Krall Hammer Spring Stop Guide

[Dave-c-g]

I've been looking at posts and stuff about spring stop guides in a quest to make my NP-02 less noisy in the mechanism. I've seen several posts and a couple of videos and have a rudimentary design.

Top is cocked, bottom fired.
I'm thinking about a 5.5mm diameter steel rod (gold) tapped into the existing hammer adjuster (black) with a 7-8mm diameter end ridge that fits inside the (possibly shortened) existing spring (grey) and can fit in the hammer recess. I'm not sure if I'll need to enlarge the recess as I've not yet stripped it to finalise the dimensions. At the front of the spring I will fit a 3-4mm thick Delrin washer (white) that is retained by the rod, but that can slide back as the spring comes under compression. If I'm correct the rod is going to be 55mm long to the ridge at the front and the washer should be a couple of mil clear of the hammer when released. This should also allow further adjustment using the existing threads in the block to tune the final float.

Can someone that's done something like this tell me if this is viable. Sorry about the lack of dimensions.

Thanks,

Dave.

 

[Neil54]

A stronger, shorter hammer spring is the easy answer. Short enough so the hammer has 1mm of free float.

The stopped spring guide you have illustrated will work fine in my opinion.

 

[Dave-c-g]

A stronger, shorter hammer spring is the easy answer. Short enough so the hammer has 1mm of free float.

The stopped spring guide you have illustrated will work fine in my opinion.

Thanks Neil, I did expect I'd need to shorten the spring, mostly to allow for the floating Delrin washer. I might just try a shorter spring first and see if that helps with the noise.

 

[Hmangphilly]

That delrin washer is going to take a beating

 

[32:1]

Your on the right path, Ive made a few now and have found you can shorten the hammer stroke too, I’ll pm you but heres a couple for a puncher and an Akela

 

[JerryM]

I made an SSG for a friends NP02 a couple of years ago, I used a shorter stiffer spring and had to drill out some material from the hammer to accommodate the central pin of the guide fitting into the recess in the back of the hammer. Cant remember whether I tried using a delrin buffer, but ended up with a mild steel top hat for durability. pic shows the original hammer spring as well, Sounded much better when fitted.

 

[Dave-c-g]

That delrin washer is going to take a beating

Really? Any suggestion what else I might use that isn't steel?

 

[Dave-c-g]

Your on the right path, Ive made a few now and have found you can shorten the hammer stroke too, I’ll pm you but heres a couple for a puncher and an Akela

View attachment 1021968

View attachment 1021969

What is that front washer made from, looks like it may be rubber or is it just dark steel?

 

[Dave-c-g]

I made an SSG for a friends NP02 a couple of years ago, I used a shorter stiffer spring and had to drill out some material from the hammer to accommodate the central pin of the guide fitting into the recess in the back of the hammer. Cant remember whether I tried using a delrin buffer, but ended up with a mild steel top hat for durability. pic shows the original hammer spring as well, Sounded much better when fitted.

View attachment 1021975

Thanks, making a top hat is more difficult for me with limited tooling. What diameter is that bolt?

 

[32:1]

Thanks, making a top hat is more difficult for me with limited tooling. What diameter is that bolt?

M6

Remember you need room inside hammer to allow SSG to travel

 

[JerryM]

Thanks, making a top hat is more difficult for me with limited tooling. What diameter is that bolt?

Hi

I haven't got access to this gun anymore to check, but I’m sure that was a 60mm M6 hex head bolt, although a 50mm M6 would probably have been ok, as the hex head partially protruded I had to machine a recess in the back of the hammer, I remember that none of my HSS drills worked on the hammers steel, so I had to resort to a tungsten carbide bit. Nowadays I make decent notes on the mods I do, but back then, not so much!