Sizing for 150gr 30-30 bullets

[Sharktown]

I have been casting for my Marlin 30-30 and need some suggestions as to what diameter to size the bullets to. I am using a Lee 150gr flat nose GC mold to cast the bullets. Question is what would I size the bullets to - .309 or .310? I haven't bought the sizing die yet or slugged the barrel so I a wanted to ask here first.

Thanks - Sharktown

[Shasta]

Slugging the barrel would be the first thing you need to do. I like to use pure lead round balls, or even a fishing split shot, so long as it is larger than the bore being measured. Once you have established the bore size, get a sizer die that is .001"-.002" larger and you are in business. My 1894 Winchester .30-30 required a .309" sizer and shoots cast lead bullets very well.

SHASTA

[Rusty]

Yep, really need to slug the bore first. Oil it up good and use dead soft lead.

[harry]

Sharktown there is this guy I know that can give you lots of help with your question. Just give this guy a holler: Terry Murbach

Harry

[Canuck Bob]

The gurus I listen too suggest sizing for the throat. You can research this on the cast boolits forum.

Oversize is required as the gases will cut past a slightly undersize bullet. To get started I slugged with fishing weights and bought sizers .002 oversize. I can open them a bit if I choose later.

Another thing to watch is that regular dies may leave the neck small enough to swage the cast bullet undersize while seating. It is suggested to pull one and measure. Folks like the Lyman M die for sizing. Custom expanders are available to accomodate cast bullets if required. Many guys report no problems though. My RCBS 444 dies did not downsize my purchased cast bullets. My 303 did a little bit.

[Charles]

Sharktown...You asked a simple question, so I will give a simple answer. If you are choosing between .309 and .310 go with .310.

[AJMD429]

Sharktown there is this guy I know that can give you lots of help with your question. Just give this guy a holler: Terry Murbach

That's baaaaad...

[Tycer]

I do em all .311

[Sharktown]

A thank you goes out to all who responded with their suggestions and thoughts. I figured to slug the barrel but wanted to get some opinions, you guys gave a weath of information. I always like to ask the question first as I know there will be good information on this forum from people willing to help and have already been doing what I'm asking about.
One other question I have - my Marlin was rechambered to 30-30 improved some years ago and have only been using jacketed bullets so I was wondering if there will be any issues using my water quenched cast bullets at improved velocities?
Thanks again for your help.

Sharktown

[jlchucker]

I have been casting for my Marlin 30-30 and need some suggestions as to what diameter to size the bullets to. I am using a Lee 150gr flat nose GC mold to cast the bullets. Question is what would I size the bullets to - .309 or .310? I haven't bought the sizing die yet or slugged the barrel so I a wanted to ask here first.

Thanks - Sharktown

Until you slug the barrel, all anyone can do is offer their best guess. I don't mean to contradict anyone's comments this morning--they all mean well. Slug first, and use a decent mike when measuring, then go from there. Every barrel is a tiny bit different, and until you slug and measure, none of us will really be able to opine as to what will work best in your gun.

[3leggedturtle]

Seat an unsized bullet in empty case and see if it chambers and adjust from there. I have both .308 and .309 sizers never really noticed much of an accury difference between the two diameters. All the Lee flat point .30cal molds have shot good for me.

[Griff]

Slugging the barrel would be the first thing you need to do. I like to use pure lead round balls, or even a fishing split shot, so long as it is larger than the bore being measured. Once you have established the bore size, get a sizer die that is .001"-.002" larger and you are in business. My 1894 Winchester .30-30 required a .309" sizer and shoots cast lead bullets very well.
SHASTA

+1.

[KCSO]

Until yo slug the barrel who knows? Then is it micro groove or ballard? I just finished a coversion with an old cut rifled barrel on a Marlin 336 and the bore went 307, for that tube we are starting at 310 sizing and may go to 311 depending on accuracy and leading at +2000 fps. If it is a modenr mico groove barrel you will want a bigger harder bullet say 311 to start but you really ned to slug first.

[Sharktown]

Yes, it is a micro groove barrel - I believe I bought it in 1976 or 1977. Had it rechambered to AI and reblued around 7 years years ago too.

Thanks - Sharktown

[3006mv]

Is recovering a boolit in wet sand and measuring base a way of slugging? Or is that a bit off due to deformation, even if base does not seem deformed and has good grooves/cuts

[Griff]

Is recovering a boolit in wet sand and measuring base a way of slugging? Or is that a bit off due to deformation, even if base does not seem deformed and has good grooves/cuts

Let's just say that it's not quite as good as pushing thru a lead slug. The pushing thru a lead slug will also tell you if you have any "tight" or "loose" spots in the barrel that can also affect accuracy... or not.

[Sixgun]

I would not concern myself with slugging a 30-30. They are all within specs. I must have slugged 2 dozen of them and they all came out at .308-.309.

I size all 30 calibers, no matter the cartridge at .311, sometimes .312. The bigger, the better as the fatter diameter helps to center the bullet concentric with the bore,------------6

[Ji in Hawaii]

I don't even size um, I just shoot um as cast.

[1894c]

Here is a list from beartooth bullets... :)

Marlin Micro- Groove Bullet Diameter - Copy.jpg

[Borregos]

I have never slugged a 30-30 barrel, I started using cast sized at .310 and it worked extremely well in all my levers and my Contender barrels so I never bothered.

[Griff]

One of the most accurate bullets in my first 3 or 4 Winchester .30-30s I've ever found is the .307 dia Sierra 150 grain, so when I started to load cast, I went to .309 gaschecked, cast very hard and run them just as fast as those jacketed Sierras. Accuracy is just about the same, if not a mite better with the cast.

[Charles]

.310 or .311 will do just fine. Be aware that some of those Marlins have little or no throat/free bore, making the use of cast bullets with a driving band out of case neck problematic. Not all, but some...