Hey all. I want to replace my Spring & Buffer, but would like to know how much it weighs.
My LGS weighed it and he could only weigh it in Grains. He got 1273.6 grain which came out to 2.91oz.

Seems light to me. Is that what you guys are getting? Roughly 3oz?

Standard carbine buffer, ~3 oz. Here's a chart:
Slash's Heavy Buffers | Reference

You may want to go to a H or H2, I usually use an H for more reliable ejection.

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ΜΟΛΩΝ ΛΑΒΕ

I have a M&P/Magpul middies. I changed out the carbine buffer and spring, for a Tubbs spring and H2 buffer. The H2 was too heavy and the cases kind of "fell" out. I switched to an "H" buffer and it functions perfectly. You have a carbine length gas system, so an H2 buffer would probably work fine.

Why do you want to replace the spring and buffer? How many rounds do you have through the gun, and what problem are you trying to correct?

All M&P rifles come with the cheapest buffer there is (CAR). I generally recommend folks run AT LEAST an H buffer and prefer an H2 buffer.


BCM Buffers at G and R Tactical



C4

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S&W M&P Armorer
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S&W AR's are over gassed so a heavier buffer reduced felt recoil.



C4

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OMG! Here we go again.

In the world according to C4I, ALL S&W's are over gassed because, well they just are. In his world, they are over gassed because the average S&W buyer will, of course be shooting cheap underpowered ammo because they have a cheap rifle. Colts, on the other hand, are not over gassed and will choke on the cheap stuff, but of course the Colt owner would never shoot the cheap stuff.

I think I have that about right.

Spot on. I've always wondered how a buffer can reduce recoil, a claim I see on a regular basis.

All my AR's, regardless of manufacturer have reliable ejection straight from the factory. Never could understand why anyone would buy a rifle that was not reliable and change parts instead of sending it back to the manufacturer as many times as necessary until it was.

I have to admit I put a little bit heavier buffer in my Cybersport and the other day when I was shooting I was shooting it and the new Sport with the stock buffer. They both ejected fine but the new one jumped more than my older one with the same ammo. I do not think that I will replace the buffer though, it did calm down the recoil but the recoil is not that bad and I have had second thoughts about the necessity of it.

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Grover Oathkeeper

I know with my 15-Sport, your statement is true. Given that I know of a few 15-Sport owners that have installed a heavier buffer, I feel comfortable generalizing your statement to the 15-Sport.


Stebo... breathe man... breathe...

The Colt vs everything else in the world thing does get me riled up. C4IGrant does rub me the wrong way at times (and vice-versa), but:

Many civilian AR15 rifles are over gassed. Over gassing provides more pressure to act upon the BCG, ensuring that the rifle cycles most ammo. A rifle that cycles most commonly available ammo reduces the vendor's customer service call center workload. Most AR owners won't ever realize their rifle is over gassed because they'll never bother to learn more about the AR platform other than "it shoots".

So the Colt is gassed at whatever is considered "normal"and gets to use a semi-auto BCG with a carbine buffer. Who cares? Say the Colt owner decides to avail himself of inexpensive ammo. The carbine buffer is the lightest buffer (that I am aware of). They would have to then use a reduced power buffer spring.

The point being that there are so many combinations to get your rifle running exactly the way you want. Semi-Auto BCG v.s. the heavier Full Auto BCG. Carbine, H, H1, H2 buffers. Regular, reduced, increased power buffer springs. Part of the fun of AR15 ownership, at least for me, is trying to get my rifle just right for me.

You're right. The recoil energy produced by a given round of .223 ammunition is always the same. Regardless of the position where the spent case is thrown, ejection of the case is ejection of the case.

What we're discussing is reducing perceived recoil.

Round of ammunition is fired > hot propellant gasses are bled off down the gas tube > the bled off propellant gas has to overcome resistance of the static mass of the BCG, buffer, and compress buffer spring.

On the return trip, the spring has to provide enough resistance to arrest the rearward motion of the BCG, then use the stored energy in the spring to drive forward the BCG & push a new round into battery.

Too much gas and the BCG cycles faster/harder increasing perceived recoil. Not enough gas and the BCG will not fully cycle, but perceived recoil is greatly reduced.

The different weight buffers is the easiest way for me to increase or decrease the total static mass on which the propellant gasses must overcome.

Finding the right buffer weight puts my rifle in the "Goldilocks" zone. The BCG action is not too fast or slow, felt recoil is reduced, the action reliably cycles, ejection patterns stabilize, and I'm a happy camper.

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-John

Thanks, John. Feelin' good now.

