Is there a way to get heavier/harder hammer strikes without a heavier main spring?
I recently bougt a M-28 that will not fire factory 357 double action, but fires fine in SA. There appears to be a Wolf reduced main spring in it, double action is not heavy but not super light either.
I have a k38 with a standard spring that hits primers very hard, but the double acton on that revolver is very heavy, and I do not want a very heavy double action.
Doble action sear, can that part be tampered with?

Swed,

One thing you can do is pry the anvil out of a spent primer and place the cup over the end of the strain screw, then tighten the screw all the way(NOTE: You may have to grind the cup down around the mouth to get it in the opening between the frame and the hammer spring.). This effectively lengthens the screw, putting more tension on the hammer spring.

Regards,
Andy

Yes, install a longer strain screw. Commonly needed with Wolffs' Reduced Mainspring when using "hard" primers. I replace the original strain screw with an 8-32 socket set screw, adjust it for good ignition and secure it with Loctite.

Replace the Wolff with a stock factory spring.

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Why, I aughta.....

To give you a more specific answer to your question, without doing some rather extensive and careful preparation the answer to your question is NO.

You'll need to increase the tension in your mainspring to produce a Double Action trigger pull in the 9 to 9.5 lbs. range to obtain reliable ignition with most brands of primers in an N frame revolver. If you limit yourself to ONLY Federal ammunition featuring the older "toxic" (lead stipanate) primers you can take the trigger down to perhaps 8.5 lbs. However, any ammunition with a Non Toxic (lead free) primer will probably require a distinctly heavier primer strike and higher mainspring tension, perhaps as high as 12 or 13 lbs. Hint, avoid any ammo labeled as "non toxic".

Now, what can be done to improve things slightly. First is to fully polish the frame recess for the lockwork to minimize friction between the hammer and the frame recess and sideplate. Another step to reduce friction is to grind the width of the hammer slightly on a surface grinder and then install small diameter shims between the frame recess and sideplate. Basically, you want small shims on each side of the hammer to reduce the friction producing bearing area. Next step is to LIGHTEN the hammer by reducing the width of the hammer spur and machining in some lightening cutouts. While this seems to be opposite of what common sense might tell us primer ignition is a function of Kinetic Energy. Since Ke is a product of Mass time the Velocity Squared it becomes obvious that getting the hammer moving faster will result in an increase in Kinetic Energy even when the mass has been reduced. It's why almost all of the current Performance Center revolvers now feature teardrop shaped hammer spurs. That far from the pivot center a few grams saved can mean a lot. The final stage is really going whole hog. That is to re-fit a new hammer pivot pin that can allow the installation of a really tiny needle bearing in the hammer. Naturally, the hammer will also need to be machined to allow this needle bearing to be pressed in place. Do all of this and you may be able to get an N Frame revolver that is reliable with a DA trigger as light as 7 lbs. Of course doing this won't be cheap, it's actually a good deal of work.

BTW, the smaller hammer used on the current L frame permits a DA trigger pull of 8 lbs even with total reliability with standard primers from most makers (it's were my model 620 is set). The K frame with the standard narrow spur can go even lighter, I have my model 67-1 tuned to 7 lbs. 9 ounces.

Thanks for Your answers!
If I want to buy a stock s&w spring, is there a place to order it online? Brownells seems to have only Wolf type springs?
Living in Sweden I am limited to online shopping and the god will of shops/manufacturers willing to ship parts to Sweden..

Brownell's sell genuine S&W parts for the Model 28.
New mainspring is Part number 40:

N-Frame 28 | World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools - BROWNELLS

You can also order a new spring direct from S&W:

Contact Us - Smith & Wesson

Unfortunately that will give you the "very heavy" DA pull you said you didn't want in your first post. A longer strain screw (more mainspring preload) with your Wolff Reduced Power Mainspring can give you relaible ignition with the lighter DA pull you seemed to want.

It's not kinetic energy, it's just velocity. It's the nature of the primer mixture. Harder primers cause the firing pin to lose more velocity while "denting" them. So, more mainspring is necessary for "hard" primers so the hammer has more velocity and can lose some to the primer shell and still have enough to set off the primer mixture.

You can have a heavier, slower hammer and no ignition while a lighter, faster hammer with the same energy will light the primer.

I may be able to help.
PM sent.

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-jwk-
US Army '72-'95

You can take an expired credit card and cut off a small piece to act as a shim between the strain screw and the mainspring. It works. Is there some type of tool or gauge that measures the energy transferred from the firing pin to the primer?

Not really and it would be meaningless. It's the velocity of the strike not the energy that is what the primer is sensitive to.

I respectfully disagree. Although the velocity is more important than the weight if something extremely light like the head of a stick pin were to strike the prime at twice the speed of a normal hammer you would have a failure to fire. Its still kinetic energy. No weight, no bang.

You guys are splitting hairs. Your both right in a way.

Its kinetic energy which is a result of mass and speed. Lighten the hammer and you need to increase speed. Slow the speed and you need to increase the mass of the hammer.

Of course there are limits to how far you can go with either variable.

My solution would be to legnthen the set screw with the wolff spring or just get a factory spring. Don't permenently alter any parts.

Sent from my SCH-I535 using Tapatalk 2

Are we sure the existing strain-screw is tightened all the way?

Mike

Now lets deal with reality.

The kinetic energy of the hammer (regardless of hammer weight) is the mainspring and how much it's preloaded. That at the hammers' most rearward point is the hammers kinetic energy. If you want to get technical it's potential energy until the hammer is released to fall.

To get lighter DA pulls (to allow lighter mainspring tensions) we lighten the hammers. My FMFP N frame hammers are literally half the weight of stock hammers. K/L frame FMFP hammers are even lighter. There's precious little left to remove and the only way to get appreciabley lighter would be if S&W smiled upon us and offered titanium hammers.

As hammers are lightened we can go to lighter mainspring tensions. LESS HAMMER / FIRING PIN KINETIC ENERGY. Lighter hammers allow primer ignition with less kinetic energy.

What is the threshold we can't drop under? Hammer / firing pin velocity.

See the trend? As we lighten hammers we reduce mainspring tension, lighten our DA pulls, lessen the hammer/ firing pins' kinetic energy but keep enough VELOCITY to maintain reliable ignition.

I run my CF revolvers with ~ 5 1/2 DA pulls. I can run them down in the low 4 lb area reliably. If I put a stock hammer in one of these guns, with the same spring and strain screw settings, same kinetic energy, I just get clicks, no bangs. Same kinetic energy with reduced hammer velocity results in no ignition.