Velocity seems a bit high

[Foxyboy43]

Hmmm. According to Sako’s own chart - 150 gns Hammerheads are trundling along at 850mps (2,788 fps) and as you say likely to be out of a 24” barrel. Accepting this and reducing velocity by 25 fps per inch of barrel lost your rounds would be struggling to make 2,700 fps.

 

[User00044]

So I chronied it - average velocity was 2741fps over 5 shots. Did it a while ago but completely forgot about this thread

I just ran StrelokPro, no Sako bullets listed so used a same weight , similar construction Sierra.
Using your zero and validation distance / drop = 2744 fps . BC wouldn’t really come into play at that distance .

 

[JTO]

A chonograph? ~Muir

Didn't notice how old this thread was!

 

[Hook'N'Bullet]

Hmmm. According to Sako’s own chart - 150 gns Hammerheads are trundling along at 850mps (2,788 fps) and as you say likely to be out of a 24” barrel. Accepting this and reducing velocity by 25 fps per inch of barrel lost your rounds would be struggling to make 2,700 fps.

Hey FB, all I can do is tell you the numbers on the chrony. the 25fps per inch is a rule of thumb so wouldn't expect it to be 100% accurate all of the time. I've also heard it is 50fps per inch so

Shot the 5 shots over the Caldwell chrony and average speed was 2741 so thats what I'll be going with

 

[Bowland blades]

To start off, I'm shooting a 20" .308win using 150grn Sako Super Hammerheads (I love them)

I was curious as to what speed my bullets were scooting along at. Without access to a chrony, I decided to do the old, shoot a group at 100 (zeroed range), then shoot a group at 200 and fiddle the speed in the ballistic calculator to match the drop. Unfortunately, my max range I could get in the area was 186 meters. It will have to do. First group at 100 was bang on the money. Couldn't have been happier. I actually surprised myself. Next group at 186 meters was good too. Drop between the two groups was 3 inches.

I went into my Sako Balistics App, input my barrel length, cartridge info, scope height etc and fiddled the velocity to match the drop. To mimic a 3 inch drop between 100 and 186, the velocity would have to be running at around 2900fps.
Now to me that seems way too fast. The advertised velocity on the box is 2805fps which I assume is from a 24" barrel. I was expecting a number more towards 2600 - 2700.

Anybody have an ideas? Have I missed something?

A lot of early published data was based on trajectory and a lot of old data is very wrong indeed. if you haven't got a chronograph borrow or buy one , mine isn't used much but its been invaluable when it has been .

 

[Hook'N'Bullet]

Yeah I've

A lot of early published data was based on trajectory and a lot of old data is very wrong indeed. if you haven't got a chronograph borrow or buy one , mine isn't used much but its been invaluable when it has been .

Yeah since making this thread I've updated it since buying a chrony if you read on. Avg fps is 2741