Looking for NES Braintrust help on this. Lower functioned perfectly on a 16" upper with 3oz buffer and basic spring. I switched to the Geissele Super 42 Braided Wire Spring with H2 weight buffer and a 12.5" upper. With that configuration I was getting occasional failure to fire, click no bang. I switched to an H1 weight buffer and had no more failure to fire, but now get failure to go on safe. If I fired a few more shots, it would go back on safe. I'm not sure what else to try besides going back to a 3oz buffer and basic spring.
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AR15 tuning question
- Thread starter tech77
- Start date
Im just not sure how the buffer is a problem with those malfunctions
Only remote possibility I can come up with is a round was fed and the trigger did not set?
Are you sure the trigger set?
the safety only “switches” when the trigger is “set” ?
I pulled the trigger and the round fired, so I would assume the trigger was set. this happened multiple times. Its a jp trigger with anti-walk screws. Maybe those came lose and were causing the issue? I'll take a look and see if I see anything else. Trigger feel felt consistent with how its been in the past.
Rick O'Shea
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You lost me when you made 3 changes and had a problem. Do only one thing and test for reliability. The answer will appear very clearly.
No idea how the buffer and spring would affect the trigger and safety like that either.
It sounds like you did test it with too many changes. Should've tested the 12.5 upper using the basic spring with 3oz./H1/H2 buffers.
It sounds like you did test it with too many changes. Should've tested the 12.5 upper using the basic spring with 3oz./H1/H2 buffers.
You said fail to fire?
Is the 12” barrel pistol or carbine length gas system?
Anyhow start over. Return gun to original configuration and re test.?
Proof out the lower functions before changing anything , Do lower function with both uppers with the standard buffer
im not familiar with no walk pins, can they be over tight?
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1903Collector
NES Member
They are really not needed unless it's a FA gun, and even then....at least that's what I have always understood. That being said I have installed a few KNS sets and have never had any issue with them.
1903Collector
NES Member
When you say "no bang" was a round chambered? Agree with what was said before, you need to go back and start from scratch.......Why do people change the buffer? unless the gun is over gassed why would you change it? I have never had to put anything more than a standard buffer in anything I have built. Not criticizing, just curious why you used the heavier buffers?
Buffer isn't gonna cause failure to fire a chambered round. Either your trigger group isn't put together right or yo have a spent primer or something floating around inside your lower receiver jamming up the works. I've seen it happen in classes before, random failures of all sorts, pop the rifle apart and shake it upside down and a spent primer or pebble or something falls out, rifle goes back to normal. Incorrect buffer spring/weight will either cause erratic ejection or short stroking, possibly failure to return to battery, it won't cause the rifle to not fire on a fully closed bolt.
Thanks for the additional thoughts.
Let me clarify the current and only issue is that about 50% of the time I attempt go safe after firing, it won't engage. If I pull the trigger, it fires and then I can switch to safe.
Trigger: AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN
J P ENTERPRISES AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN | Brownells
"Each JP Enterprises’ Fire Control Module drop-in trigger includes JP Anti-Walk Pins that remove all slop movement of fire control components for solid reliable function, and a JP reversible, ambidextrous safety selector which has a unique drum design that ensures perfect safety function"
Anti-walk pins are part of this trigger, not an add on. I have about 500 rounds through the trigger and never had this issue until today. So, I'm thinking things may have loosened up on the trigger install. It is a drop in trigger, so there isn't the same type of assembly as with a traditional trigger.
Yes, this is the Geissele buffer made for the spring. My understanding is that a heavier buffer is recommended for shorter barrel length. This is a mid-length gas system. When I previously ran the Geissele buffer with their additional weight to make it H2 with the 12.5 barrel, the issue there was occasional fail to fire. My assumption was H2 and heavier spring was too much, so switched back to the Geissele buffer at H1 weight.
I'm going to re-install the trigger and will then test it out. I'll bring standard spring+buffer and another upper to test.
Let me clarify the current and only issue is that about 50% of the time I attempt go safe after firing, it won't engage. If I pull the trigger, it fires and then I can switch to safe.
Trigger: AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN
J P ENTERPRISES AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN | Brownells
"Each JP Enterprises’ Fire Control Module drop-in trigger includes JP Anti-Walk Pins that remove all slop movement of fire control components for solid reliable function, and a JP reversible, ambidextrous safety selector which has a unique drum design that ensures perfect safety function"
Anti-walk pins are part of this trigger, not an add on. I have about 500 rounds through the trigger and never had this issue until today. So, I'm thinking things may have loosened up on the trigger install. It is a drop in trigger, so there isn't the same type of assembly as with a traditional trigger.
