I finally finished my 9mm sbr and took it to the range today and it does not cycle properly. it has a 5.5" barrel and am using it with a trident 9 suppressor. When I fire it the bolt goes back far enough to load the next round but not far enough to recock the bolt. I thought it was an ammo problem since I was using 147gr subsonics but it did the exact same thing with 115gr wwb. I was thinking maybe the buffer spring is to strong but I dont really know.

what kind of buffer and spring?  BCG?  did you get the same results without the suppressor?

fatkid

New build?
What's your setup (parts run down)?
Does it re-cock the hammer when you hand cycle it?

it is a spikes ramped BCG and the spring and buffer I dont know the maker but it looks like its 11 inches long and the buffer looks a normal black 9mm buffer

yeah its a new build I bought a new complete rra 9mm lower from a guy at my range and it is a brownells mag block I believe. I bought a spikes ramped bolt and the upper is a 9mm upper with a 5.5 inch barrel. it cycles and fires fine when I pull the charging handle but after it fires it will chamber the next round but it does not recock itself.

Try a lighter buffer ?

Hmmm,,  std 9mm lower, add a ramped bolt, and it will not reset hammer when fired, but will set hammer when bolt manually operated with charge handle,, Hmmmmmmm..

The cure ––-

Some guns need some break in before they run smoothly.  I'd try a lighter buffer and maybe a different action spring if you have others you can swap.  I bend the ears on my hammer springs also - might help.

SBR7_11 already answered the question for you. It is your hammer.Get the DPMS hammer and your issues will go away. I had the same issue as have many others here. That hammer "WILL" solve the problem.

Spikes states that the CMMG ramped bolt will not work with a dedicated 9mm hammer.

You would think the trigger wouldn't reset at all if the hammer was the sole issue - it seems odd that the trigger will reset when manually cycled, but not under live fire.

RRA says their 9mm hammer will work with a .223/5.56 upper and I have run .223/5.56 uppers on my lowers that have 9mm hammers and they work just fine (hammer reset manually and under live fire) - I have also run an ADCO ramped bolt on a lower that had a RRA 9mm hammer in it and it too worked fine (hammer reset manually and under live fire) - I thought the whole purpose of all you guys that run these ramped 9mm bolts was to put a ramp into them that mimics the ramp on a .223/5.56 bolt and reduces the "stresses" on the hammer so the hammer pins won't break prematurely or egg out the receiver holes prematurely.  If a 9mm hammer will work with the same ramp on a .223/5.56 bolt, I guess the CMMG ramp must be deeper/longer than that, which is why it doesn't seem to work.

I know ADCO went a different route with their ramp and its shorter than the CMMG one and the one M60Joe has pictured on his site - maybe that's why an ADCO ramped bolt and an RRA 9mm hammer worked fine for me since they say their ramp job works with a wider variety of hammers.

I bought the complete 9mm lower but swapped the 9mm hammer out for a 556 because I bought the ramped bolt. that is not the problem. it just seems to be short stroking. I am going to try today and put a std 556 carbine buffer in it and see if the lightend buffer will let it slide farther back to recock it

YOU LIE!!!

What kinda lube you using?

I'm with brother Kevin.....   pics or it did not happen  

If it is loading the next round but "NOT" resetting the hammer, then your issue will be solved by using the DPMS hammer shown above. Trust me. I was having the exact same issue with a LRM 169 with standard 5.56 hammer and ramped bolt. The same reply and pics were sent to me. Swapped the hammer and my gun went from a single shot tofunctioning 100%. You asked for help and the correct answer was given.

The DPMS hammer is a M16 hammer with the sear filed off. It is not a standard 9mm hammer.

I was just joking around since you and 2 others jumped so quickly to the hammer as the culprit.  I wasn't really siding with you.  A pic would help though to confirm the hammer being used, but I'm still leaning towards something other than the hammer.

Yeah, which "556" hammer is a big deal.  Not only would a hammer reset issue be pretty independent of the hammer being used, but there are a lot of other variables.  What lube and how much?  Which buffer and which spring?  What stock is on the gun?

Most people tend to go UP on buffer weight with a 9mm setup,  But way too many people don't take into account how a really new gun needs to be broken in mechanically so that all the parts slide properly on each other.  And while plenty of suppliers ship their parts with a protective coating, that's not necessarily a functional gun lubricant let alone enough of a lubricant to enable the gun to cycle smoothly.

Yeah, I do drone on, don't I?

I will take pictures of my lower and post it today. the hammer is a rra 556 hammer I stole out of one of my extra lpk.

If it's a notched hammer, you may have to replace it with a round top one.  It is unfortunate, but some ramps are cut way deeper/longer than necessary and don't work well with some hammers.

The ramp ADCO does is not as long, nor as deep, and is supposed to work with a wider range of hammers.  I run all non-ramped bolts, but if I decided to run a ramped bolt, I would go with an ADCO ramp.

I still think it is odd that your gun works when manually cycled and am still leaning towards a short stroking problem, but it's hard to say for sure without seeing/test firing the gun.

I took it to someone today and he figured out that the secondary on the disconnector was not catching only the primary was and he filed a couple thousandths of an inch off and put it back together and it works perfect now. I dont really understand how it worked I think it brought it up just slightly so the secondary would catch. The funny thing about it was that the secondary worked fine when the upper was not attached but when the upper was attached and fired it never caught. I was just going to let everyone know the end result since I would have never figured that one out on my own. Thanks for everyone who gave suggestions on my problem

That can happen - after you replaced the hammer, did you function check the lower?  Function checks should be done by manually cycling the action with finger off the trigger and with the trigger pulled and held to make sure the disconnector works as it should.  Especially after you swap fire control parts around - not everything is "in spec".

Glad to see you got it figured out.  Have fun with it...

yes it worked fine without the upper attached but when the upper was attached the secondary didnt catch

The upper needs to be on the lower to do a proper function check - if the gun doesn't pass a function check, it should be fixed before you attempt to shoot it.

Question: How do you perform a functions check on the AR15 Rifle?

  1. Place the selector lever on safe.  If the selector switch will not go on safe, pull the charging handle to the rear and release.  Place the selector lever on safe.  Pull the trigger to the rear, the hammer should not fall.
  2. Place the selector lever on semi.  Pull the trigger to the rear and hold.  The hammer should fall.  While holding the trigger to the rear, pull the charging handle to the rear and release.  Release the trigger and pull it to the rear again.  The hammer should fall.