First five shots from cold, clean bore

[garandman]

Would it be normal to see a slight decrease from shot to shot thru the first 5 shots (a shot every 20 seconds) in a modern bolt action rifle?

I noticed it today in both my 6.5CM - and my 1884 TD Springfield.


CM went 2732 - 2710 - 2706 - 2687

TD went 1263 - 1211 - 1081

Curious... I would expect that a bit more in the TD carbon steel barrel, not so much in the CM stainless steel barrel..... heat expansion?

 

[Captain Kirk]

Don't always test your chronograph. I have ran my 243 over the chrono shooting steel at over 1k yds, it would often show a SD of as much as 50 fps in some lighting conditions, while I was able to put rounds in a tight group horizontally. This wouldn't be possible with a SD swing like that, I use POI and data to come up with velocity #s.

With that said, it is common to have a fairly substantial swing in velocity with your CBS and especially a CCB.

 

[McLarenross]

I quit trusting my Chrony when it started giving me these readings from my 308. As the Captain said above, reverse figure your muzzle velocity from actual dope taking into account actual atmospherics and BC.

 

[garandman]

LOL..... I got some 4500 fps readings today.

I thought "Dang.... I won't need to build that 338 with this kind of muzzle velocity."

 

[scudzuki]

I quit trusting my Chrony when it started giving me these readings from my 308. As the Captain said above, reverse figure your muzzle velocity from actual dope taking into account actual atmospherics and BC.

I'd suggest you back the charge down on that load.
Those are a little hot.

Joe