AR getting really, REALLY hot.

rotarymike · Jul 27, 2012

Went out to try my slidestock today, and started out with the regular A2 stock on there. Shooting moderate 6.8 loads, 16" barrel/midlength gas. Rifle has a Hogue aluminum FFT.

After about 8 shots (not rapid fire) it got so hot it was uncomfortable to hold. Waiting until it cooled, I ran 10 through with the slidefire stock and could not touch the handguard at all. Second set of 10 I had a round jam in the bore, and couldn't rack the bolt back until the gun cooled down ~30 minutes later.

I don't recall this ever happening with the stock handguards. Is this normal with a freefloat?

Thinking about milling some holes or slots in the top of the handguard; it could pull cold air in from the end and convection-current rise up. If I do so, should I just vent the portion near the barrel nut or the whole length of it?

Guess this means that the .22LR upper I plan to build for the slidefire should use a heavy barrel. :roll:

11B3XCIB · Jul 27, 2012

What kind of freefloat rail are you using? If it's a rail, do you have any rail covers on it?

I'd recommend getting a set of thin leather gloves from Lowe's/Home Depot in case you have to clear a jam from a hot weapon. Here is a link for military flight gloves that they issue to infantrymen in the field. They are made of nomex and leather to prevent burns.http://www.uscav.com/search.aspx?search=flight+gloves&tabid=548&os=1&catid=5090

Take your pick; I used this type of glove on a couple deployments in Iraq. They saved the skin on my hands several times.

rotarymike · Jul 27, 2012

Free float tube is a Hogue knurled tube; no rails, therefore no rail covers, but I have some inner-tube stretched over it for a rubber grip.

I have and use nomex flight gloves; I was a flying crew chief and went through them like bubble gum. They don't work as well when they've been doused in JP8 or turbine oil

The round was actually seized in the chamber; I was afraid it would cook off. It wasn't too hot to run the charging handle, I had to pound on it even after it cooled down to cycle the gun.

11B3XCIB · Jul 27, 2012

Nice to see a fellow vet on here. I'm still active, so I don't have "vet" status quite yet. I always blew out the seam of the fingertips and would DX the gloves about every 2 months for a new pair. I liked the fit and feel of them and they were free so I never bought any of the fancy Wiley-X or Oakley gloves. Like my last post, I was an infantryman. I hated Blackhawk rides over Baghdad. I felt like any halfwit with an AK could have shot us down.

What are the dimensions (length/diameter) of the tube? Something came to mind that might work for you depending on the size. There's a company called Elite Iron who makes nomex heat wraps for suppressors to break up the heat mirage off of long range rifle cans so the optic doesn't get distorted. They might make one that fits the dimension of your free float.

http://www.eliteiron.net/wraps/productnow.html

11B3XCIB · Jul 27, 2012

I said they were nomex in my last post, but I don't know what material they are. Nomex came to mind as a heat resistant fabric, but I am not sure.

I would be careful if you select a route like this because a wrap will enable you to handle the foregrip, but will actually RETAIN or trap heat. I would suggest getting the correct diameter but maybe a slightly shorter one, so some of the free-float remains exposed so it can cool. The website says it's not made for sustained fully auto fire, so I'd only put it on the tube after you are done shooting for a period of time. This may not be the right product but may give you something to think about as an alternative.

If the rail is aluminum or stainless, drilling a few holes shouldn't be a problem for hot air to escape.

rotarymike · Jul 27, 2012

I think the tube is 2". I'll look over the site.

However, even the upper was getting too hot - I understand if I was doing mag dumps, but after ~20 rounds I shouldn't burn the crap out of myself on the bolt release (trying to lock the bolt back to let it cool). I'm shooting 6.8 reloads, but I double-checked and they are NOT hot loads, maybe 2000 fps.

