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GP100 Hammer modification

This is a discussion on GP100 Hammer modification within the Gunsmithing forums, part of the Firearm Forum category; Fritz, I have actually done this hammer modification on a couple GP-100s and a bunch of S&Ws, all with great success but a lot of ...


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Old February 23rd, 2009, 08:10 PM   #16
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Fritz, I have actually done this hammer modification on a couple GP-100s and a bunch of S&Ws, all with great success but a lot of work. I will agree ... it's no job for a kitchen table gunsmith and I would not recommend it because Ruger won't sell you a new hammer if you screw up.

I do not have a way to measure locktime nor firing pin energy but here are my results:

After completing the modification, the hammer weight was reduced from 1.5 oz (42.5 gm)to about 1 oz (28.35 gm). The 13 lb GP-100 factory hammer spring was replaced with a 10 lb spring. Some of the Federal standard primers actually ruptured so I reduced the hammer spring to 9 lbs. The 9 lb spring worked well with both standard and magnum primers. In all, this was about a 30% reduction in DA trigger pull and a considerable reduction in locktime. The primer dents with the modified hammer and 9 lb spring were deeper than with the factory hammer and spring. That tells me more energy is applied to the primer with a lighter hammer and weaker spring.



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Old February 23rd, 2009, 08:47 PM   #17
 
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Aftermarket titanium hammer with hardened stainless steel sear insert?
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Old February 23rd, 2009, 09:36 PM   #18
 
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Iowegan, as usual, you are pretty right. But it is not a question of the hammers kinetic energy being higher due to a reduced weight and thus increased speed. It is a question of pulse. And the inner energy (the part of the hammers kinetic energy which is transformed to heat) is determined by the hammers speed to the sqaure whereas the hammers mass only is a linear factor (and small in comparison to the guns mass).

BTW this should also have another positiv effect on accuracy, as the accelaration of the gun by the hammers hit is smaller.

Your observations are approved by theory ;-)

@firesocut: Where is this aftermarket hammer available?

Fritz
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Old February 25th, 2009, 04:37 PM   #19
 
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Just to make it easy to see the effect of lighter hammer consider the following:

Imagine you are standing on a skateboard. Your back is hit by a mass of 10.000kg (10 tons) moving with a speed of 1m/s (2.23 mph). This will not hurt you and after the collision you and the mass will travel together at approximately 1m/s (2.23mph) with together approximately the same kinetic energy as it had the mass before.

Now take a mass of 100Kg (220lbs) traveling at 10m/s (22.3mph). The kinetic energy of this second mass is much the same as the mass before. But this time you will be kind of deformed by the impact. After the collison you will travel together with the mass at a lower speed. There will be quite a bit of the kinetic energy be lost. It is gone in the deformation of your body - chances are that you wont survive the second scenario.

That is why speed of the hammer matters. The kinetic energy of a lighter hammer will stay much the same, it is only determined by the springs force and the hammers way, which both stay constant. But the "inner energy", that is the part gone in deformation and heat during impact, will considerably vary.

Why do they than opt for such a heavy hammer at Rugers? Well, think of the tiny obstacles in the hammers way (machine marks, roughness of cast...) as causing tiny collisions on the way. A lighter and faster hammer will lose more energy on its travel than a fat and slow one. The latter travels, better "cruises", over the imperfections without "noticing" them. The fat hammer cures for the imperfections of the manufacturing.

So if you have cleaned up the hammers way, you should have the possibility to go for a lighter hammer and even a lighter spring, as you will get the same effect on the primer with putting less kinetic energy in the hammer.

Fritz

Last edited by Fritz; February 25th, 2009 at 05:13 PM.
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Old February 25th, 2009, 05:50 PM   #20
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Fritz, I don't think your analogy applies much in this case. First, the part of the hammer that does the work (impact energy) is the face and spur that form the hammer's head (which you don't change). You do eliminate weight from the "handle" of the hammer where it doesn't contribute to impact energy. The hammer spring just sees a mass that it needs to move. If some of that mass doesn't contribute to the energy applied to the primer, then it isn't needed. Of course you can't remove too much metal or you will affect the strength of the hammer.

