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Gentlemen,

This question, I suppose, is directed to Marshall and company, but I'd like to hear from anyone that has experience in this area as well.  

On page 89 of the BTB Technical guide, under "Atmospheric Conditions", Mr. Stanton states the following:  "High temperatures can cause premature bullet lubricant failure in high pressure or high velocity rounds."

I live in the Southwest, and typical summer temperatures run well over 100F.  I still shoot.  I try to utilize as much available shade as possible, but my guns and gear still get hot.  The question is this:

Under what conditions can I expect this lube failure, and what are its symptoms?

I am still a neophyte in the cast rifle bullet realm and I am seeking to eliminate as many variables as possible in the chase for the ultimate loads.

Incidently, I must highly recommend the Technical Guide.  I should have purchased it earlier.  I have had to learn a great deal the hard way.  Had I read it first, I would have shortened my experimentation dramatically.  I had sought answers to specific questions from several self-styled experts and bullet manufacturers, to no avail.  This simple and inexpensive resource addressed each question in a very practical manner.  Just buy it.  It will pay for itself many times over.  

Cordially,

Smith
 

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Smith

Sorry to be so latent in answering your query, but as you know we've been very busy.

The lube breakdown I'm speaking of in the Tech Guide in high temperatures is basically a loss lubrication that is prematurely initiated by high ambient temperatures.  As with most lubricants the viscosity of the bullet lube will dramatically decrease with temperatures over 95 degrees, and once you get into the triple digits that degredation of lubricity is greatly mulitiplied.  Couple this breakdown with loads that are already near the maximum working threshold of the bullet lube at normal (comfortable) temperatures, and you've got a recipe for bullet lubricant failure which will lead to barrel leading, perhaps dangerous pressure spikes in a load that was otherwise perfectly safe at twenty degree cooler temperatures, and bullets that will shoot absolutely wild, not grouping at all.  

This type of breakdown is most evident in softer bullets BHN 11-16 and with plain based bullets that are pushing the velocity envelope for plain based bullets to begin with.  This isn't to say that a good, hard gas-checked bullet is immune to the plagues of bullet lubricant failure, they just don't display classic symptoms as early, or as dramatically in most cases.

The temperatures I've listed here are for the bullet lubricant that we use on Beartooth Bullets.  We've tested literally scores of bullet lubricants, and many of them actually have a VERY narrow temperature tolerance in which they are effective.  Many commercial lubes begin losing their lubricating qualities at much lower velocities, and at much lower ambient temperatures than the thresholds listed above.  Too those same bullet lubricants fail miserably in many cases when the temperatures get much below thirty degrees, and fail totally below twenty!  

Hope this helps!

God Bless,

Marshall
 
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