I had to join to respond. I have a little pet peeve. It really bothers me when talking about firearms and someone says the gun will "blow up". It is more often used is regard to reloading but also in regard to tubular magazines. What this boils down to is a risk assesment. Yea you can set of a round in a tubular magazine, but that doesn't mean you are going to loose a hand or ruin the gun. I bought a Marlin 94 and have the opportunity to buy a lot of 38 special RN FMJ really cheap. SO I have to perform a risk assesment. What is the likely hood that I will have a proble, hurt the gun, or myself. The answer is slim on it happening and next to none as far as damage is concerned. You can ask a group of older lever action shooters and most of them will not hesitate to say teh RN FMJ is OK. They base this on their experience and the fact that LRN was about the only thing availible for years.
My new Marlin 94 manual says not to use "some" Pointed or FMJ, and then goes on to tell you to ask the bullet manufacuter. CS Lawyers!!! Like some one said above I have fired RN FMJs without a problem. Yea I know it doesn't mean there wont be. I have a chance to buy a bunch of 38 special RN FMJ cheap and was surfing around trying to get a warm and fuzzy for using it in the Marlin. Just becuase I did it when I was young doesn't mean I do now. I am not bullet proof anymore.
I have done a lot of research (and some stupid things in my youth) and would like to share a few things regarding tubular magazines.
This has concern has been expressed a long time but it seems as though its push in modern times is realted to the introduction of flat nosed bullets by a cetian manufacturer. In that year they went from listing RN loads for lever actions to indicating that RN loads were not safe in tubular magazines.
The design of most cartridges in the tube is such that under spring pressure they cant or tilt in the tube due to thier tapered shape. In many cases this alone protects you from a problem as it keeps the bullet from getting a straight shot at the primer.
In some cases however this tendancy may have contributed to the problem. Supposedly Buffalo Bore had a few complaints of this happening with thier HPs in thier hot 45-70 loads. The story goes the the cartridges tilted enough to let the hard edge of the JHP strike the primer just right. The problem was supposedly corrected by switching to small rifle primers and setting them lower in the pocket. Could be an internet myth, I wasn't there, but, my current BB 300 grainers have the small rifle primer.
Smokeless powder in tubular magazines is not likely to have a chain fire even if you somehow managed to get one to fire. And they are even less likely to "blow up". Once the bullet seperates from the brass its usually over. I know this for a fact as I have actually loaded .308 FMJ ball into a tubular magazine. We fired probalby 40 rounds at the range before we touched one off in the tube. Hardly knew it happened. Tube did not bulge, it didn't even jam the action.
This concern got started in the very early days of lever guns. It is not something new, but our new smokless powders and non corrosive primers make it much more
unlikely than it was in the old days. The older mercuric primers were much more unstable than our current breed of primers. It took less to set them off. Couple with that the fact that black powder is an explosive and it is possible that blowing up mag tubes with RN bullets was probably a more common occurance.
I can find only one instance where someone was hurt with a discharge in a tube with smokless powder and it was from a 1968 article by Elmer Kieth, so no telling what actually happened.

What little I found of the article was not very descriptive of the situation.
I have taken the ball and powder out of a round mounted it in a fixture (scrap angle iron with a hole drilled in it mounted in my vise) and set the RN FMJ centered on the primer and then whacked the stuff out of it. It is surprising hard to get the primer to fire, even hitting them with a ball peen hammer. You can actually hit them pretty hard and dimple the primer until the RN hits the edges of the primer pocket without it firing.
That this will happen with military style ball FMJ is not arguable. It will.
Will it happen with the soft lead pointed bullets? The chances are significantly less than FMJ due to the soft lead. I have shot them without problem, but that doesn't mean anything.
Will it happen with RN FMJ? I doubt it, especially in the pistol calibers but i did get one to go off when hit with a ball peen hammer. So hard it deforemed the brass.
Will it hapen with LRN? Apparently it did in the early days but I haven't found anything to indicate that it has with modern primers and several manufacturers still load lead RN bullets for the 30-30, 35 remington and other so the LRN
might be completely safe.
Plain and simple selection of flat nosed bullets is obviously prefferred but even their use does not GAURANTEE you will not have an accedental discharge in the tube. All it takes is a little foriegn material in the wrong place or even the edge of a JHP canted just right to hit the canted primer of the round in front of it.
From a statistical standpoint it is very hard to make this happen with anything flatter or softer than RN FMJ, coupled with the fact that smokeless powder in a propellant and not an explosive even if it does happen you are not likely to sustain any gun damage and even less likely to sustain human damage.
Based on my testing RN FMJ are probably even OK but I still haven't pulled the trigger on the cheap ammo.