All,

Between operational/reliability considerations -

What is the difference between the M&P15TII series and both the lower priced Sport and XV series?

Obviously there is a difference in form-factor/furniture/features, but I am curious on the aspects that affect reliability.

For example - it appears the barrels are the same 4140 steel. From the outside looking at that spec it would appear to me the lifespan of the barrels would be equal - you would loose performance at equal rates over the long term. If there are differences in the specific 4140 mix that make a difference I don't see then that would be something to know.

What about recoil, trigger pull, and overall reliability - IE - more stout butt stock vs lighter butt stock (more/less durable), more/less robust firing mechanism, easier/harder to jam, smoother/rougher trigger mechanism, etc, etc?

4140 spec steel, give or take allowable variations in alloy percentages, is all the same. You're allowed a slight variation within a given range in the various components like carbon and whatever else makes steel 4140. The last two numbers refer to carbon content. Without looking at actual ASME specs, that seems to be the only difference between 4140 and 4150.

NO AR builder/manufacturer makes all the parts. They're all pretty much buying from the same sources. It makes no supply chain reason to buy different quality stuff for the products coming out of your factory. We bought M&P15s as soon as they were available and they ran right along with Colt 6920s. In fact they seemed better than the Colts (Yeah, I know that's heresy in some quarters, but ya can't argue with demonstrated fact.)

This was in stark contrast to the performance of another "name" brand that obviously was using fire control parts-and bolts- that obviously had failed to meet specs in some manner. But, I expect the were both cheaper and available.

IIRC, the Sport lacks a heat shield in the handguard. Check the factory website for details between the selections.
ETA: check the factory website about receivers. Edge to the forged receiver over the billet.

Thanks for the reply.

Not to derail my own thread, but I wanted to ping on your statement below:

That may be true with most manufacturers, but I am not sure that is true with all. I know for a fact Daniel Defense does a lot of machining, molding, and engraving. That isn't to say they have some smaller parts they may outsource, but the primary parts they use are made in-house. I've been up close to them being made myself.

As to the S&W options - that would be surprising to me. I thought their products were mostly US made by them. I did find the M&P 22 I have being made by Walther interesting back in the day, but I could see that with it being a lower end model and not a true "M&P" pistol.

However, I am just starting to scratch the surface on researching them beyond just looking at products and guessing - which is why I started the thread. The only AR I have is an S&W M&P15-22, which doesn't really count as its a rim fire .22 (fun and cheap to shoot, for sure).

In looking at the 5.56 caliber vs affordability - what I am trying to decipher is what the value is in the options. My first gun was a S&W and I have several more since so I am a bit partial to them, but am open to other options. Depending on which way things go on the "value" - if opening the budget is a better route then I might make the jump to Daniel Defense. However, I think my money can go further with a lower priced option.

I didn't either state or imply that any outside vendor supplied parts weren't US made. I will note that it makes little commercial sense to create production facilities that already exist elsewhere and make quality products. There are a few builders, like LMT & Daniel Defense, that do special projects and do make more parts than many others. And charge accordingly.

Example: if you look about, you can find a list of forge marks of various forging companies that have made the raw forgings for AR receivers. The count is somewhere in the 20's, I don't feel like looking for my list. This doesn't mean that they're all currently forging receivers. Some only made receiver forgings under contract to either Colt or FN. Others apparently dropped out of the business. Back in 2012, there were about 5-6 forges (outside any proprietary forging facilities) making the raw receiver forgings. We had Colt 6920s that had lowers forged by a variety of forging companies, some of which are listed below.

Forge/hall marks include: stylized head of a cardinal (bird)-Cardinal Forge, hollow square-BAFE (think I got the letters right), there's also a broken A for Anchor Forge. All produce outstanding raw forgings.

Bolt carriers are also a foundation part made by a variety of manufacturers. The vast majority meet military specs. At least in the important areas. Some makers don't hard chrome the bolt recess on some of their products to reduce prices.

