I have two magazines, both by Ruger with one being 7 rd and one 8 rd, that I use in my SR1911 that will drop away from the chamber when I shoot. These are two that I bought from another 1911 shooter. I have the two originals that work just fine. What should I look for that makes these two pop loose. They don't do it with every round but at least every other round. Any help appreciated.

Near the top, left, front of the magazine you'll see an oval hole.  That is the part of the magazine that the magazine release of the gun engages when it is fully inserted.  Is there rounding on the top edge?  Are there any dents or deformations along that edge?

Do not dismiss the possibility that there is something marginal about the magazine release  on you pistol that is being revealed by lower quality magazines.  In other words it could be a combination of things having to do with both the magazine and the pistol.

The only good use I've found for Rooooooger magazines is keeping them in the box that they came in for future resale of the gun.

Would you please tell us which brand of magazines you prefer?

everyone has their likes and dislikes but I choose wilson combat 47d,  they are pricey but I have never had an issue with them.

I have 10 dedicated  for each one of my pistols,  I also prefer the wilson combat range bag,  you can put the mags on the side of the bag,  makes it convenient.

the bags are around 30 dollars.

I have a couple of Wilson's that I like but most of my mags are CMCs and Kimber, of which a few those are marked CMC.  I don't have my Kimber anymore because it sucked but the mags are good.  I also have a ton of GI 7 round ones I use as range mags.  I need to get a few more Wilson's and 30 bucks is not bad for a mag.  I have GI mags to abuse.