Recently purchased an m&p 15 OR and just got the 12" quad rail I had ordered in, it is a 2 piece drop in. I now know I have to replace my gasblock with a lopro one and that will be in tomorrow, after I replace the gasblock should the rail fit into the delta ring or am I going to have to remove that somehow? Also wondering if there needs to be something at the end barrel section to support the end of it like a barrel clamp of some sort. This is my first post on the site and any help will be greatly appreciated! Looking at the forums on this site helped me decide on the OR, Thanks fellas!

We need more information, like what quad rail are you trying to install... make and model # go a long way to helping us help you.

12in drop in?

Like Cypher says it would help to see what you actually have... but I'm guessing you got a rifle length handguard designed to use with the rifle length gas system, and just "drop in" (not remove front sight, or in your case the OR gas block rail.). See below pic. Bottom rifle is rifle length.

Send it back.
Get a free float handguard of any length you wish along with a low profile gas block.

The guys here really know their stuff. I'm no expert but have installed drop ins and one free float myself and I'm sure these guys would agree that they will need the exact model number of the "Drop in" you are trying to install. From the very little experience I have I can tell you that if you have to mess with the gas block then it is not a drop in. As I understand it, "drop-in" hand guard mans exactly that, a drop-in, meaning quick and easy, my two cents

I admit I bought a fairly cheap $50 dollar rail from amazon without fully doing all of my research. This is a picture of the end of the rail that I would assume go into the delta ring but it has nothing to hold it in there. I'm assuming it won't work even after I install the gasblock. So would I need to take off the delta ring and install something in its place? Sorry for the late reply

Actually I just realized I have no idea how to put pics on here, any insight? Lol I'm sorry

You don't need to change your gas block for a drop in if you get a carbine length rail, are you set on the longer rail? If you are, then install your low pro gas block and then get a free float longer handguard and return the drop in. There are reasonably priced free float rails. The drop in needs support in the front to attach to the barrel so you can't just slap it on top of the low profile block, it needs a way to support the front and a low profile gas block does not do that. If you are going to replace the gas block to a low profile then just get a free float at that point. The free float only attaches at the receiver end and never touches the barrel at the front, thus why it "floats" the barrel.

Yes, you will have to remove the delta ring and possibly the barrel nut (depending on what rail you get) to free float the barrel, but that's the best way to do it and if you have the low profile block, you might as well. It's really not hard. The hardest part will be getting the old gas block off, the rest is easy.

And yes, sorry tuff love. You should have done your homework first before ordering anything, you need to understand the rifle and how it is put together and works before you start swapping stuff. You ordered a rifle length drop in hand guard and you have a carbine length gas system, it won't work on your OR as it sits.

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Still carrying my S&W 642

Well the rail is 12 inches, and my rifle came with carbine length gas setup so I'd have to install a lopro gasblock because the current one has a little rail on top of it that the quad rail will not fit around, basically I ordered one too long, but I like how a 12 inch would look so was trying to see what I could do to make it work...if I could figure out how to post pics I would post em up

Tossing in my 2c worth here (also a OR owner,) the others are correct.

The two piece won't work, it's designed to have support at the front and rear.
If you're set on a 12", then get a free float rail (which will require swapping out the gas block, and *THAT* is a PITA,) and will also (I believe) require a change to the barrel nut. I could be wrong on the last part. I had a local gun shop put in my free float rail, they had a lot of "fun" getting the gas block off.

Somewhere on here, there's a topic about someone who just took an angle grinder to their OR gas block, rather than trying to get it off...

Presuming it worked, attached is a pic of my OR with the free-float rail.

Attached Images

IMG_20150506_184236.jpg (198.1 KB, 654 views)

Again, you can't do what you are describing. The 12" drop in was meant for a rifle length barrel and a rifle length gas system. It just won't fit the carbine (shorter) gas system and barrel. If you want the longer rail look, you have to free float it as we have been saying. Drop in rails fit between the gas block and receiver, not over top of the gas block. Free float rails fit over the gas block.

I think you need to do some reading before you do anything to your rifle. Lots of reading and YouTube videos also.

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Still carrying my S&W 642

What do you want to do, use a low profile gas block and then mount your OR gas block rail and handguard cap up front just so you can install a "drop in" dime store handguard?

Forget about it. If you want a 12in handguard, get a free float and be done with it.

Looks great! So was the OR gas block really hard to get the pins out just like the A2 front sight posts? Hardest part of a free float swap IMO.

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Still carrying my S&W 642

Return or sell what you have. You can't use it on this rifle.

Buy a "carbine length drop in quad rail"

Installs just reverse of the stock handguard removal. That's the simplest solution.

According to the guys at the LGS I took it to?
Yes...
Bad enough that when I brought it back in to have them mount and bore-sight a scope, the gunsmith remembered me and the gun!

Hi, sounds like you might be a glutton for punishment!

I just built a CQB AR, and now in the process of building a match upper. If you want any degree of accuracy, you want a free floating handguard. The current free float handguards come with a barrel nut, so you will need a barrel wrench, a torque wrench, and an upper receiver vise block.

Before you actually start taking your upper apart, give serious thought to what you want for your efforts. When I built my CQB, I spent about $225 on the upper, less tools. The gas block was the last unit installed, and it required about 15 minutes.

Remember, it takes only about 3 minutes and 2-3 hands to swap uppers, and you still retain the benefits of the S&W warranty!

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Judge control not gun control!