Note about QC inspections: the OCD inspections that got written into the military specifications were from Fairchild Industries who developed the design and began production. Fairchild was in the aviation business and on aircraft parts, you can trace every single person who performed any kind of work on any part. They also test each and every part to make sure it meets specs. In most industries, except for critical parts, QC testing is done on random samples unless problems are noted.

Also, the design originated in the 1950s. The QC on materials has improved exponentially since then. Lot to lot variation in materials has been greatly reduced. As has the tolerances produced by CNC machining.

ARs are kinda like cars. There are Buggattis, Rolls-Royces, Mercedes and down at the bottom, Yugos, Checkas and a couple of others. Most of us are happy with something in the equivalent of Chevy/Ford.

Do you really need a barrel from 4150? Not really, unless you're doing full auto. A hard chrome finish bore/chamber is really worth the extra $40 or so. Per the now retired CO of the USAMTU, the melonite coatings don't stand up to rapid fire. Neither does a plain finish bore, we'd destroy them in one CQB training rotation.

@WR Moore - thanks for the detail. There is definitely a lot I havent known about the gun production industry so that is good to know. As to the traceability of materials/processing - that is an important aspect of what I do for a living. We make parts for the energy, defense/military (nothing weapons related - lots of other stuff), and auto industry. Every piece of metal we make a part out of, by nature of the supply chain, is traceable. However, only certain things on our end require the traceability of the work. So I get all that.

Ill do some more digging on what you listed about the finish on the barrels. I can't remember all the details on the Daniel Defense ones but I do recall at the time we were there they had just implemented a machine that takes the barrel stock and work hardens it as the barrel is formed. That was a pretty slick process. As to what other manufacturers do, or forges, I dont know. But you gave some big clues with the various coatings.

Good stuff. Thanks.

Daniel Defense has been hammer forging their barrels for quite some time. They have a barrel blank with a hole drilled in it. A mandrel is inserted into the bore with the chamber and rifling form on it. Then they start hammering. I'd kinda expect a stress relief operation following forging.

From what I understand, the differences between the M&P15T-II and the Sport II are in the accessories. The M&P15T-II is basically a Sport II rifle with the following upgrades:

* M&P M2.0 style pistol grip with interchangeable backstraps (like the grip on M&P M2.0 pistols
* Magpul CTR buttstock
* Radian Raptor charging handle
* Magpul MBUS sights front and rear (as opposed to rear only in most Sport II models)
* 15 inch MLOK freefloated handguard/rail system
* Ambi safety selector
* M4-E enhanced flash hider

For someone wanting a one and done proposition with regard to their rifle, the M&P15T-II offers a pretty competent package ready to go right out of the gate. For others, it makes more sense to buy the Sport II and add the specific accessories that they prefer. As an example, I still prefer the older quad rails over the newer and more popular/lighter MLOK or Keymod options that are everywhere. I also have no problems with the standard “birdcage” flash hider or A2 pistol grip, and while I like ambi safety selectors and charging handles, I am okay without them.

For someone like myself, the added accessories of the M&P15T-II would be largely wasted. Of course, just today I got an email from Bud’s Gun Shop advertising that model for only $779.99 which is about what Sport II rifles sell for in my area, so it wouldn’t hurt to go that route even if I were to strip the parts I didn’t want as I could sell them and recoup some of the cost making the rifle a real honey of a deal. Normally however, those rifles are nearly twice the price of the Sport II, and I just don’t see the added accessories as justifying that much of a price jump.

Do you have any thoughts on Del-Ton Inc? Here is an example I found and some detail for discussion's sake:

Del-Ton, Mid-Length Rifle

A couple things that catch my attention in there:
- Chrome Moly Vanadium barrel
- Heat Treated and Chrome Lined components associated with the Bolt and Carrier

Last question for now - on the rifling - I see a lot of barrels 1:8 and 1:9. They are seldom down to 1:7, which this is. Wouldn't that speed up the spin and drop the velocity (the shorter the twist the faster the revs)? In what ways does that matter?