Lower Mass Hammer = More Striking Energy?

[bountyhunter]

It was my understanding that one of the benefits of going to a a reduced mass hammer (autos or revos) is the higher velocity they can attain gives a better energy tranfer from the mainspring to the firing pin. Ergo, you can use a lighter mainspring (which gives a lighter trigger pull) and still get reliable primer ignition.

The question arises from the "bobbed hammer" often done on a carry revolver (which is admittedly, a small change in hammer mass but is located farthest from the pivot). Some have said this actually increases hammer strike energy slightly.

I recall somebody here selling low mass comp hammers for revos for the express purpose of getting lighter trigger pull.

Any expert gun tuners who can comment on this?

Thanks. Always want to make sure I am not propogating an urban myth.

[Bob Hostetter]

The purpose of a reduced weight hammer, just like a reduced weight firing pin, is to reduce the lock time, and make it easier to get a reliabile low weight trigger pull.

These modifications tend to reduce the energy with which the firing pin strikes the primer, in some cases causing problems with light hits................

Edited January 4, 2006 by Bob Hostetter

[Crusher]

What Bob said, faster lock time = faster ignition= less time to screw up a good sight picture in warp speed shooting.

[lim10gm]

... a good sight picture in warp speed shooting.

That's funny.

[Randy Lee]

Figure I better chime in here in regards to revolvers. This is a pretty complex issue. If it were a simple linear motion, we could distill it down to F= ma. In the S&W revolver's case you need to look at whether it is the old style hammer nose set up or the newer frame based firing pin system as to the potential benefits of lightening the hammer.

For a NEW DA Smith revolver, lightening the hammer has certain advantages above and beyond lock time. Inertia is a b**ch. A body at rest will tend to stay at rest until acted upon by another force. In the case of a heavy target hammer falling, it will take a longer time for that hammer to reach a minimum terminal velocity necessary to ignite a Federal primer. So the threshold mainspring force as measured at the hammer face has been say 2.0 lbs for reliable ignition. Now, the necessary spring force required using my hammer is 1lb 13 oz. So a net reduction of 3 oz. of force is achieved on a conservative estimate. Depending on the gun, as little as 1 lb 9.0 oz has been reliable. End result is that less mainspring tension is required to achieve the goal of reliable ignition. One test revolver measures a trigger pull of 2 lb 13 oz double action. If there is no advantage to a lighter hammer, this should be doable with a Target wide spur hammer.

Another advantage of a lightened hammer is recognized in the pull of the trigger. The greater the mass of the hammer, the more energy is required of your trigger finger to get it to move rearwards. The greater the mass, the greater the inertia- can't get away from that.

* an important note- it's not only removing the metal, but where you remove the metal that is important.

In regards to the newer Smith revolver you really need to look at the types of collisions between the hammer and firing pin, and then again between the firing pin and the primer.

Energy is conserved and as a result, so is momentum between the colliding parts. BUT one type of collision imparts TWICE the momentum of the collision found in the older hammer nose firing pin system.

It all boils down to - yes, a lightened hammer in a Smith makes a difference in the quality of a trigger job. Ask Jerry Miculek, Jason Pettit, Vic Pickett or John Bagakis what they think about the skeletonized hammer. These are the guys who know what works.

~Randy

Edited January 5, 2006 by Randy Lee

[Carmoney]

These modifications tend to reduce the energy with which the firing pin strikes the primer, in some cases causing problems with light hits................

This was the old-school line of thinking, but it has been soundly disproved now for several decades. To boil down Randy's engineering perspective to common parlance, fast slap always beats slow crushing blow.

Take a S&W revolver, new or old, either firing pin type, and adjust the action down to the bare edge of reliability (wherever that might be on that particular gun). Now cut all unnecessary weight off the hammer, like this:

Or this:

You will find that you can then take down the mainspring tension even further and still maintain full ignition reliability. That's empirical proof. It's also not a new concept. My skeletonized hammer shown in the second picture was largely copied from a picture from a 25-year-old book I have here on my shelf.

There's a reason why my revos don't wear spurs, fellas. It ain't just to make 'em look cool.

[Radical Precision Designs]

Randy Lee made some excellent observations above.

It is really a formula of margins as needed for ignition. Let's say in a specific ignition set-up the primer requires an approximate minimum of 4 lbs per square inch (not verified, just theoretical) as transferred by the firing pin to properly crush and detonate the primer, and this impact transference to have an average "dwell" time of energy transfer of let's say one second (slowed down a lot just for ease of comparison!) for "lock time".

Now let's play and rearrange things. Let's continue to say that an average Colt Commander original hammer along with an 18 lbs. mainspring will provide a formula of 8 Lbs. @ 1.5 secs. This of course exceeds the minimum requirements and ignition will be acceptable. But we want to "soup" it up for performance. Diferent formulas are available. It's almost like composing music. The easiest perceived trick would be to lower the mainspring weight for a perceived "no fuzz" ligther trigger pull. So we go to let's say the same hammer weight with a 17 lbs. mainspring. Now the formula changed to "7" lbs. @ 2 secs. While we gained a slightly ligther trigger pull, we lost in lock time and energy transferred, but in this case it's still adequate to ignite the primer. There was a trade off of lock time for trigger pull. While this may be acceptable for some as a quick fix, you are only fooling yourself. The real acceptable gain would be to manipulate the formula into having a lower weight/mass hammer/strut that would be overcome faster/easier by the spring weight to achieve a faster lock time while maintaining minimum "acceptable" mass for inertia/energy transfer.

