I recently built a rifle in 7.62x39. It has a rifle buffer and a carbine gas system with a linear compensator. The recoil is a lot more harsh than I expected. Because of conditions at the range I do not know what direction it was ejecting, so I am not sure if it is over/ under gassed. Each spent case seemed to be ejecting around the 3 o'clock position, but the barrier (indoor range) was bouncing them back at me so it is hard to say for sure. I fired the first few shots without the linear compensator, and then I screwed it on and fired the rest. The compensator did not seem to affect recoil much.

What I would like to know is if it might be worth it to add or change the weights to the rifle buffer to slow the action down. Would this be worth the effort? Could this cause more problems for me?

With carbine gas, you're almost certainly over-gassed. You could try a couple things - an adjustable gas block (JP, Syrac, SLR) or you could try using a couple carbine buffer setups varying the number of weights in them, or use a Spikes ST-T2 or ST-T3 heavy buffer.

I would go put a heavier spring and buffer. Check out Sprinco. I believe there website is tacticalsprings.com . They should have a recommendation on there or call them. Something like a blue sprinco spring and h2 buffer is a good place to start and adjust from there.

I have a carbine length 16" 7.62x39 that could use a little more tweaking as the recoil is sharp and I've noticed the buffer face is getting marked up a little indicating it is bottoming out in the tube pretty hard. X power springs should help with more reliable extraction in some cases where the extractor has very heavy springs preventing the extractor from fully seating over the rim when manually working the bcg. But a kies adjustable gas block ($33) is most likely the next cheaper step an will probably solve the issue.

The receiver extension, buffer, and spring are for a rifle. If I start putting carbine buffers and springs in the tube, I'll need a spacer. I'm hoping to avoid changing the gas block.

I have another build on the back burner right now that will need a buffer, and I was thinking about buying an H3 carbine buffer, and swapping the tungsten weights from the H3 with the steel weights in the rifle buffer, so that I'll have a standard carbine buffer for that build and a heavy rifle buffer. I a wondering if a heavier than normal rife buffer could cause me further issues.

You could swap buffer weights if you wanted.  A rifle buffer is already around 5oz, so I would probably get an adjustable gas block.        
 

Thanks for the replies everyone.

Definatly get an Adjustable Gas block. My brother has an MGI with an SLR adj. gas block and we had to adjust the block all the way down to about 1/4th open to have it just enough to feed a round. We also took the weight out of the buffer to make it a 1oz buffer to reduce recoil.

After you adjust the gas block, the BCG is cycling slow and a buffer is not really needed.

Here is a video after the gas block was adjusted:

http://www.youtube.com/watch?v=kXFjeDkJ09M

We got .3" groups CTC with a scope at 50 yards.

Buffers serve for more than just adding weight.  I would prefer to reduce weight on the carrier and keep reciprocating buffer weight.

Buffers serve for more than just adding weight.  I would prefer to reduce weight on the carrier and keep reciprocating buffer weight.

**Update**

I modified my existing gas block to be adjustable, and it helped a lot. I ran 40 rounds through it today, and it shot considerably more smooth than before.

Any info/pics of the work you did?
I just ordered my 7.62x39 barrel for my build.

Drilling the first hole was slightly nerve-wracking. It isn't exactly obvious where to drill, and I didn't want to miss the gas passage. Feeling the drill bit break through the wall and into the passage was VERY satisfying...Start with a small drill bit and work your way up. The last bit size that I used was a #36. I used a 6-32 tap to cut the threads.

Unfortunately, I broke off the end of the first tap in the gas block. I used an inverted can of computer duster gas to freeze the tap, and then I hit it with a center punch to shatter it. That sort of worked, but most of the tap ended up deeper in the gas block, so I had to disassemble everything I did on that barrel up to that point to remove the gas block and fish out the rest of the tap.

You will either need to slightly overdrill the hole or use a bottoming tap to finish cutting the threads, since the tapered point on a standard 6-32 tap will bottom out before the threads are cut all the way through.