I own an Excam bta-90 that was mfg,in jan 1988. it is compact steel with a 12 rd mag. I need xtra mags but cant determine which to order? also I developed my first problem yesterday. Previously, I have shot ball ammo exclusivley with 0 problems,then i loaded 12 147 gr hp and fired 3 rds perfect, then three rd ball again perfect,then i loaded hp,ball.hp,alternating. first hp fired but the mag dropped, disengaged.only happened with hp ? coincidence? Help?Thanks for any info .hdrider9