Primer Ignition With Bobbed Hammer

[Racer]

I've only had physics 101 in college but if I remember correctly if you remove weight from an object it will not exert same force as the heavier. So if I bob hammer I'm going to get a lighter primer strike all else equal correct ???

[Boom-Boom]

Let me take a stab....

force = mass * acceleration

So removing mass will reduce the force if the acceleration is constant.

However, the hammer spring is what provides the energy to accelerate the hammer and w/ less mass, it is easier for the spring to overcome inertia to accelerate the hammer. This leads to faster lock times (good thing), but not necessarily reduced striking force.

So my guess is that hammer spring weight has more to do w/ primer ignition than hammer mass. If you have good ignition w/ the hammer spring setup you have, you will probably have good ignition after you bob the hammer.

[Bill H]

IIRC Jack Weigand told me that you could improve ignition by bobbing the hammer. He could make a lighter weight pull with the bobbed as opposed to the stock weight which required more spring to be as consistent.

Bill

[Round_Gun_Shooter]

I've only had physics 101 in college but if I remember correctly if you remove weight from an object it will not exert same force as the heavier. So if I bob hammer I'm going to get a lighter primer strike all else equal correct ???

Now the short answer.

Not correct

I have bobbed a lot of hammers and never had a problem.

Regards,

[old shooter]

I have used bobbed hammers on a double action k frame a long, long time without any problems. Make sure the hammer doesn't rub on the frams and you will be ok.

Mike

[Greg G]

I have found that if you are having trouble with primer ignition with a light trigger pull it sometimes helps to shave the front of the hammer ( on older S&W's) to get more consistent ignition

[Racer]

Thanks guys. It's going in my mill vise first thing tomorrow morning. It's a 686 38 super with black magic kit using the longest hammer spring. I'm using Federal primers, Starline brass and thought I had it made @ 6.5#'s until I shot my first match with it and had one no go on first strike out of aprox. 90 rounds . Of course everything was fine when practicing after initial setup and firing 200 + rounds. And I did loctite the strain screw.

[SpeedStick]

Racer,

In our experience, you are Correct. With a revolver set up correctly, taking away weight will make a lighter hammer strike.

When you get a trigger pull in the 5.5 lb to 6.5 lb range everything must be set up correctly. Headspace at .008, this is a MUST before you start changing other parts. Shaving the hammer face (in models without the frame mounted firing pins) or adding an extended firing pin won't help IF you have the headspace set correctly, at least our experiements has proved this.

My 38 super 8 shot has a 5.75 lb double action trigger. I thought that if I installed the extended firing pin I should get the trigger pull lighter? Well it did not work. With the stock firing pin and the extended firing pin it took the same amount of force to ignite the primer. Now, if my headspace was more than .008 the extended firing pin may have worked where the stock one didn't?

The use of Federal primers is a must and all our experiments were done WITH Federal primers. With other brands there may be a difference.

[dajarrel]

Boy, I'm fixin' to dive off into some memories gone cold here!!!!

Kinetic Energy = 1/2 * Mass * (Velocity squared)

energy (at the interface of the hammer and firing pin) is a result of the mass of the hammer times the square of the velocity. In other words, You can reduce the mass of the hammer by 1/2 (for discussion) and if you maintain the velocity of the hammer you have cut the available energy by 1/2. However, if the speed of the hammer doubles (again for discussion) as a result of the bobbing, you have increased the energy by 4 times (because it's squared) which actually increases the energy at the firing pin.

The long and short of the matter is that the speed of the hammer is increased by at least enough to overcome the loss of mass on the bobbed hammer. If it was any other way, it wouldn't go "bang"

dj