Buffer spring question.

[Carter]

I'm going to be purchasing a 20in upper for my ar-15 to replace the 16in upper that I have. Do I need to replace the carbine buffer spring with a rifle buffer spring to ensure reliability?

Ill be using the standard carbine lower with the 20in upper. I know its not exactly a "kosher" idea, but I like it, and plan on replacing the stock or entire lower at some point to help balance it out a little more.

Finally, I usually run silver bear and brown bear for target practice to save on money. Will this effect reliability in the lower pressure rifle length gas system? And if so, which spring would help prevent this.

Thanks.

I'm kind of knew to customizing ar's so forgive my ignorance.

 

[Bartholomew Roberts]

No, you'll pretty much have to use the carbine action spring because it is shorter than the rifle action spring. You may need to play with the buffer weights to get the ideal function; but it should run with what you've got.

 

[Carter]

Okay, thanks.

Not really sure how the buffer weights vary, but google shall answer I'm sure.

Little reading said to use an H2 buffer weight.
Anyone with experience have a comment on that?

 

[Joel P]

Carter,
Tha carbine buffers are from H1 to H3. The rifle buffer is an H4. Please don not put a rifle buffer, (H4), in the carbine stock. The rifle buffer is longer and heavier which will not fully compress the carbine spring. The Heavy duty H3 is most likely your best bet. You can get a heavy duty buffer AND a heavy duty, (stiffer) spring, (both together) for a carbine. Probably just need the HD buffer for most applications.

You would probably only need the heavy duty buffer and spring for the hotter tactical loads. Since I don't shoot Wolf or Bear thru my AR's, I don't know if they are light or on the warm side. I would highly suggest to reload for your AR. It really brings out the most bang-for-your-buck with quality ammo, (my opinion).

Just my $.02 worth,

Joel

 

[Bartholomew Roberts]

OK, the first buffer to be developed for the M16 series was the rifle buffer. It weighs 5.2oz. When the requirement was made for the Colt Commando XM177 series of rifles, they introduced the carbine buffer and action spring, which weighed 3oz, and was designed to work in the shorter lower receiver extension that the telestock used.

Over time, the M4 was developed and it was determined that the original carbine buffer did not do the best job of slowing the cyclic rate and giving proper timing, so the "H" carbine buffer was introduced (The H is for "Heavy"). This weighs 3.8oz and has an "H" stamped on its face.

Subsequently, people began playing with the buffer weights to adjust the timing on the various ARs for specific uses (suppressed, SBR, etc.) and you have the H2 (4.6oz), H3 (5.4oz). All of these are carbine length buffers and do not work in a rifle length stock extension. That is pretty much all there is in terms of Colt buffers designed for the 5.56mm M16 FOW.

Vltor makes a carbine buffer they call an "H4" which weighs in at 6.8oz. However, it is not a rifle buffer. Vltor also makes what they call an A5 stock kit that uses a slightly longer lower receiver extenstion and a slightly longer buffer that is neither carbine nor rifle.

However, my advice would be to shoot what you have. You should see ejection between 3 o'clock-5 o'clock. If you are getting in front of 3 o'clock and the action spring is good (between 10.75" and 11.75" long for standard military carbine action spring), then consider a heavier buffer. If you are getting behind 5 o'clock and the action spring is good, then consider a lighter buffer.

 

[TonyAngel]

If you are just going to be running the 20" upper with a carbine length buffer tube and buffer, I'd say just run it and see what happens. Odds are that it will run just fine. If you left the carbine in stock form with a stock buffer and spring, you're probably good to go.

Like B. Roberts said, take note of your ejection pattern. If it's kicking the brass out front, you're over gassed and a heavier buffer will likely be in order (but this is not likely with a 20" upper). If it is kicking it out to the side, then all is good. If it is kicking the brass over your shoulder and behind you, the buffer/spring is too heavy or you have a gas leak or bad rings.

I wouldn't worry about it unless a problem manifests itself. I ran an 18" upper with a carbine recoil system for a long time without issues.

 

[tkcomer]

The springs are the same with both stocks. Carbine buffer with a carbine stock. Rifle buffer with a rifle stock. Put the upper on and don't change a thing. It should work OK. When you get a rifle upper, then you'll have to change out the buffer.

 

[Z-Michigan]

Carter,
Tha carbine buffers are from H1 to H3. The rifle buffer is an H4. Please don not put a rifle buffer, (H4), in the carbine stock. The rifle buffer is longer and heavier which will not fully compress the carbine spring. The Heavy duty H3 is most likely your best bet. You can get a heavy duty buffer AND a heavy duty, (stiffer) spring, (both together) for a carbine. Probably just need the HD buffer for most applications.

This isn't quite right.

Standard rifle buffers come in only one weight, which is simply "rifle buffer." They contain 5 sliding little steel weights. It's possible to take one apart and add tungsten weights to make it heavier, but that's not normally used and I don't think it's even commercially available.

Carbine buffers come in:
carbine (standard weight, 3 steel weights) (no marking on flat end)
H1 (flat end marked "H") (contains 1 tungsten and 2 steel weights)
H2 (flat end marked "H2") (2 tungsten, 1 steel)
H3 (flat end marked "H3") (3 tungsten)
oddballs like Spike's ST-T2
9mm buffer

There is also the brand new VLTOR A5 system, but you aren't likely to encounter one of these unless you special order it. It uses an intermediate length tube and an intermediate sized buffer, with a rifle spring.

OP: I have a 20" rifle running with a carbine lower, with a carbine buffer and spring, and it runs 100% reliably, no problems. Balance is a little off but it works fine. Canadian forces use a similar setup as their standard rifle.

Easy to remember rule: all components of the recoil system must match each other, but do not need to match the upper setup (in terms of barrel or gas system length).

So, use either carbine buffer, tube, and spring, or rifle buffer, tube, and spring, and don't mix parts from one type with the other.

Rifle recoil setup generally works with nearly all uppers. Carbine recoil setup is a bit more finicky and often benefits from trying different buffer weights to get the best match.

 

[Bartholomew Roberts]

The springs are the same with both stocks.

This is not correct. The action spring for a rifle length lower extension (buffer tube) is longer than the action spring for a carbine lower extension. This is why action springs are sold in carbine and standard lengths.

 

[Z-Michigan]

Re: springs, they are different not only in length but also in stiffness, with carbine being significantly stiffer. You can actually feel the difference if you work the action on the two systems side by side. I am noting this so that no one tries to simply clip some coils off a rifle spring to get what they're hoping would be a carbine spring.