The biggest mistake made by some "tunners" is to both lower the mainspring weight and the hammer weight for a gain of a minimum trigger weight with the resultant loss of lock time and ignition reliability. The real gain would be to install a lower mass/weight hammer that has been lightened first in it's "pivot/pin" area and then lightened outwardly in its arc area. Combine that with the same or a "heavier" mainspring weight, and you will realize a true performance gain without loss of reliability. Analize this. By reducing hammer mass/weight you decreased "potential" lock time (by increasing possible travel speed), but you also lost a little bit of potential energy at delivery by decreasing the mass, so the only way to increase and balance this formula you need a litle bit more speed to gain more momemtum which can be achieved by increasing (not decreasing) mainspring pressure/weight. The way I see it, lighter mainsprings belong with heavier hammers (slow lock time), and lighter hammers belong with heavier springs (fast lock time). Of course whichever formula you use it must develop enough energy to ignite the primer consistently. (You must also consider that lowering or increasing your mainspring weight will also affect your recoil spring weight requirements...)

As for obtaining a light trigger pull, regardles of your combination: it's all done with mirrors! ...and that's another thread...

Edited January 5, 2006 by Radical Precision Designs

[Randy Lee]

Thanks Mike,

It took me what, five paragraphs to say what you did in one sentence?

[Carmoney]

As I see it, the whole point to this exercise is to get the lightest possible mainspring tension that is still 100% reliable with properly-seated Federal primers, right? Because mainspring tension is one of the key elements (but by no means the only one) in determining the eventual DA trigger pull weight that the shooter will have to overcome.

It's not just a matter of energy transfer. Primers ignite more readily and more reliably with a fast slap (within reasonable boundaries obviously) than a slow blow--even if the actual energy transfer is the same. The lighter hammer can speed up lock-time to a meaningful degree, meaning the more optimal fast slap can do its thing. You can therefore reduce the amount of stored energy in the mainspring (i.e. reduce its tension) to some degree and still get 100% ignition.

The little feature in AH does a lousy job of explaining this, but everybody needs to understand that nobody's saying that simply installing the Randy hammer, or some skeletonized version of a factory hammer, will lower the gun's DA pull weight to any meaningful degree, in and of itself. Installing the lightened hammer, however, will allow the DA pull to be tuned to a lower weight (i.e. reducing mainspring tension a bit further than you could otherwise get away with) and still remain reliable.

It took me what, five paragraphs to say what you did in one sentence?

Heh-heh! Now I've just gone and made it all complicated again!!

(Actually the "fast slap beats slow crushing blow" is a line I stole from you anyway, so you deserve the real credit for being clear and concise after all!)

(Furthermore, I think we'd all agree that there are other realms of life in which a slow blow is much better than a fast slap....)

[Randy Lee]

(Furthermore, I think we'd all agree that there are other realms of life in which a slow blow is much better than a fast slap....)

Man, I gotta get out of the shop more often...

For the revolver, I also forgot to add that reducing the mass of the hammer and therefore the mainspring weight also reduces the load that the rebound slide has to overcome in order to reset the hammer.

Edited January 5, 2006 by Randy Lee

[Radical Precision Designs]

As I see it, the whole point to this exercise is to get the lightest possible mainspring tension that is still 100% reliable with properly-seated Federal primers, right? Because mainspring tension is one of the key elements (but by no means the only one) in determining the eventual DA trigger pull weight that the shooter will have to overcome.

It's not just a matter of energy transfer. Primers ignite more readily and more reliably with a fast slap (within reasonable boundaries obviously) than a slow blow--even if the actual energy transfer is the same. The lighter hammer can speed up lock-time to a meaningful degree, meaning the more optimal fast slap can do its thing. You can therefore reduce the amount of stored energy in the mainspring (i.e. reduce its tension) to some degree and still get 100% ignition.

The little feature in AH does a lousy job of explaining this, but everybody needs to understand that nobody's saying that simply installing the Randy hammer, or some skeletonized version of a factory hammer, will lower the gun's DA pull weight to any meaningful degree, in and of itself. Installing the lightened hammer, however, will allow the DA pull to be tuned to a lower weight (i.e. reducing mainspring tension a bit further than you could otherwise get away with) and still remain reliable.

It took me what, five paragraphs to say what you did in one sentence?

Heh-heh! Now I've just gone and made it all complicated again!!

(Actually the "fast slap beats slow crushing blow" is a line I stole from you anyway, so you deserve the real credit for being clear and concise after all!)

(Furthermore, I think we'd all agree that there are other realms of life in which a slow blow is much better than a fast slap....)

L.O.L.

[Jasonub]

too complicated.

I put a koeinig hammer on a sv titainium strut and an sti titanium cup. 15 pound ismi mainspring.

it ignited 26000 rounds plus in 2 years in my sv 40 using winchester wsp primers. trigger pull is about 1.2 pounds.

ahhh simple. it works thus i stopped tinkering

[bountyhunter]

Thanks for all the information. Very enlightening.