So I just bought a M&P sport 15 last week and finally got to the range yesterday. Really like it. Got this one.
Product: Model M&P15 Sport

Im thinking about changing the handgaurd as stock one has no rails and feels a loose/flimsy.

Also though about replacing the front sight/gasblock so I can put mbus as front sight. Has Rear mbus already.
Plan on putting somekind of reflex/red dot sight on and want to have mbus as backup.

Ive looked up how to change the handgaurd/gas block.
Watched video on brownells made changing gas block look easy.
Im new to working on firearms but am one of those people who can fix anything (well just about)

So im just wondering if its as simple as it looks and also are gas blocks pretty much standardized? Any particular gas block needed for M&P sport or just find one that I like.

Any info/tips/advice would be greatly appreciated

Congrats & welcome to the club.

From the specs I assume you live in California?

The advantage to the stock one is that it's light and it's of a slimmer circumference than other handguards. It's real comfortable in the hand.

Even though I swapped mine out, I kept it in the parts box and will not let it go.

Depending on your shooting pace, it is inadvisable to affix a polymer Magpul MBUS on a gas block. The gas block gets hot and will melt the polymer sight.

Some here are slow fire precision shooters. They can use a polymer front sight on a railed gas block because at their pace of fire, the gas block won't get hot enough to melt the polymer.

Always a good plan. I still advise practicing with iron sights. If you become proficient shooting with iron sights, a red dot becomes a convenience not a necessity.


Being mechanically inclined and being able to visualize how things go together is 99% of the battle.

This video is pretty good, and he has a whole series on assembling & accurizing AR's.

AR-MPR AR-15 Build: Upper Part 2: Barrel, Gas Block, Gas Tube - YouTube

Gas blocks are standardized in the way they operate, but not in their height or the way they affix to the barrel. The key is to find a gas block with a top rail that will be at the same height as the rail on your upper receiver.

Some are held in by roll pins, some by set screws, etc...

I believe that the S&W gas block uses tapered roll pins and must be driven out from a specific side. Someone else will know and chime in. ***COUGH ONEYOPN COUGH***

Your post doesn't state whether or not that you're new to the AR platform, but alludes to it. If you're new, one of the biggest tips I have is to pay attention to how the rifle feels.

If you pull the trigger and the recoil feels light, the action does not fully cycle, the action barely cycles, etc...

STOP SHOOTING

You're on a shooting range, not in a firefight. Pause and take the time to safely inspect your rifle for any obvious failure and barrel obstruction.

These threads are worth a read:

http://smith-wessonforum.com/smith-w...-explodes.html

http://smith-wessonforum.com/smith-w...xperience.html

The tactical malfunction drills are appropriate in a firefight when your life is on the line, but not while on a range where you have the luxury time because you're not being fired upon.

Also a common sense reminder. Keep factory ammo in the box they came in. The boxes have production lot numbers. If a factory round of ammunition is determined to be the cause of a catastrophic failure of your firearm, your ability to file a claim with the ammo manufacturer for compensation hinges upon keeping that box and the remaining rounds in it.

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-John

The pins come out right to left. Use a .750 gas block. It is pretty easy, just use with the right tools.
Good luck, stay safe and happy hunting.

As always, sound advice Japes.
After installing the new gas block you'll want to make sure it is properly aligned to the hole in the top of the barrel. I would suggest running some cleaner down the gas tube, through the gas block and be sure you see it seeping out into the barrel.
I had a friend who didn't do this, his gas block wasn't lined up and he wasted a trip to the range with a non-working gas operating system. What a dummy he was!

I was so consumed with my friend's mistake I forgot to welcome you to the board Bobby...Welcome!

Welcome to the board and to the M&P. These are great ARs and are proving to be extremely reliable, quality fire arms. I may be part of a minority but I would recommend hitting the range at least 4 or 5 more times with your current set up. I was die hard set on getting a rail and then fell in love with the hand guard. Of the rails I looked into, many were heavy and WIDE. You would likely add rail covers only to add to the width. I was also not a fan of the A2 sight and went with the M&P OR. Now, I'm considering swapping my gas block for an A2 sight. It's solid, reliable and doesn't interfere with a red dot or scope. Get to know your AR before you start to make big changes. Enjoy!

Another dummy here. I have mis-aligned a couple of gas blocks...even after running some break cleaner down the gas tube and seeing it come out into the barrel. Both rifles were short-stroking so the holes weren't 'perfectly' centered. I didn't see it as a wasted trip because I went to the range specifically to see if the rifle was working properly...I did forget to take my tools with me the first time though. Live and learn.

