7mm-08 speeds slow

[williaada]

Just started working up a load for my 7mm-08 and I just bought a chromo graph and my loads seem to be about 150ft slower than what nosler has for the reloading data. Any reason why this would be? I did have my chronograph set roughly 7ft from the muzzle.

 

[MThuntr]

Nosler numbers are often high. Their data was from a 26" barrel so the potential for most 24" hunting rifles would be close to 50-75fps slower right from the start. Take a rifle down to 22" and you could lose 150fps (not always but could). I've found Hodgdon data to be closer to what I get but even then they'll never be the same.

some guns seem to be faster but distance to chrono could be different, etc

 

[Vern400]

That's not surprising.

 

[williaada]

When you get the muzzle velocity from the manufacture how is this measured? Would the Caldwell chrono measure to similiar speeds right from the muzzle? Caldwell suggested 10-15 away from the muzzle

 

[EdP]

What mthntr said. You always have to consider the barrel length used for the test vs your rifle. Some calibers are more likely to have a large difference and I think 7mm-08 is one of them. The 7mm-08 makes a great lightweight rifle but that also means a short barrel.

 

[wildwilderness]

How many shots through the barrel? a new barrel can take a lot to break in and will speed up

 

[williaada]

Between 100-150 rounds.

 

[seand]

Just started working up a load for my 7mm-08 and I just bought a chromo graph and my loads seem to be about 150ft slower than what nosler has for the reloading data. Any reason why this would be? I did have my chronograph set roughly 7ft from the muzzle.

Lots of reasons

1- your chrono sucks.
2- the recipe in the Nosler book may use a different barrel length
3 the recipe in the Nosler book was developed in a different rifle, it’s only going to be ballpark for charge weights vs pressure in your rifle. If your chrono is accurate, your recipe matches the Nosler book (same exact components), and your velocity is 150fps lower than what Nosler lists for max pressure, you aren’t at max pressure in your rifle

Years back I doubled down on cheap chronos. Was going thru the same issue as you and didn’t trust my shooting chrony so I bought a prochrono and shot thru both of them with the same fired rounds. One or both was way off, no way to tell which one. I was done with light chronos, got a magnetospeed. Velocity is the best approximate measure of pressure we have, more accurate than reading pressure signs or using book charge weights.

 

[Rob5589]

Mostly just ball park numbers for a lot of data. I have found that the Barnes data is very close to dead on with their velocities. I have two 7/08, curious what your components consist of.

 

[LookinforDirt]

Could be related to how you loaded the rounds, difference components, humidity and air temp, elevation, barrel length, barrel itself, different lot of powder, chrono accuracy, a combination of any of these, etc. A lot of factors are involved. IMO, unless you require high precision data for competition shooting, I wouldn’t sweat it to much. Chronos are only a reference point. Ultimately, if you want accurate ballistics of your load, you will need to shoot at actual distances and record the data. If you want it to be as close as you can get it just loading and shooting at 100, 200 yards, you will need to invest in some higher precision reloading, shooting, and chrono equipment. But you will still want to confirm your data with real shooting before competing or shooting at game.

 

[JFK]

What kind of rifle is it? Tikka factory barrels are typically a little slower. I have a Sauer that’s about 100-125fps slower than my other American made 270’s with the same exact handloads and same barrel lengths. Not a huge deal. The bullet makers often use longer 24-26” barrels for their testing which pumps their numbers up a little.

 

[williaada]

What kind of rifle is it? Tikka factory barrels are typically a little slower. I have a Sauer that’s about 100-125fps slower than my other American made 270’s with the same exact handloads and same barrel lengths. Not a huge deal. The bullet makers often use longer 24-26” barrels for their testing which pumps their numbers up a little.

The rifle is a model 70 Winchester supreme super grade

 

[EdP]

The rifle is a model 70 Winchester supreme super grade

From what I see it has a 22 inch barrel vs the 26 inch used by Nosler (per mthuntr). 150 fps for 4 inches is no surprise. I bet that rifle is a beauty.

 

[Pharmseller]

What’s your load? Include brass, primer, and temperature.

Whats your velocity?





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[Pharmseller]

From what I see it has a 22 inch barrel vs the 26 inch used by Nosler (per mthuntr). 150 fps for 4 inches is no surprise. I bet that rifle is a beauty.

25-30 fps per inch has been my experience. 150 fps is a bit aggressive but not unheard of.




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