In addition to a 44 mag Rossi (which I am now considering getting as a 16" carbine instead of a 12" sbr project) I am doing some research on the 20" 454 Rossi rifle. I currently only cast one bullet for my 45 colt loads (lyman 454190)  but I am concerned about it causing issues when loaded in a tubular mag.

This is the bullet

My concern has to do with the small meplat on the nose contacting the primer of the round in front. I don't think it will be as much an issue when I am shooting the bullet in 45 colt loads in the rifle but if I loaded it up for the 454 it might be. The meplat is .215" and the standard large primer size is .210" In other words while its not pointy it rests completely on the primer of the round in front of it.

What do you guys think?

I'd be a bit leery ... enough so that I would think seriously about buying some different bullets ... maybe even hollow-points for the .454, unless you are going to load bunny-farts.

Well for the 454 I probably will buy a different mold to cast either heavier bullets or at least something with a gas check and larger meplat when shooting 250's I'm sure a 250 doing 2200 at the muzzle will lead a little bit. Most of what I shoot would be 45 colt cowboy loads that I have on hand for the 1873 but they are with this bullet listed above. I would hate to change bullets from what I already normally shoot in the colt since the point of the rifle would be to have something that will shoot the same load at the revolver but also handle 454's for hunting, shooting TV's or what ever.

I wouldn't think they would cause a problem. I've never loaded for or even fired a .454, but hot loaded .357's or .30-30's have never caused me any problem and they have flat or round nose bullets which set directly against the primer. I was always told to avoid pointy spitzers in a tub mag, but that's it.

Maybe check around on a reloading forum to see what they have to say. I'm not the one firing it so...

Well good points. I imagine in the 454 I could get away with rifle primers as the only 454 I would own at this point would be the rifle and because if I recall correctly 454's use rifle primers to deal with the 60k cup pressure they can develop. Apparently the 454 uses a small rifle primer at that so with a .175 ish primer diameter I actually wouldn't have problems.

I probably wouldn't have problems with the powder puff 45 colt loads either when I consider that original lever gun cartridges seemed to have even round nose bullets frequently and the 38spl lever guns can be used with round nose bullets as well.

I'd put the bullet up to the base of a round to compare the flat to the diameter of the primer.  If it's larger, you're GTG because the bullet nose will impact on the case base before the primer but if not, then the smaller it is in relation to the primer, the more risky it is because it will act more like a firing pin.  I'm guessing from the look of it that it's smaller than the primer though.

Bingo

Looks like you answered your own question then.



 

Fear not. I own and reload for 3 Marlins. An 1894 CBC in .38 Special, a 1894 CB in .45 Colt and an 1895 in .45-70 Govt. This issue comes up with Cowboy Action Shooters who are concerned about commercial .38 round nose ammo in their lever guns. My Marlin manual states ANY factory ammo is safe to use. Check if your Rossi manuals for ammo info, if it is not advised against use it. (All firearm manufacturers advise against reloads) Also, consider the ram used to seat the primer. It is smaller and you use a lot of pressure to seat the primer. I have shot thousands of round nose ammo thru my .38 Marlin at Cowboy matches. Try this to ease your mind. Prime an empty case. secure in a vise, grasp bullet with pliers, place bullet nose to primer, rap with a small hammer. Please note this is an unloaded primed only case.
The issue is with .30-30, .32 Special reloads with pointed FMJ bullets intended for bolt actions. Just my 2 cents

I agree with most everything you said except bold. Google image "metal piercing .38 special." It's pretty rare, but I have seen it at gun shows in the early 90's. No way would I load that into a tube magazine!

Well your analogy of the primer seater makes sense as for the metal piercing ammo, I think one would have to go way out of their way to make that happen since the stuff is so collectable. The average person who has gotten into shooting in the last decade is probably unlikely to end up in that situation with this type of firearm.