So here's the deal, I accidentally bought a "Commercial Buffer Kit" awhile back and when I started my Lower Build I realized that "I bought commercial and Not Milspec" being my

spare Milspec stocks didnt fit. My Lower is for "Carbine" and that is what I bought and am looking for more of:

The Commercial Buffer Tube is "1 Inch Longer" than The Milspec Buffer tube on my M&P15.

Everyone keeps saying I can just get a new Buffer tube and that the Spring is interchangeable but Would "1 Inch make a major difference in the way the spring

would fit a Commercial and would be 1 Inch of more Pressure inside of a Milspec Tube. The spring in my "Commercial Kit is a rusty Bronze color and has a "Made in China" sticker on it, its from "FTF Industries"

I was convinced they were interchangeable until I ran across this "Milspec Spring" last night that says "Will not work in Commercial Tubes" which If they are interchangeable I don't know why

http://combatoptical.com/catalog/-AR15-M4-.223-5.56-Mil-Spec-Buffer-Spring.-728.html

That is one of my others questions: Recoil Springs range from a 5 dollar DPMS replacement spring to 40-50 dollar springs, Is the DPMS Spring good enough?

DPMS uses Commercial Tubes/ Specs if I'm not mistaking, so now Im even more confused on this Spring length and Buffer tube length and I just want a spring/buffer tube like My M&P15 SPORT

Also Is it normal for a Commerical Buffer tube to be an Inch longer? About half of that inch is extra threads

Buy yet people say they are interchangeable but 1 inch Difference Buffer tube sizes will make a major difference with the same spring in 2 diff sized tubes.

This is the 5 Dollar DPMS Spring
http://www.brownells.com/rifle-parts/receiver-amp-action-parts/action-springs/carbine-buffer-spring-prod32438.aspx

In depth advice would be great, everyone says they are compatible, but I stress the point that "Function" will definately be different because of Buffer tube size

So do I buy a "Mil-Spec spring? with a Mil-Spec Buffer Tube? Wondering if my M&P15 Sport has Mil-Spec Spring or normal spring being its Milspec, atleast the Buffer Tube is, the barrel and other parts arent.

Unless you have something unusual the depths of standard collapsible stock tubes are the same/springs same/ buffers same.
The ad you link too says on so likely it is just a mistake since springs go in the tube not on it.
Tubes are about 7" to 7 1/16" deep.
I have never worn a regular 3-5$ spring out yet and never had one drop below minimum allowed length that I can remember.


Brownells has their own brand ar springs a little cheaper for the standard m4 recoil spring http://www.brownells.com/rifle-parts/receiver-amp-action-parts/action-springs/ar-15-m16-action-springs-prod41438.aspx?avs|Manufacturer_1=BROWNELLS

May need to take my loses with the Commercial kit and get this one unless you guys have better suggestions. The Carbine "Commercial Tube" is 100% a inch longer than my Mil-spec carbine tube. Maybe the company had crappy stuff. I have my eyes on this whole new kit unless any of you have better suggestions around the same price as the KIT below that I just found:

http://www.amazon.com/MIL-SPEC-AR15-Receiver-Extension-Tactical/dp/B00CX786J0/ref=sr_1_cc_2?s=aps&ie=UTF8&qid=1382572368&sr=1-2-catcorr&keywords=AR+buffer+tube

Not sure why you are focusing on the outside length when it is the tube inside depth that matters for the spring and buffer.
Made in USA. Site sponsor cost less
http://damageindustriesllc.com/product/kit-complete-buttstock-m4-telescoping-mil-spec

The buffer and spring are IDENTICAL between MIL-SPEC and commercial receiver extensions/buffer tubes.  NO problem at all.  The only functional difference between the two types is the OUTSIDE diameter of the tube, which affects what type of stock you can put on the extension - and have it fit well.

But you do realize Commercial Tubes are an Inch longer right? I didn't think about the inside not being as deep as the full length though so thanks for advice.

Is it a known fact that Commercial tubes about an inch longer overall or do I just have an odd type one?

Yes they are generally longer with an angle on them but should measure the same depth inside as a flat ended shorter collapsible stock tube.

That "Buy 1 Get one Free Enhanced Recoil Spring" Seems very tempting at 10 bucks. Wonder if its any good?

Enhanced Spring "Buy 1 Get 1 Free" 10 bucks...Good for 750,000+ cycles

Seriously, do it.

I just compared two different rifles, one with a commercial tube and the other with a MIL-SPEC tube; with the stocks fully retracted, there is about 3/4" difference in length with the commercial tube being shorter.  From the back, the commercial stock has a 3/4" space between the end of the tube and the end of the stock.  Yes, I compared, and the stocks themselves are identical in length.  I think what it comes down to is that MIL-SPEC is a set standard which includes diameter and length, and commercial is completely unstandardized.

I would lose the commercial tube and buy a mil spec tube and problem solved.  Then you can use the extra stock.  We are not talking about a lot of money.  You have made this way more complicated than necessary..  

I see what you mean but my question became "How does a spring work the same on 2 different tubes when their is an inch difference."

I found the issue though, The "Commercial tube" was an almost an inch longer but on the inside of it, it was an almost an inch shorter than the exterior. Didnt think that the end of the tube would be longer or have that much extra space on the exterior but it does. And to the other guy above, you are mistaking, the Commercial is the longer one. You can even view specs online.

Spring tension was my main concern but now that I know that the Commercial tube wasn't almost 8 inches on the inside like it was on the outside, that EXPLAINED my issue.

Whomever recommended that I measure the inside of the tube, thanks for your advice.

Since the spring and buffer are completely interchangeable between commercial and MIL-SPEC receiver extensions, as long as the INSIDE dimensions of a receiver extension tube are the same, your buffer and spring will work.  Remember, commercial tubes are made to allow the use of standard buffer parts.  Your spring and buffer are good to go.

I agree that you should probably just get a MIL-SPEC extension and stock.  That completely eliminates the confusion factor.  Of course nowadays you have to read carefully to see that you're getting a MIL-SPEC receiver extension instead of a "MIL-SPEC diameter" tube.

There is no commercial spec.  The picture you're referring to comparing a milspec with a "commercial" is just illustrative of some company's commercial stock product.

Most of the "milspec" tubes out there are not milspec, either - they're just "milspec diameter", but not the correct milspec material or processes.

Yea, I picked this one out, hopefully its good quality. Price seems about right

http://www.amazon.com/MIL-SPEC-AR15-Receiver-Extension-Tactical/dp/B00CX786J0/ref=sr_1_cc_2?s=aps&ie=UTF8&qid=1382572368&sr=1-2-catcorr&keywords=AR+buffer+tube

You can buy the whole outfit, stock, tube, spring, and buffer from Palmetto State for $33 bucks.
Palmetto State

The $33 Palmetto kit has a "MIL-SPEC diameter" tube, while the Amazon item from Tactical Intent is a "MIL-SPEC" part (proper alloy and everything).  I'd go with that one instead of the PSA kit, even at a higher price.

My commercial tube is the same length as my mil-spec  with the exception of the slant

The fact you guys' "Commercials" are same length as your milspecs must mean I had a bad quality one or an "Oddly Made One", just goes to show me that I don't want to trade it back for a milspec kit from that company. With an inch longer commercial tube I have to wonder about their quality. Their CAR buffer in my Commercial Kit also weighed only 2.6 ounces which is below the 3.0 Car buffer standard.

It was from "FTF Industries"...