My brother is picking up a Colt 6520 this weekend.  I just want to know if he should have a D or O ring.  I find that I need them in 11.5s, but have no experience with 16s.

Obviously, he should run the gun and see, but his opportunities to shoot are very limited b/c of his job.  So I'd like to know if people find the rings or heavy springs necessary in this application before I send him on his way.

Thanks in advance,

Sam

I have not found them necessary, but I usually add one just for insurance.

Thanks.

You make a good point.  It's not like they're expensive, all things considered.  

Sam