Round vs. Triangle handguard caps, when do you use each one?

AR/M4 AR Technical Discussion
1

Is there a standard for when you use them? I usually use free float tubes so I haven’t done any of these. I am going to be putting on some Magpul carbine and midlength handguards soon. I’m not sure which handguard caps would work for these.

Thanks.

2

One of my carbines with magpul guards has the round and one has triangle. I like the looks of the round better, both fit fine.

3

Carbine length systems usually have round handguard caps. Rifle and midlength systems usually come with triangle handguard caps. I’ve never seen a triangle cap on a carbine, but I have seen round caps on rifles built by Palmetto state armory.

4

My PSA middy has triangle. Colt and cmmg carbines have round.

5

Thanks!