I picked up a thirty-some year old (1977 mfr) Marlin336 in 30-30 today and am planning on reloading for it, mostly with home-cast 170 grain flat point bullets.  Does anyone have any comments or experience in reloading cast bullets with the so-called Marlin "micro-groove" rifling?  From my understanding, "micro-groove" rifling was intended to optimize performance with jacketed bullets.  Being cheap, my intention is to use cast bullets almost exclusively.  What sayeth the peanut gallery?

It can be done successfully, but you are going to have to pay extremely close attention to hardness and diameter.  You do have a copy of the Cast Bullet Handbook, correct?

Why, yes I do, actually.  Are you going to tell me something crazy, like I actually have to read it?   

I *assume* you mean (going by memory here) that I need to get the bullets to be about 0.001" oversize, after slugging the bore?  I have a 308 bullet cast bullet sizer I was planning on using.

For hardness, well, I'm having trouble there.  It used to be a year ago that the water-quenched bullets I made out of a wheel-weight type alloy would end up about BHN 19.  I tried it a few weeks ago expecting to confirm that I was still making nice hard bullets, and to my surprise they came out (a week after casting) at BHN 9 not 19.  I've been meaning to read the cast bullet manual again to understand the metallurgy better.  I suspect I've been casting at too cold a temperature (perhaps 650 to 700F) and maybe that's why the antimony and other good hardness constituents aren't dissolving properly.  Think if I turn up the heat another 100 degrees I can get my water-quenched bullet hardness up again?  I don't mind frosted-appearance bullets, if that'll make them harder.

Re-read it again yes.  And while I agree with going hotter, you have another issue to address-  If you go to hard, they can actually shatter on impact.  Not good if you're hunting live critters of the medium or big game variety.

Fortunately I'm not hunting with cast bullets, just punching paper.  Being quite new to hunting, as in I've been meaning to learn from someone and haven't gotten around to it yet, if I d start I'll only use good quality jacketed softpoints or the like.
Thanks for the hints about temperature and the other stuff.  My 30-30 mould and other reloading stuff should be here later in the week and I'm looking forward to working out and up some 30-30 cast loads.

One area to watch is your velocity. If you push these lead bullets too fast, you risk leading the barrel which will have a drastic consequense. IMHO

Absolutely.

I have a multi-pronged approach to preventing leading. With rifle cast bullet loads, I like to work up loads with cream-of-wheat filler above the powder charge and under the bullet.  As much as it takes to fill the empty space in the case, with the bullet very mildly compressing the cream of wheat and powder charge.  In my experience, when the round is fired, the cream of wheat gets compressed under the bullet into a tight plug that both acts as a gas-check to prevent leading. It also seems able to scrub out existing leading from the bore.  This works very well for me in bolt guns, and I have also used it in gas guns like the SKS and M1 Carbine without problems, too.  In the SKS/AK bits of the cream of wheat have gotten spread out and into the action, but it's been absolutely clean in my M1 Carbine.

Using case fillers is not entirely without risk.  Loads need to be worked up with case filler independently of published data.  Compressing a charge can adversely change a powder's burn rate and significantly raise pressures.  And, since the case filler is being pushed underneath the bullet, the effective bullet weight for tabulated load data is the weight of the bullet plus the weight of the case filler added.  I have not had any problems in doing this, but I think I am very cautious in approaching this and I work up cast bullet/cream of wheat loads very gingerly, with a lot of chrono-ing and examining fired brass for pressure signs on the way up.  This approach may not be for everybody.

I plan to check for leading nonetheless, and the other prong of my approach is to use my reverse electro-plating "Foul Out" system, if i do get leading.

