View Full Version : Fixed FSB / LPVO Mount height question
Howdy, all
Currently have a micro t2 on my Colt 6920. I’ve got a 1-6 Trijicon Credo on the way, along with a Geissele Superprecision M4 Mount. That mount supposedly puts center of optic 1.54 above the rail. I like the fixed fsb and run a rear buis under the optic, so I’d rather not shave off the fsb. My question is as follows:
If running a 1-6 on 1x-2x, will the 1.54 height be adequate to use the reticle with the fixed fsb, or would a 1.93 / 2.04 height mount be a better choice?
Thanks!
The 1.54 will give you, or a very close to, co-witness reticle with the FSB pin.
What do you mean “use the reticle?”
If you mean the dot, just ignore the fsp like its a red dot
If you mean the bdc or mil/moa marks, i would think is a non issue since the fsp disappears at 3-4x with a 1.5” hight.
BUIS under th e scope with a G$ mount are kind of pointless since it’s not a QD Mount.
pyrotechnic
03-22-20, 10:13
BUIS under th e scope with a G$ mount are kind of pointless since it’s not a QD Mount.Unless you clumsily trip, fall, and smash your optic perfectly on a rock. You can then use a Gerber or something else in camp to remove the optic and still be able hunt or LARP or whatever you were doing without having to go home and bitch about not having BUIS on M4carbine.
Sent from my SM-G950U1 using Tapatalk
What do you mean “use the reticle?”
If you mean the dot, just ignore the fsp like its a red dot
If you mean the bdc or mil/moa marks, i would think is a non issue since the fsp disappears at 3-4x with a 1.5” hight.
The FSB "disappears" but still blocks the lower half of the reticle, rendering it useless.
As stated, if a variable power optic is used, and is set to 1-2 power, the FSB will be blurred.
At 3 power and above, the FSB will disappear
turnburglar
03-22-20, 13:48
I don't think you can use a BUIS through an LPVO, even if you turn it down to 1x. Also if you don't have a QD mount, a buis is kinda silly cause its highly inaccessible.
Your better off loosing the FSB.
The FSB "disappears" but still blocks the lower half of the reticle, rendering it useless.
Mine is visually not blocking anything, but havent tried to use it like that.
Do you mean its going to bend the light and alter accuracy?
Hi, all
I know co-witnessing isn’t a thing with lpvo, I’m not concerned with that. I’m just wondering how much of the reticle will be blocked by the fsb at 1-2 magnification. If it’s just part of the bcd or lower part of the duplex that’s fine, it won’t bug me. I’ve run the t2 for a long while and am used to it. If, however, the fixed fsb rises all the way through the center of the reticle and gets in the way of the aiming point, that’ll be a concern.
Regarding the buis, yes I know you can’t use them with the lpvo on. I also know since it’s not qd removal is slower. I still like the backup irons. Let’s not get hung up on the qd part, the buis still have value in the field to me, qd or not.
Since they’re both in the mail, why don’t you wait until they arrive and tell us. Or maybe ask this question prior to buying them.
Since they’re both in the mail, why don’t you wait until they arrive and tell us. Or maybe ask this question prior to buying them.
I’ll be happy to post what I find out when they arrive. Are you able to answer my question?
NoveskeFan
03-22-20, 19:37
At 1.5” center height, the FSB will be visible to about the middle of your view in the optic and will be blurry up to about 3-4x. Higher than 4x, the focal plane will be beyond the FSB and you may notice a “shadow” if you look for it instead of focusing on your target. That’s my experience, anyway.
Since they’re both in the mail, why don’t you wait until they arrive and tell us. Or maybe ask this question prior to buying them.
If we keep this going, his post count will get high enough for him to start dumping what he doesn’t need on the EE.
Thanks to all who replied. No need for further.
Mine is visually not blocking anything, but havent tried to use it like that.
Do you mean its going to bend the light and alter accuracy?
I'm not sure about the theory how all that works. What I do know is that any part of the reticle that's blocked by the FSB is unusable. If there are hash marks for holdovers blocked by the FSB, you won't be able to line them up with the target. When I didn't know any better, I mounted a 6x-20 on a 20" Colt that had an FSB. As I was an ignorant and broke cheap bastige, I mounted the scope directly to the rail with rings just tall enough for the objective to clear the handguards. Long story short, the FSB blocked the center of the crosshairs and I could not get them to line up with the target. The crosshairs kinda just slipped to the left or right. Very frustrating until I figured out what was going on. That's why when I build any upper that'll be scoped, there's no FSB.
Much like most, Ive run an acog with an fsb and yes there is a shadow in the lower part. That being said, id look for the larue 1.93" (correct me if im wrong) mount height. It helps a ton.
So, I decided to try both the 1.54 and 1.93 heights. I preferred the 1.93 so I stuck with that one. The Geissele super precision is a first class, excellent mount. Highly recommended. At 1x the front sight post and ears are only visible in the bottom 1/4 of the field of view, perhaps not even that. Real world you never notice them. Of course at anything higher than 3x they’re gone.
For those who might be wondering about the Trijicon 1-6 Credo because it’s newish I can only give first impressions, it has not yet been to the range:
1. Build quality seems very fine.
2. Glass is nice. Quite clear to my eyes.
3. Mine is the green segmented circle with the 55 grain bdc. I don’t care anything about the bdc, but the reticle is useable and easy to pick up on 1-6 power. Yes, the green can wash out in bright sunlight, but the reticle is still useable and works great in black or turned off.
4. Eye relief is good.
5. Eye box is forgiving. Though no Aimpoint, the optic is certainly useable for cqb. It reminds me of my 1-6 VCOG in some ways, a good GP design which should be useful for many things.
6. Unable to comment about durability, in use, etc., at this point, but so far I like it very much.
That’s about it. Thanks for all the help.
Belmont31R
03-27-20, 20:00
Its impossible to get a true 1X like an EOTech or Aimpoint with a LVPO so even with a FSB the FSB will be a blurry shadow at most even on '1X'
Elcan's actually flip lenses internally when you change from 1x to 4X which is why early versions had issues with POI when changing magnification.
Really, though, you don't want to use any magnified optic with an object in the way that close. Its kind of like occluding part of your vision, and while you can 'see' around it theres no way to actually make up for having something so close to the optic.
The only reason the 1.93" mount height exists is because that's what put the original S&B Short-Dots above a PEQ on a M4 carbine.
The FSB is very distracting to me with a 1-4 just mocked up in my office. Is it not an issue when shooting, or do you just train past it? I was using a standard height mount.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.