AR pistol new build with issues

[Rex B]

I bought 2 kits from a national brand company at a gun show last year. One of these was the 7.5" AR pistol complete kit less lower.

Since completing this build recently, I am having cycling issues. The gun does not return to battery. All is well in the upper, but I note the buffer is 3-oz. Shouldn't a 7.5" 5.56 upper need a heavier buffer? What would you recommend?

 

[Rex B]

Since that first post I did some research on buffers. All the guidelines say a 10.5" pistol should use an H2 (4.6-oz) or H3 (5.0-oz) buffer. My kit came with a 3-oz buffer, which makes it an H1 - for 16" barrels.
So I took it apart. the housing, crosspin and pylon tip all weigh 1 oz, and the weight itself weighs 2.1 oz. The weight was s long as the cavity, and made of mild steel.
So I had some brass stock, which is heavier than steel. I turned a weight to max length and weighed it - 2.7 oz. for a total assembly of 3.7-oz - far short of the 4.6+ oz goal.
The only way I know to get more mass in this carbine-length buffer is with lead, which is too soft, or tungsten, which is much more expensive than any of these.
So this company packs a 10.5" pistol kit with the wrong weight buffer to save a dollar or so.

I'll order some buffers and try it again.

any other suggestions/insights welcome.

 

[mavracer]

They sell just the tungsten pucks to make the heavier buffers. IIRC they weren't that expensive.

 

[Shawn Dodson]

FWIW, there's no such thing as an "H1" buffer. It's just "H" then H2 and H3.

As mavracer noted, you can purchase tungsten weights to make H2 and H3 buffers. KAK sells them, $10.75 - https://kakindustry.com/buffer-weight-tungsten

 

[Rex B]

Shawn, thanks, bookmarked. Looks like it would take 3 to get where I need to be.
So, if the weights needed do not fill the tube, do people usually fill the balance with aluminum, nylon or something?
I have had some where the weight can move back and forth inside the tube. Is there an advantage or disadvantage to this? Or makes no difference?

Does anyone use lead? Any reason not to?

 

[mavracer]

So, if the weights needed do not fill the tube, do people usually fill the balance with aluminum, nylon or something?

BUFFER WEIGHT SPACER

Enhance your firearm's recoil management with our buffer weight spacer. Fine-tune your shooting experience for improved control and accuracy.

kakindustry.com

Does anyone use lead? Any reason not to?

I don't, the tungsten pucks are the easy button so my question would be why use lead?

 

[C-grunt]

In my opinion the 3 oz buffer is pretty much never the correct one to use. A heavier buffer will slow down the action and give you more oomph when chambering. Both things should improve the reliability of the pistol.

 

[Rex B]

BUFFER WEIGHT SPACER

Enhance your firearm's recoil management with our buffer weight spacer. Fine-tune your shooting experience for improved control and accuracy.

kakindustry.com

I don't, the tungsten pucks are the easy button so my question would be why use lead?

Because I'm going to the range tomorrow and would like to experiment with what I have on hand. I have lots of brass on hand. I"m considering making a buffer entirely of brass, except for the plastic tip.
I turned a brass weight to fill the tube which got me to 3.9-oz. I'll see if that makes any difference.

I suspect I'll end up buying a range of weights rather than the pucks. Just personal preference.

In my opinion the 3 oz buffer is pretty much never the correct one to use. A heavier buffer will slow down the action and give you more oomph when chambering. Both things should improve the reliability of the pistol.

That's pretty much what I'm finding out. I'm about to finish a 16" carbine, so the H1.5 buffer I just made will likely end up in that.

And now I need to test-fire a couple of carbines I put together years ago and never fired.
I think I'm going to order an assortment of buffers, and probably some of those tungsten pucks.

 

[Ethan Verity]

Shawn, thanks, bookmarked. Looks like it would take 3 to get where I need to be.
So, if the weights needed do not fill the tube, do people usually fill the balance with aluminum, nylon or something?
I have had some where the weight can move back and forth inside the tube. Is there an advantage or disadvantage to this? Or makes no difference?

Does anyone use lead? Any reason not to?

The weights are supposed to slide back and forth slightly in the buffer tube to act like a dead blow hammer. This is to dampen bounce back when the bolt slams into battery, specifically to prevent a malfunction in a full auto rifle where the hammer will already be falling again the moment the bolt hits home and triggers the auto sear. For a semi-auto only AR, this is less important, maybe even completely irrelevant.

 

[Shawn Dodson]

Shawn, thanks, bookmarked. Looks like it would take 3 to get where I need to be.
So, if the weights needed do not fill the tube, do people usually fill the balance with aluminum, nylon or something?
I have had some where the weight can move back and forth inside the tube. Is there an advantage or disadvantage to this? Or makes no difference?

Does anyone use lead? Any reason not to?

You should already have a tungsten weight in your buffer, if it's an H buffer; therefore, you'll only need two more tungsten weights to make it an H3.

The weights are supposed to slide back and fourth inside the buffer. The loose weights act like a dead blow hammer to reduce bolt bounce when the BCG goes into battery.

Carbine buffers have three weights in them, either all steel for a standard carbine buffer or a combination of steel and tungsten for H, H2, and H3 configuration.
Vltor A5 buffers have four weights.
Rifle buffers have five weights.

Aluminum weights are non-standard.