So I have a fresh build, and right from the get go I was experiencing what seemed to be severe bolt bounce and replaced my buffer with a Spikes H2.  This seemed to eliminate the problem for a bit, but after maybe a a hundred rounds down the pipe the gun doesn't want to return to battery.  

Yes it's been cleaned after a complete tear down and lubed to fairly wet status, but still I find myself having to use the forward assist to get things in a firing condition.  It hasn't short stroked or given any other issues, and man am I happy with what it does at the range, it's just freakin' annoying to not be able to do a mag dump if I were so inclined.  

Soooooo, now I'm wondering where I should go next.  My inclination is to a higher strength buffer spring.  My thinking is that since the carrier is a bit heavier than standard I think it seems I could use a little more oomph to get things properly shut up after the bcg starts its trip forward.  As an aside to this.... if I simply allow the carrier forward easily, shouldn't the gun still go into battery (it won't)?  

Am I simply being impatient and not getting the gun broken in as it's only got maybe 150 rounds total through it and my new bolt and barrel need to mate like a piston to a cylinder?  With all of my research I've become quite informed about putting one together, but an expert on figuring problems out I'm not.  That's why I come to you, the gurus.... Help me Obi Wan(s)!


Thanks to help here by team member ReconRover and proactivity on the part of Jacob at Adams Arms.  He jumped in on the discussion, (Recon nailed the problem, bent op rod) and dropped parts in the mail for me less than 24 hours after my post, no questions asked beyond what my address was.  There is no beating customer service like that.  FYI had similar experiences with Kahr and RCBS.  I know folks always want to post the bad, but the good really needs mentioning too.

Does the piston move freely? might check to see if the piston is binding at all.

Everything seems to move nice and easy

I've built several, here are a couple of thoughts:

1.  Do the old business card gap test.  The gap from the rear of the piston block and the barrel should be about the depth of a business card.  See if it's possibly come loose and moved forward.

2.  Pull the op rod out and see if it's slightly bent  (just roll it on a flat surface, you can tell quickly)

3.  Check your charging handle.  If it fights tight or doesn't move freely, chuck it and put in a new one  (I ran into this last month from an out of spec charging handle)

4.  Weirdness check....ensure your bolt has the gas rings removed

5.  If  you are still having issues, the only other thing I've run into, is the brass "olive", inside of the upper receiver can be installed too low, crooked, or crushed slightly.  This would bind up the op rod.  How do I know...I did it when I installed one of them, and had to drill it out just a hair.  The op rod wasn't moving freely thru it.

I'll give all those a look and get back with a report this evening.  My inclination is that all of that is ok as the Op rod goes right into the  gas tube hole when reinstalling and I can cycle the action holding the op rod (as far as it will let it go into the upper at least), but who knows.  Anyway I'll take a look tonight and post what I see, and thanks for places to start at least.

Thanks Jacob, that's what customer service is all about.  

I would like to ask, and I'm sure others wanting to use your piston system would like to know, what spring/buffer combination is recommended for midlength systems?  If it matters I'm running a Ranier Select 18" and their nitrided bolt bolt as well, and a NiB coated cam pin.  My thinking was with the nitride coating on the BCG and the bolt, and the NiB on the cam pin this thing should be as slick as cow snot before a drop of oil were to hit it.  If you have any thoughts please feel free to share.

Sure enough Recon you called it... ever so slight of a bend in the Op rod.  not detectable to the naked eye but the end of the rod goes in about a 1/4 in circle when rolled on a flat surface.

Soooo Jacob, buddy ol' buddy ol' pal... I've heard lots of good things about your customer service.  Can you help me out here?

That's exactly what's happening Jacob.  The bend appears to be just enough that it is causing a bind.  When the op rod is removed (which takes a little bit of effort now, btw) the system is incredibly smooth and no matter how slowly I let the bcg go forward or even if I stop it immediately before entering battery it will still completely close.  Put the op rod back in and I have to use the forward assist.

As for bullet weights I typically shoot a little heavier projectiles.  I have a 1:8 barrel and it likes the taste of the 62-75g stuff which is why I think when I went to the H2 it was cycling perfectly there for a little while.  I haven't noticed anything unusual in the ammo, it was all factory stuff.  Any clue what might have caused this?  I did take a pic of the op rod next to a straight edge to email you.  I looked for damage or something that might have given me a clue as to where or how it might occurred but the only thing I find imperfect is the straightness.

You mention the spring and bushing.  Are you saying that I can run the system without them or just asking if the rod moves freely?

Anyway I emailed you last night from my personal email but I'll do so again from work since that's where I am now.

Thanks again for actively taking an interest in the problem and reinforcing my decision to go with the Adams piston.

Sounds like you found the problem, but just something else to check is that the gas block is completely straight in line with the receiver , if not this will cause the piston rod to bind , another important check is the piston rod to gas block gap, this small gap keeps the piston rod from getting hit by the carrier when returning to battery, no gap will bend a rod too. You probably already know this but its good for all to remember. AA will take care of you with a new rod.

I'll definately go over it with a fine tooth comb as I put it back together.  I'd hate to think Adams is having to take care of a problem I caused.  I didn't find anything other than the rod out of spec but like I said, I'll be sure to recheck everything.  Thanks.