If you have a flash can type device, a KVP Mach 3 in this case, that is a close fit into your hand guard, how much clearance would you speculate you need? I can slip a strip of ordinary typing paper in the gap, the barrel isn’t torqued in yet, but the paper slides all the way around but does get pretty snug in one spot. Is .005” enough clearance? What says the brain trust here? Pic because you know you want to see it. Lol
What’s the material on the hushpuppy. Coefficient of thermal expansion will drive the answer. What I wonder the most about though looking at what you have pictured is I have a feeling that setup is gonna get hot.
It’s made from 6061-T651 aluminum according to KVP.
yeah i would worry more about heat than anything… personally on my rifles i prefer at least a 1/4 or so space between the base and the handgaurd if it is the same diamater or larger. if it fits inside, idaf as long as the opening is past the end of the handguard.. def dont want the barrel tucked under the handguard without a muzzle device or a can makeing it protrude further out.
Temperature management will be your biggest problem once you get to 400 or so you’re close to anneal temps for 6061, with no vents and a can I reckon it won’t take a bunch of rapid fire to creep up past that.
Before thermal expansion i would be concerned about barrel flex.
This is a pencil barrel, but all barrels flex.
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I don’t doubt that the barrel could flex to some extent, but do you think s 5” 9mm barrel will flex enough to matter?
I am concerned about the linear comp swelling possibly and if it does then essentially it’s no longer a free floating hand guard at that point. Ideally I need to find a 3” long linear comp with 1/2-28 threads about an inch in diameter but I’ve come up empty handed so far.
I think you need to add the space of a crush ring and not just screw the end cap on the barrel to check clearance. Contact the manufacturer about that.
I need at least 18” of clearance if not more…preferably more…
Are we talking about then same thing? 
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Does not use a crush ring, manufacturer said to torque it to the barrel shoulder. They said you could use a crush washer if you wanted to time the flash hider just for aesthetics but it’s not needed otherwise.
I would not be worried about swelling. I would be worried about it hitting the rail by flexing.
This is what happens when people don’t ask the right question:
“How much clearance do you really need?” For what? 22 NATO rounds? 22 Long Rifle? 9 mm Makarov? You are posting in a Rifle section of a forum.
For 9 mm LUGER the answer is NONE. Pistol ammunition is lower pressure, heating of the barrel is not a concern as 9 mm Luger operates at at least 20,000 psi lower pressure than 223 and barrel harmonics and residual stress do not come into play on a 5 inch barrel.
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this is why i like a 1/4 in before my muzzle device unless it fits under the handguard and even under i want a good spacing around the handguard then.
I posted in the non-PSA AR15 section. There is no AR PCC section. There is a pistol section but it’s marked as non-AR. Sorry if I picked the wrong place to post.
im sure your post is fine.
If a man only knew a man with a metal lathe…
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You know me
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That’s Plan B if this comp gets too tight when it warms up. It’s too thin to shave any material off the comp but I might be able to open the hand guard with a boring bar in the mill.
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It’s hard to tell from over here, but I was thinking more along the lines of a chamfer or small step, maybe to both the handguard and the muzzle device.
They only have to not-interfere with one another, and you’re Golden.
Oh, it would take a little more than a chamfer. That comp in the photo is about 3.5” long, only the last .5” extends past the hand guard. I used two of the three included spacers, the whole thing looks like this:
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