You might try just loading up some old school shells. Load some old fibre wad coulmn made with your favorite hunting load. You may find that it opens up enough with just using the old wads your gun was designed for that it shoots a good full choke pattern instead of being to tite to shoot at all but the farthest birds.
This is all assuming that you have already shot patterns and know that you have a problem. Jeff
Try a few loads with card wads. It bight be a whole lot easier then having a choke reamed and the impact re-regulated on a sxs double. You might be suprised at how open a load of chilled shot and card wads will be at 40 yards. You could even try some of the spreader wads.
An overchoke situation at 40 yards is one thing. If you are talking about shooting pen roosters over a pointer there is no load combo that will make up for a choke that tite as your birds will be close.
If it's tite at 40 yards shooting wild birds you might just manipulate your handloads a little.
If you decide to spend the money to have the choke reamed then do it right and have a known person who knows how to regulate the impact do the job. An open pattern that shoots 18 inches low at 30 yards won't do you much good. I have seen a lot of " gunsmiths" buy a reamer and start doing choke work.
It's like getting a pretty good heart surgeon.
Some things you really want the best. Good luck and a really good guy may make putting briley thin walls in both barrels look like a pretty good option. They will make sure the barrels stay regulated as part of the price. They did a set for me on an old Browning SXS and the impacts were perfect. Jeff