M&P Sport2 AR-15 5.56 Barrel Diameter?

Thirsty Traveler · May 9, 2023

Hello,

I just recently purchased the M&P sport 2, A.R. 15 chambered in 556 with the front A2 fixed sight. I’m looking to replace it with just a Picatinny gas block. However, I’m having a hard time finding what the right size barrel diameter is. I know they change the barrel to a 1/9 twist, don’t know if this has any effect on the barrel diameters outside dimensions. Can anyone hear help?

TT

DixieRanger · May 9, 2023

S&W AR Sport ll gas block is .750. This help?

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Thirsty Traveler · May 9, 2023

DixieRanger said:
S&W AR Sport ll gas block is .750. This help?

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Thanks DR, I found an old thread on AR forum, from 2006 where there were multiple post saying it also could be .625″. But I know since then, once S&W came out with the sport2 they made some changes and added the forward assist and dust cover on the ejection port, then went from a 1/7 to a 1/9 twist, so I just want to be sure.

TT

DixieRanger · May 9, 2023

If may ask...replace w/ piccatiny gas block to add flip-up front sight?

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Thirsty Traveler · May 10, 2023

DixieRanger said:
If may ask...replace w/ piccatiny gas block to add flip-up front sight?

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Hey DR, no, I just put a long range scope on it, and it sits about an inch from the front sight, although not really that visible, except for a very faint shadow, it looks a bit goofy and it’s bugging the heck out of me! It’s got a go! I know I can just cut it off, but I would love to just change that gas block with one with a pic rail on top that fills the A2 sight gap that’s in my drop in handguard and is the same height as the receiver rail. I’m finding it very difficult to find the right size, I guess I need to order a few and use a micrometer to figure it out.

TT

DixieRanger · May 10, 2023

TT...just my thoughts. Not gonna get best performance w/long range optic on carry handle. Bore vs. height of carry handle. Couple o' pics...only S&W flat top no optic. Front sight never fired. Others JP's. One w/front site, flat top w/ACOG. See shadow of front. Last a JP w/1x8 Valdata lighted horseshoe dot reticle. Shot 3gun from Ft. Benning to Va. for 28 yrs til 2018. This is last one used in matches. Paper & steel. Hit 3" steel to 400yds. Bottom line is jf gonna shoot long range would suggest flat top upper. Lot on market. Anderson is good. Get stripped & use your internals. No serial# so no paperwork. All mine have free float tube which helps accuracy. If go to match, see what setups are used for distance. i learned by watching/talking with experienced shooters. Up close not so important but flat top & free float tube made difference distance wise. Again...just my experienced thoughts.

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DixieRanger · May 10, 2023

Oops...Valdada optic

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Thirsty Traveler · May 10, 2023

DixieRanger said:
Oops...Valdada optic

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Wow! Very impressive! I’m new to AR platform. I started shooting & hunting small game when I was 12 with my Dad.( I’ll be 59 this year) I only have experience shooting iron sights with shotguns, revolvers and SA pistols, (as I was an LEO for 8 years before going to FD). I kinda put sport shooting on the back burner for a while until I moved down south about 9 years ago. I’m not familiar with some of the things you mentioned. I have much to learn. But I’m no competition shooter, nor am I interested in doing so. I just like to protect my family and myself and go to the range occasionally. I purchased this rifle at a pretty reasonable price, $539, I consider it my AR learning rifle. I have other home defense weapons that are much more readily available.

I started out with a 3X Prism scope on this rifle because I have Astigmatism and wear corrective glasses, so I had a hard time with red dots. And I couldn’t see targets very well past 50 yards with the 3X prism I had. So another person, on another forum, recommended this cheap scope as a starter. So far I can see pretty far with this 6x18x50mm SFP scope. It’s not mounted on a carry handle. Hers another photo. I don’t mind spending a little cash on this rifle, heck I got $1,200 in to a Kel Tec Sub2K 9mm PCC! But I’m in the learning phase when it comes to AR’s and optics! I’m also a sucker for good deals, so the only upgrades I’ve done is purchase stuff on sale, like a new Geissele 2 stage 4.5 lb trigger, the drop in handguard and the scope. I said I’m a sucker for a good deal but I’m cautious not to buy something of to low of a quality, I know you get what you pay for, right now I’m looking to just learn for when I buy or build my next AR. I’m just looking for an inexpensive solution to get rid of that front sight without just cutting it off, and have that gas block slot in my handguard filled up with a picatinny rail to match my current rail if possible.

