Hmmmmm SIRs dissipate(sp) heat pretty good, don't they?



I thought you heat freaks would enjoy this picture
HUNTER

Quoted: Quoted: Hmmmmm SIRs dissipate(sp) heat pretty good, don't they? forums.hostileintent.org/uploads/post-11-1082231625.jpg I thought you heat freaks would enjoy this picture HUNTER That is a perfect example of how well the SIR does cool, notice what happens to the surpressor since it represents when something has no venting, it can't cool. Part of the gov't and commercial tests done, included how much longer a weapon could fire with a suppressor with a SIR vs. standard handguards, that went less than half as long as the ones with a SIR. The thermal couplings all over certain known heat sink area's verified all the heat variations, on all variations of rail and non railed weapons, and scenarios. Jack

Gosh you know so much Jack! Its almost like you were threre!

Info on the TWL barrel: www.ar15.com/forums/topic.html?b=3&f=12&t=246154


C4

Quoted: Yes and mostly no, if considering the fact that alum. handgurds cant' be held as they get too hot and must have covers over them to be able to grasp the weapon a little long, before needing a forwar pistol grip. The panels prevent the cooling just like insulators are supposed to do. The polymer handguads take much more firering before getting as hot as the alum. covered by panels.  .                                                                                                                                                                            .Aren't you same same guy that just posted about the dangers of eccesive heat damaging our barrels. If your HG's not getting hot it's because it's not conducting heat away from the barrel like good ole aluminum will.

This is my point as well. I want something to assist in pulling heat from the barrel.



C4

Hi guys,
Sorry I was out all evening, and just got back in and saw this discussion going on.

I think alot of good points have been touched upon here, and on various subjects too.

I've been involved a fair bit with some of these issues myself, and know some other people who have also.

I think that basically, the handguard systems work in two ways, which are somewhat contradictory in nature. That is, they serve to help to cool things in a certain way, and they also serve to hold heat inside in certain ways too, depending upon the design involved.

Basically, the issue of insulating the heat from burning the hands is one way of solving the hand-hold problem, but as 3rdtk mentions, this also has caused overheating of the working parts of the gun and is not an ideal solution. Alternatively, we have seen other types of handguards which are quite popular now, that seek to allow airflow to provide some cooling for the barrel, but since they are aluminum they tend to have some thermal conductivity properties that cause them to get hot on the hands because of the close proximity to the hot barrel and the hot air coming off the barrel.

Solutions for all of the issues at hand may not be so simple to find, but there are methods at our disposal to deal with all of them.

From my perspective, the primary item of importance is to keep the working parts of the gun as cool as possible so that it maintains its usefulness for the longest period of time during  high volume firing conditions. That is item number one, and basically begins with barrel cooling, or thermal conductivity of the barrel material. Barrel cooling is accomplished by using materials which will have high thermal conductivity ratings and large amounts of surface area through which the heat can be transferred to the air around it in the most efficient manner possible. Steel has a decent thermal conductivity as  materials go, but of course aluminum, copper, silver, and the newest carbon fiber materials can go way beyond the thermal conductivity of steel. For example, aluminum, which is the most common heat sinking material has a thermal conductivity rating of about 205w/mk. Silver, which is about the best metal for thermal conductivity has about double the rating of aluminum, 405w/mk. Then we have the new carbon fiber micro tube or nanotube products which are used in the thermally conductive matrix of the ABS Carbon Fiber barrels which have a thermal conductivity rating of about double what silver is, between 700-800w/mk. This is about 4 times the thermal conductivity of aluminum, and aluminum as we all know is far in excess of the abilities of steel in thermal conductivity.

So, we now have a barrel material which when wrapped properly around a steel gun barrel, can conduct the heat away from the barrel at a rate approx. 4x faster than an aluminum barrel heat sink could do. It also has a much better surface contact area than any metal heat sink could have to the barrel itself, so it has maximum potential to do its job of conducting heat away from the barrel. Of course, this heat must be able to be transmitted to the surrounding air for the job to be completed, so a large diameter barrel is effectively used to provide a high amount of surface area exposed to the surrounding air, so that the air can move the heat away from the barrel.

The rate of heat transfer will be dictated by the speed of the thermal conductivity of the material, and also the delta between the inner barrel temps and the outer air temps. Since there is a large delta between the barrel inner temp and the ambient air temp, there could be a rapid transfer of heat if the material can allow it.

