[voruzon]

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.

http://www.compusa.com/products/product_in...cmid=&pfp=srch1

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

V.

 

[cajungeo]

I don't know voruzon. Maybe a couple things to consider. That type of heat sink material is thin, not for large gap filling. Also the tube is very small, it may take several to fill, gap between barrel, and the rail. It thins, and may run down into the slide area.

 

[voruzon]

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.

V.

 

[BillVan]

Vourzon,
You may want to try it only at the gas block and the Ultimak clamp near the receiver. If it truly works as a heat transfer agent, the heat will be drawn to the mount. This also will solve the problem of trying to fill a large space. Follow the instructions for installing the Ultimak and upon reinstalling the top of the gas block, put down a layer of compound and tighten up in a cross pattern using the hardened cap screws. You may want to use a feeler guage to make sure it is evenly spaced on both sides. Sounds like a good idea... it should move some heat from the bbl. too bad we don't have a way to measure the change. Good Luck!

 

[patmando]

I'm new to the mini-14 (stls/syn for 4 months) but lots of years with hot cpu's. Instead of the white grease, how about using thermal tape?

info:
http://www.3m.com/converter/product_doc/101092.pdf

one source via google search.
http://2cooltek.safeshopper.com/50/94.htm?397

Pat.

 

[voruzon]

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.

V.

 

[bushwack]

voruzon---You might want to check with an industrial HVAC suppy house & see if they have thermal transfer paste, It's used for the samething as the CPU/heatsink paste & may be a little less expensive. I have a jar from Honeywell but can't remember how much it cost me. I use it when installing temperature gauges & RTD's in thermal wells. For this kind of thing to work the Ultimak mount will have to be a very close fit to the barrel, very close. Just getting rid of the plastic (Insulated) hand gaurd will probably help quite a bit in radiating heat from the barrel.

Good luck
Bushwack

 

[cajungeo]

Just thinking out loud, if the underside of the Ultimak is black, this would help absorb heat, the aluminum construction would aid the heat transfer to the outside of the ultimak lugs, which would act as cooling fins, by increasing surface area.

Hmmm, now ya got me looking at my std shroud, the first 5 inches which would be the hottest part of the barrel, is not vented. I may be doing a little research in this area. I wonder if venting it there would cause the scope to become covered with gas smutt from the gas pipe/slide rod assy?

 

[voruzon]

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.

V.

 

[bushwack]

"Pecheneg" This must be the Russian word for "Bic". I can't imagine a machinegun with a permenently installed barrel. I've seen M-60's so hot you could light a cigarette off of the barrel & even with chrome lining a barrel that gets that hot is trash. I hope this doesn't catch on.

Later
Bushwack

 

[voruzon]

"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.

V.

 

[voruzon]

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.

V.

 

[mtnwatcher]

speaking of the ultimak...could the fellows who have one and fired with it tell about how it performs as a heat sink?

 

[voruzon]

Maybe this weekend.

 

[BillVan]

Mtnwatcher,
On my Ultimak... mounted on 181 Series Mini GB, seems to cool better than the factory handguard. My original reason for this mount was to allow for dot type scope mounting and it excels at this. Holds zero upon remount with ARMS #22 low rings.

Fired about 50 rds in 20 min. when I first got it. Really didn't notice it being hot. I was concentrating on the optics but I'm sure I would have noticed if it was smoking or my red dot melted off the rings.

I also have one on a FA AK. It will cook anything you put on it but it is actually replacing the gas tube so all the heat is applied to the mount. Just have to reduce my rate of fire. Will be a good test for the durability of the Aimpoint! :cannon:
If it is acutally cooling the barrel, just another plus for a well thought out design. Sure makes the GB look good. I keep taking it out of the safe just so I can stare at it!

 

[mtnwatcher]

you are correct, sir. the ultimak looks badazz. wouldn't mind gettin one myself, if i wasn't on such a strict budget. plus i'd like to try a scout scope config eventually.