Crono speed results

[bigfish_7]

Borrowed a crono to check a few handloads this weekend and actually read the directions before I tried to use it.. yea pictures sucked.

anyway 338 lapua with 92 grains retumbo behind 300gr vld I believe the book shows 2750 crono showed 5 shots averaging around 2775fps
30-378 weatherby with 111 grains retumbo behind 175 berger vld 5 shot average around 3625fps
Hodgons reloading data shows 113 gr retumbo behind 180 gr at 3460fps
Will a five grain smaller bullet make that difference in speed with a 2gr less charge?

Any imput will be appreciated.

 

[Sako man]

What Chrono was it? The results for the 338 look about right, slightly on the fast side. Might be right if your around 53-54k CUP. How long was the barrel?

The optical shoot through Chronos are notorious for being inaccurate and difficult to set up. The new magnetic ones are the way to go, much more accurate.

 

[bigfish_7]

The model was called a crony I think, folded out then sticks went in then shoot thru. 28" on the 338

 

[mdmp5]

Forget hodgdon's velocities, or any other manual for that matter. They are rarely on target with reality, often understated. You have to take into account that they are often using a different rifle, as well as different barrel length.

 

[Sako man]

The model was called a crony I think, folded out then sticks went in then shoot thru. 28" on the 338

Ok, well Chronys suck, I have had two of them. No offense. But that said, if the barrel is 28" (very long by the way) then it's quite possible that the 338 MVs are close. So the Chrony might be close.

 

[bigfish_7]

Gonna order a magnetospeed seems to be the forum favorite

The 338 was close we had a 6.5 x 284 within 20ft of published velocity then the 30-378 was way off. But the vel on my 308 was around 150fps faster
than it should have been. Maybe the crony, maybe operator error, hopefully the magnetospeed will do the job

 

[Sako man]

Gonna order a magnetospeed seems to be the forum favorite

The 338 was close we had a 6.5 x 284 within 20ft of published velocity then the 30-378 was way off. But the vel on my 308 was around 150fps faster
than it should have been. Maybe the crony, maybe operator error, hopefully the magnetospeed will do the job

Published speeds are only waypoints. There are so many variables to each and every action, cartridge, powder, barrel, temp..etc…etc.. There is not way that a standard recorded MV and pressure could be a one size fits all answer.

 

[former naval person]

Shoot your load out as far as you can on measured ranges, then plug them into JBM and play with them. You'll get the velocities without the chronograph expense and doubt.

 

[Dmart036]

Shoot your load out as far as you can on measured ranges, then plug them into JBM and play with them. You'll get the velocities without the chronograph expense and doubt.

Good advice. I used to do that before I bought a chronograph. I might go back to using this method.

 

[rustyinbend]

Shoot your load out as far as you can on measured ranges, then plug them into JBM and play with them. You'll get the velocities without the chronograph expense and doubt.

I use a Labradar and get consistently reliable data. Not sure I understand the "Shoot known distances then use the Web Site" concept ... but I guess I don't need to.