Casting for my brand new marlin 336W with it's microgroove barrel

[TupariSD]

I keep seeing stuff about casting and oversizing boolits for microgroove barrels. Mine is 3030, and I've seen a few posts saying the Lee .309 molds work great in these barrels, I bought a 170 and a 150. I was wondering what size die I should run them through? .309? .310? Etc? What is everyone's experience? Thanks in advance,
Casey

[Yodogsandman]

The boolit needs to be sized to fit YOUR chambers throat, .001"-.002" over bore groove diameter. You find the measurements by doing a pound slug of your chamber (see below). The quick and dirty way is to measure the inside diameter from a case neck, from a case that's been fired in your rifle. Your size will probably be more like .310"-.311".

http://castboolits.gunloads.com/show...o-a-pound-cast

[TupariSD]

The boolit needs to be sized to fit YOUR chambers throat, .001"-.002" over bore groove diameter. You find the measurements by doing a pound slug of your chamber (see below). The quick and dirty way is to measure the inside diameter from a case neck, from a case that's been fired in your rifle. Your size will probably be more like .310"-.311".

http://castboolits.gunloads.com/show...o-a-pound-cast

So if I size to .311 and it fits a fired neck it should work OK?

[TupariSD]

The boolit needs to be sized to fit YOUR chambers throat, .001"-.002" over bore groove diameter. You find the measurements by doing a pound slug of your chamber (see below). The quick and dirty way is to measure the inside diameter from a case neck, from a case that's been fired in your rifle. Your size will probably be more like .310"-.311".

http://castboolits.gunloads.com/show...o-a-pound-cast

I'm getting a bad link there

[Gray Fox]

My 336 likes either the Lyman 31141 or the 165 Ranch Dog RNFP sized at .311 with gas checks. My alloy is COWW with 2% tin and water dropped. The 45-45-10 lube recipe works fine on both. I've used IMR 4895, 2400 and Leverevolution with good results. GF

[TupariSD]

I did buy a .311 die for the used lube sizer I have on the way

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[Strtspdlx]

I did buy a .311 die for the used lube sizer I have on the way

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So if your molds are designed to throw a .309 size boolit that. 311 die won't do you any good. It hasn't been mentioned yet but I thought I'd say it. I would without a doubt make up a soft lead slug, and slug the barrel and see what size would really be appropriate for your barrel. Otherwise you may be very dissappointend with the results.

[Dan Cash]

As stated, the bullet needs to fit your rifle. I have had good results with bullets a bit under throat diameter but a couple thousandths over groove diameter. In all probability, a .311 - .312 bullet, if not too hard, will work very well in your .30-30 Marlin. I load for a Mod 36 and a 336 with ballard type rifling and a 336 with Microgroove. All three guns use the same .311 bullet with great success.

[RPRNY]

Post #2 for your needs.

In my experience (1968 Texan), keeping speeds below 1800fps has proven very useful with all cast I have used in it. Above 1800 fps with everything 150 grs and over has delivered poor accuracy. Mine is most happy with Lyman 311041 at .310" and @1650 - 1700 fps. I can get 2.5"-3" 5 shot groups (after a fouling shot) at 100 yards (aperture sight) if I am shooting well.

[mdi]

I have read that shooting cast in a Microgroove barrel can be more problematic and requires different tactics than a standard barrel. I quickly looked here, but didn't see any of the past threads, but IIRC, the bullets need to be slightly larger than the "normal" .002" over groove diameter "standard" for ballard rifling, along with a few other hints...

[RPRNY]

I have read that shooting cast in a Microgroove barrel can be more problematic and requires different tactics than a standard barrel. I quickly looked here, but didn't see any of the past threads, but IIRC, the bullets need to be slightly larger than the "normal" .002" over groove diameter "standard" for ballard rifling, along with a few other hints...

That's correct guidance, but you have to find out what works in your rifle. For example, mine will actually size down by shaving about a 10th of an inch ahead of the crimp groove on a 311041 sized .311" but sized to .310" is very happy. Why we have to slug bores and check chambers and throats.

I had an early 70s Glenfield that really wanted almost .312" boolits. It became a 35-30/30.