Buffer lengths/weights- effect it has on rifle with collapsable stock... info?

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RacerSTA

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Hi There;

This may be a dumb question.... I'm just trying to educate myself a bit more on the AR15 so my apologies if this is covered somewhere. Search did not help me to much...

Question:

I understand that if you use a collapsible stock you need to use the carbine length buffer and spring. Why? Is this because of a physical size limitation of the 6 position bufffer tube or another reason?

For example if I switch my A2 stock on my rifle length AR to a collapsible 6 pos. stock the gas system and bolt are not changed, so I assume the buffer and spring are only changed due to size constraints. If the answer to this is yes, its only due to physical size reasons, than are you loosing any performance on a rifle length AR by installing a carbine buffer/spring?

Any thoughts or explainations are really appeciated so I can understand whats happining here and how buffer length/weight affects performance in 16" mid-length and 20" rifle length AR's...

Cheers!
 
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Buffers and springs

RacerSTA said:
Hi There;

This may be a dumb question.... I'm just trying to educate myself a bit more on the AR15 so my apologies if this is covered somewhere. Search did not help me to much...

Question:

I understand that if you use a collapsible stock you need to use the carbine length buffer and spring. Why? Is this because of a physical size limitation of the 6 position bufffer tube or another reason?

For example if I switch my A2 stock on my rifle length AR to a collapsible 6 pos. stock the gas system and bolt are not changed, so I assume the buffer and spring are only changed due to size constraints. If the answer to this is yes, its only due to physical size reasons, than are you loosing any performance on a rifle length AR by installing a carbine buffer/spring?

Any thoughts or explainations are really appeciated so I can understand whats happining here and how buffer length/weight affects performance in 16" mid-length and 20" rifle length AR's...

Cheers!
Click to expand...

Unmatched springs and buffers will cause short stroking and or failure to feed.
The carbine buffer tube and spring are different from the rifle, the spring being shorter and the buffer a different weight. The spring length allows for maximum buffer movement, the tension for chambering a round.
The buffer weight needs to be lighter for less powerful ammo ie - 55 grain .223 as oppsed to 62 grain nato ss109.
The buffer also needs to be lighter for shorter barrels especially with an efficient muzzle (less back pressure) brake as oppsed to a flash hider (more back pressure)
Also extremely short barrels dont build as much gas pressure as longer barrels as the powder is not efficiently burnt in the bore, less bolt thrust, thus requiring a lighter buffer.
The shorties also blow a lot of unburnt powder onto the bolt and the grit slows the action down, thus requiring a lighter buffer --:ar15:
 
Chopper1: Great info and it does help me understand this stuff better in a general sense, thanks very much!

I am still baffled about this though... I understand the carbine buffer and spring are different than in the rifle because the gas system is a different length and has different characteristic that impact the cycling. What I am still trying to understand is why when switching a rifle (or mid-length) to a collapsable stock do we need to change the buffer and spring to the carbine version, and more importantly does it have any detrimental effects on performance or is the change negligable?

I would have thought that since the gas system is unchanged that the buffer and spring (although maybe required to be physically different in length, size, weight, etc to fit the tube) would still need to have the same characteristics as the rifle parts for proper operation.

Very sorry if I am thick headed and just not seeing the obvious here...
 
Juliet Lima... Ok I understand there is a physical difference in length of the buffer tube so that accounts for why we need to change parts int he first place.

Since we are still dealing with a rifle gas system though I would have thought that the lighter spring and buffer of a carbine would not be ideally suited to a rifle. I can only assume that since it works that the changes must be negligable but I can't help but still wonder if the rifle bolt/carrier is not taking a bit of a beating by the lighter carbine buffer not providing as much resistance.

I am very likely missing something in my understanding so I do appreciate your responses...
 
A heavier buffer is often used with short barrel ARs to improve function and reliability due to the extremely short and violent nature of action cycle created by the abreviated gas system. The heavier buffer serves to delay cycling enough to ensure there is enough time for proper feeding of rounds while reducing the actual physical beating the rifle would otherwise take from such a violent action cycle. Makes for a better, more enjoyable shooting experience. Going with a lighter buffer in a shorty is definitely not recommended! I usually try to get away with an H/H1 Buffer in my shorty builds, if I can, but some builds simply demand an H2. I haven't had reason to use anything heavier thus far.
 
Buffer weight

X-man said:
A heavier buffer is often used with short barrel ARs to improve function and reliability due to the extremely short and violent nature of action cycle created by the abreviated gas system. The heavier buffer serves to delay cycling enough to ensure there is enough time for proper feeding of rounds while reducing the actual physical beating the rifle would otherwise take from such a violent action cycle. Makes for a better, more enjoyable shooting experience. Going with a lighter buffer in a shorty is definitely not recommended! I usually try to get away with an H/H1 Buffer in my shorty builds, if I can, but some builds simply demand an H2. I haven't had reason to use anything heavier thus far.
Click to expand...

Always use the heaviest buffer that matches.
Only go to a lighter buffer if you have a short stroking problem because of above quote.
Fine tune the weight to exactly match your gun and ammo,which can be done by drifting out the pin in the buffer and adding or removing weights.
U can use 45 cal wadcutter bullets trimmed shorter if you dont have buffer weights.
But tuning only if your gas tube and and front gas block and barrel hole are all correct.
Usually done on short short A R's that are prone to short stroking due to insufficient gas dwell time in the extra short gas tube.
You want to attain the optimum cycling reliability with the optimum recoil battering for the ammo.
The hotter the load the heavier the buffer.
 
