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burning exposed lead tip?

 
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  #22  
Old 10-02-2013, 07:44 PM
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Join Date: Aug 2010
Location: North West Washington
Posts: 80
Re: burning exposed lead tip?

Coming from an elastomer molding back ground it strikes me as odd that designers would incorporate materials that would resist deformation from recoil in magazines and yet melt at roughly half the temperature of most plastics. Even nylons melt between 374 and 663F. Most thermoplastics begin to liquefy at around 350F.

It makes very good sense that the highest temperatures midrange would be about the center of the ogive. As in an airfoil the highest degree of frictional heat buildup is where the highest angle of incidence occurs and not necessarily at the actual leading edge. A spitzer meplat offers the least surface area for air friction to act upon whereas the ogive is the surface that actually does most of the work in forcing the air mass apart. I conceded that there is some degree of heat buildup at the very point of a spitzer bullet; however, I find it difficult to see a lead point being exposed to enough time/heat to actually become plasticized and be thrown off.

If indeed this happened all the time, one should see the “grey streaks” all of the time regardless of bore condition or spin rate. Merely using a “good” bore would produce little improvement.
One should also be able to see the grey streaks at a specifically defined air temperature and velocity (i.e. scientifically repeatable).

One can only wonder if the rough throats (and most probably bores) of the rifles you were using, combined with thin jackets and rapid spin rates contributed to damaged jackets allowing centrifugal forces to overwhelm the integrity of those projectiles and lead to their destruction.
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“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”

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  #23  
Old 10-02-2013, 09:19 PM
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Join Date: May 2012
Location: N.D.
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Re: burning exposed lead tip?

I've been working with cast bullets in both pistols and rifles for many years now and I've never had any bullet noses ablate off due to heating, and those bullets have a heck of a lot more metplat than a spitzer does. I'm not saying a bit of erosion due to ablation or dust in the air doesn't occur, but the amount is miniscule enough to be of little concern to the average long range shooter. I'm at 1,200 fps to 1,600 fps in my 44 pistol with cast and 2,000 fps in my 375 h@h with cast and both will shoot as well as jacketed or mono bullets in the respective weapons. I hope to get to 2,300 fps with a cast 288 grain 405 slug with my 405 with minute of buckhorn sights accuracy; that'd be a good brush load for mule deer in the badlands.

Lyman has done some odd things over the years and one was a paper patched lead pill in 30 cal that was capable of 3,000 fps out of an '06 sized 30 cal with moa accuracy capabilities (lyman cast bullet handbook page 114); the bullets were making it to the target so I do doubt they were vaporizing on the way there. The moulds aren't available at this time but from what I've seen over on castboolets there are a couple of specialty makers making moulds specifically for paper patching lead to get good velocity from it.

I've been doing a bit of reading on commonly used lead based alloys and the consensus is that most of them will melt within 100f either way of 600f. With only about 900 degrees on tap to heat with melting a lead bullet to any significant extent will take quite a bit of time. A bit like passing with a car in 5th gear when it's a gutless 4 banger to start with.
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