Just put together my first DPMS 308 lower using their LPK. I am not very happy with the mag catch that came with the LPK. I recall from when I put together my MA10 lower that I used an Armalite AR-10 mag catch. I went to look it up on the Armalite web page and I see they now make two different AR-10 mag catches. From their pictures, I can not tell the difference between the two. One says its for the "A" rifles-the one that take Magpul mags and the other is for the "B" series which uses the Armalite only mags. I am 99.9% sure that when I built my MA10, there was only one style for sale which should have been the "B" Series.

Can anybody tell me what the differences between the two are?

Would either one work with the DPMS lower?

Thanks

Armalite "A" guns use different magazines from their "B" guns.  The A models can use modified M14/M1A and "waffle" style mags, while the B models use Armalite's "Gen II" magazines.  The catches are a little different because of this.

Your DPMS uses SR25-type magazines, which are compatible with Armalite's "A" model guns.  Check out that catch....