I am building a rifle chambered in 300 BLK with the intention of shooting cast through it. With the a cast bullet being sized anywhere from 0.309 to 0.311 combined with the thicker neck of converted brass from 223/556 chamber becomes problematic. This is a common problem with this chambering and cast. I would like to open the neck area of the chamber 0.004 - 0.006" above SAAMI specs to allow for smoother chambering. Who does this type of work? Dlask no longer does.
Opening up 300 BLK Chamber
- Thread starter gvanzeggelaar
- Start date
Don't mess around with your chamber, RCBS has a line of "small base taper crimp dies set" has a 7 degree crimp angle that is designed for auto loading rifles.
The crimping die chamber limits the expansion of case to exact specification of the casing, any grossly oversize bullet will either be deformed by the die or simply not going to seat at all.
The crimping die chamber limits the expansion of case to exact specification of the casing, any grossly oversize bullet will either be deformed by the die or simply not going to seat at all.
On second thought if your cast bullet measures anything over 0.309 you are probably using a the wrong bullet mold. A proper 0.308 mold has 0.309 cavity, metal shrinks as it cools not expand so it is impossible for the bullet to be larger than the mold cavity. the only way the bullet would come out of the cavity over 0.309 is the bullet mold is actually meant for a 30 carbine or 7.62 X 39 bullet which has a cavity that is 0.312.
- Location
- Western Manitoba
Perhaps is being overlooked that cast bullets are often then "sized" - run through a sizing die that confirms diameter and usually applies a lubricant - after casting. Can have a bullet casted to .3105" and then can run through a sizing die to make it .3090" or whatever. Some rules of thumb were to size bullets to be about .001" or .002" larger than groove diameter of the barrel; Veral Smith was big proponent to size the bullet to completely fill the ball seat / freebore area ahead of the chamber - so, typically, some dimensions from the particular rifled bore and throat area, set the desired diameter of the cast bullet to be used, in that barrel.
- Location
- Western Manitoba
Perhaps to be aware of a product called Cerrosafe - an alloy of specific metals - melts much less that 200 F - less than boiling water. Pour into a mould as a liquid - indeed does shrink as it solidifies, so removes easily, but then starts to grow - about 60 minutes after solidify, has grown to pretty much perfect exact size of the mould interior, and keeps on "growing" - is used to do castings to measure stuff like throats and necks inside chambers - can get precise, accurate measurements, but only at that 60 minute mark.
And, might be a function of "shrinking less" - but for sure, can get multiple diameters of bullets cast from the exact same bullet mold, by varying the alloy that you use - from pure lead, to lead-tin, to lead-tin-antinomy, etc. and variations thereof.
Update on this:
Barrel has been opened up to suite my 240gr cast hand loads for a cost of 250$. (I kept the reamer) Barrel cost 400$. Some say the barrel is now ruined. I disagree. It would have added value to a fellow caster.
Subsonic rounds are costing 10-15 cents a round and are 100% reliable. Seem decent accurate for plinking but haven’t run accurately tests yet. They chamber and extract with ease. No more sorting brass and dealing with super tight tolerances. 1:8 barrel stabilizes the 240gr cast at subsonic velocities. Payback vs 220gr jacketed is somewhere between 400-1000 rounds depending how you look at it. All in all if you cast 300 blackout I highly recommend going this route. Especially with a firearm that takes a readily available barrel that can be replaced if needed
Barrel has been opened up to suite my 240gr cast hand loads for a cost of 250$. (I kept the reamer) Barrel cost 400$. Some say the barrel is now ruined. I disagree. It would have added value to a fellow caster.
Subsonic rounds are costing 10-15 cents a round and are 100% reliable. Seem decent accurate for plinking but haven’t run accurately tests yet. They chamber and extract with ease. No more sorting brass and dealing with super tight tolerances. 1:8 barrel stabilizes the 240gr cast at subsonic velocities. Payback vs 220gr jacketed is somewhere between 400-1000 rounds depending how you look at it. All in all if you cast 300 blackout I highly recommend going this route. Especially with a firearm that takes a readily available barrel that can be replaced if needed
.30 Carbine is and always has been .308" Molds also vary somewhat, sometimes a lot. A few thousandths over is meaningless as far as increasing pressure and is very likely beneficial to accuracy and avoiding leading, unless it won't chamber of course. I have a 247grn NOE mold inbound for my .300. If it doesn't fit I certainly won't be opening anything up. I don't use converted brass so I doubt it will be an issue. I thought properly converted brass had the necks turned but I guess not?
Mold is here, no idea when I'll be casting as I still need to set up a fume hood in my basement. Feel free to PM in a month or so. I also have the LEE 230 I will be trying out both with and without gas checks.
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