TT

DixieRanger · May 10, 2023

Understand TT. Not meant to push to any setup you do not need muchless want. Step at a time to get what you want or need. Can pour lotta $$$ in parts & guns. Like PCC's too. Built & bought few in last several yrs. 75 now slowing down after 54yrs of work. Born with love of firearms & do still. Stay safe.

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DixieRanger · May 11, 2023

TT...didn't see pic last nite. Misunderstood, thought was carry handle upper. Better understand settup after pic. Gave way to much info for your needs. Windham Weaponry (formally Bushmaster) has a clamp on picatinny rail gas block for .750 barrel. Measure barrel diameter to insure size. If so this oughta do it.

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Thirsty Traveler · May 11, 2023

DixieRanger said:
TT...didn't see pic last nite. Misunderstood, thought was carry handle upper. Better understand settup after pic. Gave way to much info for your needs. Windham Weaponry (formally Bushmaster) has a clamp on picatinny rail gas block for .750 barrel. Measure barrel diameter to insure size. If so this oughta do it.

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Thanks DR,

I hear ya. I’m good with everything I did this far. Was it a mistake to buy the rifle with that A2 front sight?, Not at first because I had a raised prism scope on it, and I figured irons are always a good backup. Then I realized how bad my eyesight was. I could use a new eyeglass RX I’m sure, (ins. Only allows 1 every 2 years). Then I changed my mind about how I was going to use the rifle, long range only with a micro optic, canted, as a backup.
Like I said I’m still learning and feeling it out.

Thanks for that recommendation on that gas block, my biggest challenge, I’m finding, is to make the gas block’s picatinny rail sit even with my current rail and within that slot opening on the handguard I have.

I’ll keep searching and asking questions.

TT

DixieRanger · May 11, 2023

Way 'i' see what you want to do...with a 50mm lens can't use either rail to mount? Canted reflex dot mounted on scope for backup...large lens may be in way sighting thru. With canted reflex gonna have to pick a distance to adjust dot for impact at that yardage?...accuracy? Never used canted dot or that large an optic. Canted dots i've seen used are for close in work. i just turn rifle 90 degrees & know impact will change ittle in close. Hope you get encouraging answers. That's a Large scope for that rifles capabilities but only you know your eyes.

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Thirsty Traveler · May 11, 2023

DixieRanger said:
Way 'i' see what you want to do...with a 50mm lens can't use either rail to mount? Canted reflex dot mounted on scope for backup...large lens may be in way sighting thru. With canted reflex gonna have to pick a distance to adjust dot for impact at that yardage?...accuracy? Never used canted dot or that large an optic. Canted dots i've seen used are for close in work. i just turn rifle 90 degrees & know impact will change ittle in close. Hope you get encouraging answers. That's a Large scope for that rifles capabilities but only you know your eyes.

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Yes, pretty much that’s it in a nut shell. The canted micro optic sight is just an after thought for the possibility of QCB, but really not necessary as this is just a long range rifle for now.

I’ve been in bed all day with an illness, (I think the grandkids gave me), so I’ve emailed and searched my brains out! I found no clear solution for a gas block that will fit that gap perfectly. One company said they have one that would fit perfectly but the set screws that keep the gas block in place may damage the pin slots on the barrel.

I may just cut off the sight after all, and cover it with one of those flat rubber picatinny rail grip covers, and call it a day. I suspect down the road I wil change the gas block out to a low profile one and a buy a free floating handguard.

TT

DixieRanger · May 11, 2023

TT...keep thinkin' & act accordingly.

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M&P Sport2 AR-15 5.56 Barrel Diameter?

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