AR safety stiff when bolt locked back?

[HammsBeer]

A couple of my AR's when the bolt is locked back (hammer cocked) and I rotate the selector lever to safe it's really stiff and binding. When the bolt is in battery (hammer still cocked) the selector freely rotates to fire and safe. I'm using ACT triggers and BAD-CASS selectors. It seems there's not enough clearance between the trigger bar and selector when the hammer is pushed down by the BCG, but I don't want to just start blindly messing with it.

Range requires bolts locked back and safety on when down range. Any ideas how to fix this or a similar issue in your selector/trigger? And no, leaving it on fire is not an option.

 

[moxie]

It should rotate freely. Only way to tell what's wrong is take it apart and find out what's binding. In the interim I'd assume the safety does not work.

 

[jrmiddleton425]

Why are you opening the bolt before engaging the safety? The reason you're having a problem, is that you're trying to do something the rifle isn't supposed to do.

 

[HammsBeer]

When a mag is shot empty I engage the safety and drop the mag. When I load a fresh mag and send the bolt home the safety is already engaged, reducing the likelihood of a AD. The rifle is supposed to be able to engage safe with the bolt locked back. One rifle works just fine but two of them I can force it into safe, but it's not a simple thumb flick.

I will have to remove the selector and trigger bar and see if there is a slight burr or casting flash.

 

[Blade First]

Occam's Razor...seems you have an interference fit on aftermarket parts installed. Not sure how you accomplished that since you're using quality parts.

Two suggestions:

1. Operate the AR as designed. If the RSO at your range can't understand the procedure of mag removed and bolt locked back, suggest to mgmt. of range that remedial training is in order. I'm an RSO and insist on being able to see that the chamber is clear. Don't really give a rat's butt if the "safety" is engaged or not if there is no magazine in the firearm.

2. Get your terminology in order; there is no such thing as an AR-15 trigger bar. Do you mean the disconnector or tail of the trigger?

Lastly, if you do not know how to conduct a simple safety check of fire-control group operation, learn it and use it before you hurt yourself and/or someone else.

 

[HammsBeer]

1) The selector of an AR should freely engage safe regardless of bolt position. This was SOP when I was in the Army and that's what I expect of my AR's now. If there is a clearance interference fit between the selector and trigger, then cycling the bolt with safety on will aggravate parts wear.

2) I'm referring to the rear surface of the main trigger casting that intersects with the half circle of the selector, not the disconnector. Sorry I don't know the exact terminology of this part.

3) I perform a function safety check on all firearms especially after each cleaning (does selector block trigger movement to release hammer, does disconnector stop the hammer until primary sear reengages, does decocker drop hammer without impacting firing pin, etc).

So if you can tell me how to check the trigger to selector clearance please let me know.

 

[Tirod]

Adjusting the trigger reset to it's minimum can interfere with the safety. Quality parts have nothing to do with it, it's the screw pushing up that causes it, and it can be done with all GI parts, too.

One solution was to grind more clearance on the offending part, ACT apparently didn't, and there is the issue. Too little reset.

 

[HammsBeer]

What screw are you referring to? The ALG ACT is just a polished and coated milspec trigger and there are no screw adjustments for trigger travel or reset.

 

[joem1945]

All, as in everyone of my AR's (bushmaster, Colt, RR, DPMS) can operate the safety freely with the bolt in the rear position.

 

[HammsBeer]

Removed the triggers and checked for casting flaws and nothing wrong there. Noticed when swapping uppers that sometimes it functions better depending what upper is pinned on, so I think it's more of a tolerance stacking between the upper curve of the hammer and the machined underside of the BCG.

 

[Blade First]

Have used the ACT ALG and QMS products and find it hard to believe that they would be out of spec...their QC is top notch. No experience with that particular BAD selector...are you sure nothing is binding because it's an ambi?

What brand are your lowers? If the selector holes weren't drilled true, interference would be a distinct possibility. Are you sure that the proper detent [the "rocket" as I call it] and detent spring are installed and not binding? You didn't clip the spring, did you?

If not, my next step would be to remove the spring and detent and try to duplicate the interference. If that doesn't "fix" the problem, you are going to have to remove the offending parts and mic them to make sure they are of proper size and profile.

Have you yanked one of the selectors to see what the wear pattern is, especially in the channel where the detent rides? Are the dimples in the channel the proper depth?

"...does decocker drop hammer without impacting firing pin, etc)."

No decocker...simply a function of the disconnector properly doing its job by catching the hammer.

By the way, I'm not arguing that the disconnector should be harder to rotate to 'safe' with the bolt back...it shouldn't. Was just trying to address your range issue. Sorry if I wasn't clear.

Moving the selector to 'safe' means rotating the circular bearing surface over the tail of the trigger. If you don't find a problem with any of the above, insufficient clearance between the selector bearing surface and the tail of the trigger is the likely problem. No clearance when you have the selector on 'safe' will "lock" the trigger in place. Normally, it will still move several thousands of an inch to the rear.

 

[MachIVshooter]

so I think it's more of a tolerance stacking between the upper curve of the hammer and the machined underside of the BCG.

Nope.

Your issue is the interface of the hammer and trigger. There are 3 possible cuplrits:

1) trigger too tall at sear surface
2) hammer radius too large behind sear surface
3) pin holes in lower not drilled quite right.

The reason it only does it when your bolt is back is that in that position, the hammer is held further back than when bolt is in battery, causing a different part of the radius on the bottom of the hammer to contact the trigger just aft of the sear surface. Once the BCG is forward, the hammer rotates forward slightly, allowing the sear to engage and, in the case of your rifle, letting the trigger come forward just enough for the selector to clear.

Just carefully clearance the hammer a little in the radius behind the sear surface, your problem will be solved.

 

[HammsBeer]

Lower is an Adams Arms and the other is a forged Mega lower. Proper detent is installed and no modifications to the detent spring.

I think MachIVshooter found the issue. I pulled the hammer and trigger and installed them outside the lower. Pic one is the BCG forward and the sear engaged.



Pic 2 would be if the BCG is locked back. That radius behind the hammer sear surface you mentioned is pushing down on the trigger, and I can see now how it's causing the rear of the trigger to push up too far. To relieve the binding clearance issue between the trigger and selector I'll gradually emery the hammer radius contacting the trigger in pic 2. Thanks!

 

[Blade First]

Sheesh...my uncle out in Elbert Co. is *always* correct.

Seriously, glad the diagnosis appears correct. Remember the rule, however...you can take off material pretty easily but putting it back on is a real hassle. In addition, I'm curious how the FCG parts you assembled didn't like the idea of playing together. You certainly didn't skimp on lowers.

Don't forget that a range report is absolutely mandatory for this thread. Make us proud!

 

[moxie]

Understand you've got quality aftermarket parts installed. Has anything been gained? Is it possible that one or more of the parts are out of spec even though high quality? Have you discussed with ALG? Battle Comp? They might like to see your pics in post #13.