It's amusing that our resident lurker/S&W basher should jump in to trash the M&P (once again) and then advertise his website to M&P owners. I'd have to be really, really desperate to ever buy from this guy.

I've attached a chamber pressure chart that visually reinforces your comments. A carbine length gas system is what it is.

Attached Images

Chamber Pressure.jpg (19.3 KB, 156 views)

Stebo..shouldnt that ammo have been 5.56x45? The listed chamber pressure far exceeds the safe published limit for .223 ammo at least according to SAAMI. The pressure indicated was in the Range listed for 5.56x45, I suppose it is not a big deal it was just one of those things that make me go hmmmmm!

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Grover Oathkeeper

I know it is a hard pill to swallow, but there are SET STANDARDS for two of the three gas systems. The GP size for the 14.5" M4 barrel is .063. This same size is also used for the 16" barrel (though that makes it slightly over gassed IMHO).

With the mid-length gas system, there is no set standard for it and so companies like BCM, DD, Noveske, etc do cyclic rate tests on their GP sizes to establish a baseline of about 700-800 RPM.

The above mentioned companies + LMT, KAC, etc will all shoot lower pressured ammo (like Wolf). These companies also use H buffers in their guns. So if you think about it, if these guns will run lower pressured ammo with a heavier buffer than what S&W uses, what does that say about S&W's GP size????

My earlier post wasn't trying to get anyone to NOT buy a S&W AR or to sell the one they have. It was an effort to educate them that there AR has more felt recoil than other brands (because it is over gassed) and how they can remove some of it. If they don't want to follow my advice, that is fine with me, but at least I shared some technical knowledge in attempt to get their AR's to run better.


C4

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Mr Grant. I do appreciate your sharing your knowledge with us. I happen to agree, that the Sport anyway, is slightly overgassed because a slight weight change in the buffer will smooth out the operation. Sir in light of some of your previous posts you do seem to have the ability to put the bulk of us on the defensive, after your derision of our rifles, I am included in that group. But thanks again.

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Grover Oathkeeper

Reliable means different things to different manufactures. The Govt says that a 14.5" barrel with a carbine gas system MUST come with an H buffer. This adds cost to the guns price as it issues one Tungsten weight.

So if you think about it, how can a 16" barrel (that has more dwell time than a 14.5" barrel) use a CAR weighted buffer (which is what S&W uses) and achieve optimal reliability???

When we add heavier buffers to guns it is to reduce felt recoil, lower the cyclic rate and slow down the unlock time of the bolt. On top of this, if you are using a Suppressor, you would change that H buffer to an H2 or H3 (depending on barrel length) to help slow down the bolt head speed thusly making the gun more reliable.

Realize that most gun manufacturers (RRA, DPMS, BM, S&W, Oly, etc) DON'T include H buffers in their guns for ONE REASON. Cost! So when you look at people adding H, H2 or H3 buffers and think that they are changing the reliability of their AR (in a negative way), think again.





C4

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S&W LE Distr.

You know what is funny is that on other forums, I am known as the S&W "Fanboy!" Imagine that!

We are a S&W Distributor. We make our living selling S&W products. I am a big fan of S&W firearms and many of the AR's you see today is a DIRECT reflection of my input to S&W.

With that said, the TRUTH IS THE TRUTH and I am not the kind of dealer that lies about the products he sells (I know that is a 180 from other dealers that will tell you every firearm is perfect/best).


C4

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S&W LE Distr.

I could walk onto the Colt, Ruger, DPMS, BM, etc dedicated fan website and everyone would tell me that THEIR gun is perfect in every way and nothing is wrong with it. This phenomenon is called "being married to your purchase." If people perceive that there is something wrong or not perfect with their gun, car, house, etc, it is a direct reflection on who they are as a person. This is of course SAD, but is the norm on every gun forum I read.

For instance, Colt doesn't make a mid-length gas system. Why? Their engineers believe that there is no benefit (from a reliability standpoint) to make one. While this quite possibly true, the fact remains that the commercial market LOVES middy gassed guns and to not offer a gun with this gas system in moronic!

If I stated the above on a Colt fanboy forum, they would scream from the hills that I was a Colt "hater." Funny how both the S&W AR owners and Colt AR owners would both equally hate me (even though I sell both brands and am fans of both companies).

I am not trying to put "down" anyones AR choice. I am simply trying to get people to realize that it can be made better with small changes. That is all. At the end of the day though, I would much prefer everyone save their money and attend some training classes so they could actually learn how to properly run their firearms.


