I did a search, but didn't find anything. What are the T marks on a flat top for?

They are for relocating optics and such on your receiver, for those that insist on removing their optics and can't remember where they had them.

Now ... where did I mount that ACOG ....  hmmmmmmm  

Quoted: Now ... where did I mount that ACOG ....  hmmmmmmm

My rule is one optic - one rifle.  If you have an extra rifle, it needs its own optic.  If you have an extra optic, it needs its own rifle.  There will be no unmounting remounting in my house.

I'm leaning toward the "T" numbers being a bling thing.  Half of my rifles have them, but I have yet to reference them for mounting anything.

I agree with Mongo.  Every optic needs it's own home.  Besides, life would be boring if we did not have constant projects to look forward to.  Buying optics is just an excuse to build additional dedicated uppers.

I have had Colt flattops for years, and none of them ever had T numbers.  I find there are not many different places to mount Aimpoints and ACOGs for me.  I don't understand this obsession with mounting/remounting/swapping optics.  The only time I ever take off my optics is to clean the rifle after a range session.  Other than that, I am content with where I usually put them on the upper.

Quoted: Buying optics is just an excuse to build additional dedicated uppers.

And building additional dedicated uppers is just an excuse to build additional lowers upon which  to mount those uppers.  

The T stands for top. If you look at the M5 RAS you'll see that it also is marked with L, R, and B number prefixes. Since you now know what T designates, the meaning of the other three should be obvious .

Seriously, the mounting positions for the large array of military add-on equipment found, for example, in the SOPMOD kits will vary with the specifics of the mission. The alpha-numeric designators provide the operator with a suggested mounting position. For example - where to mount the AN/PVS-17A, AN/PEQ-5, AN/PEQ-2, and VIL possibly all at the same time.

While the "T marks" may look cool and many of us want them just for that reason, they really do have a very good reason for their use in the military.

BTW - those of you that scoff at switching optics should try switching between an ACOG and a Comp M on an M4 style carbine. Great when you're changing from close to longer range targets, and you won't lose enough zero to speak of.

It comes in handy.  I just got a SAM upper and installing and uninstalling the scope for zeroing and practicing with the BUISs is just that much easier.  Consistency is key.

Quoted: Quoted: Buying optics is just an excuse to build additional dedicated uppers. And building additional dedicated uppers is just an excuse to build additional lowers upon which  to mount those uppers.

It is truly a vicious cycle, but in a good way.

Quoted: Quoted: Buying optics is just an excuse to build additional dedicated uppers. And building additional dedicated uppers is just an excuse to build additional lowers upon which  to mount those uppers.

Hmm...  I find the ability to swap optics around on my uppers a good excuse to buy those quick release rings at $100 a pair.

Quoted: Quoted: Quoted: Buying optics is just an excuse to build additional dedicated uppers. And building additional dedicated uppers is just an excuse to build additional lowers upon which  to mount those uppers.   Hmm...  I find the ability to swap optics around on my uppers a good excuse to buy those quick release rings at $100 a pair.

besides.., it is fun re-zeroing on differen rifles/carbines, if i don't like a certain optic on one rifle, i swap'm around till i find the right combo for the right gun

Quoted: The T stands for top. If you look at the M5 RAS you'll see that it also is marked with L, R, and B number prefixes. Since you now know what T designates, the meaning of the other three should be obvious . Seriously, the mounting positions for the large array of military add-on equipment found, for example, in the SOPMOD kits will vary with the specifics of the mission. The alpha-numeric designators provide the operator with a suggested mounting position. For example - where to mount the AN/PVS-17A, AN/PEQ-5, AN/PEQ-2, and VIL possibly all at the same time. While the "T marks" may look cool and many of us want them just for that reason, they really do have a very good reason for their use in the military. BTW - those of you that scoff at switching optics should try switching between an ACOG and a Comp M on an M4 style carbine. Great when you're changing from close to longer range targets, and you won't lose enough zero to speak of.

Good for the armorer who may be setting up a rifle for a shooter, but anybody issued a SOPMOD kit can likely mount everything they need on their rifle in the dark or blindfolded.

Quoted: Quoted: The T stands for top. If you look at the M5 RAS you'll see that it also is marked with L, R, and B number prefixes. Since you now know what T designates, the meaning of the other three should be obvious . Seriously, the mounting positions for the large array of military add-on equipment found, for example, in the SOPMOD kits will vary with the specifics of the mission. The alpha-numeric designators provide the operator with a suggested mounting position. For example - where to mount the AN/PVS-17A, AN/PEQ-5, AN/PEQ-2, and VIL possibly all at the same time. While the "T marks" may look cool and many of us want them just for that reason, they really do have a very good reason for their use in the military. BTW - those of you that scoff at switching optics should try switching between an ACOG and a Comp M on an M4 style carbine. Great when you're changing from close to longer range targets, and you won't lose enough zero to speak of. Good for the armorer who may be setting up a rifle for a shooter, but anybody issued a SOPMOD kit can likely mount everything they need on their rifle in the dark or blindfolded.

You're quite sure about that? Remember the 'three ball bearing test'? I think I've met the operators who invented it .

Sad to say that some of the recruits that are hitting the sand today couldn't hang an AN/PEQ-2 on their rail without getting the numbers from a Sgt. Elites aren't the only ones being issued HSLD goodies in "TODAYS ARMY".

Thanks guys. I figured it had some kind of military background. "T" for top crossed my mind, but I didn't think it could be that simple.