I was in Kuwait a couple of times, and the UAE lots. I was in C17s though, so it would have taken something serious to take us down. We did get shot at in Sarajevo and Kosovo, mostly "snipers" taking potshots at any IFOR troops they saw. I put snipers in quotes because if they had been real marksmen/trained snipers, we would have lost a lot of people. More like someone hanging out an upper story window and popping a few off from an AK. Still gets the sphincter some exercise.

If you ever need legal help, I do discounts for military, vets and their families. I'll also be certified by the VA to handle claims next month, so if you run into problems using your GI Bill or med or disability bene's I can help you - and most of that is free.

Mike

11B3XCIB · Jul 27, 2012

Here's a quick idea:
http://www.midwayusa.com/product/19...nting-hardware-ar-15-handguard-aluminum-black

Drill a few holes in the bottom of your free float (with it uninstalled) and bolt a section or two of this ALUMINUM picatinny rail to it. Plastic might melt. Then you can attach a shorty foregrip or something that'll give you a hand-hold without burning yourself.

I am going to send you a PM about one of the things you mentioned.

rotarymike · Jul 27, 2012

I actually had a rail section on the bottom of my normal handguards with a VFG - didn't like it, I'm not a tactical shooter - I'm a tactical wrencher. That's why I went with the hogue FFT instead of one of the quadrails. Of course, in hindsight most of the quads have lots of cooling holes.

11B3XCIB · Jul 28, 2012

rotarymike said:
I actually had a rail section on the bottom of my normal handguards with a VFG - didn't like it, I'm not a tactical shooter - I'm a tactical wrencher. That's why I went with the hogue FFT instead of one of the quadrails. Of course, in hindsight most of the quads have lots of cooling holes.

Well, mounting a single 2" picatinny section minimizes the amount of rail on the otherwise spartan free float, especially if you put it on the bottom near the front (provided you don't have a 24" barrel or something...you gotta be able to reach it). I really like the look of it. It'd be great if you weren't shooting at high rates of fire. :mrgreen:

11B3XCIB · Jul 28, 2012

That's a DMPS vented free float tube. It is vented, but I bet it'll still get hot to the touch. That runs about $90 at Brownells. You could get vents like that machined into your tube, but it may be cheaper just to buy a new one.

If you have some ideas about what route you want to take, whether it's modifyig your existing tube, adding a rail, buying a new tube, etc, let me know and I'll try to do some digging for you.

bigfutz · Jul 28, 2012

If you're building a 22LR AR with a Slide Fire, you should check this rig out, built by a local gunsmith in the upstate, Wheaton Arms.
viewtopic.php?f=4&t=4469

rotarymike · Jul 28, 2012

Thanks - the Hogue is just like that without the slots. I have a tiny milling machine that could handle slotting the aluminum, so it wouldn't cost me anything but time. And trying to get the damn inner tube off and then on again - that was a pain.

The main problem has been that it is a midlength setup - 9" handguard instead of carbine or rifle length. Not a lot of choices there looking through Brownells or Midway. The Hogue was originally rifle length and I cut it down on my lathe. Since it was just a solid tube I didn't have to worry about existing holes or anything. Also got it for $50 - that helped the decision. I started with a Rock River upper, had the barrel turned bu Chester to a lightweight profile, changed out the A2 gas block to one of the gas block/folding sights, and added the FFT all to shave some weight off it. Pretty happy with the result, and I've shot it a few times since I completed it and although it got hot like any AR will, it wasn't cooking temperature. Of course, it wasn't 100+ outside either...

rotarymike · Jul 28, 2012

bigfutz said:
If you're building a 22LR AR with a Slide Fire, you should check this rig out, built by a local gunsmith in the upstate, Wheaton Arms.
viewtopic.php?f=4&t=4469

Groovy.

I was thinking of building a normal .223 upper and getting a Ceiner-style conversion. That way I can shoot real bullets if I want to. To address the weak recoil, according to Slidefire installing a light trigger and using a longer barrel both help. The booster/reverse brake is a nifty idea too.