from the muzzle, you will still pick up most of that muzzle blast acceleration with that configuration. If memory serves, the Doppler plot showed the acceleration was mostly done in the first two or three calibers of travel from the muzzle.

 

[Don Fischer]

Take the ammo and shoot it in several different rifles using the same cartridge and you just might get several different velocities!

 

[DaleA]

How the rifle is held against the shooter's shoulder can have a big effect on bullet velocity.

From all the comments here this is apparently common knowledge.

This site, along with mirrors, weighing myself and scoring my targets keeps me humble.

This site is a great place to lurk and learn.

 

[sako2]

I must be holding the rifle right because I shot loads with it that had single digit es and sd.

 

[44 AMP]

I must be holding the rifle right because I shot loads with it that had single digit es and sd.

Must be!

now the important question, can you do that again tomorrow? Next week??

 

[reynolds357]

I must be holding the rifle right because I shot loads with it that had single digit es and sd.

I have had that happen. Gone back a few days later with temp 20 degrees different and whole nother story.

 

[sako2]

Shot them last weekend and again this weekend. Trust me I learned a lot from the people on this forum.

 

[JasoninSD]

I once had a Winchester 70 in 7 STW. The load manuals were telling me I should have been getting tremendous velocity. Well, then I went and bought a chronograph. You can imagine my disappointment when I found my max loads were about 300 fps slower than the published data. I was burning a lot of extra powder to duplicate the velocity of the 280 Remington. I sold the rifle but kept the chronograph. Most of my other rifles keep the velocity reasonably close to the published data.