So I just replaced my handguard/16" barrel/gas block assembly which was a carbine length. It cycled flawlessly for the 2k+ rounds it saw. It now has a 16" Midlength, and I had a couple cycling issues over several hundred rounds. I'd say it happened probably 4-5 times over those several hundred rounds. The case wasn't being pulled out of the chamber, and another round was being loaded, causing it to jam. My understanding is that would be a symptom of too much gas. That seems a little odd to me considering it's a midlength. Cases were ejecting strong at around 4:00 from what I remember.

 

So when I had it apart to clean and check everything, I weighed the buffer. To my surprise it is significantly lower than the 3oz advertised weight. It weighed in a 2.3oz. Yes, it was loud but, also cycled perfectly in the previous system so, I left well enough alone.

 

What I'm thinking is, the extremely light buffer is allowing the BCG to travel back too soon? The way I understand it is that the case is still expanded as the gas is traveling back to the BCG and should be timed so that the case is shrinking as it cams to unlock the bolt. If too much gas comes back too soon, the bolt would come back while the case was still expanded, leaving the empty case in the chamber, then cycling a fresh round into the back of the empty case.

 

Do I have this all right? Would a heavier buffer fix my problem?

Type of ammo? What does the rim of the case look like?

 

Agreed increased bolt carrier / Buffer weight increased the dwell time before the bolt unlocks but I'm not absolutely surer that's your problem.

 

If you want to go that route find some buddies weigh their buffers and swap them out for 50-100 rounds.

I had a similar problem with my 20" Colt MT years ago. I upgraded the extractor using a kit similar to this: http://www.brownells...TOR-UPGRADE-KIT

 

It solved the problem 100%.

just by changing from a carbine to mid length gas system should have lowered the overall pressure. So my intuition says that if it was too much gas, then you would have at least had the problem prior to switching barrels, it should have actually been worse. So my gut says it's either the ammo or the extractor.

If you have a 16" barrel, a midlength gas system block will be closer to the muzzle than the carbine gas block. That means less dwell time for midlength and less gas to operate the bolt. I had to switch to a spacer, carbine spring and H2 buffer on my Spikes 14.5 midlength upper. It would get exactly the same problem that you had with a rifle tube, spring and buffer.

I dont think its the ammo or extractor. Shooting the same PMC Bronze that I have been for a while without ever having issues. It was previously ejecting at about 2-3 o'clock with that ammo in the last system, so I know it has the pressure I need.The bolt is fairly new (1k rounds) and clean, but Im going to try the extractor spring kit from BCM just in case. I think I'll get a H and H2 buffer and see what works. I'll try it one peice at a time and report back when I do it.

The PMC ammo had the pressure you need for the carbine upper. It may be slightly undergassed for the new middie upper. I think testing with the H and H2 is the smart move. Use the heaviest one that still functions reliably. Considering this happens only once every hundred rounds or so, I bet the H2 is your ticket.

I dont think its the ammo or extractor. Shooting the same PMC Bronze that I have been for a while without ever having issues. It was previously ejecting at about 2-3 o'clock with that ammo in the last system, so I know it has the pressure I need.The bolt is fairly new (1k rounds) and clean, but Im going to try the extractor spring kit from BCM just in case. I think I'll get a H and H2 buffer and see what works. I'll try it one peice at a time and report back when I do it.

 

Depending on the manufacturer, most newer bolts will not require this kit... Also if you have never tried to assemble a bolt, without the proper tools DO NOT take your bolt apart, it is a severe PITA to get back together.

I've never had a problem assembling a bolt before. I'm not even sure I can imagine why it would be so hard lol.

I dont think its the ammo or extractor. Shooting the same PMC Bronze that I have been for a while without ever having issues. It was previously ejecting at about 2-3 o'clock with that ammo in the last system, so I know it has the pressure I need.The bolt is fairly new (1k rounds) and clean, but Im going to try the extractor spring kit from BCM just in case. I think I'll get a H and H2 buffer and see what works. I'll try it one peice at a time and report back when I do it.

 

If you have a carbine buffer and buy a H3 buffer you can take them apart and make any buffer weight you need (H, H1, H2, etc) http://njgunforums.com/forum/index.php?/topic/33539-ar-buffer-question/page__p__447494#entry447494

 

If you have a carbine buffer and buy a H3 buffer you can take them apart and make any buffer weight you need (H, H1, H2, etc) http://njgunforums.com/forum/index.php?/topic/33539-ar-buffer-question/page__p__447494#entry447494

 

I was actually thinking about that, but I'm a spare parts kinda guy. Plus I have no intention on having just 1 AR, nor do I intend to build them the same. So for me, I just consider whatever parts don't work for me now, will work for something else later.

I've never had a problem assembling a bolt before. I'm not even sure I can imagine why it would be so hard lol.

 

Extractor is easy provided you have reasonable pinch strength, which some folks don't. The ejector is a bit more of a PITA from a *SPROING* wtf did it go perspective on reassembly.

I've never had a problem assembling a bolt before. I'm not even sure I can imagine why it would be so hard lol.

 

The extractor pin is not as bad to install as the ejector pin and tolerances do vary between manufacturers but it can be a real PITA if you do not have the correct tools to assemble/reassemble a stripped bolt. The first one I did back in the mid '90s was from DPMS and it was a task with ordinary hand tools and no vice. My Colt's bolt was much easier altough I didn't touch the ejector and I have assembled a few from various manufacturers since with the benefit of having had prior experience. If you are going to attempt it make sure you have what you need to do the job corectly before you start; that is all I'm saying.