Advice on what's going wrong with my load!?

[jca57jd]

Hey guys I worked up a great Berger load for my 700 varmint 243 last December. I am shooting 43 grains of 4350 with 87 vld hunting bullets. I found my sweet spot to be right at the LANs, 2.277 to the ogive and I was shooting 3070 fps. I shot this load on 12-8-12 and had awesome results; I had 5 bullets loaded, all touching at 100 yds, and the last two touching at 300 yds.

I went out to shoot this gun and load for the first time since December this morning. It didn't shoot worth a crap this time!? I didn't even measure it since it was so bad. My velocity was a little slower due to being colder out, 3030 fps, but I would have never expected it to go down hill that fast.

Here are the wether specs for the time of shooting and picture for the first time in December:

60 degrees
Barometric pressure 30 hg
Humidity 84

http://i1097.photobucket.com/albums/g341/jca57jd/image_zpse5f600d8.jpg


Here is the info for today:

43 degrees
Barometric pressure 30.25 hg
Humidity 46

http://i1097.photobucket.com/albums/g341/jca57jd/image_zpsf05b0d6c.jpg


What is your opinions on what my problem might be? Thanks heads up thanks for any of your inputs!!

 

[MNbogboy]

Was this last Decembers loads or new ones?
Sitting for even a month or two often "cold welding" can occur between the bullet and case mouth...Thought to be caused by "Galvanic" action of two disimilar metals where the molecules of one material migrate to the other and intertwine for lack of more scientific terms...

Whatever the cause of this "cold welding" causes the value of neck tension to increase dramatically and may affect your loads but not always the case...

If these are new loads with any component change (i.e. same bullets but from a different lot or same powder but a new can)....These changes can make lots of difference...For instance Berger replaced the dies for my 6.5 140 VLDs...The base to ogive measurement moved over .015 thousanths and the diameter actually dropped a full 1/2 thousandth.....Length increased an average of about .030.....Result whole new bullet as far as I am concerned...My pet loads at .045 off really soured and when all was said and done now I am at .010 off.....

I doubt that the drop in temp only 17 degrees should make that big a difference but a rise in temp by that amount can put you over the top if you are at max at the lower temp....

Just a couple of thoughts,
randy

 

[jca57jd]

Hey Randy,
After they shot so well I reloaded about 30 rounds; weighing the cases, and bullets out individually and sorting them. I might load up 3 more new rounds and see if it shoots different for your reason. Thanks a lot for the advice!

 

[Lefty7mmstw]

dollars to pesos you just have a load that is no good in cold weather. I've had it happen with I 7828 in my 7rem with 140 grain sierra pills. If the temp. dropped below 40 the accuracy went from 1/2 moa to three moa. The 150 nosler bt's with 7828 shoot well in both hot and cold temps in my 7rem though. I went to I 4064 with the 140 sierra and it's sub moa in both hot and cold. rl22 also does well though in both ranges with a 140 and it's almost as slow as 7828; go figure.The problem is the bullet wasn't loading the powder enough to burn as uniform in lold weather, even with a mag. primer. If you go to a bit faster powder the problem will probably go away.

 

[jca57jd]

I have some imr7828, rl17, imr4064, varget, and imr4831. Which ones are going to be good starters? I have read the burning rate charts but they don't even start to rate the temp sensitivity. Thank you a lot for your inputs so far!

 

[MNbogboy]

jca57jd,
A quick test for the "cold welding" is to try to seat a bullet deeper in one of the old rounds....I often can feel and hear a snap as the bullet starts to move....Every summer I usually use my last years left overs for practice..They often shoot well despite the fact that they are not new...It was only a thought that that might be the cause of your problem......

Your drop in MV is another indicater that my "cold" welding theory may be off...the increased neck tension most likely should have raised pressure slightly and possibly increased velocity.... I will test some when & if I think about it and see if that theory holds water..

Personally I have had pretty good luck shooting h4831, h4831sc, H4350 and imr4350 in all my midsized stuff without a lot of variation with temps except in the summer when we see 70s, 80s and 90s...Sometimes a drop in charge size has been called for as velocity increased and pressure signs would indicate as those temps climbed....

After receiving a barrel in Jan the rest of the winter weekends were busy with load development..Temps below zero on several occasions...Shooting was miserable on the fingers but loads & groups didn't seem to fall apart inspite of the cold.

A few degrees can make a big difference on an upswing, So I would believe as Lefty7mmstw stated that it also can happen on a temp decrease...Every barrel, load and rifle sometimes is a law unto itself, so by all means don't rule it out...That 40 fps drop in MV may have easily dropped you over the edge of an accuracy node...

Good luck,
randy

 

[Lefty7mmstw]

If you have 4064 and varget, either will do well. Often the trade off with the milder overbore rounds like the 243 is slightly faster powder for better accuracy and uniformity.
I've rarely seen cold welding on my rounds. I have thousands loaded and sometimes don't get to them for a couple of years. I realize there is a remote possibility, but if you keep your rounds clean and dry and use cleaned brass to start with it'll drop the cold welding chances a lot.