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View Full Version : F Marked front sight base vs Standard A2 front sight base.. which one?


ohlone
11-27-2011, 9:37 AM
for Del-Ton upper, on a flat top upper, which will be installed a detachable carry handle or a flip up rear sight, which front sight base should i choose? F marked or Standard A2?, and what differences do they have?

thanks

hdvss
11-27-2011, 9:41 AM
F-marked is .04" taller than non F mark. Should match up with the detachable carry handle and/or flattop mounted rear sight.

FeuerFrei
11-27-2011, 9:44 AM
Consult "the chart"...see "F" Height Front Sight Base... Here (https://spreadsheets.google.com/pub?key=pwswheghNQsEuEhjFwPrgTA&single=true&gid=5&output=html)

dieselpower
11-27-2011, 10:31 AM
Consult "the chart"...see "F" Height Front Sight Base... Here (https://spreadsheets.google.com/pub?key=pwswheghNQsEuEhjFwPrgTA&single=true&gid=5&output=html)

LOL... I give the chart an "F"...

The chart is wrong once again.

The "F" is for "Flat top". Its dimensions are different because the flat top mounts rear BUIS higher above the bore. The "F" marked are NOT more desirable as the idiot chart says. You merely need to match your parts.

If you are buying a flat top rifle, to make life easier for you if you are buying a Fixed A2 type FSB, get one that is marked "F". You don't have to, but it makes life zeroing easier.

Ubermcoupe
11-27-2011, 10:34 AM
F-marked is .04" taller than non F mark. Should match up with [a] milspec detachable carry handle

Non F marked are still okay if you use correct CH.

But yea, itís that small height difference. Bushmaster sells (or did sell, not sure, never bought one) a special front sight to adapt an non-F to an F.

dieselpower
11-27-2011, 10:56 AM
So he buys a "F" marked FSB... the Chart says "Good job" you are all joe-tacticool now and he buys carry handle.... I guess since the chart doesn't address this issue there isn't one...

http://i655.photobucket.com/albums/uu272/Wiringguy/CHcom-2.jpg
http://i655.photobucket.com/albums/uu272/Wiringguy/BUISwheels.jpg
because the "chart" is all a person needs to know, there is no other knowledge out there...

the fact there are THOUSANDS of rifles without "F" FSBs and they run fine is not addressed by the "Chart"...why because the "Chart" only cares about tacticool joe and how to be tacticool joe.

nitroxdiver
11-27-2011, 3:43 PM
You can run either and it will work fine. F marked would be the correct one for your flat top. One thing you might have trouble with though is running an A2 and a detachable carry handle modified for revised improved battle sight zero. You may run out of front sight post adjustment. You can get taller sight post inserts to cure that, not do the RIBZ, or just start off with the correct fsb to begin with.
Take care and good luck.

DasBoost
11-27-2011, 7:52 PM
Question: I am looking at a CMMG upper and it has the option of standard A2 front sight or F-marked and it's a flat-top upper (shown in pictures with standard A2 front sight). All I'm looking to do is mount a detachable carry handle, could I leave it alone or would the F-marked option be better?

nitroxdiver
11-28-2011, 8:04 AM
Dasboot,
Like I said in the post above your post, either would work, but the F marked would be the correct one for a flat top, as it is slightly taller. If you've got the choice, then I would get the F. If you happen to already have an upper that has an A2, don't loose any sleep over it, it will work just fine. In case you couldnt get it to zero properly, especially if you decide to set up the rear for revised improved battle sight zero, you could just buy a longer front sight insert. No biggie. Hope this helps answer your question.

dieselpower
11-28-2011, 8:24 AM
Question: I am looking at a CMMG upper and it has the option of standard A2 front sight or F-marked and it's a flat-top upper (shown in pictures with standard A2 front sight). All I'm looking to do is mount a detachable carry handle, could I leave it alone or would the F-marked option be better?

Dasboot,
Like I said in the post above your post, either would work, but the F marked would be the correct one for a flat top, as it is slightly taller. If you've got the choice, then I would get the F. If you happen to already have an upper that has an A2, don't loose any sleep over it, it will work just fine. In case you couldn't get it to zero properly, especially if you decide to set up the rear for revised improved battle sight zero, you could just buy a longer front sight insert. No biggie. Hope this helps answer your question.

This is spot on. You just need to match your BUIS when buying a Carry handle as the picture I posted shows. Bushmaster makes both the lower commercial sized carry handle and the taller front post.

So if you have a F marked FSB, you can buy Flip-ups and Mil-spec carry handles. If you do not have an F marked FSB, you can either buy a mil-spec handle and buy a taller front post, or buy a commercial sized carry handle, or buy a mil-spec flip up rear and a taller front post...or just don't worry over it because its not that big a deal if you mis-matched them.

As long as the top of your front post is 55mm above the bore, you can zero at 25 yards and have a cross-zero at 375 yards...give or take some wind and twitching from you.. LOL