Brain fart on the relay time was thinking about Smallbore.

Boats

It's not so much the quantity of lube as where it is situated.  Lots of lube doesn't do anything if you have very deep, narrow grooves.   In order to be effective, the lube needs to be in contact with the bore - everything that's slung off the bullet when it exists the muzzle (like on your chrono skyscreens) is totally useless.  Which is where the contact surface becomes important.    One can have a bullet that has lots of lube in the wrong place and won't work - and another that has much less lube capacity and won't cause any issues whatsoever.

MartiniBelgian's comment is certainly valid.  The following is from an article on Browning .40-65 BPCR bullet design I'm currently writing. 

"...when using a blow tube, not only must the bullet carry sufficient lubricant to coat the bore to the muzzle to eliminate leading, the lube is also essential in helping to keep the powder fouling soft in hot and dry condition.  Not only is the lube quantity important, sufficient lube must contact the bore.  Adding up the width of the lube grooves determines the lube contact length.  A well-known bullet designer and shooter found through rigorous testing that 0.250” of lube contact length is optimum.  The width and depth of the grooves determines the lube carrying capacity.  Although the lube contact length may be adequate, if the grooves are not deep enough to carry sufficient capacity the bullet may run out of lube prior to reaching the muzzle.  An excellent method to determine if the bullet holds enough lube is to check the muzzle for a lube star, lack of which indicates insufficient capacity or possibly poor quality lube. But the presence of a lube star does not verify adequate contact length."

"An excellent example of marginal (I consider it inadequate) contact length and insufficient lube quantity is the Lyman Snover with a contact length of 0.200" and only 1 gr (0.07cc) of lube.  It's a nice looking bullet with an aerodynamic nose design & under the right conditions it can be very accurate, but when the ambient temp. increases & the humidity drops the inadequate lube grooves become a liability when using a blow tube."

Wayne

Excellent. You'll have to show us the way with your scores at Raton this July.

svartkruttgris#369 wrote on Apr 3^rd, 2016 at 2:48pm:

I was there one day when I thought my rifle would blow off the line.  The cover didn't do any good.  Rain from the thunderstorm was coming under it hitting the windshields of the vehicles in the parking lot. 

I think the blow tubes and wiping rods ended up between Mexico  City and the Panama Canal somewhere.

svartkruttgris#369 wrote on Apr 3^rd, 2016 at 12:22pm:


Grisen,

Note that I previously said that under the right conditions the Lyman Snover can be very accurate.   And I don’t consider the “operative variable to be amount of BP burned, hence amount of powder fouling”.  I have found that the operative variable is temperature & humidity.  Generally accuracy was fine and even excellent at all distance out to 500 meters (the longest range I tested the bullet) under moderate temperature & humidity conditions.  But when 500 meter tests were run in typical central Texas summer ambient weather conditions (temps in the mid 90’s to 100 degree and humidity approaching 30%) the lube capacity was not sufficient when blow tubing.  BTW, I use a high-quality proven lube, Swiss 1.5 and a good 0.060” wad between the powder and bullet base, so blow by was not an issue.

I expect the bullet to do well in similar condition if wiping between shots, which I plan to test in the future.

Wayne

Wayne,

I agree that temp and humidity can play decisive roles with BP loads. My lifelong standard for BP loads is different than what most BPCR shooteers use. I almost never wipe or blow tube between shots and do not want to. I do wipe out nearly all powder fouling after each 15 shots of a BPCR relay (1 fouler, 4 sighters, 10 for score). Being a slow old guy I need all the time to concentrate on shooting. I am not a long time BPCR shooter even though I have been using small grouping BP loads since a teenager for hunting.

My goal is for group size to remain constant for at least 15 shots, no matter if cool and wet, hot and wet or hot and dry. After 1 fouler my groups are consistant for at least following 14 shots (that does not mean I never let off a bad shot). I accepetence test loads for 10 shots, no messing with bore. Sometimes my best shots are late in 10-shot string, when I finally get my act together (I have more contrary body parts than just shoulder). My best loads have maintained group size/score on steel critters even at 90+F and less than 15% humidity -- with NO HARD FOULING in bore.

One of my best grouping loads with Lyman Snover 410663 used 60 gr Swiss FF, 2 0,060" wads, 0,25" compression, bullet slightly pushed into rifling. Muzzle velocity about 1290 fps in 20C at 5000feet, less than 50% humidity. It is very clean burning in my rifle. I quit using it because my mangled shoulder did not do well with even 15 shots in row.

Going to loads mangled shoulder does tolerate -- at least last year -- resulted in 1100 or so FPS with same bullet and about 50gr Swiss 1,5F, and, of course, a multi-wad column to bring bullet into snug fit into rifling. All this in Starline or reformed Win brass. Same basic load with Saeco 640 is at least as good, perhaps better grouping. Putting Lyman 300 grainer for .405Win in top -- not touching rifling -- gives larger groups, but chickens never complain. Hope to try RCBS 300 grainer this year for pigs, maybe turks.

My basic, underlying requirement is same as for wipers and blowers -- uniform bore conditions from shot. Difference is that I build that into load itself.

NONE of these loads are even close to acceptable with any Goex powder, even the highly touted Old E. They develop hard powder fouling in less than 10 shots, powder fouling I never could remove in time available between relays. BAD misses!!

Grisen