C4

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I do agree with your last statement. I grew up hunting and fishing. I then had a lot of training in the Marine Corps. And I mean a lot. Everything from cold weather survival to jungle operations training. I didnt buy my Sport to be used as a tactical rifle. I bought it to hunt varmints with it. But people who buy this platform with a tactical intent should take training courses, you tend to do what you practice. In case of a TEOTWAWKI situation, I would hunker down in the mouth of my late 50's early 60's era Nuclear Fallout shelter and pick off the bad guys at a distance. I wouldnt be runnin and gunnin. LOL (to old and fat)

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Grover Oathkeeper

LOL, your not "old and fat," your wise and husky! :-)


C4

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Grover,

I offered the chart to visually show the difference in pressure between a rifle length and carbine length gas system. You can see that the carbine approaches twice the rifle.

A statement that "So when you look at people adding H, H2 or H3 buffers and think that they are changing the reliability of their AR (in a negative way), think again" is patently false. I should have my 20" rifle length system up and running within a couple weeks. I am using a carbine weight buffer, not because it's "cheap" but because I expect it to run fine with that weight. Since that is the "cheap" way to go, should I use, say, an H2 (heavier is more expensive=better, right?). Heck no, using an H2 my new system would probably choke, maybe not cycle at all. So can you affect the reliability of your AR by installing too heavy a buffer? The answer is maybe, and as you install heavier buffers, the answer approaches certainly.

The weight of the A2 buffer and the H3 buffer are almost identical (FYI).


C4

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And the A2 tube/spring is 1.5" longer than carbine tube/spring (FYI). Apples and oranges.

You comment implied that an H2 buffer would cause short stroking in a rifle length gas system due to the weight. I simply stated that the A2 and H3 are the same in weight.



C4

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I'd bet full auto cyclic rate and suppressor back pressure is beyond the scope of most discussion on this board. However, other items that are seldom considered during any discussion of dwell time and "over and under gassed" are the total weight of the bolt carrier group and the compression rating of various rebound springs. Changes in either could increase or decrease the bolt head speed.

More importantly, I have never seen any discussion of powder burn rate and port pressure. Any of us that are old enough to remember when the M16 was first fielded and the powder was changed to a burn rate different than the design specifications well understand exactly how that will affect function.

I cut my reloading teeth on M1 Garands. Too slow a powder will damage the platform by "over-gassing" the system. Too fast a powder will cause short stroke malfunctions by "under-gassing". The DGI operating system of the AR15 is much more forgiving, but you can change the functioning by altering the powder burn rate.

Even though Grant and I disagree on some things, I'd still buy from his store.

Prices are decent. More important is that the business owner is active on this board. Most guys would be happy to take my money and not converse with me.

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-John

I built a dedicated suppressed 10.5 several years ago. I selected an out of spec GP size (too small to cycle the gun reliably). I then put a suppressor on the gun and used an LMT FA Enhanced Carrier. The suppressor generated enough back pressure to not only cycle the gun, but to lock it back on the last round! The LMT enhanced carrier has three vent holes in it to remove more of the excess gas (instead of just blowing it into the receiver). This combo proved to be a VERY reliable setup (probably the most reliable gun I have ever built).

It would be interesting to mess with faster and slower burning powders to see what that does!



C4

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Thanks. We are gun guys and shooters just like you folks are. I enjoy sharing information and learning (which is what forums are about).



C4

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I really think people tend to over think the buffer "issue". I am currently only running CAR buffers because I actually get better reliability with them in my Spike's 14.5'' middy. I do have a couple spikes T2 buffers I may try in my sport, but running cheap ammo in a 14.5'' middy seems to want a lighter buffer.

My very first AR was a RRA 16'' CAR with a non chrome lined bore/chamber running a generic stock and CAR buffer. That was the most reliable and accurate AR I have ever owned. We used to shoot 500 rounds a day with that thing without a hiccup. This was before p-mags, and I was running a CAR buffer with SA bolt carrier with wolf ammo. According to the internet my rifle should not have worked. In four range sessions I shot 2k rounds of wolf with no cleaning or lube and it still ran like a top.

That's because 14.5" AR's barely run do to the lack of dwell time. So a car buffer does make sense in this gun (especially with **** ammo).

All AR's will run with a CAR buffer. The reason why manufacturers use them is because they are CHEAP. RRA AR's are typically over gassed and bet you could use an H3 buffer (and it would run).


C4

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I run a 5 oz buffer in my m&p 15A. Gun ran fine with the stock car buffer but the ejected brass hit the deflector so hard it put a sever dent in it. Switched the buffer to a 5oz and the dent is now just a mark. Works best for me since I reload the dent made me think it would be weak in that spot.