So much for the barrel.

Now we have a circumstance where we have moved the heat away from the inner part of the barrel and are transferring it to the surrounding air in the handguards. As we mentioned before, the delta in temp is a key factor in moving the heat, so keeping the air circulating so that the hot air is evacuated and cooler air replaces it aids the cooling process. This occurs by convection, unless some forced-air system is employed.

A properly designed handguard system should employ some form of aiding natural convection  in the air around the barrel. A "chimney effect" is one of the best forms of this, if it can be engineered into the handguard effectively. Properly done, a chimney system would use the hot barrel as a "motor" to drive the convection, and venturi effects to speed the airflow in and out of the handguards. If this design is good enough, then less heat will be transferred into the handguard materials, thus keeping the hand-holding areas cooler and more comfortable. However, some physical constraints generally restrict the designer's leeway to design this system properly, and so compromises must be made, because of the size and shape of what we need in a handguard.

No matter what we really try to do with a handguard, the compromises are great enough that a somewhat significant amount of heat will find its way into the handguard material if we fire the gun enough times rapidly. So, to keep the shooter's hands comfortable, some form of insulating technique is required at the hand-hold positions. The VFG is a good example of an insulated grip that extends away from the hottest parts of the handguard, thus keeping the shooter's hand insulated from the heat as much as possible. It does the job, and does not cover any radiating surfaces of the handguard materials to hold heat in, as 3rdtk pointed out earlier. There are other things which can be used for different hand-hold positions, but the VFG shows a good example of an effective method. And, the protective gloves previously mentioned by other posters can also provide a similar insulating effect.

So, to recap, we want to move the heat away from the barrel rapidly.
We have to move the heat thru the handguard effectively and quickly, so that we don't heat up the handguard so much, and so that the primary function of barrel cooling is attained, without overheating the handguards.
Because we won't be 100% successful with this, we need to employ a certain amount of insulating for the hand-hold areas to ensure comfortable holding of the weapon if things get extreme.

Those are the main issues.
How any particular designer achieves them is up to him.
In addition, the other needs of stable accessory mounting must still be met.
Weight should be minimal, considering the carrying and handling needs involved.
And the system must be robust enough to not be broken or fail under expected use.


And, by the way, the ABS carbon fiber barrels are working, and they DO work as advertised, and they ARE under consideration by military, law enforcement, and government agencies as we speak. They are different than ALL of the previous types of carbon fiber barrels from the past, and the process is patented. The main issue in adoption of these barrels is not effectiveness, but cost. They are double the price of a normal barrel. As we know,  gov't procurement is price sensitive, so we can see the dilemma clearly.

I hope that my comments are useful to this discussion at hand.

Yes, I've seen it, and that is the company that makes the barrels which I'm marketing on the Equipment Exchange pages of AR15.com.

I own some of them, have shot them and used them myself, and numerous members of this forum also own them. The Advanced Barrel Systems carbon fiber match barrels are currently the state of the art in gun barrels, and are a revolution in barrel design.

I'm the factory representative for ABS barrels, and serve as their marketing outlet on this website.

Actually, the use of carbon-based thermal management systems does not have to result in brittleness. It can be done in certain ways that can be very strong and not subject to cracking or chipping or breaking. And, in fact, it is being done without these problems resulting.

IDK,
Correct, we are moving the heat at a faster rate, but it is still the same amount of heat that has to be moved. And it must be moved to the surrounding air that is inside the handguards.

Thus, it is paramount to have good airflow. This can simply be holes, but it is possible to go further than that. Natural convection can be used more efficiently than just random air movement thru holes in the handguard. But, the size, shape, and function of the handguards often restrict how much we can do.

For keeping hands comfortable, there is a very inexpensive and very appropriate material that can be used to insulate the hand-hold areas of the handguards with very little weight or bulk, and it would look great too. I can't discuss it right now, because it will probably wind up on one of our upcoming designs.

I have numerous advanced prototypes of different handguard designs here in my office, which exploit  advantageous ways to deal with moving air thru the handguards. Maybe one day, they will come on to the market. We currently are working on something way more radical.

