Front Sight Towers....

AR/M4 AR Technical Discussion
1

I wanted to share a bit of information regarding front sight towers. We haven’t seen a lot of discussion regarding these and reviews are very scarce. Perhaps one reason is price. They are in the $150-$250 dollar range, sometimes more. What they are, exactly, is a gas block with an integral flip-up front sight. I recently had some experience with a few and I wanted to share. While I have only had them for a few months, there are some important details I wanted to share.

First, I tried the MI front sight tower for the first time. Here is a picture:

I mounted fine, but the pinhole for the gas tube was a bit too tight. I got it mounted up properly and went to shoot. After 1 round using my EOTech 512, I decided to flip up the front sight and give it go to sight it in. I just so happened to notice a crack in the block by where the set screws were!!! Needless to say my day was over. I went home immediately and contacted MI. They were closed for the day and left a message. They never got back to me. I contacted Bravo Company and problem solved- they offered a full refund. I sent it off and did not manage to get a pic of the crack. Subsequent is a picture illustrating where the crack was in red.

Before sending it off to BCM, I purchased the VLTOR front sight tower. This one has 2 set screws that were larger than the MI ones. Here is a picture for reference:

While I just recently installed it and have not yet shot it, I can comment on differences of the installation process. The VLTOR seems to be crafted better as far as design. The 2 set screws make it so that you can’t apply unequal torque like in the 3 set screw scenario that could cause a crack. The VLTOR is also lighter than the A2 front sight and takes over 100ft pounds of torque to move according to testing at VLTOR. Here is a video:

http://www.vltor.com/VSTCtest4.wmv

The VLTOR seems to be the industry standard as far as I can tell with regard to front sight towers. GG&G makes one similar in design to the MI block, but runs more than both cost wise and no one offers the testing figures VLTOR does. As far as the flip-up part of the FST, the VLTOR uses an AK style post that is same spec as F front sight post. MI also offers the F spec, but uses the A2 style post. The VLTOR provides the front sight tool with the sight (Troy ind. makes). I will report back after 500 or so rounds. Again, there is hardly any information about these “front sight towers” out there so if anyone has any experience with them feel free to add. The VLTOR seems like a nice piece though and I’m excited to give it some abuse.

It bears mentioning that YHM makes a FST too in about the $80 range. While I have never shot or used one, YHM typically gets mixed reviews on their products. I think it is commonly accepted that MI and VLTOR are first class gear, so those are the only “first class” blocks I know of, minus GG&G.

Also, another thumbs up to Bravo Company for honoring their produce with no questions asked.

2

Wouldn’t it be a little warm after a few mags fired through the rifle?

Then swapping to your irons would be a bit tougher because of forcing yourself to grab onto the hot gas block?

Just a thought/ question. I’ve never used this style of sight. So I would be curious as to how hot it would get, and if that would make it more difficult to deploy the front sight.

Thanks for the good info!

3

You should check out the KAC design, pricey but an excellent piece of kit. Vltor also makes one that uses taper pins.

Sent from my Droid using Tapatalk

4

This might be a dumb question, but what’s the purpose of the rail? Seems like anything you mount to it would have to come off every time you raise or lower the sight.

5

You know I didn’t even think of this. I will let you know.

I didn’t know KAC made one. I will check it out.

As far as the purpose of the rail on the VLTOR block, I thought about that. It doesn’t make much sense unless they are considering the fact that the irons are strictly backup and anything mounted on it would be removed in the hopefully unlikely scenario backups were needed. That’s all I can think of.

6

Can you help me find it? I searched internet, went through KAC site, and downloaded their latest catalog. Not there. Now interestingly I see it on a gun they have in one of their pictures, but it is never mentioned as a part and is unlisted everywhere. Any help? THANKS.

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Hey 87GN, I see you got one. Well…How is it so far? Any issues? I see that you use the rail to mount a light so I am assuming you run irons only and keep the front base deployed.

9

That pic is 3 years old…if not more. I was still using it until December, put it on a 308 that I sold. It worked fine.

No, I always had an optic.

10

i had a VST-1 on an upper before, i loved it. never failed.

the KAC version is really nice and can be found here:

it needs ot be pinned to your barrel and sells for $448…

11

pacrimguru, thanks for posting. About how many rounds did you put through it with the VLTOR on? Did you give it good abuse (classes, duty, etc)? I do have a bit of an unsettling feeling with screw-on blocks, but I went with VLTOR because I figure if I am gonna do the screw on thing, I am gonna go with someone trustworthy. I think I can still get it pinned by ADCO or somewhere in the future, but I guess I just want some reassurance from someone who has used them that these things don’t come loose. I used red loctite on the screws. THANKS!

12

You should be fine for normal use, but I wouldn’t trust it for self defense. Pinned, then set screw, then screw/clamp in that order for gas blocks.

13

Clamp gas blocks are superior to set screw gas blocks.

14

I’d love to try the Vltor unit out. I kinda like that you can use it to clamp a light on, as that’s my preferred location (usually use MI part MCTAR-01 to put a light on the FSB). But, the price is a bit painful. I think it would be a cool setup if they had the same design but non-folding…less parts, and maybe a little lighter. Of course, I’m probably the only one that would like it.

I’ve always pretty much stuck with a standard FSB and recently cut down the FSB on one of my barrels to try a longer rail with folding sight. Regretting that, so I might end up biting the bullet and getting the Vltor sight block.

15

I would like to see something that proves this.

My thinking: A set screw with a dimple has metal displaced inside of the barrel, and the sheer pressure to destroy that set screw in such a way to have the gas block slide freely off of the rifle is probably a lot more than the clamping force that the screw and threads on the gas block are exerting on the barrel. True, the surface area on the barrel is more, but the actual PSI is spread out over a larger area as well. Same reason why we use rivets to attach two pieces of metal together instead of clamps when building tall buildings. Different application, same principle.

16

Seems like Knights knows something. :eek:

17

I know you’re right. I am gonna run it like it is hard for a while then I am going to send it off to get pinned on. I would just rest so much easier knowing it ain’t movin’.

Now here is a question: Anyone ever have or see a set screw or clamp on gas block move/ come loose? Brand or style of block come to mind if yes?

**Oh yeah…To answer another poster’s question- Do these things get hot?- Oh yeah, they get damn hot. You only need to touch the post for a second so it ain’t too bad and if I find myself having to use them then I am in deeper shit than a hot finger anyway. Gloves eliminate the problem all together.

18

Meanwhile, in the world of things relevant to rifles, Vltor demonstrated the strength of their gas block/front sight by showing that the barrel index pin would be destroyed before their VST would twist out of place. But, for those who want it, they do offer a version that needs to be pinned. Google “Vltor VST Test.”

And set screw gas blocks have a pretty bad reputation, although there are some quality ones out there - generally they’re best when the fit between the barrel and the gas block is very tight, meaning that their manufacturers are one and the same. The others…they tend to come loose. Early and often.

Are you seriously handing out advice here on M4C on what would be best for “self defense” based on building construction - and zero relevant experience with the parts you’re discussing?

19

I don’t think anyone is still using rivets. Every steel building I’ve built uses bolts.