Ruger hammers as well as most other brands are made for looks, function, and ease of manufacture. I must say, a skeletonized GP-100 hammer is pretty ugly.

Skeletonized hammers are not new. Browning Hi-Powers started this trend back in 1935. Colt Commanders have always had skeletonized hammers and Colt started shipping 1911s with radical skeletonized hammers in 1980. They boasted reduced lock time without sacrificing primer detonation. So, this is a well established technique, only not a factory feature on any revolvers that I'm aware of. Believe me, it does work.
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Old February 26th, 2009, 08:49 PM   #21
 
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So Iowegan, in your opinion is it worth it? How thick would you leave the solid portions of the hammer.....1/8"? Like I said before I am interested in doing this, especially since I have all of the proper equipment available to do so.
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Old February 27th, 2009, 03:33 AM   #22
 
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Well, excuse me for thinking aloud. Take it as an invitation to correct and help me.

Where the mass sits doesn't matter at all. The energy is determined by the force and the way, which remain constant, whatever mass with whatever distribution you are accelerating (with a given spring).

Due to the moment of inertia massreduction farther from the axis are more efficient. The hammer gets much more velocity.

The analogy with the carpenters hammer doesn't realy apply. With the carpenters hammer you don't want to smash the nail but you want to drive it. So you need high energy at low speed - remember, the inner energy, i.e. the part transformed in deformation and heat on impact, is proportional to the speed squared. That is why a carpenter hammer needs to have quite a bit of mass on its exterior.

The revolvers hammer just needs enough mass to surmount the obstacles on its way (machine marks, cast roughness and the like) and the faster it gets, the higher is the portion of its kinetic energy which will be transformed on impact.

Well, so for a revolver with the hammer hitting the primer my reasoning appears not to be to bad. But in the case of the Rugers, we have the firing pin between the hammer and the primer. So there might be some more consideration neccessary. The catch is, that this is not an plastic pulse but an elastic pulse. At least it should be. So, don't get to fast, otherwise you will smash your firing pin.

The more and more I think about it, I tend to give it a try.

Fritz

Last edited by Fritz; March 1st, 2009 at 12:48 AM.
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Old May 23rd, 2009, 03:46 PM   #23
 
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Update

So I tried to drill thru the hammer per IBOK and I ended up with a butchered hammer, I could not do it with a bench top drill press. My hammer looked like crap, I decided to visit as gunsmith (Dave Norin, over 36 years of experience in the field, and is a member of American Handgunner magazine's Club 100 Gunsmiths.) he tried and gave up! he said its ruger stainless steel and there is nothing he can do!! WTF!!

... and than it came to me! lets narrow it down!!- reduce weight and get rid of the holes that I previosly drilled!
I used a mounted dremel holding the hammer in my hand (so it doesn't get to hot)
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Old May 23rd, 2009, 03:56 PM   #24
 
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damn, I don't know how to post pictures, went to my control panel per FAQ but the "pictures and albums" is not there ... I'll try later...
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Old May 24th, 2009, 03:37 AM   #25
 
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Talking

OH NO!!! Not the dreaded heavy hammer,less than stellar lock time fiasco that has plagued all Ruger double action revolvers since the dawn of time! My God, the horror,the horror.Just last year we were besieged by the light firing pin strikes on revolvers that actually went BANG when you pulled the trigger.That required us to machine off some of the step on the hammer face so that the gun would go BANG even more when you pulled the trigger. How dare they follow that up by installing heavy hammers that need to be drilled and lightened. Those Ruger designers and engineers can be so cruel.Those guys working at Ruger's Parts Dept. must be having a good chuckle. I know I am. You just know the price on their hammers is going up again!
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Old May 24th, 2009, 08:01 AM   #26
 
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Quote:
Originally Posted by PaPaPork View Post
So I tried to drill thru the hammer per IBOK and I ended up with a butchered hammer, I could not do it with a bench top drill press.
PaPa,

Just found this thread. It sounds like you have solved your problem. However, I am writing this in case anyone else wants to try.

