Cold temp Cold barrel Warm chamber

[harvey13118]

I'm working on varmit loads for my stock 22-250. On the chrono, shooting 1 rd approx every 30 sec, 5 rd lots I gain/vary almost 100 FPS.

Wander down to target mark or change and come back settle down write notes and resume test. Pretty much the same. I use a 10-10 RCBS and hope that is not where the spread comes from.

Usually 8-11 different lots of 10 rds each per session.

Temps are around 15F as day warms up the FPS also picked up a tad.

Powders are imr's 3031, 4046, 4895. I've just loaded some Varget and waiting for weather to warm up above 20F and the wind to die down some for next session.

Any thoughts?

 

[Preacher]

Varget will handly the temp swings more than the others you use.
It sounds like your not quite to that sweet spot yet.
100 fps velocity spreads is not a good thing.
If your load for 15 degree temps are anywhere near max, you will be in big trouble in 70 degrees temps.....

 

[jwv2001]

First of all, with these velocity swings, how are your groups? There are so many things that could account for the velocity to vary that I don't know where to start. First, how confident are you with your chrono? Second, I'm willing to bet that the Varget will be more consistent, but you should stick with one powder and test it until it passes or fails. Third, you didn't mention what primer you were using. Primers have a big effect in making a load more consistent.
So, you are testing a particular powder, charge weight, bullet, seating depth, and primer to determine pass or fail of a given load. In the end, more than anything else, accuracy will be the goal not standard deviation.
If I were you, I would go to the old standard H380 and not use a bullet lighter than 55 gr. Blitz Kings or Vmax's. Vary the charge weights, seating depth, and primers until you find the right combination. You should be able to stack them one on top of the other. Good Luck

I just re-read your post and noticed you didn't say anything about cleaning. When testing, I usually set up some kind of consistent cleaning regime. Just running a couple of wet patches with Butch's and then 4 or 5 dry patches between sets. Powder fouling can give you some bogus chrono readings.

 

[harvey13118]

Shooting 40gr V-max with Varget or 4064 gets me around .65" average on 5 rd groups at 4000-4100 fps. 55 gr bullets so far various powders various fps various bullets I'm lucky to stay under 2".

The 100 fps variation with the 40's the faster tends to hit left side of group.

The kicker is the longer I shoot without cleaning 40-60+ the tighter the 55 groups will get and the 40 will open. Cleaning every 10 rds the fouling rds,55gr) will hit with in 3" but usually to the right. The 40 will nail it and the 50 is open and group 2-3" to the right and low.

I'm guessing I need to look at 1 bullet and work on the load from there. The 40 is good but runs out of steam at 300 or so. Would like to shoot the 50's or 55's so I guess I have to go back to the beginning and the basics to build a load that will shoot in a clean barrel. I'd really wanted a couple of different rds and loads for different vermin.

I'm also being much more picky about how the scale reads and comes up to weight. The 250 seems much more picky then the .30's.

I appreciate ya-alls insight most of this is just talking myself thru the problem seeing it in writing and getting some feedback.

Harvey