AR advice needed

[Butch]

I picked up a used 'home built' barely shot AR and wanted a little advice.  This is my first, so the only things I know about ARs are what you can find on the internet, but have no hands on experience.  Everything looks pretty good (reputable name parts, setup the way I was looking for (barrel length, twist rate, handguard length, etc.)  The one thing I have come across is that it has a lightweight BCG, but does not have an adjustable gas block.  I'm thinking I have a couple options here and wanted to see what some of you might recommend.  I could buy a 'standard' BCG to go with the standard gas block.  This is pretty straight forward and requires the least amount of effort on my part.  Or I could buy an adjustable gas block since I already have the lightweight BCG.  This would require a bit more work and a few more dollars, but doesn't seem that difficult.  The current gas block is not a 'clamp on' style as I was a little concerned with getting the gas ports lined up properly, but with the set screw type gas block, this seems more straight forward.  This would give me the benefit of less recoil once I get it dialed in right, etc. and I think it would be within my capabilities and I don't mind tinkering around with it to get it right.  Lastly I could shoot it a bit like it is to see how it cycles currently before making any changes.  On this one, I'm not sure I would know if it is 'slightly off' if it cycles properly.  Like I said, it's my first AR, so I really don't have any other to compare it to.  Slightly too fast of a BCG beating up the rifle and having stronger than typical recoil would be something I don't think I would know was happening if it isn't jamming, or having other types of failures.  

Any advice?

[ReconRat]

Changing to a heavier buffer spring and/or buffer would compensate for the light weight of the bolt group. Might borrow a heavy buffer, put it in there, and see if it functions, see below.

Lots of variables with that. Here's a list of light weight bolt carrier groups with pics. If you can find which one you have, the manufacturer's website might indicate what spring and buffer should be used. Lots of different weight bolt groups are considered light weight. https://www.recoilweb.com/preview-guide-to-super-light-ar-15-bolt-carrier-groups-65941.html

Otherwise... if firing the rifle results in failure to eject, failure to load, or failure to hold back on last round; you might have not enough movement, which could be anything from a loss of gas pressure to parts that are too heavy.

Since it's a light weight bolt, which should be confirmed by examination, the opposites might occur, the bolt group and mass might slam back too hard. Might feel that, and might not. Might want to compare it to an ordinary rifle/carbine setup, and see how it feels.

Really needs some one to look at the parts and see what you've got in there, as well as to fire it to check function and recoil.

[ReconRat]

And there's nothing wrong with a regular bolt group and matching spring and buffer. Unless the barrel has some really odd gas port system. I'm guessing maybe the light weight bolt group was for faster cycle time, like for in competition. Or the entire rifle was trying to be some sort of unique ultra lightweight.

[ReconRat]

I'm finding all sorts of interesting stuff on the internet.

https://www.guntweaks.com/ar-15-reliability.html

https://www.guntweaks.com/ar-15-reliability-test-cases.html

I'm still building an ultra lightweight. Don't know what to expect.

Edited November 20, 2018 by ReconRat

[Butch]

Here is a pic of the disassembled bcg.  Looking online it looks a lot like a AIM surplus LW bcg and weighed 8.9 ounces which seems to match.  The buffer weighed 3 oz.  Everything I see online says I'm asking for trouble by running a LW bcg with a non-adjustable gas block.  Or at least not getting the benefit from it that I should.  I'm leaning towards getting an adjustable gas block (probably SLR or else Odin works), rather than buying a standard weight bcg.  SLR seems to have pretty high reviews, but the Odin works 'adjustable' is a little cheaper or they also offer a 'set and forget' style 'tunable' block that is quite a bit cheaper.

I will probably fire off 20 or so rounds in the rifle as is to make sure how it acts now so that once I put on the new gas block and run it wide open it should act like it does now to make sure I put everything together correctly.  Then I'll work to dial down the gas to the right amount.

[ReconRat]

Well shoot... I'll probably get an adjustable gas block also. Weighs the same anyway. I won't be able to switch the gas block later. From what I read on it, people use anywhere from stock parts to a different buffer spring and weight, to go with the lightweight BCG. Many combinations work. The difference is in recoil. Barrel jump or drop.

edit: And that's probably the same BCG I bought. It's not all that much lighter, so I wouldn't expect much problems using it.

Edited December 1, 2018 by ReconRat