Quirky Problem

[BABore]

Veral,

I recently purchased some of your LBT Blue lube and really like it. I've been concentrating on load developement for two different rifles and ran into a quirky situation. I shot both rifles in 35-40 F weather. They are both using bullets cast from an alloy of 50% WW's and 50% Pb then heat treated to 22 Bhn and lubed with LBT Blue. The lube and the alloy are the common denominators.

Rifle #1 is a T/C Encore in 338 WM using a 225 gr GC bullet. Using WC-872 mil. surp. powder plus a small kicker charge. Working in the 2,200 to 2,500 fps range. Working up loads in 1/2 gr increments in sets of three.

Rifle #2 is a 1895M, 450 Marlin using a 420 gr GC bullet. Working in the 1,700 to 1,800 fps range with H322. Working up loads in 1/2 gr increments in sets of three.

Here's what happened. Both rifles had clean bores and then had 3-5 foulers shot through them. In the 338 Wm, from a cold barrel state, the first round went 5 to 6 inches high. The following two rounds grouped together. I shot the next three rounds immediately following the first set and they grouped together. I left the barrel cool completely then went to the next set. The same thing happened. Made this happen a total of three times. My first thought was the lube didn't like the 35-40 F temps. I also considered the tension of my front hanger bar screw, but it is barely snug and Lok Tited as I've always had it for accuracy. Incomplete ignition of the slow WC-872 was also considered. Then I went to my Marlin.

The same thing happened. First shot was 6 inches above the sight adjustment. The second was about 3 inches. The following 3 were well grouped. I repeated this again with the same results. I then warmed the remaining ammo to approx. 60 F. It helped a little, but it seemed like a warm barrel was the cure. All rounds, for both rifles, were fired from a benchrest using soft bags fore and aft. Front bag position was consistent and in the particular rifle's sweet spot.

The quirky part is I have shot the same stuff 5-10 F and didn't notice this pattern. I may of missed it too. I know it's not gun related, but it has to be the lube, alloy, or a combination of the two. I'm currently going back to straight OHTWW's in my Marlin as the gun just doesn't care for the 50/50 alloy that well. Any help would be appreciated.

[Veral]

LBT lube is tough stuff and not much is required for such light loads.  Go to lubing just one groove + the check shank and I believe the problem will go away.  I have benchrest customers running 2600 fps with one tiny groove plus check shank filled with lube, and winning matches regular.  For year round ammo, use enough lube (just enough grooves filled)  to prevent leading in the hottest weather you think you'll be shooting in, and normally the cold weather /  cold barrel high shot won't be a problem.

  It is an overlube problem, which seems to only show up in longer barrels.  No one has ever mentioned it in handguns, nor have I encountered it.

  This problem is common to any lube that is handling the load to easily.  It isn't notices with most lubes and the loads you are shooting because you are working at the limit for all other lubes I know of.

[BABore]

Thanks Veral, I'll give it a try. Any idea why it shows up when the barrel is cold, but not when it's warm? Lube buildup in the bore solidifing perhaps. Just my guess.

[Veral]

There is never really a lube buildup, but the film is heavier and thicker between bullet and barrel, which lets the bullet slip easier, causing higher velocity, higher impact.  The problem will be most pronounced in guns which are sensitive to bullet weight / velocity, so far as bullet impact.  Leverguns being the worst offenders I've encountered.  For example, in 357, 44 mag and 30-30, bullet weight or velocity change, even small changes has required a substantial sight change in all guns I've toyed with.  In the 30-06's Ive owned, bullet weight and velocity can be changed quite dramatically without moving the point of impact greatly, and the high cold shot is never noticed on game out to 400 yards.  My longest shot on live target was 525 yards on a feral dog, and he quit bothering my chickens.  I've taken elk and deer to 450 yards, and the first cold shot has always landed where I wanted it to.