Buffer spring questions

[pcar]

still new on learning the mechanics of the AR-15 so please forgive any stupid questions, I am making the most out of my new rifle that is short-stroking.

• is the buffer spring considered part of the gas system?
• will the length of the spring decrease a non trivial length after use?
• is there a variance in spring length (not coils, but distance between) with same make/model of rifles and still be in spec?

[joelogic]

There are two different springs. Carbine and rifle which must be used with their respective buffers.

Which are you using?

I guess.
Yes.
No. All springs of a given type should be the same length.

[pcar]

There are two different springs. Carbine and rifle which must be used with their respective buffers.

Which are you using?

I guess.
Yes.
No. All springs of a given type should be the same length.

I have a Daniel Defense m4v2 from several years ago that has an H buffer and the spring length is 10.5". 3k+ rounds, never any problems. I did not think to measure the length when I purchased it.
I just got a DD m4 v5 lw that also has an H buffer, spring length is 10 3/4".
So I am pretty sure they are both carbine buffers.

[m16]

Yes there is a variance.

Download copies of the technical manuals for the M4 and M16 and read them, there are minimum and maximum lengths for both types of springs.

[Full Race]

I'd like more info on your rifle and how you know it's short stroking. Did you build it yourself or buy it whole? Could it possibly have an adjustable gas system? If you built it yourself, did you use a parts kit or buy the parts individually?

The spring won't matter as much as the buffer itself, as a rifle buffer is too long for a collapsible stock. If it turns out to be the spring causing the problem . . . which I highly doubt . . . it is easy enough to cut the spring.


If you bought it new, have you cleaned and oiled it yet? AR's are very sensitive to oil and need it to function properly. It may be greased from the factory, they don't run when greased.

All in all, more info please.

[joelogic]

Did the gun come with a H buffer? New springs are only a couple of bucks.

http://www.midwayusa.com/product/889492/ar-stoner-buffer-spring-ar-15-carbine

[m16]

Free length spec for a carbine spring is 10-1/16" to 11-1/4"

See page 47:

http://www.kdeguns.com/ar-manual/M4%2016%2023Pchange8.pdf

[pcar]

I'd like more info on your rifle and how you know it's short stroking. Did you build it yourself or buy it whole? Could it possibly have an adjustable gas system? If you built it yourself, did you use a parts kit or buy the parts individually?

The spring won't matter as much as the buffer itself, as a rifle buffer is too long for a collapsible stock. If it turns out to be the spring causing the problem . . . which I highly doubt . . . it is easy enough to cut the spring.


If you bought it new, have you cleaned and oiled it yet? AR's are very sensitive to oil and need it to function properly. It may be greased from the factory, they don't run when greased.

All in all, more info please.

I bought Daniel Defense M4 V5 LW. I have not made any modifications, and it did come with an H buffer.
The DD technical manual does not state regarding the action spring length but I found this from the Army TM 9-1005-319-23&P technical manual
"CARBINE ONLY: Free length
should be 10 1/16 in. (25.56 cm) minimum to 11 1/4 in. (28.58 cm) maximum."

My rifle is well lubed (Frog Lube, heat treated).
Several types of magazines which have no problems when shooting XM855 or when shooting from my other rifle.
I have taken it out a few times and the most common response I seem to get is, shoot it more and it will work better. So in part I am trying to figure out why it works better.

Today I went out and shot around 200 rounds total.
XM855 - no problems the entire day
XM193 Federal - shot a few magazines early and while there were no feed issues, the bolt did not lock back on empty 2/5 times. 100 rounds later, I did not have any problems.
.223 PMC - Start of the day 90% of the time the next round did not feed from the magazine. Last round did not open the bolt. At the end of the day I shot this ammo again. The round did get pulled from the magazine but the bolt did not close (like this, but this is not my rifle)

Unsure of the relevance but my brass was being ejected at 4 o'clock. Looking at the brass there were no markings that would clearly indicate any extractor problems.

The biggest difference between my two rifles is the gas system, I was just surprised to see a fairly significant difference in the spring length.

[Jason25]

I bought Daniel Defense M4 V5 LW. I have not made any modifications, and it did come with an H buffer.
The DD technical manual does not state regarding the action spring length but I found this from the Army TM 9-1005-319-23&P technical manual
"CARBINE ONLY: Free length
should be 10 1/16 in. (25.56 cm) minimum to 11 1/4 in. (28.58 cm) maximum."

My rifle is well lubed (Frog Lube, heat treated).
Several types of magazines which have no problems when shooting XM855 or when shooting from my other rifle.
I have taken it out a few times and the most common response I seem to get is, shoot it more and it will work better. So in part I am trying to figure out why it works better.

Today I went out and shot around 200 rounds total.
XM855 - no problems the entire day
XM193 Federal - shot a few magazines early and while there were no feed issues, the bolt did not lock back on empty 2/5 times. 100 rounds later, I did not have any problems.
.223 PMC - Start of the day 90% of the time the next round did not feed from the magazine. Last round did not open the bolt. At the end of the day I shot this ammo again. The round did get pulled from the magazine but the bolt did not close (like this, but this is not my rifle)

Unsure of the relevance but my brass was being ejected at 4 o'clock. Looking at the brass there were no markings that would clearly indicate any extractor problems.

The biggest difference between my two rifles is the gas system, I was just surprised to see a fairly significant difference in the spring length.

The picture on your link shows a mid length and states carbine. There is a difference and will function differently when it comes to buffer weights. If you have a mid length gas system,
Try running a standard buffer. If you're positive on 4 o'clock ejection, that is good. However, 4:30 and farther is under gassed. Different ammo will hinder the performance due to different pressures. Your problem is probably just the ammo you are using. Im not sure of the difference between the XM 855 and the XM 193, but I'll bet that the 855 runs at a slightly higher pressure, therefore you experienced no problems. The PMC is well below these two. Lower pressured ammo will not cycle properly with a heavier buffer. This is where tuning comes into play. Get yourself a standard buffer and run it when using the XM 193 and PMC. Use the heavy buffer for the XM 855. Or just stick to one type of ammo that works.

* I just noticed the V2 has a carbine length gas system. So, the first part about a midlength gas system is irrelevant. However, the mechanics will be the same. Try a lighter buffer and swap them out per the ammo you use for the day.