Ignition problems

[JoeCB]

Hello all,   I have been lurking here for several years, but never posted.

I had finished my gun back in 2008 but was having broken firing pin issues with my home made (0-1 and heat treated) pins. Finally bit the bullet and installed the ejector pin types. Anyway, out to the range the other day and was getting several mis- fires. not isolated to any specific barrel. Evident was not very heavy indent on case rims. First suspect was wimpy striker / spring. Upon checking all seem pretty good and strong. Next thought , excessive head space. Checked head space and yes, I\'m on the high side of the SAAMI max spec of 0.051 ( spec is 0.043 - 0.051). So I thought that I would share some info and get your thoughts on a couple of related issues. Oh\'\' , bolts are RGG design, firing pin 1/16 dia with flat face.

 

Striker springs 0.038 piano wire 15 coil 1-1/2 \" free length , 1-3/8 installed length , Force at full cock (1/2\") is 8.5 lbs. 

questions... 

 

1.  Is my bolt and striker set-up up to par? I would hate to have to go to a stronger spring? 

2. Is a flat face 1/16 firing pin what you are all using successfully. Chisel pointed would be the other option perhaps. Pins are at 0.032 projection from bolt face. 

3. Head space is obviously critical, how tight have you all run? the SAAMI spec for the .22 rim is 0.043 - .007.  Having a 0.043 head space would be minimum and tight. 

 

Appreciate your thoughts...

 

Thanks 

 

Joe B 

 

Photo of the G attached 

[Sparky_NY]

Great looking gun !!

 

My guess to the misfires is that the several things mentioned each are contributing a bit to the problem.    If your headspace is fairly consistent barrel to barrel why not decrease it by adjusting the nuts on the mainshaft?      The spring rate sounds low,  I believe most are using springs north of 10-12lbs.   A radius on the ends of the pins will impart more force to the rim hit,  similar to why flat pins are shaped like a chisel on the end. 

 

Worth noting that you could experiment with some spacers behind the firing pin springs to increase tension.   Cutter once sent me a diagram where he did experiments on spacers and the resultant increase in strength.   The spacers can be made 2 piece for ease of installation in testing.     I assume you verified the pins move freely in their bores,  any drag will hurt the pins acceleration.

 

The gun is firing, so you are not way off.    A little bit here and there can eliminate the misfires.

[Cutter]

For what it’s worth.

These are the springs I used.

After a few trials a force just under 2 lbs.

worked best for me.

 

Good luck

[Cutter]

This video was taken at the time rerunning the

light hit cartridges.

[Sparky_NY]

Pretty sure those force numbers Cutter has in his drawing are the preload force,  NOT the force pulled back when firing.      Quite a difference in the two parameters but both are important.

[JoeCB]

Thanks guys for the info... I just checked and I measured about 4 - 1/4 Lbs when I pull back the striker 1/4 inch. At full cock of 1/2\" I measured 8.5 lbs. Sure seems adequate. My next step is to close up the head space. Since my rim recess is cut into the barrels I will have to shave off a few thou from the barrel plate and barrels. The bolt faces now close up tight to the barrel plate, no adjustment there. 

How about the reshaping of the flat firing pin face to a more chisel shape, anyone done that? My pin heads are so shaped (not round) so that the pins can not rotate but a few degrees. Should ensure a radial strike on the cartridge rim. 

 

Joe