Ok, now I am getting the relationships. Thanks very much guys!!

Ok, can I assume then that even thought the physical buffer tube length is different in a carbine vs a rifle, that the carbine weight buffer and carbine spring rate setup is designed to end up giving roughly the same overall cycling performance as a rifle weight buffer and spring rate. Hence when using a carbine buffer and carbine spring in a rifle (when using a collapsable stock), virtually no performance is given up and no buffer tuning is needed?

I think I am worry about nothing... but its fun learning!
 
yep

RacerSTA said:
Ok, now I am getting the relationships. Thanks very much guys!!

Ok, can I assume then that even thought the physical buffer tube length is different in a carbine vs a rifle, that the carbine weight buffer and carbine spring rate setup is designed to end up giving roughly the same overall cycling performance as a rifle weight buffer and spring rate. Hence when using a carbine buffer and carbine spring in a rifle (when using a collapsable stock), virtually no performance is given up and no buffer tuning is needed?

I think I am worry about nothing... but its fun learning!
Click to expand...

Should be good 2 go :)
 
juliet lima said:
The carbine buffer is heavier, not lighter.
Click to expand...

This is incorrect. I don't have the exact weights in front of me, tried to find a chart I'd seen but was unable to.

The rifle buffer is longer than all the others, it's also the heaviest.
The others I've listed from heaviest to lightest.
9mm
H3
H2
H
Carbine

The original Carbine buffer is usually found to be too light and results in stoppages this is why all the other buffers exist. I can't tell you what buffer will work best for you, too many variables with gas tube length, gas port location, size of gas port, etc.. I will tell you that when the Army switched to the C7A2, which uses a 20" rifle barrel with a collapsible stock, they put the H2 buffer in. Apparently it was found to be the most reliable buffer weight for the greatest number of barrels (10", 14.5", 16", 20") since some small units use more than one upper per lower.

If your upper works fine, than I probably wouldn't bother messing with it, but if you can't resist than try an H2 and work backwards from there if it give you problems.
 
weights

Leg said:
This is incorrect. I don't have the exact weights in front of me, tried to find a chart I'd seen but was unable to.

The rifle buffer is longer than all the others, it's also the heaviest.
The others I've listed from heaviest to lightest.
9mm
H3
H2
H
Carbine

The original Carbine buffer is usually found to be too light and results in stoppages this is why all the other buffers exist. I can't tell you what buffer will work best for you, too many variables with gas tube length, gas port location, size of gas port, etc.. I will tell you that when the Army switched to the C7A2, which uses a 20" rifle barrel with a collapsible stock, they put the H2 buffer in. Apparently it was found to be the most reliable buffer weight for the greatest number of barrels (10", 14.5", 16", 20") since some small units use more than one upper per lower.

If your upper works fine, than I probably wouldn't bother messing with it, but if you can't resist than try an H2 and work backwards from there if it give you problems.
Click to expand...

Rifle - 5.2 Oz - 5.905"
Carbine - 3 - 3.250"

H - 3.8 Oz. - 3.250"
H2 - 4.6 ''
H3 - 5.4 ''
 
Leg/Chopper 1: Thanks for straightening this one out... I was pretty sure the carbine buffer was the lighter of the bunch.

One also obviously has to take into account the spring length and spring rate as well when looking at the overall package as the buffer weight and spring rate relationship factors in.

Leg: Any idea what spring length/rate the army used when using the H2 buffer in the C7A2?
 
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RacerSTA said:
Leg/Chopper 1: Thanks for straightening this one out... I was pretty sure the carbine buffer was the lighter of the bunch.

One also obviously has to take into account the spring length and spring rate as well when looking at the overall package as the buffer weight and spring rate relationship factors in.

Leg: Any idea what spring length/rate the army used when using the H2 buffer in the C7A2?
Click to expand...

Carbine springs are all the same as far as I know. Some companies do make extra power springs, flatwire, chrome silicone, etc.. but I don't believe that they're in use by any military. For all intents and purposes their are only two spring types, standard and carbine, the only difference being that the standard spring is longer because of the longer buffer tube.
 
Just for info, I have two full length rifles I have fitted with "Carbine" butts so that shooters of shorter stature can use a rifle that fits properly. My wife's rifle has a 26" SAKO barrel (We had it lying around) with a free flat tube (Houge) and a magpull butt stock. The other one I built has a standard M-16 lightweight barrel on on old Colt A2 upper with a 6 position carbine buttstock. Both function very well with no ill effects from the rifle barrel and carbine butt combination observed. I actually find that there is less "Felt recoil", such as recoil is with .223, and shot placement is improved with a proper length and fitting stock!

Scott
 
Now that we are on to all this technical wonder... I prefer shooting the 16" midlength barrel/gas tube because of the less violent action found in the abbreviated gas tubes of carbine reputation. Mind you my wife's 14.5" carbine was a perfect setup, she loved it and never experienced a FTF or FTE or any other magazine problems. :D

So can any of you AR experts confirm that joy of using the 16" midlength ?

Cheers,
Barney
 
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