Handguard mounted front sight POA/POI change testing after being dropped

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12-28-18, 13:51
Biggy

Handguard mounted front sight POA/POI change testing after being dropped

It is never going to happen, but I think it would be interesting to test all the current top tier free float handguards (quad and the newer slick sided small diameter ones ) to see the POA/POI change on their rail mounted front sights or other aiming device after let’s say one or two 4 ft drops on the ground from different angles. I would also like to see the same test on rifles using the standard barrel mounted forged front sight. IMHO, as it is now it seems to be a blind leap of faith regarding the testing and POA/ POI holding capability each company does with their handguards. I may be wrong, but I have my doubts that *any* free float handguard supported on only one end by a 2-2.5" barrel nut would retain its absolute POA/ POI after dropping them on the ground from 4ft one or two times. Everyone running free float rail mounted front sights or other aiming devices will have to decide on what would be, could be, might be "good enough or close enough " on holding their POA/POI after being dropped one or two times from let’s say 4 ft. In inches, how much of a POI change would you be okay with?
12-28-18, 17:56
Artiz

That's pointless, but not for the reason you think.

It's pointless because there isn't a FF handguard on the market that is rigid and strong enough to NOT change the rail mounted front sight's POA vs the barrel's POI under normal use. They all flex under load depending on the position the pressure is put and how much is being put on it. That's why in my honest opinion, rail mounted front sights are absolutely not "fighting rifle" worthy.

The only front sight that will keep a true POA/POI is one that is mounted on the barrel itself, if the barrel flexes/moves, the front sight moves with it.

Now, testing the POI/POA shift of a rail after drops it's clear to me that the more mass the rail has around the barrel nut, the tighter the rail is clamped to the barrel nut, the stronger the rail itself is, and the stronger the barrel nut/rail interface is, the less POI/POA shift you'll encounter. Also consider the strenght differences of 6061 vs 7075 aluminium.
12-28-18, 18:34
GH41

Quote:

Originally Posted by Artiz

That's pointless, but not for the reason you think.

It's pointless because there isn't a FF handguard on the market that is rigid and strong enough to NOT change the rail mounted front sight's POA vs the barrel's POI under normal use. They all flex under load depending on the position the pressure is put and how much is being put on it. That's why in my honest opinion, rail mounted front sights are absolutely not "fighting rifle" worthy.

The only front sight that will keep a true POA/POI is one that is mounted on the barrel itself, if the barrel flexes/moves, the front sight moves with it.

Now, testing the POI/POA shift of a rail after drops it's clear to me that the more mass the rail has around the barrel nut, the tighter the rail is clamped to the barrel nut, the stronger the rail itself is, and the stronger the barrel nut/rail interface is, the less POI/POA shift you'll encounter. Also consider the strenght differences of 6061 vs 7075 aluminium.

Maybe you need to clear up a few things for me. So the flexible fixed handguard floated with a sight on it is less accurate than a barrel not floated with a FSB?? Do you mind explaining your technique for getting the fly shit out of the pepper? I am having trouble wrapping my head around how removing a few specks of shit will change anything enough to measure.
12-28-18, 19:07
Artiz

Quote:

Originally Posted by GH41

Maybe you need to clear up a few things for me. So the flexible fixed handguard floated with a sight on it is less accurate than a barrel not floated with a FSB?? Do you mind explaining your technique for getting the fly shit out of the pepper? I am having trouble wrapping my head around how removing a few specks of shit will change anything enough to measure.

Ehhh......you're seeing things I never wrote.

Why don't you get off your high horse, re-read what I wrote, acknowledge, and then read what you just wrote.
12-28-18, 19:41
hk_shootr

Why concern yourself with accuracy and not precision?

In my opinion, a rail mounted front sight is a BUIS, back up iron sight. I’m only going to be using that if the optic fails.

If I’ve dropped my weapon three times, all from a height of four feet, I have a shit load more to worry about than the zero of a back up sight that I may or may not use.
12-30-18, 05:16
AndyLate

I have a build plan in the back of my mind that involves building an "irons only" AR-9 with a DD front mounted on a free float rail.

Is this completely impractical given the poa/poi issues stated above? It will be a Matrix Arms rail, so definitely not top tier.

Thanks

Andy
12-30-18, 06:54
jsbhike

Quote:

Originally Posted by AndyLate

I have a build plan in the back of my mind that involves building an "irons only" AR-9 with a DD front mounted on a free float rail.

Is this completely impractical given the poa/poi issues stated above? It will be a Matrix Arms rail, so definitely not top tier.

Thanks

Andy

Maybe not ideal as irons only, but not really flawed since you are picking up the full time benefit of less weight/improved handling due to ditching the barrel mounted front sight versus what if catastrophic damage.

In theory, the 9mm makes for short range so somewhat less practical effect on POI changes since you aren't likely to be lobbing bullets 500 yards anyway.

If you are doing this up in pistol/sbr format with a corresponding shorter rail I would say even less of an issue with front sight movement due to impact.
12-30-18, 08:30
joedirt199

I switched out some standard barrel nut clamping style free float tubes for the cheaper ALG propriatary barrel nut tubes. Noticed on one of my clamp tubes that the barrel was not centered in the handguard. Retightened the handguard to center it but did not feel comfortable about it as it was on mounted on a full size grendel build and has not been used much. ALGs fit pretty tight to their barrel nut, have anti twist tabs, and six bolts instead of just 2 clamping.
12-30-18, 10:19
AndyLate

Quote:

Originally Posted by jsbhike

Maybe not ideal as irons only, but not really flawed since you are picking up the full time benefit of less weight/improved handling due to ditching the barrel mounted front sight versus what if catastrophic damage.

In theory, the 9mm makes for short range so somewhat less practical effect on POI changes since you aren't likely to be lobbing bullets 500 yards anyway.

If you are doing this up in pistol/sbr format with a corresponding shorter rail I would say even less of an issue with front sight movement due to impact.

I would almost never shoot it past 100 yards, but it would be a 13.5" rail.
01-18-19, 11:41
Nocalsocal

Handguard mounted front sight POA/POI change testing after being dropped

On my 12 in. SMOS rail pistol/carbine build I put the front sight on or about where a midlength gas block (9-10in?) would be. I remember reading about Kyle Defoor concluding that placing the front sight about 14 in or so from the rear he is nearly as fast as RDS. I'm right around that mark but I mainly run red dots on that pistol build so I'm not %100 if Defoors conclusion is the same with me.
One benefit I figured was that the front sight would suffer less deflection if the rail takes a hard fall the further it is from the end.

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