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Rifles, Reloading, Optics, Equipment
Gunsmithing
J-B weld for bedding compound?
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<blockquote data-quote="Kennibear" data-source="post: 942776" data-attributes="member: 51650"><p>JE Custom</p><p>Thanks for the +1.</p><p>Something to consider; the shrinkage after cure is different for each epoxy. Post cure heating causes some epoxies to shrink quite a bit. I suspect that Brownell's picked a combination of epoxy/filler to minimize that. A barrel can get pretty darn hot, especially with the hot rock calibers long range shooting gravitates towards. I tape a thermocouple to my barrel during testing and pump air from a fan through the chamber end to bring the temp down. I try to shoot at a constant barrel temp. But it is easy to reach 250 degrees which will cause most hard epoxies to shrink and it will soften the 5 minute variety (which are not really epoxy actually) right away. Under recoil the softening would let the action hammer the bedding- bad ju ju!</p><p>I am concerned about the trend to aluminum bedding blocks and people's attempts to bed an action into them. My experience (in boats etc.) with epoxy bonded aluminum is that the aluminum must be cleaned and etched (phosphoric acid) before bonding for the epoxy to bond adequately. And by before I mean two, maybe three <em>minutes</em> before! It may require an interim bonding layer of an aluminum specific bonding epoxy painted on the bedding block and the bedding compound applied on top before the aluminum bonding has reached gel stage. </p><p>I'm seeing it as a two person job with somebody doing the final etch as the other mixes the bonding and then the bedding. How fun!</p><p></p><p>Never mind me, just the ramblings of an old guy...</p><p></p><p>KB</p></blockquote><p></p>
[QUOTE="Kennibear, post: 942776, member: 51650"] JE Custom Thanks for the +1. Something to consider; the shrinkage after cure is different for each epoxy. Post cure heating causes some epoxies to shrink quite a bit. I suspect that Brownell's picked a combination of epoxy/filler to minimize that. A barrel can get pretty darn hot, especially with the hot rock calibers long range shooting gravitates towards. I tape a thermocouple to my barrel during testing and pump air from a fan through the chamber end to bring the temp down. I try to shoot at a constant barrel temp. But it is easy to reach 250 degrees which will cause most hard epoxies to shrink and it will soften the 5 minute variety (which are not really epoxy actually) right away. Under recoil the softening would let the action hammer the bedding- bad ju ju! I am concerned about the trend to aluminum bedding blocks and people's attempts to bed an action into them. My experience (in boats etc.) with epoxy bonded aluminum is that the aluminum must be cleaned and etched (phosphoric acid) before bonding for the epoxy to bond adequately. And by before I mean two, maybe three [I]minutes[/I] before! It may require an interim bonding layer of an aluminum specific bonding epoxy painted on the bedding block and the bedding compound applied on top before the aluminum bonding has reached gel stage. I'm seeing it as a two person job with somebody doing the final etch as the other mixes the bonding and then the bedding. How fun! Never mind me, just the ramblings of an old guy... KB [/QUOTE]
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Gunsmithing
J-B weld for bedding compound?
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