Did you ever find a "Carbide" drill bit? There is a distinct difference between "Titanium", "Cobalt" and "Carbide". You can easily find the Titanium Coated and Cobalt bits at the local hardware stores. This is not what is needed. These drills are only slightly harder than ordinary tool steel. They work Ok at home but they are not what is needed.

Carbide bits are machinist bits. They are designed for hard materials. You will need to find a store that supplies machine shops in order to get them. (Grainger or McMAster-Carr for example.)

The downside of Carbide is that is very brittle. You need a good drill press that is straight and square to the table and you need to hold the piece down securely. If the piece spins or twists you are going to more than likely snap the bit. You also need to lubricate well with a quality cutting and tapping fluid. You could do this with a table top drill press if you set the unit up well. However, a larger industrial drill press would be preferable.

Just my 2 cents. Cheers.

Last edited by chezrad; May 24th, 2009 at 08:07 AM.
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Old May 24th, 2009, 05:06 PM   #27
 
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this is 96%finished (needs final polishing)






Last edited by PaPaPork; May 24th, 2009 at 05:45 PM.
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Old May 25th, 2009, 05:50 PM   #28
 
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PaPaPork;
I don't think I'd polish it. At least I wouldn't because I'd never be able to get the new surfaces flat enough to look right. I'd either blast it with fine 80 or so Garnet, or peen it with glass beads depending on the look you prefer. Or I would sand it in a manner that would leave that nice brushed look.

Another option I was thinking about for people who want the weight loss but prefer the oem look: Basically you would honey comb it from the front edge using a bit ~.200-.250" or so and drill 95% the way thru. Maybe 3 or 4 holes starting at the firing pin relief would do the trick, maybe some smaller holes around the bigger ones, or if you had a mill you could machine it hollow. You'd only be able to see the holes when it's cocked and you're looking for them, and if you really wanted to be slick you could plug the holes with thin little tapered plugs of matching metal, sand smooth and match the finish and they should be invisible. If you plugged it you even drill one long one from the top as well. The end result would be a stealth hammer.

Another thought: Sanding .100" or so off the very top of the hammer would be very easy for most people and it would look factory to most. If you sanded it inline with the barrel you'd get even more off the back side and I think it'd look better to boot.

Another: Does anyone ever modify/lighten the transfer bar?
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Old May 26th, 2009, 08:20 AM   #29
 
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Well... as a mechatronic engineer, i'm glad to see you guys have (some) decent mathematical background

I think I'll pull my hammer off in a while and lighten it up. I have a full machine shop at my disposal, as well as a CNC and MasterCam.

I'm in agreement with Iowegan. As soon as I disassembled my GP and felt the weight of that hammer, I immediately knew that it will be a REAL B***H to machine. Luckily for me, my school's shop has more carbide bits then I can shake a stick at . I was thinking about removing weight in a much different manner than PaPaPork, but he did a decent job. I was going to put the hammer in the CNC, and do a pocket mill cut in the shape Iowegan designated. I wanted your opinion-how deep should I go? I was only thinking about maybe a 1/16th or so on each side...

And about machining the transfer bar- I think that its mass out on its little radius arm is pretty inconsequential, since its movement is so small as the hammer hits.

Last edited by MagnumWill; May 26th, 2009 at 08:22 AM.
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Old May 26th, 2009, 08:35 AM   #30
 
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+1 on the comments by Chezrad on needing a carbide drill bit and a lot of coolant. The carbide bit will get very hot as it turns and will not progress very fast. The hole will not be smooth sided after you are done.

It may be better to use a Dremel with a small cutoff wheel than a bunch of holes. You will probably end up using it anyway along with a die grinder to clean up after the drilling process.

Earlier it was suggested to use a wire EDM. This will give you the intended result with nice smooth interior surfaces. It would be worth the money to have a tool & die shop do this work.
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