Strange shot groupings.
 

So I was trying to sight in my scope and I've notice something strange. My gun is a stock JG M4A1 and I've mounted a scope on for plinkering. After zeroing it to the best that I can, I notice the grouping was about 1 1/2 to 2 inches from 35 feet. Now thinking back when I had a RDS mounted, I remembered the grouping was much tighter. So I took off the scope and mounted the RDS and zeroed it. I took about 100 shot at 35 feet and the grouping was about 1/2" to 1". I find this very strange because the scope has 4X magnification and I believe it should give me better groupings. The RDS has no magnification and trying to aim at a little dot from 35 feet wasn't easy. Before any test, I cleaned out the barrel and used the some kind of BBs. Has anyone else had this experiences before?

Try it with the gun resting on something?

It's just you affecting the groupings. Putting on a different sight doesn't magically change the gun.

The gun was tested resting on a bipod. Testing both of the sights were done pretty much the same way. I wouldn't think that changing the sights would do much but may give a better grouping if it was magnified.

If you want to test groupings you have to have the whole gun on a rest, not pivoting and you changing the point of aim every shot like you're doing.

That could be the reason. Thanks for your response. I'll trying doing the test all over again but this time the gun will be clamped down.