Replacing plastic handguard on PSA 10.5 with FSP with modern mlok rail, technical question

[eugevita]

Greetings AR experts!

I have a PSA 10.5 just like the link below with the plastic handguards and front sight post and am thinking of replacing the handguards with a modern MLOK rail.

https://palmettostatearmory.com/psa-10-5-5-56-1-7-nitride-upper-w-o-bcg-or-ch-507020.html

Would the below Geissele 7" MLOK rail be a good fit given the front sight post? I know the front sight post has to be removed for installation. Is this overly difficult or can a competent armorer do it without too much hassle. Would like to use this rail as I like the geissele rails and the deal is solid given that it is a blem.

https://geissele.com/7-super-modular-rail-mk14-m-lok-ddc.html

Would appreciate any feedback from those who have installed rails on uppers with front sight posts, etc. Thank you!

 

[Ranchhand]

I think it is plenty doable.
Front sight gas blocks come off easily usually.
I have no experience with that type of handguard though.
Ar15s are legos for men.

 

[S197]

Yes, a 7” rail will run right up to the front of a carbine gas FSB.

 

[S197]

You can save some money and buy one of these instead of using a smith.

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[eugevita]

sounds like my thinking is sound based on folks responses here, thank you

anyone have any pics of builds with 7" rail and FSB?

 

[...]

another option is the Midwest Industries drop in handguards

AR-15/M16 Two Piece Drop-In Handguard, M-LOK®

AR-15 two piece drop in handguards from Midwest Industries, a U.S. manufacturer of quality tactical rifle accessories. Quality components, competitive pricing, and top notch customer service. M-Lok

www.midwestindustriesinc.com

ive run these before and they lock up tight, absolutely zero wiggling or shifting from the handguards.

no need to remove the FSB, just pop out the old handguards and pop in the new ones.....you wont be free floated, but on a 10.5" i really dont think youll notices any difference.

 

[roostercogburn98]

Or a KAC M4 RAS will do the same thing and you can keep your delta ring setup as well

 

[CrabsandFootball]

If you dont plan to go with a reflex suppressor, go with the 9.5" rail. That extra real estate makes a huge difference and will ensure your low pro gas block is covered/protected.

 

[CrabsandFootball]

G rails always go on sale i never paid more than $175 for them even the 15"er. Just wait for one.

 

[Austan]

If you dont plan to go with a reflex suppressor, go with the 9.5" rail. That extra real estate makes a huge difference and will ensure your low pro gas block is covered/protected.

It looks like the intent is to keep the front sight gas block.
I have always either replaced with low pro or cut off/ ground down the front sight part and ran a longer uninterrupted rail, even if only to add a flip up sight further forward. I like more mounting options. Not sure why I despise the front sight gas block as there are work around handguards, aesthetics maybe?

 

[CrabsandFootball]

Yea The cut/grind method is the cheapest but G rails come with their own Low pro gas block.

Really no point in putting a FF rail on a 10.5" gun and keeping the FSB unless you are trying to build an early MK18 clone or something.

 

[eugevita]

another option is the Midwest Industries drop in handguards

AR-15/M16 Two Piece Drop-In Handguard, M-LOK®

AR-15 two piece drop in handguards from Midwest Industries, a U.S. manufacturer of quality tactical rifle accessories. Quality components, competitive pricing, and top notch customer service. M-Lok

www.midwestindustriesinc.com

ive run these before and they lock up tight, absolutely zero wiggling or shifting from the handguards.

no need to remove the FSB, just pop out the old handguards and pop in the new ones.....you wont be free floated, but on a 10.5" i really dont think youll notices any difference.

Great idea! Is the Midwest rail solid enough to mount a red dot on it or is it only solid enough for lights and other accessories that don't require holding a zero?

 

[CrabsandFootball]

Great idea! Is the Midwest rail solid enough to mount a red dot on it or is it only solid enough for lights and other accessories that don't require holding a zero?

No two piece rail is going to be free floated and you never want to mount an optic to a forward rail unless its a monolithic upper.

If you want a good 2 piece rail find a used KAC RIS or P&S (contract). Sharkarms has them. https://sharkarms.com/

 

[...]

Great idea! Is the Midwest rail solid enough to mount a red dot on it or is it only solid enough for lights and other accessories that don't require holding a zero?

its definitely solid enough to mount a red dot, the things are rock solid.

that being said, its typically not advisable to mount a red dot or optic on ANY handguard.....no only due to potential shifting youd get from any handguard ( a hard knock can cause any rail to shift)....but the handguard is a long way away from your eye.

you also run into issues with the FSB pretty much blocking out the red dot if the sight it too far forward.

