This is one that is even more obscure then overtravel. Lock Time is the amount of time from the hammer release to the firing pin being contacted and driven in to the primmer of the cartridge.
With lock time, shorter is better. This is true for speed guns and target rifles. As lock time increases the more time the shooter has to flinch or move off target. Unfortunately for us, AR-15’s have a very long lock time.
Here are some of the ways to overcome the AR’s deficiency. First, you can make the hammer lighter. Here is a base line of hammer weight. The M16 hammer comes in at 33.9g. Next is the G.I style single stage at 33.4g. The M-K hammers are just 21.4g. So if you’re using a G.I. or M16 hammer you can see the disadvantage you’re starting out with. Why is a lighter hammer better? With a lightweight hammer, the spring has less mass to move and overcome. This increases the travel speed and decreases the lock time. But, you need to be very careful.
You can’t just grind down your hammer or drill holes in it. If you do this you will destroy your hammer. Hammers (at least good ones) are heat treated. Cutting or grinding will take the strength out of the steel. The heat treating is also why you can’t drill holes in your hammer. You’ll have a hard time getting the hole started. You can always EDM (Electrical Discharge Machining) the hole. Put the hole in the wrong place and the hammer will snap in half or the hooks may snap off. Have a look around the Web. You’ll find some manufactures’ hammers without holes snapping in half. This is from improper heat treating. That’s how important the heat treat is and why you should try to preserve it in all critical points.
One other problem you may find with a light hammer is the amount of energy the hammer will have. You can get light primer strikes with a light hammer. Military primers are hard primers. This means they need a lot of firing pin power set off. The lighter the hammer, the less energy. A fast lock time without the ability to fire the round won’t do you any good.
Non military hunting or target primers are much softer. They will ignite with a softer hammer hit. Here comes the downside: The price of target ammo. This ammo costs much more than military surplus or military production ammo costs. If all you shoot is target ammo, no big deal. Because I’m cheap, I only shoot target ammo if I need to. If I’m just having some relaxing range time putting holes in paper or tin cans I don’t feel the need to spend $1.00 plus a round.
Springs are also a way to speed up lock time. Put a more powerful hammer spring on the hammer and it will go faster. That sounds easy. And it is easy but it has a lot of downsides.
First, the more powerful the hammer spring, the more friction is on the hooks. If the hooks have any imperfections in the surface finish, the pull will be very gritty. Remember Part 3 of trigger talk. The other issue you can run into with a more powerful hammer spring is pull weight. With more power comes more friction. Even with a perfect hook finish you will increase friction. With more friction you need more power to move the hooks apart. The only place you can get more power from is your trigger finger. This means you have to pull harder which will show up as a higher pull weight. It will show up in first stage big time. If you do not have an adjustable disconnector trigger system, you will feel the added pull in second stage too. It will come from the trigger creep. Go back and have a look at Part 2 of this post.
Here we go again. It’s sales pitch time. How dose the Wisconsin Trigger Company deal with lock time? We start with the finish on our hooks. As I have said before, we hold a very high standard to all our finishes. This cuts down on friction so we can use a strong hammer spring. This full power hammer spring gives all M-K trigger sufficient power to set off all types of primers and the speed to move the hammer quickly. The M-K hammers are lighter than some and heavier than others. Our heat treating is state of the art. We do some other things that I’m not at liberty to discuss. The end result is our hammers don’t snap in half and our lock time is very respectable. As you are starting to see, triggers are one big balancing act.
Get ready for chapter six. I’ll try to wrap it all up.