S&W MP-15 Sport Barrel Specs

Based on the specs at Product: Model M&P15 Sport?, the Sport no longer has a nitride finish. However, the 2014 catalog just downloaded shows it with "Durable Corrosion Resistant Barrel Finish", which I believe is the nitride finish.

If true, when did they stop doing the nitride.

Melonite is what they currently use. Someone might know that answer.

Melonte is nitriding. Google it.

The barrel is still treated, but S&W no longer refers to the process as Melonite, as that is trademarked. They now refer to their treatment as the "Durable Corrosion Resistant Barrel Finish"... but I agree, it appears that the specs are quite a bit looser than they once were, so who knows what you may get.

Salt Bath Nitriding using a method with a cyanide by-product = Tennifer (Austrian Made Glocks)

Salt Bath Nitiriding using a method that does not produce a cyanide by-product = Melonite (S&W, U.S. Made Glocks, etc)

Back in the day I could confidently say the 15-Sport had a Melonite Treated 1:8 5R progressive gain twist Thompson Center barrel with a carbine length gas port. Other than the advertised 1:9 twist rate, who knows what type of hot Salt Bath Nitriding process is now used.

JaPes said:

Salt Bath Nitriding using a method with a cyanide by-product = Tennifer (Austrian Made Glocks)

Salt Bath Nitiriding using a method that does not produce a cyanide by-product = Melonite (S&W, U.S. Made Glocks, etc)

Click to expand...

I keep hearing this, but I am somewhat skeptical as HEF USA seems to say the two processes are the same, and that "tenifer" is merely another trade name for melonite.

"MELONITE / QPQ

MELONITE, and its synonymous trade-name, Tufftride (or Tenifer), is a relatively straight-forward, flexible process to operate and maintain, and produces exceptionally uniform case hardening. . . ."

See HEF USA's site: http://www.hefusa.net/melonite_qpq.html

Also, there is this comment at this discussion site concerning melonite/tenifer:

"Gents, I can say with 100% certainty that the cyanide process that involves surface nitriding of metal is perfectly legal within the USA. I know this because I currently regulate 2 such processes right here in Springfield, Ohio. They both use a molten cyanide bath to introduce the nitrogen into the structure of the metal part being nitrided. Please see
Salt Bath Nitriding, PVD Coatings, Engineered Bushings and www.trutecind.com.

Jeff

Jeff Yinger
gov't - Springfield, Ohio"

Melonite vs Tenifer on semi-auto pistol slides

They are both a liquid hot salt bath nitriding process. Different routes to the same destination. Tennifer process uses alkali cyanide in the bath medium and produces more cyanide as a byproduct. The cyanide is a no-no in the USA. That's the difference.

Free float or new upper?

What is the gas block diameter of the sport, I have looked all over my owners manual and it says nothing about the gas block. Thinking of instead of buying a new upper with a free float and using my lower or just installing a free float rail myself, thinking on going with the Diamondhead VRS "T" 13.5" Free-Floating Versa Base system. I like the way it looks and have seen several videos on the install on the M&P 15 line of rifles even the sport model.

Also if anyone on here has installed a low profile gas block onto the M&P 15 sport carbine length rifle, does the barrel already have the dimples per drilled for the new gas blocks screws, if not do you have to have the barrel drilled for the screws to properly keep the gas block in the right place. I have watched the videos none mention the dimples holes needed.

Also would it just be better just to buy a new upper with everything on it I want, cause I would still have to buy all the tools needed to do the project. So far here is the price list
Diamond rail $170.00
Tools including vise $170.00
gas block $40.00
Torque wrench $45.00 (for a decent one)
New black YHM gas tube $20.00 or less, want a new tube due to new gas block, would be using YHM low profile gas block, want the match and fresh unused tube.

I have still been thinking that just getting a new BCM, YHM or DS arms. The DS arms has a complete upper without the BCG and the charging handle for $405.00 can get a BCG for $100.00 or less and that's for a auto type and either BCM or DS arms itself. Got a BCM gunfighter charging handle.
Sorry for the ranting just stuck, also has anyone on here used a DS arms upper on the M&P 15 lower if so let me know how it worked. Thanks for reading all of this and all of your replies to this subject.
I am just stuck between what I want to do. I know with a new upper I kinda get a new rifle and what I priced online using the DS Arms upper with that Diamond rail and there BCG for $75.00 I am up to $485. to $500. for the new upper, that's if the DS arms would work well with the M&P 15 lower. I know that YHM upper fit well on M&P lowers so do BCM uppers, but they are both out of stock and kinda out of my budget range for this, which is no more than $550.00
Here are some pics of my rifle, I took off that GMG extended quad rail hand guard, due to I really just didn't like it, liked the look just don't really need that much rail, which is for sale if interested. Got back on the good old Magpul MOE carbine hand guard still with the RVG grip. Also no carry handle anymore after finding out that carry handle is just non Mil-spec junk. Glad I didn't pay for it. Now I have no rear sights, Mbus sight that came with it broke at the range after a fellow shooter knocked it off the shooting table and it broke. S&W is suppose to send me a new one they took off another rifle for a custom build.
Thanks again for all replies and information

I was lucky in getting one of the Sports with the TC 1 in 8 twist and nitride finish. I installed a two-stage trigger, EGW comp and free-float tube and the gun can easily shoot sub MOA with good ammo; most times sub 3/4 MOA and I am not the most accurate of AR shooters. The decision was made during the height of the Sandy Hook run to change to a vendor for barrels and increase production. Hence, the new barrels are, IIRC, 6 groove 1 in 9 twist with conventional rifling. Nitride/Melonite or what ever Marketing calls it is still the same; a high temp salt bath application that has a Rockwell hardness close to or exceeding hard chrome for long barrel life.

Yes, I knew about the Melonite/nitride/"Durable Corrosion Resistant Barrel Finish" process. Just wondered if the Sport still had it for the barrel since the new spec's page makes no mention of any barrel finish.
Thanks for all of the replies, will check out some of the links included.

Barrel

This is what S&W told me about my rifle

Dear Customer,

The barrel is melonite coated or as we call it MCR (maximum corrosion resistant)

Smith & Wesson values all of its consumers and are happy to have assisted you to the best of our ability today. Please do not hesitate to contact us should you require further assistance.

Sincerely,

Rob

That my rifle was also made January, 2014. My barrel says on it 5.56 NATO 1:9 twist rate. All I know is that I have shot the hell out of it and it has performed great, I think the more I shoot it the better it gets.
I have been thing at tax time getting a DSarms upper with a free float rail and use my M&P lower on it this will give me 2 different barrel types and the DSarms upper is chromed line and hammer forged barrel with 1:8 twist rate. I just hope it fits well on the M&P lower.

I always laugh at "Melonite Coated". The Melonite process alters the crystalline structure of the metal to a depth deeper than a layer of hard chrome. The Melonite process imparts hardness, heat, and wear resistance of hard chrome without negatively affecting the accuracy potential of the barrel. It's also less expensive than hard chrome lining.

Melonite isn't a coating. It isn't an applied finish.