223 surplus ammo in G1 carbine not firing

[loggingloco]

I'm just getting back into shoting my Contender. It is an approx 1980 vintage.
Last week I was shooting the 17HMR carbine with no issues. Today I tried to fire 223 surplus through a new factory 223 carbine and it would not fire most times. I would check the primer and could see a faint mark from the firing pin but no dent at all. I would break open, cock and try to fire again. Sometimes it would take several tries before firing.
The barrel was sopposed to be a Contender, not a G2. everything looks the same as the 17 barrel. The firing pin spring is origional. I'm thinking that is what I should change first.
How do I tell a g1 form G2 barrel?
Aren't g1 and G2 interchangeable?
Where can I find directions on changing springs?
Thanks,loggingloco

[dave29]

Could be a lot of things, but the most likely problem is the surplus ammo. Most surplus ammo has very hard primers. Have you tried any regular .223 ammo in it?

[DEACONLLB]

Is the ammo marked 223 or is it marked with the nato cal. if it is marked with nato cal then it is to be used only in a barrel marked for that cal. I tried some of the nato ammo and would not fire in my 223 barrel and if it did it would not eject as it is coated with varnish.I think the newer barrels for the g2 have a small step in the mounting lug. but they do interchange.
 
Deaconllb

[SHOOTALL]

If its U S surplus ammo it has thicker primer cup . your gun might need a spring replacement. I have not seen good quality 5.56 military ball ammo with a coating . Some forgin steel cased ammo has/had a coating and several materials were used to coat. But I have not seen it all