Is there an advantage of one over the other?

My Chjinese rifles have double and trigger operation is smooth. My SARs and recent build have single, and they work fine. and are smooth.  What is the scoop on these––-individual preference or a good solid reason for one over the other?

they say that the double hook has a lighter pull than single. i guess it makes sence if you have two hooks the amount of force being applied against those hooks by the hammer would be cut in half, hense less friction when they slide off the hammer to release it.

We seriously need a 'single vs double hook' sticky thread/reference thread

My single double hook triggers hve pulls that are about 3#s.
My single hook triggers have trigger pulls that run from 4 to 4.5#s.
YMMV

to the contrary, when you double the engagement surface, you INCREASE the trigger pull, not decrease.  That being said, one must not confuse a real single hook, like the Arsenal type, from a double hook with one arm cut off - like the TAPCO.  They are fundamentally different.

The double hook is a 2-stage.  The (real) single hook is a long single stage.

3/4 of the way through the trigger pull on a 2-claw, the disconnector contacts the back of the hammer and adds the disconnector spring weight to the last 1/4" of pull.

the (true) single claw does not.  

a similar function can be added to the true single claw such as on the PSL bu a small dip right before release - the Arsnal USA  unmodified have an obnoxious but on both the hammer and trigger which dramatically increases the pull right before release - not a 2-stage, though, just a defect in the casting.  On some, they removed it.  can tell by sniffing for cold-blue.

Glad you're here.  That's correct friction is dependant on surface area.  What the double hook offers is more security and peace of mind.  It certainly can be worked for reduced pull but the single hook is actually sufficient for most needs.  These guns all had single hooks originally (I'm not aware of any exceptions, maybe I'll stand corrected).  You just choose what works best for your receiver/wants.  If you want lower pull then look at a single or Tapco has them with 3-4 lb pull for far less than my Red Stars cost me.  

Chinese made rifles all had double hook triggers. The Chinese never changed over to the AKM trigger and rate reducer.

I checked my IMI Galil model 372, and it has a double with one arm cut off. It came that way from the factory and I have been the only one to have owned it.  Great trigger anyway.

My Chinese both have double hooks, and Century SAR 1 has a single (US made but not marked as far as I can tell).

If a single is good enough for the Galil, it's good enough for me!

I really don't think it matters as long as the surfaces are smooth.

So there are some exceptions (not that I ever have had a Chinese version).  I suppose the reason most use single hooks is not because they wanted reduced trigger pull (the standard military trigger is around 10 lbs) but simply because full autos had rate reducers on the side and therefore no second hook could be placed there.  Having said that, I stand by the basic physics concept that friction is dependent upon surface area and typically a double hook will have greater trigger pull than a single hook.  So if you want to improve pull you may want to consider a single hook.  

The type-classified AK-47 had the double claw. The  type classified 1962 (AKM) had the single claw to provide room for the anti-bounce device (sometimes called a rate reducer, although that is a parasitic result of its function).  

Not all countries adopted all of the features of the AKM - and even those who did  had an extensive transition period.

Full auto galils, essentially .223 valmets, use the double claw. At least all the ones I saw when I was going through their jump school did.  The double claw with one cut off is a feature of the semiauto - perhaps to reduce the trigger pull for the "civilian" version.

I am unaware of any other model that uses a double claw with one cut off - but I learned long ago to avoid "never" and "always" when dealing with gun patterns.

There is more to trigger feel than weight alone.  The geometry and physics behind this goes well beyond surface area and friction.  Ideal engagment surfaces and geometry is more important than the number of 'hooks' on your trigger.

That said, some THEORIZE that a double hook is smother because it has less side loading than a single hook.  I think the design is too crude to notice such difference, almost every readily available AK trigger can be made to have a decent feel. (I personally do not like TAPCO as the hooks are too high)

I've read from several places that the original AK47 design had a double hook trigger.  The double hook had nothing to do with trigger pull.  The extra hook was simply for reliability,(if one of the hooks broke the other would keep the gun working).  It was found out over time that the hooks never broke so the double hook trigger was removed from later AK models.  It seems like a simple change with not much to gain until you consider the amount of triggers made for AK in the last 60 or so years.  I can only guess how many single hook triggers you could make from the deleted metal off the double hook design.  The rate reducing components came some time after the double hook trigger was removed from production.  All that being said, if you like double hook triggers for some reason I say why not use one.  It will not hurt a thing and some guys do like the feel of them.

Where is the best price on a G2 double right now?