My father in law just opened a colt ar-15 sporter hbar ser # early 20000's brand new and we were going to try out a tac trigger on it but when we charged the weapon the trigger would not fire. When we would turn the saftey from fire to safe we would here a small click inside the trigger housing area and then when we would place the safety back on fire the trigger was then able to fire. Each time we would charge the weapon it would not fire unless we turned the safety to safe then back to fire each time. Upon opening it up we noticed a small lever under the hammer that is catching the hammer each time it is charged and as we turn the safety this lever moves backwards very slightly just enough to allow the hammer to click up just a small bit to its normal position thus being able to fire. also there is a big metal block in the u shaped cut out area behind the hammer and in front of the buffer assy that is stamped colt is this the block that prevents you from inserting the full auto sear? any help will be greatly appreciated.

The "small lever under the hammer" is the disconnector, which is also engaged by the safety selector. This is with the original trigger or with a "tac trigger?" I'm not sure what a "tac trigger" is. Do you know who makes it? Several things can make a new trigger not work - upside down or missing disconnector spring, improper adjustment if it's an adjustable trigger, and some new triggers need to be timed, i.e. remove metal from the sear faces.

Also, Colt uses oversized hammer and trigger pins, and any replacement trigger has to use the same size pins, NOT the mil-spec pins. Really need more info on who makes that "tac trigger" before proceeding with any recommendations.

Big Bear, the tac trigger is supposed to legally simulate full auto fire.  You can see them on the TVs at the gunshows that are turned up loud enough that you can hear full auto fire 40 feet away.

Quoted: Big Bear, the tac trigger is supposed to legally simulate full auto fire.  You can see them on the TVs at the gunshows that are turned up loud enough that you can hear full auto fire 40 feet away.

Yeah, I believe they are completely external.  Its a spring loaded/fulcrum kind of thing that is supposed to help bounce your finger back and forth real fast.  I think it just clamps to the trigger guard.

I would say your rifle was assembled during or immediately after Colt's Memorial Day picnic

Oh yeah, tac triggers, I've heard of those. Well, I don't know much about tac triggers but it sounds to me like it's not letting the trigger go forward to reset. Switching the safety selector to safe and then fire will reset the trigger and allow the hammer to drop on the next pull. I'm not a big fan of external trigger devices but I've been known to bump fire on occasion.

BTW, you answered your last question correctly - that block is the sear block.

The tac trigger is fully external and does not keep the trigger from reseting forward
i am stumped
it is the original trigger in there it is all original preban colt brand new

Trojanfan,

look at the safety bar inside the receiver, how many "notches" or "cut outs" in it ?

from your description it sounds lyke you might have gotten a factory installed select fire safety installed & that is ILLEGAL !!

NO...! it's not his fault, but get it checked out !!

Part of the function test for an AR-15 is to charge the action with the trigger pulled to the rear.  After charging/cocking the hammer if you release the trigger you will hear a click as the hammer is released by the disconnector and falls to the sear.

Does this tac trigger thingy hold the trigger back?

Safety Function Check... Remove the tac trigger and do this and then let us know if it passes or fails.



If it passes, your tac trigger is not letting your trigger fully reset. If it fails, you have an internal fire control group malfunction.

I think CactusJack is on the right track.

(Of course, I've already had a few drinks tonight so I may be missing something obvious...)

I think the "lever" you refer to is actually the autosear.  Look at the back of the hammer; on the long 'nose' opposite the surface that hits the firing pin is there a small notch cut-out designed to catch the lever?  Is there a small hole above the word "FIRE" about ths same size as the trigger pin?

If you've got a converted full auto gun, get in touch with the guy who sold it to you - you've got a felony on your hands.

thanks for all the info
i will try to test it all out soon
i was very tired that night after a day of torching and welding and removing an engine so i wasnt fully on my toes but i knew something was not correct soon as i get to it i will test it all out and look for the things suggested and i will let u all know the results and if they r not positive then i will take pics to post on here to see if that helps