Looking at hop up options for this Gen 8 M4 setup…
I’ve got a few sets of Sweetheart hop ups coming in, so no problems with fitting it into that skinny Vector flash hider… I’d like the hop up to be hidden in the outer barrel and finish at the flash hider. But if I shorten the barrel length by the length of the slip on hop up to arrive at the same overall length will I be affecting the volumetric efficiency at all? 
I guess my question is if a slip on Sweetheart hop up can be counted as effective barrel when you’re working out barrel lengths…
Right up until the poi t you have a vent hole
Oh I see… okay… on that venting…
What’s that vent hole in a hop up for? I’m guessing it’s something to do with reducing air pressue behind the gel so the textured top plate can do it’s thing more efficiently?
I’ve got a hop up set in a fairly tight solid flash hider so the vents are moot… doesn’t seem to affect the performance at all.
there is no vent hole on them, just the 3 groves at the bottom,
it fits onto the barrel about 10mm deep, and the whole tube is 60mm long,
so they will stick out a little bit from the muzzle cover i think
interesting question tho, do they also add to barrel lenght…
i guess if the bottom groves count as “vents” then no,
but other wise, that’s 50 extra mm of barrel length to concider 
Hope they work out better for you though,
just tested them on my ACR now, didn’t really do much
mathematically it doesn’t have that much impact on the outcome.
physically with the sweetheart hopup i’d probably consider the ported location to be where that bottom channel starts. this is the spot where the dynamics of the hopup start to kick off.
i like these. they are a nice simple design.
With a 10mm OD they’re the slimmest hop up out there, I believe. I’d like to fit it with the end of the hop up finishing where the slots in the flash hider start… don’t really want to see it in other words.
Might not be practical but that’s just my choice of aesthetics… we’ll see. 
Simple design is good as long a it simply works otherwise its simply an expensive shiny tube 
Indeed.
I won’t be moving away from the rizer any time aoon
Well, I’ll make sure I post some feedback when they arrive and I get a chance to try them out… all in the name of research…
At $20 delivered they come in cheaper than WI and Rizers so it’s not like it’s a huge financial risk.
If they don’t work there’s always the 13mm Rizers…
