Every Marlin I own will shoot cast bullets well (.30-30, .35 Rem, .41 Mag, .44 Mag, & .357 Mag.) By well, I mean they'll group 3 shots from a cold bbl. into 3" or less at 100 yds, scope sighted. ALL are Micro-Groove bbls. Here are some of the secrets:
Bore & bullet leade: Marlins all have an oversize, some would say, bullet seat and groove dia. For .30-30 I size to 0.310" minimum, larger if my mold will cast and bigger. In .35 Rem and .357 Mag I size to 0.359" minimum, but 0.360" is better if the round will chamber. In my .44, I size to 0.432+", and in the .41 Mag, 0.412". I use 50-50 alox to beeswax lube. As a general rule, in my experience, use the largest cast bullet that will chamber in your gun.
Powder, 2400 is OK/good but I don't push it. Velocities need to stay below 1600 fps max due to the shallow rifling. Adjust your powder charge accordingly. For plinking rounds but where accuracy is still needed, Unique, Herco, WSF, and even Bullseye are good, but powder positioning close to the primer is necessary. (Tilt the gun up before you shoot to get it where in needs to be.) I don't trust Kapok fillers to accomplish this, but many knowledgeable shooters do so.
Bullets: A long full groove dia. bullet is best in my experience, as is one with a gas check. Without the gas check, limit velocity to 1200 fps or less from a rifle bbl.
Bullet alloy: I cast primarily with wheel weights. For rifle use, I water quench them (drop directly from the mold into a 5 gallon bucket of water). This produces a brinell hardness tough enough to stand the higher velocities. For commercial, check out Missouri Bullet Co's gas checked offerings with a hardness up around 18. Their flat nosed 180 gr GC is particularly good in my .30 cals. (.30-30, .308, .30-06, & .30-40 Krag)
Case prep: I use a Lyman "M" die to flare the case mouth and to expand the sized case to just under bullet dia. This prevents a too-tight case neck from resizing your bullet when seated. Using a sizing die alone, (most are machined for jacketed bullets i.e. they size the neck too small), you're in effect resizing your carefully selected over size bullets as you seat them. Invest in an "M" die and you'll find that it also helps with jacketed bullets. Too, every time you fire a case, the neck and shoulder hardens...I anneal my brass after 3-4 firings for best, most consistent neck tension.
Crimp: I don't use one. Lever actions at the velocities listed above will not set the bullet back in the tube magazine during recoil. Crimping, beyond merely removing the case mouth flare, destroys bullet fit. If you want full velocity .30-30 rounds, get some jacketed bullets that'll take the abuse...lead alloy will not.
Bore condition: I've had some success shooting cast bullets through a bore fouled by jacketed types...but not much. For best results, thoroughly clean with a good abrasive bore cleaner...JB bore paste is what I use. Then shoot 6-8 rounds of cast bullet loads to season the clean bore. Alternately, you can clean then dry the bore then re-season with a patch coated with your bullet lube, then wipe out. It helps, but the 6-8 shot method is what I use 99% of the time.
Results: Using Lymans round nosed 311291 gc or 311477 sized to 0.310" and producing 1500 fps, I expect my Marlin Texan .30-30 to shoot ragged hole groups at 30 yds from a rest. Careful inspection of bullets helps as does weighing them to identify those with internal casting flaws. At 100 yds, the same Marlin will shoot 2"+ with a 2x scope mounted for the first 3 shots. Hot barrels in ANY lever gun, will usually result in vertical stringing to some extent. Tuning the fore end and receiver/fore end interfaces will reduce that tendency as will relieving the pressure from barrel bands...a science in itself but worth the effort. And BTW, two Winchester 94's in the same caliber will do nearly as well, but suffer from the inability to mount a scope do OK with a Williams Foo Proof peep instead.
In a nut-shell: Bore riding hard cast bullet with GC, light powder charge for ~<1600 fps, over size bullet by caliber + 0.002"- 0.003", "M" die to prevent bullet deformation while seating, & no crimp.
The above works for me...it'll work for you as well with some dedicated patience and attention to detail. For further info, Cast Boolts forum is superb.
Best regards, Rod
