At the risk of sounding stupid, can anyone give me the 30 second explaination of the difference between the 2 type locks and what reasons/applications one type is preferred over the other? Thanks

Believe you'll find an adequate description here:
http://www.hallowellco.com/boxlock.htm

Regards

I wonder how heated the debates have been in those smoke filled pubs in Merry old England over which is better and why. I can just imagine.

For me, sidelocks have more of a sophisticated look and "seem" to demand a higher degree ofthe intangible. To reduce the description to minimal terms, they have more gadget factor.

That being said, I like mechanisms to simple and robust. That describes a good Anson and Deeley boxlock.

Yes, sidelocks denote "Best Gun" status for sure, and are considered on a higher plane of the gunmaker's craft.

However, regarding function, think of this....how many rated, dedicated, trap/skeet/sporting clays shooters use a sidelock.....ZERO!

Simplicity, strength, and long-term reliability favor the boxlock.

Cool, thanks. I was trying to find some obvious visual difference. This is good info!

Visually, the most obvious difference is that the action metal ends in a vertical line near the triggers, where a sidelock has steel sideplates that extend back well past the triggers and end in a tapered oval. There are some boxlocks that do have full sideplates as well, but they are just decorative and provide a place for more engraving. Most sideplates on a true sidelock gun will have pins and perhaps a small lever showing on the sideplates, as mounts for the internals, and a release for the plate to access the components inside.

I would not agree with what the hallowellco site says as it isn't in many aspects correct.

So start from here and you won't go too far wrong:

1) If hammer guns had not existed then sidelocks would not have existed. A sidelock is simply a hammer gun with the hammers moved inside.

Either a conventional bar lock as used by Purdey and Boss or the lock used on the Holland Dominion which is really the back action lock with the hammers moved inside.

2) In wet weather I personally preferred when I had one to take a sidelock out as it was easier to take the locks off to dry the thing.

3) A sidelock is easier to repair in the sense that it is easier to strip down to replace the springs if they break.

4) A good boxlock is better than a chaep sidelock. There are more parts in the sidelock so obviously if it is the same price as a boxlock then more of you money has gone on fewer bits so they should be of better quality workmanship and materials!

5) A lot of over and under guns are, and I will stand corrected on this, actually sidelocks in the true sense as they are NOT boxlocks but TRIGGER PLATE ACTION guns. Which are sidelocks but with the hammers mounted inside not on the side plate but way inside on the trigger plate.