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I have moulds for both styles (tumble lube and conventional lube) of 155 gr., .312 rifle bullets that Lee offers. I originally was planning to cast for a CZ 527 in 7.62x39 that I used to have. I already possess the Lee, press mounted sizer in .311" which does not use a top punch and which also does not lube the bullet.

I'm curious if I can get away with using the .311" Lee sizer to run either of these bullets through my bolt action. 300 Blackout? I realize that one would typically size the bullet approximately 1-2 thousandths over bore size, nominally a .308" in this case, (No, I haven't slugged to bore and currently lack a good micrometer to do so, so I have to go with the .308" bore assumption). I should mention that these 2 bullets differ somewhat in that 1 is a tumble lube design and one is conventional. Both are gas check designs.

The conventional design has a pretty short bearing surface and I'm wondering if I can get away with using it at .311" at moderate velocities in the blackout. I would still have to figure out a way to lube it - probably pan lubing and then cutting the bullet from the hardened pan of lube.

The alternative is ordering a .309" sizing die for my lubrisizer and a corresponding top punch. If I go this route I would need advice on which top punch to use. Going the lubrisizer and top punch route also means putting this project off until I get some money rolling back in after getting back to work.

I know I'm rambling on, and basically spilling my thoughts out on this matter, but I'm BORED and find myself with a lot of time for stuff like this. Thanks for reading and for any constructive advice.


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Cut to the chase and measure the throat diameter, that is what drives proper bullet diameter not groove diameter. If doing a chamber cast to include throat diameter isn't possible, a pound cast certainly should be. Google it. I bet by now there's a YouTube video since it's been in the bullet caster's lexicon for years now.


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Thanks, gnoahhh. I'll look for info on that.🙂


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The problem with those bullets is not the size (yes, you can generally shoot .310-.311 cast bullets in the Blackout), the nose profile is, specifically the "bore ride" section in front of the driving bands. You may have to seat them pretty deep.

Back when the Blackout was in it's infancy, the 155gr lube groove design was different (I have one of these), and it worked well in the Blackout. At some point Lee changed it though to be ore like the tumble lube version, with the throat interference issues that go with it. Maybe post a pic of both of yours side by side, either the bullets or the molds.

On the sizing question though - I suggest buying a .308 sizing die and polishing it out to ~.3095-.310". Those Lee dies need polishing in the taper area anyway, and it doesn't take long to open up the sizing diameter. Use emery cloth wrapped around a split steel dowel in a cordless drill.

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Yondering-

Hmmm. Guess I'll look at pushing a bullet into a case to check where the bands of the bullet sit in relation to the case mouth before proceeding any further.

Thank you.


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Originally Posted by bruinruin
Yondering-

Hmmm. Guess I'll look at pushing a bullet into a case to check where the bands of the bullet sit in relation to the case mouth before proceeding any further.

Thank you.


That's not what I was getting at. It's the straight-ish part of the nose in front of the driving bands that can be a problem, depending on which version of the lube groove mold you got. I don't recall hearing anyone being happy with the tumble lube version in the 300 Blk. Powder coating these makes the problem worse too.

Best way to find out is to load up some dummy rounds and cycle them to figure out what works and what doesn't.

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That non-tumble lube Lee version is a copy of a bullet design by C.E. Harris and moulds were originally produced by the now defunct NEI company. I bought one of the moulds more than twenty-five years ago and used the bullets in a Ruger 7.62x39 bolt-action. I don't know how close the Lee design is to the original, but the NEI bullet shot quite accurately. It does have a fat nose and my notes indicate an OAL of 2.20" with bullets sized to either .311" or .312" - either size did fine in my rifle. Most .30 caliber rifles have groove diameters of .308" and I routinely use .311" cast bullets, with the exception of a Remington .308 that does better with a .310" bullet.

There are always exceptions, but generally, the largest diameter cast bullet that will permit chambering a loaded cartridge without difficulty will be the most accurate for a particular rifle.

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Originally Posted by Yondering
Originally Posted by bruinruin
Yondering-

Hmmm. Guess I'll look at pushing a bullet into a case to check where the bands of the bullet sit in relation to the case mouth before proceeding any further.

Thank you.


That's not what I was getting at. It's the straight-ish part of the nose in front of the driving bands that can be a problem, depending on which version of the lube groove mold you got. I don't recall hearing anyone being happy with the tumble lube version in the 300 Blk. Powder coating these makes the problem worse too.

Best way to find out is to load up some dummy rounds and cycle them to figure out what works and what doesn't.


I see what you mean now. I was thinking that I may have to seat deeper to keep the bullet back from the leade, but on looking closer at the bullet, the section in front of the driving bands is darn near cylindrical. Only thing left to do is chamber the dummy round I made and see if it chambers properly.


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Originally Posted by lotech
That non-tumble lube Lee version is a copy of a bullet design by C.E. Harris and moulds were originally produced by the now defunct NEI company.


It was a copy. Lee changed it 5-10 years ago to be more like their tumble lube design, and that was not an improvement. They did not change the catalog picture to match, last I checked.


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