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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; Hello everyone, I'm new here, but I've been working with Firearms for a very Long time. I'm very comfortable with working on most handguns, and ...


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Old October 22nd, 2008, 07:44 AM   #1
 
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GP100 Hammer modification

Hello everyone,

I'm new here, but I've been working with Firearms for a very Long time. I'm very comfortable with working on most handguns, and a friend of mine has already given me the IBOK. The IBOK is full of great stuff, and I'm going to use it when working on my new GP100.

I plan on doing almost everything from the IBOK, but I was wondering how tough is it to lighten the hammer. I've already came up with where I'm going to drill the holes, but I was wondering how tough is this going to be to do. If it is really tough, then I may just skip that part of my plans. I'd like to be able to adjust the double action pull to be light, silky smooth, and not affect the timeing. However, I don't want it to suffer from light primer strikes. My goal is to have a very light, and silky smooth double action pull.

If any of you have done this modification before, I'd like to hear your experiences. Good or Bad. I don't want to end up looking for another hammer to replace a butchered up one. I know that is next to impossible to find one.

Thanks in advance,
DBAR



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Old October 22nd, 2008, 07:54 AM   #2
 
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Out of curiosity, why would you want a lighter hammer? Wouldn't that mean you'd need more acceleration via a heavier spring to achieve the same force to the primer? Kyle
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Old October 22nd, 2008, 08:26 AM   #3
 
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Quote:
Originally Posted by Conan View Post
Out of curiosity, why would you want a lighter hammer? Wouldn't that mean you'd need more acceleration via a heavier spring to achieve the same force to the primer? Kyle

Not based on what I've read. I've gathered that if you use a lighter main spring, that you will sometimes suffer light primer strikes. I've concluded from my readings of the IBOK, that if you lighten the hammer it will make up for some of the lighter main spring. The hammer being lighter should allow it to have a little more velocity. The increased velocity should allow for a better hammer strike. I may be wrong about this, and that's why I posted this thread.

Thanks,
DBAR
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Old October 22nd, 2008, 08:35 AM   #4
 
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Ok,

I just read Iowegan's Post to another thread. This whole idea about the hammer may not be the direction I want to go in. I think that changing the springs, polishing some things, shimming the trigger, shimming the hammer along with a little work to the hammer where it meets the frame may be enough to achieve what I'm wanting.

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Old October 22nd, 2008, 11:59 AM   #5
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Lightening the hammer by removing weight from the right areas does increase the velocity, apply more energy to the firing pin and reduce lock time. However, you can't just take the weight from anywhere and expect it to work.

Think of a revolver hammer as a carpenter's hammer. The driving force comes from two parameters ... the length of the handle and the weight of the hammer's head. You can't make the revolver's hammer longer but you can do some other tricks. The hammer spring is pushing weight, no matter where that weight is and because Ruger hammers are very heavy, a lot of the weight is in non-essential areas and slows the hammer's velocity.

Again, going back to a carpenter's hammer, the thickness of the handle doesn't influence the amount of striking force energy but it does add weight. A heavy handle means the carpenter must use more muscle energy to drive a nail than if the hammer handle was lighter. You can remove considerable weight from a revolver's hammer "handle" by drilling holes in the right places. You don't want to weaken it ... just make it lighter. The farther from the pivot pin, the more influence hammer weight has on the hammer spring so you want to take as much weight as possible from the "handle" area closer to the top, yet leave the head and spur alone because that's where the mass is needed.

I have done several skeleton hammers for "go faster" competition guns where the shooter wants the lightest pull possible yet wants fast lock time and positive primer hits. Here's a Photoshop picture showing the black area where you can eliminate hammer weight and get excellent results with a 9 lb hammer spring. Note: read the other post about hammers: http://www.rugerforum.net/showthread.php?t=9741



Many years ago, I worked in a firearms lab and actually got paid to do some experiments with lock time and hammer energy. I wish I could remember all the statistics but I do remember S&W K-frames had the fastest lock time of any revolver @ .039 seconds (39 ms). Ruger Security-Sixes were a little slower ... maybe in the 45 ms range (GP-100s weren't invented yet). Security-Six hammers were much easier to deal with so we used them for our tests. By drilling the Security-Six hammers and leaving the hammer spring stock, we were able to decrease lock time by a good 25% (about 33 ms). If you plug the numbers into a standard energy formula (weight times velocity squared), the actual energy striking the firing pin was increased by 40%. By trial and error, the hammer spring tension was reduced (by clipping coils) until the factory hammer energy was duplicated (lighter spring, lighter hammer). This combination provided the same energy on the firing pin and the same dent in the primer with a 9 lb hammer spring as a stock hammer with the stock hammer spring (13 lbs). As I recall, we did have to mill the top step on the hammer to get full firing pin energy.

I removed the skeletonizing technique from the IBOK and replaced it with more meaningful information. You really need machine shop equipment to do a good job and a botched job could result in ruining the hammer. These hammers are harder than woodpecker lips so you don't just go after them with a Black & Decker 1/4" hand drill. A good drill press and carbide bits are a must.
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Old February 13th, 2009, 07:46 PM   #6
 
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need advice!

So, I decided to drill my hammer! what the hell is that thing made off?? if anyone thinks it is made of typical stainless steel - You are wrong!

