One of my friend recently got a new Spike Tacttical's ST15, tried to teach him on how to disassemble/re-assemble it, and how the rifle operates.  But once I put one of the trainning round in, had a really really hard time to cycle/recharge it, Finally with clp and a gerber later it was out.
 
The extractor sinked too deep into the rim, but will it prevent a BCG having a hard time to cycle or even jam ? (can it also be a head-space for being too tight too?) 

 Picture of the round:







  it shall be fine after couple hundred rounds down range, right?

  Also one question is for KHSC, what is the typical height you guys use for the target frame? 24" will be too short, 80" is too much to fit into a car. Using it for rifle zeroing first.   Thanks in advance .

Those dry fire rounds are aluminum and the rim wears pretty fast. If rifle is new, maybe it needs a clean/lube and feed it good 5.56 ammo.

If practicing loading and malfunction drills I would recommend the brass cased dummy rounds with the orange polymer inserts.

For the rifle frame, whatever will fit in your car. Measure your trunk if you need to and build accordingly.

Those dry fire rounds are aluminum and the rim wears pretty fast. If rifle is new, maybe it needs a clean/lube and feed it good 5.56 ammo.

If practicing loading and malfunction drills I would recommend the brass cased dummy rounds with the orange polymer inserts.

For the rifle frame, whatever will fit in your car. Measure your trunk if you need to and build accordingly.

  One of the dummy I used was a standard M855, it was dented at the rim, too.  But I guess it just needs some break-in & CLP love. Time to shop @ homedepot for some lumber ......... thanks.

That's just a light paint finish on the snap cap so it wears out at the front tip where it slides up the feed ramp and rear where the extractor grabs it.  I have a hard time extracting a snap cap from the gun even with rifles that are broken in.  Maybe it has something to do with it not being brass like a real round.

  Also one question is for KHSC, what is the typical height you guys use for the target frame? 24" will be too short, 80" is too much to fit into a car. Using it for rifle zeroing first.   Thanks in advance .

I've used a square-ish design, with targets in a 3 x 3 formation.  Measured about 3' x 4' counting the post hole legs at the bottom.  So, that's about a 3' x 3' target area, or maybe a couple of inches narrower.  I made it just wide enough for the left and right targets to fit next to the verticals.  I would have gone 2' x 3', but that would put the targets directly in front of the uprights of the frame! DOH!   
 
This frame fit perfectly in the back seat of my Mercedes C240 (bolts facing away from the upholstery!).  On its side, it fit 4' across and 3' from floor to roof leaning toward the back glass.

I bought a new truck, so now I'm back to using 5' frames that fit my 5' truck bed.     

Did you try inserting a mag with good ammo and attempt to chamber and then cycle the weapon?