Yes, this is the Geissele buffer made for the spring. My understanding is that a heavier buffer is recommended for shorter barrel length. This is a mid-length gas system. When I previously ran the Geissele buffer with their additional weight to make it H2 with the 12.5 barrel, the issue there was occasional fail to fire. My assumption was H2 and heavier spring was too much, so switched back to the Geissele buffer at H1 weight.
I'm going to re-install the trigger and will then test it out. I'll bring standard spring+buffer and another upper to test.
don’t worry about the buffer
that is a relatively minor tuning topic that can be addressed once your rifle works
unsuppressed it’s never going to be all that overgassed so put that issue to the side for now
the problem is likely either your lower or trigger group
would inspect and ensure the geissele BCG, carrier key, bolt and upper look fine, but if it’s a factory geissele upper it’s likely to be fine.
personally I’d remove the JP trigger group and install a mil spec to assess where the problem is
this highlights the innumerable issues that can arise from Frankenstein builds.
what is the lower?
is it a Gucci billet lower or a mil spec 7075 forged?
if it’s an 80% I can guarantee you the trigger well wasn’t cut deep enough, as this will result in binding between the safety and trigger group
if the firing group is misbehaving during hand cycling, I would NOT run any live ammo through the rifle. You can experience hammer follow, unintentional discharges or full auto.
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these wonky problems are actually great opportunity to learn the black rifle. Recommend purchasing a copy of Chris Bartocci’s AR armorer manual. Excellent guide.
YouTube channel - school of the American Rifle - is also excellent resource. Pretty sure I’ve watched every one of his videos. at Some point i‘d like to attend his class in Maryland.
that is a relatively minor tuning topic that can be addressed once your rifle works
unsuppressed it’s never going to be all that overgassed so put that issue to the side for now
the problem is likely either your lower or trigger group
would inspect and ensure the geissele BCG, carrier key, bolt and upper look fine, but if it’s a factory geissele upper it’s likely to be fine.
personally I’d remove the JP trigger group and install a mil spec to assess where the problem is
this highlights the innumerable issues that can arise from Frankenstein builds.
what is the lower?
is it a Gucci billet lower or a mil spec 7075 forged?
if it’s an 80% I can guarantee you the trigger well wasn’t cut deep enough, as this will result in binding between the safety and trigger group
if the firing group is misbehaving during hand cycling, I would NOT run any live ammo through the rifle. You can experience hammer follow, unintentional discharges or full auto.
—
these wonky problems are actually great opportunity to learn the black rifle. Recommend purchasing a copy of Chris Bartocci’s AR armorer manual. Excellent guide.
YouTube channel - school of the American Rifle - is also excellent resource. Pretty sure I’ve watched every one of his videos. at Some point i‘d like to attend his class in Maryland.
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Mid length is a bit longer than carbine so no real need for a “heavy” buffer. A “standard” weight should be fine.
Im still not sure what those tension screws do, if you applied loctite to clean fasteners they should not come loose, but being screws…..
Seems like theres some things with that giesselle trigger that can cause problems ?
between over tightening the no walks , not using the tensioning screws, or the loctite not holding.
I look at all that and think putting milspec lower parts in is a good baseline
he’s using a JP drop in trigger group, not a geissele.
anti-walk pins are unlikely to cause an issue with the trigger or thumb safety. Even if they’re overtightened it shouldn’t affect function.
OP has not provided much other info regarding the build such as the lower, lower parts, etc. so not much I can add from here.
if the problem is only the thumb safety engaging problem and nothing else, there’s probably debris in the safety detent channel or the safety itself is out of spec. I’ve seen some gnarly machined safety selectors one of which I had to toss (cheap mil spec) during a build because it could not be taken off fire position. The decent would bind.
take it all apart and inspect the lower for debris and metal shavings. it is obvious the buffer and stock have no relevance to the function of the safety.
it really helps, if you have it, to put trigger assembly into the action chassis to inspect for issues.
the non-engaging safety means you most likely have an issue with the trigger pins. something most likely got bended, or got obstructed by debris.
the only reason to deal with buffer tuning would be issues with feeding/cycling or obvious overgassing and smashing of the buffer in the stock tube that cannot be misidentified with something else, and i have an assumption you did not have any of that.
as others stated above, if it was an 80% lower and the pin holes were drilled a bit out of alignment - that is the most obvious answer.
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failures of an 80% lower are almost always insufficient depth of the trigger pocket. The trigger is then not allowed to return to fully forward position. Very common. of course the pin holes can also be F’ed up but it seems the tolerances there are more forgiving especially if using anti-walk pins.
You have the JP drop in trigger and a Geissele safety? That specific JP trigger you linked to looks like it's supposed to use a proprietary safety. I have several Geissele triggers and they can use standard milspec safeties.
