Velocity question

[johnnyk]

Today I was shooting my Rem 700P in 7mmRemMag. Barrel has very little wear, I think. I was shooting the Hornady 154gr SST, VihtaVuori N560 and Rem 9.5M primers with Weatherby (Norma) brass. Bullets kissing the lands. Kinda warm here in N.C., 78-80F, and humid.
I started out @ 65.0 gns, velocity was 2970/2992/3011. At 65.5 gns velocity was 3024/3053/3086 and at 66.0 gns velocity was 3098/3117/3142.
I tried to let the barrel cool in between shots. Started with waiting 2 minutes, then went to 3 and eventually at 5 minutes. Even put rifle in truck with AC going to get temp back down. When I say "down" I'm not talking cold steel, just warm to the back of the hand.
Powder was double weighed on RCBS 5-0-5 beam and Ohaus GT400 electronic scale0. Question: what made my velocity climb with each shot? Anyone ever see this? JohnnyK.

 

[remingtonman_25_06]

You probly just haven't hit one of your nodes yet. A little more experimentation will probly give lower/more uniform crono numbers. A good node should vary no more then 20-25fps.

 

[Flybuster]

Just an idea. If your letting your barrel cool with a live round in the barrel, the chamber is cooking that cartridge. Which can create differences in velocity.

 

[johnnyk]

Not sure whats up. I shot some 168gr SMK's on 1/28/07 that continually climbed in velocity. Used H4831SC/Rem 9.5M and Weatherby brass. Right after that, within the hour, I shot 4 leftover (from deer season) 150gr Scirocco's (67.0gr RL22/R9.5M/Rem brass) that were somewhat more consistent. Velocity went 3168/3137/3141/3177 (3155avg.) I keep the cartridges separate from the rifle until time to fire. I usually keep my barrel's pretty clean and copper free. Do ya think this barrel likes it somewhat fouled? Knowing my luck it was the last barrel that Remington made before they realized the barrels were outta spec! JohnnyK.

 

[johnnyk]

This morning's range session went a little better as far as velocity goes. Wind was nil and temps were 65-70 'ish. Took the Hornady 154gr SST from 66.5 - 67.5gr of VV N560 (.5gr increment) with no pressure signs. Did not clean the barrel from previous load development shooting session (9 shots). Velocity was pretty consistent from shot to shot. May have varied 30 fps to the most. Accuracy however, sucked. Groups (patterns!) ran 1.4305", 1.1695" and 1.6625" The average velocity for 67.5gr was 3172 fps. I like that velocity but wish is was more accurate.
I may try backing off the OAL and see if that helps. What do ya'll think? JohnnyK.

 

[linksmechanic]

168 mk's shoot excellent out of mine as well as 180 vlds.

 

[remingtonman_25_06]

I've found the SST's to be pretty picky...They seem to have a little sweet spot if thas what you wanna call it. I worked forever trying to get a 140g SST load for a .270 win and finally got it. It shot 1.5-2" groups at 300 yards, but it took some tinkering, .5g one way or the other and groups were back up to MOA or worse!!

Also have tried a few 162g SST in a 7 RM with not very good results for preliminary work up. ALso tried the 180g SST in 300 RUM with non-satisfactory results in the accuracy department..

They did shoot decent in my 25-06, but there BC is crappy...

 

[johnnyk]

Thank you RemMan25-06. That confirms it for me. No more Hornady's. Nosler, Sierra, Swift and Barnes will do just fine.
By the way, found a sweet load for my .25-06 Sendero using the Sierra 117gr GK. 52.0 gr of RL22/R9.5M/Rem cases, OAL: 2.7985" (ogive to base). On the average getting a little better (.4") than 1/2" @ 100yds and velocity is at 3050 fps. Probably could get 100 fps more outta this bullet but accuracy is about where it should be, I think. JohnnyK.