Gentlemen,

I recently mated a pre-ban Colt lower with a Law Enforcement Only Colt CAR-15 upper using the offset pin that Tweak was so kind to tell me how to properly use.  I am also using the Colt bolt and bolt-carrier in this set-up.

There's something that the bolt carrier is "catching" on upon closing about 1/2 way.  When cycled really fast, it doesn't catch on anything, but when cycled a bit slower (by hand, although not "holding back" when letting the bolt slam home) it sometimes "sticks."

I have not fired the gun yet and don't want to until I figure out what the problem may be.  Anyone have any ideas?

Hold the trigger to the rear, work the bolt back and forth slowly several times, does the carrier still drag? Release the trigger and repeat, does the carrier still drag?

If you have a hooked hammer and a slotted bolt carrier the upper lip on hammer is probably catching the spool of the firing pin. This has been covered at length on this forum.

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Tweak, I read all the threads.  I have the notched Colt hammer and the slotted bolt carrier.  I can see at the top of the hammer just behind the notch where it is "catching" a bit.  Remember, all of these are Colt parts.

To anwswer your question, it acts just like it's supposed to when the trigger is to the rear.  It's only when I don't hold the trigger back that it "catches."

I'm not much of a "smith," and would not really want to grind on the hammer.  What kind of hammer can I buy to replace this (remember--large hole)?  Or should I just buy the regular carrier (i.e. not slotted.)  Seems like a new hammer would be a less-expensive fix.

What puzzles me, though, is why this is happening.  The bolt, bolt carrier, and lower are all Colt and came from the factory together.  All I did was take the bolt/carrier out of a 20" HBAR upper and put it into a Colt 16" CAR upper.  

Thanks for all your help.

Tweaking the top of the hammer pad is not the end of the world. All that is required is to just roll file the top edge of the contact pad that is binding to resolve the problem.

In regards to swapping parts, the hammer is only a few of the parts that you may have to change to resolve the binding problem.   The problem usually lies in the geometry of the hammer and trigger sear.  The longer forward the sear tab/section of the trigger (portion that is front of the pivot hole), the lower that the trigger will hold the hammer during cock. For the most part Colt holds a very tight tolerance on their parts, so trying to find a trigger that is slightly out of spec (longer front section) is going to be very rare.

Since your is slightly catching, little metal at the top edge of the firing pin pad of the hammer is required to be removed.

The fact that the hammer will not drag on the firing pin stop ring/edge when the disconnector retains the hammer is due to the disconnector holding the hammer below the trigger sear point until released to be caught by the trigger sear.  Basically, the hammer will always drag on the bottom of the carrier, even when cocked to the disconnector.  This is required to allow the carrier to lower the hammer past the lowest sear point, the disconnector during the cocking cycle.  The fact that during the forward stroke of the movement of the carrier the hammer catches the firing pin ring just means that the top contact edge of the hammer pad is too sharp/high and slips up to catch the pin.  


Bottom line is that the problem is easily solved by just removing a few thousands of metal from the hammer at the top of the contact pad that is catching the firing pin on carrier closer. A slightly lowered/ rounded top edge on the contact pad of the hammer will solve the problem without having to take a second out on the house to by the find the mystery out of spec part/s that will resolve the problem.

dahugo,

I like you already. [:D]

Dano has you on track, modding the hammer notch is no big deal.

Changing to a shrouded carrier is the best solution [b]but[/b] the carrier is the heart of the rifle and changing it can lead to malfs if the carrier is bad. Sometimes it takes a awhile (wear) for those malfs to develop.

Changing to a rounded hammer will often fix the bind but even rounded hammers can snag the flange of the firing pin. Changing the hammer can effect the timing of the piece and may, if the hammer sits higher up, exacerbate the bind.

Make sure that the flange of the firing pin doesn't stick past the edge of the bolt carrier's ramp like the spool of an M16 firing pin will. If it's not too large of a spool then mod the hammer hook.

Remember, when you're firing you're holding the trigger to the rear while the bolt cycles so the only time this bind is a problem is during the initial loading and during administrative handling.

Guys, I was just about to take a file to my hammer when I decided to try a much cheaper fix: both my guns are Colts, so I just swabpped bolts/bolt carriers.  Now they both work fine.

I'm not even going to try to fiture out why that is.  However, now I know what this problem is and how to fix it.

Thanks to all of you, especially Tweak.

dahugo,

If you switch the bolts and barrels you need to check the HS.

Tweak, I only traded bolt carriers, not barrels.

Thanks again.

If you swapped the bolts in the uppers you need to check the HS. With all Colt parts the chances of HS being bad are slight but tight HS can cause malfs.

If both bolts are to the same spec then how can headspace ever change just because you switched bolts when you have not switched barrels?

I don't think that is an issue. If that were the case, then everytime a person had to change a bolt then they would have to some how adjust the barrel extension.

All parts are correct within a range of sizes. If a bolt's HS dimension tends to the thick side and the chamber depth tends to the long then the HS may read alright. If the bolt is thin, the extension is thick, and the chamber depth is shallow the HS may not be fine. And so on in finite combinations of parts and dimensions. You do not KNOW if the parts are correct unless you check them. They are checked with a HS gage.