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Thoughts on mounting Ultimak mount

2006 Views 15 Replies 6 Participants Last post by  mtnwatcher
I've ordered Ultimak yesterday.
Would it make sense to take the thermal compound that is used to fill the microscopic gaps between a CPU and a heatsink of a computer and use it between the barel and the Ultimak rail?

That should improve heat transfer from the barrel to the mount, helping distribute it more evenly and cool the whole thing faster gue to increased surface.

Arctic Silver III Polysynthetic Silver ($14.99 ): Made with 99.9% pure micronized silver, Over 70% silver content by weight.

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Good point, Cajungeo.

Supposedely 80% of volume is microscopic silver particles that fill the tiny imperfections in the surfaces and increase the thermal conductivity between them. I expect that after the suspension media deteriorates or runs off or changes, the silver will stay in pace. If the fit is good, very thin layer is all that is needed.

I bought a 3 gram tube for $15 yesterday and will try it.

Upon your warning, I intend to bake the assembled barrel mount in the oven for a while - that should reduce the danger of stuff running afterwards.

I think thermal CPU tape would not be a good idea on a firearm. First, the temperature of the barrel may way exceed the temperature of a CPU. Whatever happens to the filler materials, the 80% of silver content will not melt or disapper but stay in place and work its magic.
Second, the stress during the shooting is enormous - throusands of Gs for brief (milliseconds) periods of time. Not what your CPU tape is designed to handle.
Third, before the tape detariorates it will play havoc with the barrel harmonics and after it deteriorates, there will be gap which is even worse.

With tape, the mount would not touch the barrel - by design.
With thin even layer of thermal paste and tight fit, the mount would contact the barrel exactly the same as without it plus the microscopic imperfections of both surfaces would be filled with silver.

At the temperature the barrel is operating, very small fraction of heat is radiated from it, so the color of the underside of the rail is not really important. Remember - radiated energy means emitting infraread and visible light, though if your barrel ever starts emitting visible light, you probably have a real problem and should consider surrender. :)

Much more heat is transfered through direct contact - hot fast molecules of the barrel hitting and accelerating the molecules of the air or the mount. The more direct contact between the surfaces, the better, that's why I am considering the thermal paste to fill in the imperfections.

The dark colored objects do emit thermal energy a bit better than light ones, so the dark coloring of the outside of the mount may help - though probably very little, compared to the cooling by air.

Speaking of cooling - I was looking at the specks of the new russian light machinegun - "Pecheneg", IIRC, and they changed to non-repleaceable barrel (which made it more portable) by installing the barrel shroud through which the air is circulated/pulled due to the gasses from the barrel creating lower pressure up front. That allows them to fire quite a lot of ammo.

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"Pecheneg" is the russian name for the tribe of nomads that allegedely plagued the early century russian kingdoms - though I would not be surprised if that was the other way around in real history... :)

In short, the word "pecheneg" evokes an image of something wild and swift that you do not want to encounter without a few stout guys at your side.

Anyway, Pechened is a serious light machinegun using 7.62x54R round that is derived from PKM and actually shares 80% of parts. It weights 8.2 Kg with bipod (compared to 9 Kg PK plus extra barrels).

The key improvement over the PKM is a new barrel, which featured a forced air cooling and, unlike most modern universal MGs, is not removable in the field. New barrel is heavy and ribbed, and enclosed in the metallic sleeve. During the fire, the hot powder gases emrging from the barrel cause the air in the sleeve to circulate along the barrel and cool it, so a sustained rate of fire of about 1000 rounds per hour, or about 600 rounds in long, sucesing bursts of 40-50 rounds each, can be maintained withouth any decrease of performance or barrel life. Manufacturer claims that Pecheneg is 2.5 times more effective than a PKM when fired from bipod, and about 1.5 times more effective than PKM when fired from tripod or vehicle mount. The forced air cooling give to the Pecheneg an additional advantage over the PKM - during the prolonged fire sessions there's no hot air flow over the hot barrel, unlike on the PKM, so there's no mirage to interfere with accurate aiming.
I see what you ment, guys.

For some unfathomable reason I believed that the Ultimak - that I've just got - has a tight fit to the barrel along it's whole length. Instead, it is fitting tightly in two places - at gas block and at the bracket, ~2" and ~1" respectively, and possibly at the very beginning of the barrel.

The rest is the gap of about 1/16 - 1/8 of an inch and cannot be filled with pulverised silver, even if I bought enough.

I am not sure the termal paste of any kind would be good for filling that large a gap - considering expreme temperatures and stress of banging.

My adjusted plan is to fill that gap with layered aluminum foil - aluminum is a great heat conductor and even layered it should be better than just air insulation.
What do you think?

The Ultimak feels and looks great and weights little. The Aimpoint ML2 seems super. Updates to follow.

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Maybe this weekend.
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