I took a carbine class yesterday offered by a local guy.  I enjoyed the class and learned some stuff, but I had 2 rounds that failed to fire when I pulled the trigger.  I tried one of those rounds a second time and it fired the second time it was struck.  Ammo I was using was a mix of the Hornady Frontier ammo and the Federal 55gr 223 ammo.  I saved the 2nd round that didn't fire and can post a picture of it later.  The gun has the ALG ACT trigger in it with the purple spring.  Has anyone else had issues with this spring, and is that likely my problem?  I've fired Tul Ammo, Federal, American Eagle (223 and NATO) out of this gun with this trigger without issue.  I've also used my 6.8spc upper on the lower and fired several hundred 6.8 rounds with this trigger (hornady and american eagle ammo).  Just wondering if I should swap out the spring or if I likely have something else going on.  Rifle hasn't been cleaned yet, it's been about 700 rounds since it's been cleaned.  My Father-In-Law thinks my firing pin channel might be too dirty, I don't think that's likely.  Anyone here have any thoughts?

Yes, swap the spring or if you have the means, cut the ear off the hammer and it will solve it.

Will swap the spring.  What do you mean by the ear on the hammer? I haven't heard that before.

That's what I thought was likely the problem, thanks.

I'm at home now or I'd send pics but cutting the ear off the hammer speeds it up so you can use a lighter spring for a lighter pull. Many LPK's have that style hammer but I'm 99% sure the ALG has the full size hammer.

I have been running a ALG ACT with the purple spring in my beater rifle for awhile and it reliably fires everything. I shoot wolf steel almost exclusively and I have never had an issue.