Lee 300 blk out subsonic 230 grain mold question

[newman0912]

Hi, I'm relatively new to casting 300 blackout and I only have one mold. It's the Lee 309-230-5R mold. The bullet is powder coated and looked good after molding. I keep a good watch on the pot temp (730 to 750) and I learned to preheat the mold to above 600 to get a good bullet without wrinkles. All good so far.

My question is the diameter of the bullet. This is a very long bullet and I've been told it's pretty difficult to mold (as a beginner). I put the bullet (lubricated with One Shot) through the Lee mold sizing die .309" and measured it with calipers. When measuring across the 5 ribs and a little bit above that, the bullet sure enough, measures .309".

But when I measured closer to the bullet tip, but way below the start of the Ogive angle, the diameter of that whole, long section of bullet measures .300". Is this normal? I guess I would have expected the bullet to measure .309 the whole length of the bullet up to the ogive rounded taper by the nose. Of course, the back of the bullet is tapered small, that much I know.

Thanks!

Sorry, upload photo failed - I don't know why, but you should know what's going on without a photo. Thanks again.

[wmitty]

Welcome to the forum! I don’t have that mould design but it sounds like the boolit is similar to a “bore rider” design in that the forward portion of the boolit is designed to ride on the lands of the rifling while the rear portion is groove diameter or slightly larger. The boat tail design is, in my opinion, a mistake; but it seems to work for some of us. Good luck with obtaining accuracy with this boolit design!

[Bigslug]

Welcome!

Wmitty pretty well covers it - your bullet is matched to "American" .30 caliber - nominally .300" bore and .308" groove. .309-.310" is typically how we fit the driving bands of cast to that.

Consider that dimensionally, your cartridge has to fit in the chamber and the bolt has to close. The typical chamber is cut to give a bit of a taper (leade) at the start of the rifling. From the sharp 90-degree corner cut for the case mouth, you'll start somewhat bigger than groove diameter and funnel forward until you get to the true unmolested bore. That's the space you get to play with for how much bullet you're allowed to have in front of the case mouth and what it's sized and shaped like - - that, and the length of your magazine, of course.

[gwpercle]

That forward section is smaller on purpose ... it Rides the bore ...
That design is called a bore rider and helps with chambering . If a long boolit is .309" all the way from base to where the ogive starts (and some are) you might have trouble seating it deep enough so that the loaded round will chamber ... the forward part may not enter enter the bore far enough ... in that case you would have to seat it deeper ... and deep seating a long boolit isn't a good idea ...actually it's a bad idea ... so that's one reason it's smaller at that location .

Welcome from Baton Rouge , Louisiana !
the first round's on meGary

[newman0912]

Thanks everyone. That makes a lot of sense.

[stubshaft]

I use this bullet in my 7.62X30 and 300 Whisper, I lube it with Xlox and find it very accurate. I do shoot it UN-sized though.

[Texas by God]

I'm new to this mould as well. Does anyone use gas checks on it?

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[Oldfeller]

It has no gas check shank, it has a large long taper instead (intended to help BC and flight characteristics).

[Texas by God]

It has no gas check shank, it has a large long taper instead (intended to help BC and flight characteristics).

Thanks. I know this but I thought that I read somewhere of putting gas checks on them. The boat tail doesn't seem to be designed for it- as you say.
So far(with no GC) the accuracy from my 1-7 .300BO hasn't impressed me.

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[Bigslug]

Don't know if we have a "Serious Science" thread on cast boat tails or not. . .

I'm guessing the formula for success would be (a.) to keep them down in that high-subsonic/.22LR match velocity range, (b.) cast them pretty dang hard to protect the base from deformation, and (c.) have enough barrel length that the pressure on the base of the bullet at exit is on the decline. (D? Maybe?) Dacron filler as a base shield? This is of course all before we get into the "crud in my suppressor" discussions.

Given that subsonic/transsonic is the place where boat tails really do their work, it makes sense to at least try to find a functional space for them.

[barrabruce]

I was gunna buy that mould to try it out for a real heavy bullet in my 1:8 twist 7.62x33r so I could use adi 2207 in it but may settle for a 225 grn fn bore rider instead.
Powder availability dictating projectile choices.

[mto7464]

I have used this mold and it always drops small (I have two and the same for both. PC was the only way to get them to be "big enough" but it sounds like maybe you got lucky. Plus my boolits had a taper to them in the area that contacts the bore. During sizing only a small area was sized close to the boattail it's .3095 and near the crimp goove .309 after sizing. Another coat of PC would take care of that but then the nose gets too big to chamber properly. Does not sound like much but it can cause issues. Its good for plinking. Are you shooting them in an AR? My OAL is 2.245. Any deeper and I started to lose tension since the portion that is .3095. would then pass through the case neck into the case. I think a flat base would be better I would get some gas cutting and got some lead in my bolt carrier.
Anyway I think it's a good profile, less the BT but mine were poorly cut. There are some copies that are like it but they cost more. I have a miha mold that is good but does not like PC. FYI this Lee design is not a bore rider.

[mto7464]

Don't know if we have a "Serious Science" thread on cast boat tails or not. . .

I'm guessing the formula for success would be (a.) to keep them down in that high-subsonic/.22LR match velocity range, (b.) cast them pretty dang hard to protect the base from deformation, and (c.) have enough barrel length that the pressure on the base of the bullet at exit is on the decline. (D? Maybe?) Dacron filler as a base shield? This is of course all before we get into the "crud in my suppressor" discussions.

Given that subsonic/transsonic is the place where boat tails really do their work, it makes sense to at least try to find a functional space for them.

"crud in my suppressor" I can relate to that too.