Buffer/Buffer spring for 18" Midlength

[302w 83]

My dad is building an AR, and I have no idea on what buffer he should be using. Right now he has an 18" midlength .223 Wylde barrel, and a M16A1 buffer from Sarco. Is this "right"? Is there anything that would be more reliable, and if so, why? 

 

I believe that gas system length and buffer weight need to correlate somehow, but I don't know for sure. 

[Scorpio64 5,156]

The barrel on my rifle is the same, 18" Wylde middy.  I used an A2 buffer tube and A2 buffer with an ARFX Skeleton stock.  Works good.  The length of the tube, weight of the buffer, length and tension of the spring will all affect the timing.  Basically, all the parts I used (except for the stock)  are the same for an M16 with a rifle length gas system so my set up on a mid length gas system cycles a little bit faster.  I don't have time to go into the technical details this morning but google is your friend. Others will surely chime in.

[T Bill 649]

There are basically two types of lower buffer systems for the AR platform, rifle length or carbine length.  These systems on the lower are independent of the upper used on the lower.  They are designed to be interchangeable with the uppers.  Now that said, some people prefer to tweak their operation of the rifle by using buffers of different weights to adjust the cycle speed of the bolt carrier, based on round charge, gas system on the upper, and bolt carrier.  This is done on carbine style lowers.  Rule of thumb is to use a buffer in the carbine buffer system that just allows the bolt carrier to cycle.  Making them the smoothest cycling combination possible.  If the lower has a carbine buffer system then increasing or decreasing buffer weight helps to get to this nirvana.  Carbine buffer weights are as follows.

Carbine 3.0 oz

H or H1 3.8 oz

H2         4.7 oz

H3         5.6 oz

Which one to use will depend on the factors listed above.  History dictates to start with a H or H1 and move up or down as desired.  If we are talking about 55/62  bullet weights with a mid length gas system and a m16 type bolt carrier then I would start with a H or H1 buffer.

[Vlad G 345]

You can tune either rifle or carbine systems equally well. 

 

Short version though: Any upper can go on any lower. You can use a short carbine type upper with a rifle length recoil systems and you can use a 20" rifle type upper on a carbine type lower. 

 

Don't start messing with buffer weights unless you have any issues with function, or if you want to make it smoother once it already functions. 

[Eric. 9]

Good replies, so far.

 

Just to add, the difference with the carbine length is that the bcg gets thrown back faster/harder due to the shorter gas port location.  If the bcg is slamming on recoil, that is the reason you add buffer weight.  

 

Basically, you want as little bcg action possible with the gun still reliably cycling.  The rifle length is the softest shooting length.  The mid is, well, between the rifle and carbine.  If the gun can cycle reliably, then stick with the rifle/A2 buffer.

 

Anyway, I run an 18" mid length barrel with a rifle A2 stock/ buffer.  I have no cycling issues.  

 

Also, be sure to run your bcg wet.  Lube it well.

 

 

Eric

[n4p226r 105]

if he is using a m16a1 buffer, then he has the rifle buffer tube and spring.   you would need to replace the whole buffer tube, spring, buffer, stock and get a castle nut and end plate to change that out.