With reasonably hard, water-quenched wheel weight bullets, I have been able to get the cast bullets up to about 1800-1900 fps and still have them spin stabilize.  When working up my rifle cast bullet loads, I generally load up several rounds, and incrementally work up in 0.5 grain or 1 grain increments until a satisfactory velocity is reached, or I reach the max of published data.  I hope the chrono will help me detect problems with pushing the lead bullets too fast, too.  My hunch is that my extreme spread and standard deviation in velocity should jump upwards when I reach the point of pushing them too fast, in case I failed to recognize that the bullets are going faster than the table data for that bullet weight.

It's too bad that one can't get linotype slugs anymore. We used to get it for free from newspapers, so that they wouldn't have to pay to have it hauled off. That cast some nice hard bullets just as it came.

Does Lyman still sell their "#2Alloy"? If so, it casts some good hard bullets.

Re-read it again yes.  And while I agree with going hotter, you have another issue to address-  If you go to hard, they can actually shatter on impact.  Not good if you're hunting live critters of the medium or big game variety.

Thanks!  I made some test boolits tonight and I'm happy to say my preliminary signs are that you are correct, hotter melt of wheelweight alloy while using the same Brownell's flux as before, seems to have definitely raised the hardness.  Immediately out of the mold and water quench, I'm getting BHN 13.  Hopefully after these have sat for a week or so they'll be up around BHN 19 or 20.  Before hardness testing these, I also noted that they made a tinkling sound when I was swirling them around in the bowl and applying the alox tumble lube.  Just like the raw material did before I melted it down into ingots, no more thudding.  Whether they're too hard and will shatter remains to be seen.  Any ideas on how to estimate or measure the bullet toughness?

Sorry, been meaning to reply and forgot.  Did you read up about case hardening them in an oven?  That supposedly works well, making the outer area hard enough to track rifling and not melt while leaving the inner metal soft/malleable enough to preform predictably upon impact.  I have not done this personally, but know a couple individuals that do reporting good results.

I've heard of the oven heat treat, if it's what I'm thinking of.  Going by memory it's an hour at 400F followed by a water quench?  I will have to get an oven dedicated to that purpose though, if I want to try the oven.  Shooting buddy and I have talked about getting an old one for that, but we haven't gotten any further than we did about our plan to buy a birdshot-making machine either.

After months of distractions and potting around, I finally have a bunch of suitably-hard cast bullets and enough 30-30 cases that are sized, trimmed, and ready to load up.  Ready to start working up a load.  Since I'm not in a hurry why not take the opportunity for the board here to comment on it and help me get optimal results.

I'd like to use IMR4064 powder since that's what I mostly use for rifle, except for 223 in which case I use BL-C(2).  I have not been able to locate load data for cast bullets and IMR-4064, and am of a mind to work up a load since there is load data for IMR-4064 and jacketed bullets.  I was thinking of looking up the data for this latter case (IMR-4064 and jacketed) and backing way down, like 20-40%, for a starting load charge.  Then, work up using a chrony and examining for pressure signs on the way up.  I have the data at home (not here) but the starting load of IMR-4064 for example a 150 grain jacketed bullet was about say 30 grains.  It should take a lesser charge of the same powder to get a cast bullet of the same weight up to the same speed, correct?  I was thinking of say for this hypothetical example, to start way down at perhaps 22 grains of IMR-4064 with case filler on top under the bullet, and work up in 1 or 0.5 grain increments until I approach the muzzle velocity listed in the tables.

I have used this approach to work up cast bullet loads, safely I think, for 8mm Mauser and for 7.62x39.  Especially for the 8mm, pressure-wise I could go much higher safely but I don't push the cast bullets faster than about 2000-2100 fps.  That's in the ballpark of the 150-170 grain 30-30 bullet speeds anyway, and my interest is mostly in being able to cheaply shoot my 30-30 a lot (at paper and at the plinking range, not hunting) without being dependent on an external source of bullets for loading.

Does this sound reasonable?  Does monkeying with two variables (cast bullet and using case filler too) set off red danger flags with people?

