First Rebuild- Velocity Loss??

[snowgetter1]

Just completed my first barrel swap. Changed to a 25-06 26" varmit from the 22" standard. I became frustrated waiting on Sharp shooter Supply as my wrenches have apparently been on back order for about a month now so I changed the barrel with a pipe wrench. Worked just as described. I would like to thank Lostart for the barrel and the rest of the members for giving me the confidence to complete this.

My question comes from chrono readings that are below what I had in the 22" barrel. It should be noted my 22" firing was first done on a 95 degree then again on about a 90 day then the 26" was about 80. Here are the results.
22" 26"
117gr BTSP 55gr 7828ssc LRM primer (95')=3114 fps; (90)=3070 fps (80)=3004 fps

75gr sierra HP, 57.5gr 760, LR, (95)=3740 fps (80)=3707 fps

85gr Nosler BT, 52gr 760, LRM, (80)=3310 fps

I was expecting a velecity gain not a drop or the same. The 85 gr load is published at 3443 fps. I know from my artillery days powder temp can be important but I would never think it could influence small arms like this. Any ideas?

[cowboyarcher]

Bet the new barrel has a different chamber, slightly, affecting the pressures.

[snowgetter1]

That is possible. I have not fired the 26" alot but I had noticed the pressure signs were not as evident as with the 22". The 26" appears to be an older savage barrel marked for a 112.

[earl39]

the bore could be just a hair larger also. 1/4 to 1/2 thousandth larger would also reduce pressure and give a lower chrono reading with the same load. such as a .2565 bore on the 22" and a true .257 on this one. there is more than one way to skin a cat and also more than one thing that can change speed and pressure on a gun.

gary

[tammons]

Probably a combination of things. Those mentioned above plus a 15dF temp drop.
Not sure how temp sensitive that powder is but I have seen a solid 40-50 FPS from going from 85 up to
98 or so. If your cartridges got warmed up in the sun vs cool ??