I'm building a cherry mission style bed and need to pick out bed rail hardware. I want to make sure the bed is very rigid. There are a number of bed rail connector styles and I want to buy some high quality hardware that makes a very rigid connection. Without holding or testing them to get a feel for their rigidity, it's tough to tell from the pictures what will be rigid and what will allow the bed to flex. One thing I can say from looking at these pictures, is that I think the style that screws into the end grain of the rail may be weaker than the style that screws to the rail across the end grain (simply because screwing into end grain is not as strong as across the grain. However, I also realize that the style that screws into the end grain may have 3" long screws, whereas the style the screws across the end grain could not be more than about 1" screws (or they would go through). Anyone have any first hand experience with various bed rail connections that can give tell me which ones are more rigid than others? Thanks.
I don't think you need to overthink this, while there will be some that provide greater strength it's likely that any of the common solutions produce a bed that is rigid enough.
One thing I can say from looking at these pictures, is that I think the style that screws into the end grain of the rail may be weaker than the style that screws to the rail across the end grain (simply because screwing into end grain is not as strong as across the grain.
In general this would be right, but screw type matters. The right screws (both as to length and thread style) can grip plenty strong enough for service in a joint subjected to longitudinal stress.
If only common screws are available though and you want to be extra sure the screws aren't going to pull out there's an old trick to increase their hold:
Equally, while the middle screw of three should be driven in straight the other two can be driven in dovetail-fashion to provide additional pull-out security.
So really, just pick a connector style you like or that fits the budget and go for it.
Many years ago (probably close to 25 or 30), my father built a set of twin bed frames for me and my bother as kids. For these, he used simple threaded rods epoxied into holes drilled into the end grain of the bed rails, which passed through holes on the bed legs. These were bolted down with a nut and a washer on the outside of the leg.
They held up to the two of us kids jumping around and doing other rambunctious kid stuff just fine, and I never remembered them creaking or swaying in any manner. We still use these beds, now stacked as bunk beds, in our family cabin, and they hold up just fine.
If you don't like the look of the nut and washer on the outside of the leg, there are plenty of ways to dress it up.
Another similar system is to use "bed bolts." These are ubiquitous at IKEA, and they are quite effective, regardless of how cheap IKEA furniture is. My dad and I used these in a baby crib for my nephew recently since they give a very tidy look compared to the through-bolt option.