Ok, with my SIR, should I put a front handguard cap on or not. With it off, it no doubt allows for more air flow thus better cooling. However, this will also allow more crud to get in around the barrel. Not a big deal, but thought I'd ask for some thoughts on the idea. Here is a pic with it off.

Id leave it on as a crud guard...you have more then enough ventilation.  But what to I know, I dont even own a SIR [;)]

I left my on as brush/dirt guard.

ON.

Well, I was thinking I'd leave it on, but, I am leaning towards just leaving it off. It will help ventilation, however slight that might be, and if crud does get in there, I imagine it will come out as easily as it went in. The only thing I can see being a possible problem, would be a limb or branch from a bush poking in there and snagging while moving through thick brush. Dont think that will be enough to really worry about though.
I have to decide soon because this is going to Kurt to get a brake installed, and once that's done, I wont be able to remove the front sight post to put a handguard cap on.

If that's the case, put it on!  

It's clear even by your posts that leaving the cap off has more negatives than positives.

How so? with it off, stuff that is no doubt going to get in through the side holes, will have an easier opening to come out of, and it will increase airflow around the barrel.

Pro - 1. Better air flow???  This may even be totally insignificant because the SIR already offers excellent air flow.

Pro - 2. Easier to remove debris in the hand guard.  This is also questionable because the bottom half of the hand guard comes off on a SIR giving you pretty much all the access you need for cleaning.

Con - 1. Debris now has another way to enter your handguard.  The bigger opening will allow a whole lot more stuff in then the smaller vent holes.

Con - 2. Opening may hang or snag on objects, vegatation and or gear.

Con - 3. Once your carbine has been sent to Kurt it will be a big PIA to change it back. You loose some of the ability to change to different configurations that may require a cap.


So IMHO, you have 2 pros which are both very questionable and 3 cons that can cause real problems.  

It's your rifle so you can do what you want, I'm just offering my opinion since you asked.[;)]

And I THANK you for that opinion! [:D]

Its already on its way to Kurt.
I think we are at mute points on #1 & #2. As for #3, with the delta ring and all gone, there really arent any other options out there handguard wise. [;)]

I left mine off of my #45M gun, but left it on the #50C gun. Neither really have a problem with snagging, or the ability to get crud out. It really just boils down to personal preference, and looks, I guess...

With that being said, I'd leave it on.

-Cap'n

I guess it's to late but I'da left it on.  Ventilation will be no better with it off unless you plan on installing a radiator in it's place[:D]

Although your rifle will be w/o the delta ring assy, w/ 15-20 minutes worth of work you could have reconfigured it to take the std. handguards.  Remove gas tube, remove barrel, re-install delta assy, re-install barrel and gas tube.  BUT, w/ the break permanently installed, you can't get the front sight assy off and now can't get the front cap on.  Bad.  IMHO.  
Why not have Kurt put the front cap on for you, before welding up that break?

I dont plan on changing anything on this rifle anyway, so its really not a problem.

 

One step ahead of you. [;)]