Free float handguard installation question

[gaseousclay]

I want to swap out my current drop in carbine length handguard for a longer free float handguard but honestly have no idea what this entails. My S&W m&p sport II is the basic version which I believe also has a carbine length gas block. I’ll likely bring my S&W into a gunsmith and have them install since I don’t have the tools.

With that said, do I need to buy a mid length gas block along with the new free float handguard, or can the gunsmith repurpose the gas block on my S&W?

Sorry for the dumb question. I know nothing of how to install a free float handguard so don’t know what I’ll need when going to the gunsmith.

[reynolds357]

Originally Posted by gaseousclay

I want to swap out my current drop in carbine length handguard for a longer free float handguard but honestly have no idea what this entails. My S&W m&p sport II is the basic version which I believe also has a carbine length gas block. I’ll likely bring my S&W into a gunsmith and have them install since I don’t have the tools.

With that said, do I need to buy a mid length gas block along with the new free float handguard, or can the gunsmith repurpose the gas block on my S&W?

Sorry for the dumb question. I know nothing of how to install a free float handguard so don’t know what I’ll need when going to the gunsmith.

You will have to get a gas block small enough to go inside float tube.

[TrueBlue711]

Your gas block length has nothing to do with the gas block, but rather the gas tube length. Since your current gas system is carbine length, that's the length it'll always be. So you need a low profile gas block (.750" inside diameter), a carbine length gas tube and the roll pin to join the two. If you get a new gas tube, it'll likely come with the roll pin. There are a LOT of different companies that make both, so the ones I linked above are just examples. Feel free to look around for other companies and read their reviews. Also, you could reuse your old gas tube if you really want to save an extra $15. But I would definitely get a new roll pin regardless. I personally would just get a new tube, but if you haven't shot the gun that much, the old tube is probably fine.
Have you found which free float handguard you're going to use? Lots of choices for that too.

[HiBC]

You may have another challenge.
Does your current config use the GI type fixed gas block /front sight all in one piece?
If so, that gasblock/front sight is what I might call semi-permanently attached to the barrel.You can remove it,but look at it close.They cross drill through the barrel and gas block in two places.Then they ream the holes with a tapered reamer. Then they drive in two tapered pins. The barrel and sight base become an assembly. Its not made so the parts are interchangeable.

When you remove the pins,there will remain two transverse notches in the barrel.

So the question becomes do you have a forend designed to be compatible using the original sight and gas block. There might be a Magpul you can use. I have not done that.

There might be a clamp on or setscrew type lopro gas block you can use over the cuts in the barrel,but be careful how it all fits together.

I personally don't like removing the pins. Transverse cuts across the barrel can make for some crazy harmonics and poor accuracy.

What I have done,that works, is cut the sight tower ,bayonet lug,etc off the original gas block/sight base,then grind/shape it to be a lo-pro gas block that a longer railed forend will clear in assembly. To do that,you are committed.

I;m not telling you it can't be done,I'm telling you the devil is in the details

You may utter "Well,that ain't gonna work!" a few times.

You can buy rifles and uppers in just about any configuration. Its best to buy the config you want. Just my opinion,converting a GI type non free float carbine to a free float rail forend is not a particularly fruitful conversion.

I would buy or build the upper receiver assembly I want pull the two pins and swap it out. Keep the original upper. Its close to having two rifle configurations. You can build a SDMR config and have a light M-4 config.

[gaseousclay]

Your gas block length has nothing to do with the gas block, but rather the gas tube length. Since your current gas system is carbine length, that's the length it'll always be. So you need a low profile gas block (.750" inside diameter), a carbine length gas tube and the roll pin to join the two. If you get a new gas tube, it'll likely come with the roll pin. There are a LOT of different companies that make both, so the ones I linked above are just examples. Feel free to look around for other companies and read their reviews. Also, you could reuse your old gas tube if you really want to save an extra $15. But I would definitely get a new roll pin regardless. I personally would just get a new tube, but if you haven't shot the gun that much, the old tube is probably fine.
Have you found which free float handguard you're going to use? Lots of choices for that too.

Thanks for the tips. Right now, i'm looking at handguards from Midwest Industries and BCM. But, i'm not sure which length to look for. I believe my S&W has a 16" barrel, so I was thinking a 14" handguard would work. I'll contact my local gunsmith and ask them for guidance as well. I think they've likely done many gunsmithing jobs on the m&p sport II

[rickyrick]

The free float hand-guards that I’ve installed also needed barrel nut shims to get everything clocked correctly. But, there’s many versions and their barrel nuts and hardware tend to be proprietary.

[stagpanther]

HiBC is right on.

[gaseousclay]

I ordered a Midwest Industries low profile gas block and MI 14" handguard. The gunsmith said it's not a problem at all to install and that they work on m&p's frequently. Prior to this I spoke with customer service at S&W and had a frustrating conversation. The rep was trying to discourage me from installing a free float handguard citing potential damage to the barrel. I suspect she was only saying this because it voids their warranty.

[rickyrick]

I like the solid tube handguards, but they tend to be gongs lol.
I missed the type of free float guard that you will be using.

I’m trying to imagine how a competent person could damage a barrel by adding a free float

[gaseousclay]

I’m trying to imagine how a competent person could damage a barrel by adding a free float

My thought exactly. Plus, my local gunsmith has a pretty good reputation, so i'm not worried that he'll cause damage