I am using a Drill press (bench top - nothing big, nor expensive), water as a lubricant/coolant. I decided to use 5/32 drill bit (You can always make a small hole bigger, never the opposite) and it started fine, but as soon as I got to the same diameter as the drill I started having problems! hammer is getting hot, loud squealing noise if I apply a lot of pressure, I tried titanium bit from dewalt and cobalt drill from rigid with no luck. Speeds from 620 to 3100,

Could some one pleeeease give me a clue what the hell am I doing wrong??

Last edited by PaPaPork; February 14th, 2009 at 01:33 PM.
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Old February 14th, 2009, 07:19 AM   #7
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PaPaPork, If you read my above post, you'll see I said a carbide bit is a must. Yes, these hammers are really hard stuff. That's why I removed the technique from the current IBOK. If you don't have machine shop quality equipment, you're peeing in the wind.
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Old February 14th, 2009, 09:35 AM   #8
 
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You should also use oil rather than water as a coolant/lubricant. Light engine oil will work usually ok.
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Old February 14th, 2009, 01:39 PM   #9
 
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The reason why I went with cobalt and titanium is because all the Carbide bits I've seen were for masonry- with arrow tip. I’m guessing that’s not What You had in mind??
I will definitely use some 5W20 motor oil as a lubricant
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Old February 14th, 2009, 01:52 PM   #10
 
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Sounds like a good job for a shop with wire EDM.

Jack
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Old February 14th, 2009, 03:46 PM   #11
 
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A manual mill would also work very well, but a drill press will do the trick. IIRC Sears/Craftsman should have carbide drill bits.
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Old February 14th, 2009, 07:10 PM   #12
 
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Well, to do a job like on the picture, I would say that a drill press plus a lathe and hand finish would work, that’s before I actually tried it - I am unable to even drill thru, that’s some tough sh*t there! All i know right now is that a 10 in, 0,5 hp, 5 speed drill press will not drill thru with titanium or cobalt drill (5/32). Now the question is, should I try a smaller bit, since this one (5/32) started drilling fine (stopped when I got to the same dia. as the bit). or should I try a carbide one even if it is intended for concrete and a hammer drill (arrow tip)?? or maybe a carbide drill bit for steel is available, just not in H-D and Menards??

I promise to keep everyone updated, since the older version of IBOK is still floating around and more people will try to drill thru... But I believe that this problem will be solved, It is hard to believe that something that’s repeatedly doable with expensive, floor drill press is totally impossible with a bench top one....

Just need some good advice...
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Old February 23rd, 2009, 09:01 AM   #13
 
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Well, I am lacking the english vocabulary. But perhaps it helps anyway.

The problem is, that the hammer is kind of elastic, not that it is hard. That is why it starts "singing" and "swinging" when the whole cuting edge of the drill bit is in contact.

The right bit is a question of material and geometry - more geometry than material. Any competent metal worker or hardware seller can [t|s]ell you what you need. With a drill press and (very) moderate speed (about 350rpm max for 1/5") and advancing slowly, it should work. If you can sharpen the "hammer drill / arrow tip" with a cutting edge of 45°, this might even work, as the geometry is not to far of what you need - I know, it sounds weired. But the material of the cutting edge is then far from being optimal. The drill bit should be short, the "spiral" should be short, the tip very "pointy". This reduces the tendency to vibrate.

But just go and ask a competent hardware dealer and tell him that you want to drill kind of "spiral material".

To resume:
- The right bit helps.
- A stable drill press helps.
- Much horse power does NOT help.
- Go slow.

HTH,
Fritz
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Old February 23rd, 2009, 02:59 PM   #14
 
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Taking another look at this thread has me thinking about doing this. I have access to any and all tools I could possibly need including a manual mill and even a CNC. My question is how much material are you taking out of the hammer. Obviously the schematic on the previous page is 2-D and has no depth, so my question is really how deep are you milling into the hammer? Are you milling all the way through it? My thought was to mill out some material on both sides and leave a section in the middle so as to not completely jeopardize the strength of the hammer, what I'm not sure of is how thick to leave that center section.
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Old February 23rd, 2009, 07:36 PM   #15
 
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Quote:
Originally Posted by ajmorell View Post
Taking another look at this thread has me thinking about doing this. I have access to any and all tools I could possibly need including a manual mill and even a CNC. My question is how much material are you taking out of the hammer. Obviously the schematic on the previous page is 2-D and has no depth, so my question is really how deep are you milling into the hammer? Are you milling all the way through it? My thought was to mill out some material on both sides and leave a section in the middle so as to not completely jeopardize the strength of the hammer, what I'm not sure of is how thick to leave that center section.
Me, personally, I would not do this mod at all. Force applied and the hammers way stay constant, so I don't see much possibility for the kinetic energy to change. Yes, the hammer gets faster and the velocity is squared in the energies formula. But how much faster gets the hammer? As the time to accelerate gets shorter, the plus in velocity will not be linear. In the end, everything should stay as it was in terms of energy. Thus no possibility to go to a lighter hammer spring to improve the trigger experience, which was, if I see the things right, the motivation for this mod.

Locktime will decrease, yes. And thus accuracy will profit. But that is a tack driver issue out of my scope in the case of my GP100.

I see my time better applied to smoothen the holes of the trigger return spring. On my gun they seemed to have drilled this with an age old drill bit and quite a bit in a hurry. Or to remove the machine marks in the trigger latches way on the cylinder. They are real barriers measuring in the thousands. Or to identify the half dozen rough spots and polishing them away.

Just my point of view.

Fritz

Last edited by Fritz; February 23rd, 2009 at 07:40 PM.
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