I am with JesseL on wanting a faster powder.  I would probably try the BLC2 that you have on hand.  Maybe 26-27 grains to start + .75 gr of polyfill.

Lead bullets develop very different pressure curves than cast bullets, so your safe burn rates for jacketed bullets in your M1A don't apply to lead.

For instance, for an M1 Garand, mid-range powders (Varget,  4895, etc) and mid-range bullets (150-175) are only to be used to protect your op-rod.  But, a Lee 200 gr gas checked bullet over 42 grains of 4831 is a great cast bullet load.  Violates both the rules.

For your M1A you need to read this.  BruceB at the Cast Boolits site has done LOTS of shooting of the M1A, and that thread is a log of much of his work.

I bet BLC(2) would be fine with that 170 grain in your M1A.  Bruce logs a lot of loads with H335, which is close on the rate chart.  I would guess around 34-36 grains of BLC(2) would give a decent starting point.

I finally got around to beginning to work up a cast bullet load, using BL-C(2) per above.

So far so good, after one range outing to test.  The cast bullets are the Lee 170 LFP ones which were about BHN 19 several months ago, with 7.5 grains of Cream of Wheat case filler in between the powder and the bullet, just enough to fill the space with maybe very slight compression.  Four shot strings, mostly concerned with "is it safe to shoot at this level?" and looking for pressure signs.  Plus/minus is the std deviation

23.0 BL-C(2) --> 1576 fps +/- 26
24.0 BL-C(2) --> 1686 fps +/- 23
25.0 BL-C(2) --> 1724 fps +/- 28
26.0 BL-C(2) --> 1770 fps +/- 17

Plotting these in a graph, the line is pretty linear, so I haven't reached the point yet where more powder produces less velocity increase.  I think I could/should continue to work up a bit more, approaching 2000 fps.  The 24, 25, and 26 data points are "very" linear.

I had a dozen or so rounds left over, so I used them to shoot at a 100 yard target.  I was pleasantly surprised to see that most of them landed in about 1/2 a sheet of notebook paper at that distance - I wasn't even sure if they'd be on paper or not.  The rounds are likely more accurate than that, since this is about as well as I can do with my eyes and plain old iron sights at that distance.

Anyone see any problems with continuing to work up?  The closest thing to a guide I've seen is some Hornady load data for 160 grain FTX (their "LEVERevolution" plastic-tipped bullets, of which I also loaded up and tested yesterday, also using BL-C(2) powder and the Hornady load tables).  30 grains of BL-C(2) with these yielded 1810 fps, and 33 grains got 2047 fps, both figures in agreement with the Hornady load data.  Max load of BL-C(2) is listed at 33.2 grains for this 160 grain jacketed FTX bullet.  I know they're not the same as the cast lead bullets per the discussion above, but... I'm expecting or thinking that I should be ok continuing upwards for a few more grains of BL-C(2) to approach 2000 fps?  No pressure signs at all so far using up to 26 grains BL-C(2).  Perhaps up to 29 grains in 0.5 or 1.0 grain increments, and see what velocities those yield?

I've heard that about the wheelweights.  I'm lucky that I've only used real wheelweights once (the old kind, paid a tire store guy for half a 5 gal bucket of wheelweights and other crap that was in the bucket).  My luck is that my job (medical radiation physicist in a hospital, radiation therapy for cancer) gives me access to little lead-alloy containers that once shielded radioactive material.  FWIW they never were radioactive and are not now radioactive.  They add the same good stuff to the alloy to make them hard enough to use, which makes them very similar to wheelweights just a lot cleaner once you remove their packaging.  Not to be confused with the 1/16" lead sheet used to line x-ray rooms, that stuff is pure lead and often has nasty glue stuck to it as well.

Graph your charge weights vs. velocities-

Notice how your velocity and charge weights don't increase in linear fashion?  Be careful.  If that 29 grain charge is accurate enough for you, and burning clean enough, I wouldn't push it much farther.