View Full Version : Single vs double hook
02-19-2004, 12:50 PM
ok whats the differance in single hook and double hook triggers? Ok well DUH! besides that. it seems that a double hook would have two "sear" surfaces and there would be more chance of them not releasing evenly and there would be twice as much friction and drag ( roughness? ) or does it mean lighter pull's due to splitting the forces more evenly. ? opinions any one ever used both side by side... what was the idea behind the double hook ? safety ? kind of a belt and suspenders thing ? or am I missing something ... are they " staged" help me out here.
02-19-2004, 08:04 PM
Second-guesing MTK, I'll say the second hook was insurance against a broken trigger stopping the rifle. Actually, you could use the disconnector as a sear, firing thr rifle as you release the trigger. You might get doubles and triples from this, and possibly run-away full-automatic fire. It's not something I'd want to experience, especially at a range. I only know of one person who had a broken trigger, on a SAR-1 that had been used for bump-firing a lot. And that was after 10-12 cases of ammo through it, I think.
The smoothest trigger I've ever had was a double-hook MAK-90 that had been polished, had numerous different lubricants used on it, and had fired several thousand rounds. I've never had a problem with different releases for the 2 hooks, but then how would you know if one hook was releasing early? You only feel the second one.
I've never agonized over the one-hook/two-hooks problem. If the receiver was cut for double hooks, I got a double-hook trigger; if it had only one slot for the trigger hook, I got a single-hook trigger. The single-hook trigger was easier to make, and was put into the AKM along with many other changes, several of which were objected to by MTK. The single-hook worked well enough that it, along with most of the other changes, were carried over to the AK-74.
I've never bothered to compare the hook heights on single-hook vs. double-hook triggers. The distance from the top of the trigger to the release plane is much greater on the single-hook triggers, but I don't know if that holds the hammer deeper in the receiver, or total height is greater for some reason.
When the SARs started coming in, they brought the dreaded "trigger slap". (At least, I never heard complaints about it before.) I don't know what changes in trigger geometry were made, but the Romanian rifles were imported with a disconnector that had no tail on it. The tail was used to retract the disconnector so it could not catch the hammer during full-auto fire. The tail was bobbed on most of the civilian rifles, and on later ones the selector was changed so it couldn't catch the tail even on a full-auto disconnector. The Romanian ones did away with the tail altogether, but the US disconnectors put in to replace import parts still had the tail and caused slap. Many people attributed the slap to the single-hook trigger, and replaced single-hooks with double-hooks. No one said anything about slap from the double-hook triggers, but I don't know if it was because it was cured, or because they just gave up. After this there were changes to the contour of the toe of the disconnector, and finally removing the tail completely. And I don't know if later SARs have have trigger slap. But this was the reason that many single-hook triggers were replaced with double-hook ones.
02-19-2004, 09:38 PM
Rats , now I wish I had my stock hungarian disconector to look at. I can not visualize the tail and the reason for the trigger slap. Thank you PR for the wonderful explaination and taking the time to share that with me.
02-20-2004, 07:39 AM
This is just been my experience and others may have a different opinion, but I find the double hook setups to be smoother and have a better let off then the single hooks. With that in mind, the only double hooks I've seen have been on milled recievers, so that may account for something. The Sar 1s and WASR 10s are known for having poor quality FCGs. Several well regarded builders and smiths have mentioned this. As far as having the weapon fire when the trigger is released, I think that is a no-no, since it is considered full auto. Anytime a semi auto AK "doubles" (not counting bump firing) it needs to be checked out, as it may be firing "out of battery" (the bolt is not closed all the way)
02-20-2004, 10:41 PM
If you look at the disconnector from the left side, profile, hook at the top and facing left: the toe is the bottom left, beyond the pivot hole, and the tail is the projection to the right, about the bottom of the chamber the spring fits into. When the bolt carrier comes back slapping the hammer down onto the disconnector, the disconnector goes back HARD, and that tail hits the rear of the trigger, forcing it down and moving the trigger forward against your finger. I had slap on a SA2000, and I modified the hook on the disconnector. Going up about .050" above the hook, I drew a line to the top of the disconnector, and removed the metal above that line. It gave the hammer a better mechanical advantage when hitting the disconnector, thrusting it back more slowly so it didn't slap. It was so bad you didn't want to fire a second mag through it; one was enough.
I just looked at a Saiga (it was nearest to hand) and while checking for firing out of battery, noticed that the hammer hits very near the tip of the disconnector. When I converted a Saiga to AK style, I was tempted to leave the Saiga hammer in place, and even attempted to use that, but it wouldn't work--the sear didn't touch the hammer. So I put the right, legal hammer in, and it was long enough to work perfectly. But the interesting thing is how far out the hammer hits the disconnector--it would reduce the force on the disconnector, which would reduce any trigger slap. In fact, the rifle has no slap.
On the firing "out of battery": you can't do it with an AK. Pull the receiver cover off and remove the recoil spring, then cycle the rifle (empty, of course). Stop anywhere from the hammer pivot (as a good enough place to start) until the bolt is stopped by the barrel and starts to lock and release the hammer. It will hit the bolt carrier instead of the firing pin. Only after the bolt has quit moving forward and has locked does the bolt carrier get out of the way so the hammer can hit the bolt (firing pin).
On double-hook triggers and milled receivers: the first issued AKs (I think) had milled receivers. (The first design had partially stamped, partially milled receivers, but I don't think they were issued.) There were several modifications to the rifle, including the rate reducer in the trigger group, single-hook trigger, and the stamped receiver, and this was designated AKM (AK Modified). So most of the milled receivers follow the original, and are intended for the old, double-hook trigger. The Chinese, when they switched from milled to stamped receivers (and they were making both, or had a stock of the milled receivers, when they were exporting to the US), kept the AK-47 design, putting it in a stamped receiver instead of the milled one. So all the Chinese use the double-hook trigger. Don't know if that's the reason, but most of the Chinese AKs have good triggers.
The bad FCG on the SAR and WASR is due to the US-made parts swapped to reduce the parts count. I think they had to replace 5 parts, and they went with the FCG, gas piston, and pistol grip. I heard a guy saying that he bought parts from some dealer. They were Romanian, and he swore the rifle worked better with them. I informed him that the rifle was illegal with those parts in it, but he wasn't concerned. I didn't see him after that.
02-22-2004, 11:50 AM
Packrat, you are right about the A.K. designed not to fire out of battery. Thats why they have a "tail" on the end of the bolt carrier. If the hammer falls re-maturely, it is supposed to chase the bolt carrier down the receiver, without striking the firing pin. I recently had a mis-fire, when I ejected the live round, it had a very light firing pin mark on it. I think that this is what happened and I don't want to have it happen again. I decided to invest in a quality made U.S. FCG, I haven't had a chance to try it out yet.
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