[pfc15]

For all you mechanical gurus (which I am not one): Can a hammer be too heavy causing too light a hit on a primer?

I have build my own semi DP 28 using an AR-15 FCG but I had to lengthen the hammer in order to strike the floating firing pin. I actually had it working but discovered some drag problems I had to reengineer and I changed the hammer, too. The first hammer I had I think was lighter but its been so long ago and I don't have it to compare to the one I'm using now. It is considerably larger than a normal AR hammer and as far as I can tell the firing pin is good and I have tried several hammer springs including ones that are supposed to be extra strong. I get detonation on some primers that I believe are softer but my primary ammo is very hard mg primers and it barely makes a dent in them......

I am really close to get this thing to work, it will fire and eject the short czech blanks hand loaded into the chamber (in my garage with a BFA) but won't fire longer blanks that will actually feed in the drum. Before I go and try to grind down and lighten the hammer I wanted someone elses opinion.

So again, is it possible that the hammer is too heavy?

 

[Pirate]

It could be one of several things, the first things to check are firing pin binding and to heavy of a return spring on the fp. also chect the firing pin prortusion. some of this ammo has deep primers, specially the bulgarian stuff. you will need about .090" to fire it.

 

[Dubiousone]

What Pirate said. A heavy hammer with a light spring will whack the same as a light hammer and a heavy spring. Ain't gonna go into lock time or how hammer spring tension affects cycling because that ain't the problem. You got a heavier than normal hammer and a heavy spring that should whack the pi$$ out of them primers. Firing spring is either too long or too heavy, you got some FP binding or (I suspect) the firing pin ain't got enough protrusion.

 

[pfc15]

Thanks for the info

I tried lightening up the hammer, it needed to be cleaned up some anyway. It did lighten the hit the way it looks to me but there is still plenty of energy in it so per advice I went back to the pin. I have plenty of protusion but the max position of the pin is bottom out in the bolt so it is probably absorbing alot of the energy. I'm going to try and make more travel room for it so all of the energy produced and transfered thru the pin goes to the primer. I have no return spring so no energy is lost there, the pin floats.

 

[gordie k]

dp-28

check that the hammer goes just past center so that the hammer and pin are at right angles if they dont hit squar you lose a lot of energy also check fp travel ,to much will eat a lot of the force

gordie k