My Upper is .210 - Did they change?

[southpaw187]

Hi folks, I just bought a new MP10 from my LGS. Prior to my purchase, I did research across the interwebs particular to the knowledge required to add a free float rail to this rifle. Everything I read indicated that the tang on this rifle is the same dimensions as a DPMS low profile receiver. However, I put digital calipers on mine and I am getting .210 which is the dimensions of the High Profile DPMS receiver. I opened up a chat at S&W dot com to inquire if the rifle dimensions have been recently changed; the rep said he knew of no changes to the dimensions of this rifle. However I don't think my calipers are lying to me. So I have 2 questions: 1) Do I indeed need a DPMS Pattern High Profile Rail? and 2) When did it change, and I am curious why? Thanks everyone. -Southpaw

 

[bigfutz]

Hi folks, I just bought a new MP10 from my LGS. Prior to my purchase, I did research across the interwebs particular to the knowledge required to add a free float rail to this rifle. Everything I read indicated that the tang on this rifle is the same dimensions as a DPMS low profile receiver. However, I put digital calipers on mine and I am getting .210 which is the dimensions of the High Profile DPMS receiver. I opened up a chat at S&W dot com to inquire if the rifle dimensions have been recently changed; the rep said he knew of no changes to the dimensions of this rifle. However I don't think my calipers are lying to me. So I have 2 questions: 1) Do I indeed need a DPMS Pattern High Profile Rail? and 2) When did it change, and I am curious why? Thanks everyone. -Southpaw

Where are you measuring? I have all 3.

 

[southpaw187]

Where are you measuring? I have all 3.

At the tang above the charging handle slot. I will take a pic tomorrow.


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[southpaw187]

HI everyone, aside from uploading a picture I thought I would mention something I found in a deep corner of the internet last night about this. So throughout the internet, directions can be found on where to measure your receiver to determine if you have low profile or high profile DPMS pattern upper. Here are examples from Troy and MI.

MI: DPMS LR 308 Products

Image made by Troy: DPMS A3 HANDGUARDS - 762AR.com

One would conclude that by these instructions, I should simply measure my receiver at the tang, which I am doing right now, and it measures .2010 on my Mitutoyo calipers. So based on these instructions, it should be HP right? But wait, there's more.

I found verbiage on the Troy Website in the description of their carbon fiber hand guards; and funny enough, this same verbiage only shows up on the mobile website and not the desktop website:

Troy's litmus test below does not apply to the M&P-10. The M&P-10 maintains the same rail height over bore axis as the DPMS low profile without thinning the charging handle overhang.

I am flabbergasted that I haven't found that nugget of info throughout the inter webs, but hey, that's why we post these things.

So, in conclusion, I believe that the MP10 is a unique receiver that has a DPMS low profile rail height and a charging handle overhang that measures approx. .210.

Now I just have to pick a dang hand guard....