I have had it just slightly misaligned myself, and had the brake cleaner run down the barrel. Same thing short cycle but all I have to do is go out back of the house to test. Make sure you use good quality punches, If you can find a cut ring punch, slightly cupped end, it will make it easier. also I used a block of wood but some companies ( Midway) make a front sight block that has the holes in it and holds it secure, I just figured it was an extra expense that I wouldnt use that often.
Welcome and shoot the fool out of it before you start making alot of changes or as in my case you will make a lot more before you figure out what you want it to be!!! LOL

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Grover Oathkeeper

It ain't fair!!! I have to go a whole 1/2 mile

Thansk for the responses.

I am not hell bent on changing the front sight/gas block.

I was thinking that it would block my view if I were to add a red dot. Which after looking around at pictures , seems that it will not do that.

As for the handgaurd, Im still looking around but I saw this one and liked it.
AB Arms Hand guard

I know I should shoot it more before figuring what to add. I crossed a few things off the list like a fore-grip after my first trip to the range.

Im not looking to add a bunch of lasers, lights etc.. on, know a guy who put everything under the sun on an ar-15 and you can barely lift the thing to shoot and only use any of it would be is if the zombie apocalypse came to town.

Im keeping it fairly simple, just want red dot to aim quicker when just shooting random targets not for accuracy.

Still just in the research stage of it all.
But I am now thinking I dont need to change the gas block.

I have run the AB handguard, I really liked it the only reason I dont is my barrels are free floated but it is a good handguard. The only problem with it is the top rail is higher than the receiver rail but if you get the one without the top rail it is very nice.

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Grover Oathkeeper

A fine lookin handguad. Haven't used it so I would defer to oneyeopn's assessment.
You got the right idea by posting an item and asking for advice/opinions on it rather than just asking which items are best. There are several threads on red-dots that have gone up recently, but if you find one you like post it and ask for opinions/experience as well. Most of the folks here are pretty knowledgable, have been there done that, and are willing to help.
Welcome to the M&P-15!

Sight in your rifle so that your point of impact is at the tip of the front sight post. Mount your red dot and hover the dot right on the tip of the front sight post and you're done.

If your red dot ever fails, you'll still be able to get a sight picture through the glass using your irons.

The thing to keep in mind with a red dot is the perceived size of the red dot. The other is how much one click on the adjustment for windage & elevation move the dot.

To keep things simple...

A 1MOA dot will cover 1" of a target at 100 yards. If your red dot's adjustments equal 1MOA per click, then every click will move the dot 1" on target at 100 yards.

Using this very easy relation, say you buy an inexpensive 3MOA dot. Within close quarters distance, that 3MOA dot won't be a problem. Taking a 100 yard shot with a 3MOA dot that has 2MOA click adjustments....

A 3MOA dot will cover 3" of a target at 100 yards. A click of adjustment will move that dot 2" on target at 100 yards.

So you can see how the size of a dot affects long distance accuracy. Generally, the more precise & rugged dots cost the most money. Step down from there and you make compromises.

Then add a magnifier. If the dot is 3MOA unmagnified, and you put a 3X magnifier on it the dot will also magnify. This is dependent on the construction of the red dot.

And because the next question always gets asked...

An EoTech 1MOA dot when magnified 3X is still perceived by the human eye as 1MOA. This is because the dot on an EoTech is actually 1/3 MOA but is diffraction limited by your eye and perceived as 1MOA. When you pop a 3X Magnifier behind an EoTech, the 1/3 MOA dot gets magnified to 1MOA.

Also, there is no end to fiddling with an AR. Every time I've said "I'm done. I'm happy." the next week there was a new part coming in for my rifle. Welcome to the money pit.

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-John

You know...

We have new members in this sub-forum all the time. Maybe one of the forum moderators wouldn't mind if we contributed some basic intro information to sticky at the top.

Basic Cleaning
Gas Block
Handguard
The dangers of barrel obstructions
Optics

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-John

I have an inexpensive 3 MOA red-dot, and the adjustments are 1/4 MOA, so it was no problem to sight in, and it works very well out to 400 yards, which is the max at my range.

It is true that a 3X magnifier will make the dot 3X larger, but it also makes the target 3X larger.

The only issues I have with using a magnifier, is the narrow field of view compared to a 1X red-dot scope, and you lose the unlimited eye relief a 1X red-dot provides.

If you install a free float rail, I suggest looking at all your options.

I have a carbine length YHM Diamond Rail on my OR that butts up to the railed gas block. It was installed before I bought the gun.

If I was to do it myself, I would probably change the gas block to allow a mid-length, specter length, or even a rifle length rail for several reasons.

What was explained in an earlier post, is mounting the red-dot to co-witness with the sights, or BUS.

Another option is to have the sights co-witness in the lower third of the red-dot to have less obstruction in the red-dot view.

Another option is to get a gas block with an integrated flip-up front sight.

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*Aim small, miss small...

YHM makes a decent replacement. Midway (and others) sells them. Looks to have gotten decent reviews, minus the gorilla that snapped one of the allen screws.

I have a YHM part on both of my AR's.

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*Aim small, miss small...