Quoted: The rail system having covers on it or not is about the least important aspect of keeping a barrel cool.  The barrel itself and the barrel nut and the area which is attached to it is where all the heat is.  Very little heat is transfered to the rail itself.  If the rail has adequate ventilation and does not have a heat sheild it will work fine.  For example I can run a DD rail full auto and the barrel nut are will bliter flesh on contact and the rail is just very warm to slightly uncomfortable to hold.  Heat radiated from the barrel to air and off the barrel nut assembly is what is important... not heat radiated off the handguard. I would surmise you could not find a statistical difference in rounds till cook off using a rail system that does or does not have panels installed.  Even if you could it will be an issue for 0% of the readers of this forum.  Even the people who shoot lots of full auto will never have an issue with cook off or barrel failure because the rail system they use has rail covers on it.  Much of the arguing here is just silliness.  Or rather it is a spokesman for ARMS trying to spread misinformation about how the SIR so very superior in terms of handling heat compared to the other quality rail system manufacturers.  This is simply not true.  Its a NON ISSUE for all the shooters here.

Good point. If the SIR was as good as DICK Jack says then the Military would buy them by the boat load. This just isn't the case.



C4

Quoted: You wouldn't know just like you don't seen to know about contracts to three weapons systems, that are made by KAC, ARMS, and Dandiel Defense. I seems that I remember reading about it on here. Convienience of memory loss again? The Gov't must not know you don't sell any of those systems, or they wouldn't have chosen them, and ignored any all test results on products you don't have a clue about. what was offered and accepted and or why Jack

They didn't choose the SIR now did they. I am also willing to bet that you (ARMS) doesn't see any of that contract.  KAC and DD will get the majority of it.

It is also rumored that the Govt. has gone to awarding blanket contracts on certain contracts as they don't want to get sued every time they announce a winner. Know anothing about that Dick??


Good shootin,


C4

Quoted: They didn't choose the SIR now did they. I am also willing to bet that you (ARMS) doesn't see any of that contract.  KAC and DD will get the majority of it. It is also rumored that the Govt. has gone to awarding blanket contracts on certain contracts as they don't want to get sued every time they announce a winner. Know anothing about that Dick?? Good shootin, C4 Well, according to the published reports by Crane, the three companies each got a multi-million dollar contract for rail hand guards. You always say your looking for dick, is that your first and foremost interest? Obviously you don't know ,Jack!

Have you (ARMS) received a single order yet (other than what your required to provide for testing)? Didn't think so.

As far as looking for "Dick" your the only one I ever see on this board.

C4

Quoted: Quoted: Quoted: They didn't choose the SIR now did they. I am also willing to bet that you (ARMS) doesn't see any of that contract.  KAC and DD will get the majority of it. It is also rumored that the Govt. has gone to awarding blanket contracts on certain contracts as they don't want to get sued every time they announce a winner. Know anothing about that Dick?? Good shootin, C4 Well, according to the published reports by Crane, the three companies each got a multi-million dollar contract for rail hand guards. You always say your looking for dick, is that your first and foremost interest? Obviously you don't know ,Jack! Have you (ARMS) received a single order yet (other than what your required to provide for testing)? Didn't think so. As far as looking for "Dick" your the only one I ever see on this board. C4 Well first you say only KAC and Daniel defense got the contracts, then I point out to you your wrong, and like to give out false info all the time, depending on your position instead of the facts and truth, then you change your position when called on it. Then if any descusion is going on that doesn't put money in your pocket, even if it is science that might help a soldier and his weapon, you chime in with stupid bs. If you want to know what any of those three companies are doing, call and ask them. I'm sure you are very important to them and they will tell you anything you want I wish you luck in your search for dick Jack

Dick, I know its hard to drink your JD and post, but please try and keep up. I never said that KAC and DD were the only ones to win the contract. I said that I bet they are the only ones to get any actual order over the 30 required for testing!

This discussion has nothing to do about selling anything. It is about you hiding behind a fake screen name and telling everyone that the ARMS SIR is the best.

If you would just come out and say "I am Dick Swan and I think the ARMS Sir is the best" I would leave you alone. You choose to play this little school girl shit and I call you on it and will continue to call you on it until the day I die!



C4

P.S. in almost every thread you have posted in the last several days, someone has asked you if you are either an ARMS employee or Dick S. himself. What does that tell you??? Do you REALLY think your fooling anyone???

WTF...