6mm Arsenal Mold

[YEMX]

Okay, so a member here (D-Rig) was kind enough to help me out, and cast some of these 6mm (.243) boolits from my Arsenal "Bowman" mold.  I pushed one through my TJ barrel to slug the bore, and I'm getting .235" on the flats...  They're dropping from the mold at .245".  What size sizing-die should I get?  I want to get some sized for Jim at WAR, so I can finally send him my barrel and slugs so I can FINALLY get my 6mm Flex

[K.O.]

Hi  Tom

what you want is groove diameter not bore... Most .243-.244 are .243 groove and .235-.237 bore... so I am pretty sure you mean it has a .235 bore diam when you say across the flats..?

[rsterne]

I would size them to the groove diameter, which on a TJ's barrel is about 0.243".... I would push the bullet into the breech end (after deburring the bore) and then back out the same end (the muzzle of the TJ's barrels have a label indicating that, and are slightly smaller because of the way they are hammer forged)…. Measure the maximum OD of the bullet across all three pairs of barrel grooves (the "bumps" on the bullet), average them, and size to that diameter for the bullets you send to Jim to cut the chamber diameter.... I usually go 0.001" larger than the groove diameter for the chamber ID, but what Jim does is up to him....

Bob

[YEMX]

Hi  Tom

what you want is groove diameter not bore... Most .243-.244 are .243 groove and .235-.237 bore... so I am pretty sure you mean it has a .235 bore diam when you say across the flats..?

It's a bad picture, but you should be able to make out the "flat"...  I should have paid more attention to everyone's posts dealing with casting and slugging a bore...   

I would size them to the groove diameter, which on a TJ's barrel is about 0.243".... I would push the bullet into the breech end (after deburring the bore) and then back out the same end...

Bob

Bob, please see pic above- I did exactly as stated above, minus deburring the bore...  The picture is the result...

[YEMX]

Side question- should I do any work on the barrel before sending it to WAR?  i.e. deburring?

[rsterne]

You are measuring the grooves in the bullet, which gives you the LAND diameter.... You need to measure BETWEEN the flats, where the bullet is the largest in diameter to measure the GROOVE diameter.... THAT is what the chamber should measure....

Bob

[D-RIG]

That picture says a lot and it looks like your getting very good marks
on the outer edge of your slug thats the diameter your looking for it
should be right at .243 or .244" and those are the two sizing dies I
would look at buying if it were me .

If your going to cut the lead I would size the slug at .244" if the
barrels at .243" . Good luck Tom .

[YEMX]

Gentlemen, I thank you!!  I understand now, very good explanations!  Sometimes you just gotta break it down Barney style for me!   

I re-measured, and y'all are correct, it's hovering right around .243".  I'm measuring to the best of my ability, and accuracy of my micrometer.

I'll order a .244" sizer as soon as I can!

[rintafile]

If you order sizing system and dies from NOE take few those dies..Like .243 .244 ..245 for sure. Those cost under 10$ pc so if alloy changes or some molds drop larger diameter you had your dies ready. it wont change shipping fees or anything.  Well thats what i usually do and haven't regret that.

[YEMX]

If you order sizing system and dies from NOE take few those dies..Like .243 .244 ..245 for sure. Those cost under 10$ pc so if alloy changes or some molds drop larger diameter you had your dies ready. it wont change shipping fees or anything.  Well that's what I usually do and haven't regret that.

Yessir, I was already planning on getting both a .243 and .244 after thinking about it- after I posted my last, of course! 

[rsterne]

I would purchase a 0.242" bushing from NOE at the same time.... Your barrel may like the bullets snug, groove size, or 0.001" under, and only trying all three will tell you for sure.... Only $10 more, and no extra shipping....

Something to consider regarding velocity.... With my .22 cal Disco Double (0.217" groove diameter) I tried 4 different bullet diameters with the 29.6 gr. BBT....

0.216" = 972 fps
0.217" = 963 fps
0.218" = 956 fps
0.219" (as cast) = 956 fps (but much harder to chamber in the 0.218" chamber)

In the case of the 0.219" bullet, it was being sized by the chamber, hence when fired the velocity was not lower again....

Bob

[KnifeMaker]

Bob, Dale and Teemu are on the money here. My .25 Storm, and the Talon/Dor both prefer a bullet sized 1 thou. to 1/2 thou under bore.


Now, the Barney method of measuring. Measure the widest dia. of the bullet after pushing and removing it from the bbl. Your There!!!   No need to try to measure the rifling indentations. (Striations)  a mic. won't fit there anyway, and a dial caliper, especially a digital isn't accurate enough.


Mike