 

[eugevita]

its definitely solid enough to mount a red dot, the things are rock solid.

that being said, its typically not advisable to mount a red dot or optic on ANY handguard.....no only due to potential shifting youd get from any handguard ( a hard knock can cause any rail to shift)....but the handguard is a long way away from your eye.

you also run into issues with the FSB pretty much blocking out the red dot if the sight it too far forward.

i only ask because I like to sometimes run a eotech g33 behind my dots. In which case my dot would have to go on the rail. sounds like it may not be best option if I want to use magnifier. Otherwise if I stick to just dot it seems like a great fit.

 

[...]

i only ask because I like to sometimes run a eotech g33 behind my dots. In which case my dot would have to go on the rail. sounds like it may not be best option if I want to use magnifier. Otherwise if I stick to just dot it seems like a great fit.

what red dots are you running?......you should be able to fit most red dots far on the receiver rail and still have space to mount the g33

 

[eugevita]

what red dots are you running?......you should be able to fit most red dots far on the receiver rail and still have space to mount the g33

I mainly run eotech 512, sig Romeo 5. It would fit if I did not have a rear buis but since I do it does not. NBD but it is a limiting factor. Hence my question on the rail. Not too worried as I may not even run a magnifier on this upper, just wanted to see what the options were.

 

[eugevita]

Yea The cut/grind method is the cheapest but G rails come with their own Low pro gas block.

Really no point in putting a FF rail on a 10.5" gun and keeping the FSB unless you are trying to build an early MK18 clone or something.

The G rails I looked at do not include a gas block though I could buy one from them. If I were to get a low pro G gas block would it fit my barrel and gas tube if I remove the front sight post? Not sure if it is interchangeable so just curious....

 

[eugevita]

I suppose a polymer magpul MOE is also an option should I want to spend less $$$ and still have something functional that lets me mount slings and lights.....given the price this actually seems attractive!

 

[roostercogburn98]

Any carbine length tube will work but you have a tube already. If you are changing the fsb to a gas block, just reuse current tube. As for gas block, it should be a standard .750 block. Will need an armorers wrench, and some way to hold the upper steady to get everything apart if you are going FF. Plenty of options out there in the gas block world

 

[CrabsandFootball]

Geissele Super Modular Rail MK14 M-LOK Free Float Handguard AR-15 15

The MK14 is the latest entry to the Geissele line up of Super Modular Rails. The MK14 handguard design offers a smaller diameter and overall height to...

www.midwayusa.com

Its the best rail on the market no question. Just buy it and never have to worry about it again.

 

[S197]

The G rails I looked at do not include a gas block though I could buy one from them. If I were to get a low pro G gas block would it fit my barrel and gas tube if I remove the front sight post? Not sure if it is interchangeable so just curious....

Going with a 7” rail, the low profile gas block will be exposed. As for the site combo, if you run a foldable rear site it will fit under the magnifier.

have you thought about just saving up some more funds and building another upper? Also, there are also allot of fairly priced factory built uppers available and you already have a bcg.

 

[eugevita]

Going with a 7” rail, the low profile gas block will be exposed. As for the site combo, if you run a foldable rear site it will fit under the magnifier.

have you thought about just saving up some more funds and building another upper? Also, there are also allot of fairly priced factory built uppers available and you already have a bcg.

The more I think of it the more I think maybe a different upper is a better option. I already have one of the PSA 10.5 uppers with Geissele rail and FN barrel so perhaps I will sell this one and build a 14.5 or 16 that can be an LPVO host.

Decisions Decisions

Appreciate yours and everyone else's help!

 

[S197]

What’s your budget without selling, and what would you like the upper to do?

 

[Sogan]

If you wanted a longer rail AND If you are decent with a dremel, then you can cut down the F front sight block yourself and just reuse that block for your new rail.

Pic is from the internet but I did it without much hassle at all.

 

[eugevita]

What’s your budget without selling, and what would you like the upper to do?

to be honest, I would have to sell to at least partially fund another upper. my original thought was to make this 10.5 a slim railed CQB build for 150 and in using just a red dot and some sort of rail to hold a light. That said, if I decide to ditch this build I would not do another 10.5 since I already have another 10.5 with Geissele rail and FN barrel that has both a red dot, magnifier, and light.

If I were to sell the 10.5 in question I would want to buy or build a 14.5 or 16 with a LPVO capable of reaching out past the capabilities of my 10.5 I am also building a 18" barreled 6 ARC rifle off a larue ultimate upper kit so a new upper would essentially have to fill the role between the 10.5 and the 18" 6mm ARC.