I don’t feel qualified to write this piece because I have never shot a lever action in my life.   But someone needs to write it, because there are more things that can and do go wrong with lever-action bullets than with any other type of gun.

Won’t chamber because the nose is hitting the rifling   This is the number one problem.   Many lever actions have very short throats.   The rifling may run all the way up to the case mouth, or very close.   My standard bullet designs may need at least 0.100″ or even as much 0.200″ of freebore to the chamber.   If your gun has a very short throat, you have several options 1) a bore riding design with a minimal front band or 2) a reduced diameter front band or 3) trim the cases just enough to allow the bullet to chamber or 4) seat the bullet deeper and use a factory crimp die to crimp or 5) rent a throating reamer that has a gentle taper and make the throat longer, which will may improve accuracy, anyway.  How do you determine the throat length?   Either by making a cerrosafe casting of the chamber, or by upsetting a pure lead slug in the chamber, or by making a dummy round with a jacketed bullet loaded backwards, and gradually seating the backwards bullet until it just barely will chamber.   Once you determine your rifle’s throat length, you can use the online bullet design program’s “lead length”, the approximate amount of freebore required for that particular bullet, to determine if a bullet design will chamber in your gun.

Won’t chamber because the case neck OD is too big when loaded with the proper size bullet.   Some of the old 40-65’s are like this.   It happens when the groove diameter is oversize, requiring an oversize bullet, but the chamber is snug at the case neck.   A cerrosafe casting will tell you the diameter of the chamber at the case neck.   Then subtract the thickness of the case walls (measure the neck OD of a round loaded with a bullet of known diameter, subtract the bullet diameter, the remainder is the thickness of the case walls) to determine the maximum bullet diameter that will fit in the neck.   Here’s an example:

30-06 cerrosafe neck, corrected for expansion = 0.342″

neck OD when loaded with 0.309″ bullet = 0.333″

0.333″ minus 0.309″ = 0.024″ total neck wall thickness

0.342″ minus 0.024″ = 0.318″ maximum bullet diameter allowed by chamber neck

In this case, we are good to go.   But what if the chamber neck only allows a 0.308″ bullet and the groove diameter is 0.309″?   I could 1) rent a chamber reamer to open up the chamber slightly or 2) use a case neck turner to make the neck walls thinner or 3) shoot undersize pure lead which should bump up to fill the barrel or 4) run the loaded round into a sizing die and size it down slightly.

Won’t cycle because the cartridge is too long   If you don’t know the maximum COL for your rifle, you can experiment with dummy rounds, or play it safe by specifying a nose length that is known to work.

Won’t cycle because the nose is too blunt   So far I have only encountered this problem in bolt actions, not levers, but it could happen.   The only way you might be able to predict this is to experiment with dummy rounds.   To make a blunt dummy bullet, you can file down the nose of some other bullet.

Won’t chamber because the throat diameter is smaller than the bullet diameter   Very rare, usually, the throat diameter is too darned big.   But if you do have a tight throat, you can specify a reduced diameter front band.

Poor accuracy  If you are unable to get decent accuracy, you might want to make a cerrosafe casting of the chamber, if you haven’t already.   There are some awful chambers out there, typically with the rifling starting abrubtly instead of having a gentle taper or having grossly oversize dimensions.

What’s the right bullet diameter?  For reliable chambering, I like to make the front band diameter 0.001″ smaller than the throat, and maybe tapered, too, but I prefer to make the body diameter at least throat diameter or 0.001″ bigger.   As for the groove diameter, I don’t even bother to measure it.   The throat diameter rule may not apply to seriously obese throats, like the 375 H&H; throat that was 0.388″.   Here’s some examples of the diameters that have worked well for me (not lever guns but the same principles apply):

357 revolver with 0.3585″ throats …… 0.359″

44 revolver with 0.433″ throats ……0.433″, 0.434″ might be better but limited by case neck OD

308 rifle with 0.312″ throat …….0.313″, MOA despite the sloppy chamber

30-06 rifle with 0.3095″ throat …..0.311″, groups doubled with 0.309″

7-30 rifle with 0.285″ throat ……0.286″

375_BC_255   is designed for chambers having a minimal throat.   The front band is only 0.050″ long.   If the throat is too short to take even this puny front band, you can trim the cases until it will chamber.   The bore rider is a potential problem, as bore riders always are.   If the bore rider diameter is too big, it may be difficult to chamber, but this problem can be fixed by nose sizing.   If the bore rider diameter is too small, accuracy may suffer.

375_FC_255   has no crimp groove.   For short throats, seat it just deep enough to chamber and use a factory crimp die.   For longer throats, you might be able to crimp in the upper grease groove.   This may be the way to go if you have more than one 375 rifle, because you could use the factory crimp die to fine tune the seating depth for each rifle.

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