7.62x40 WT

[358156 hp]

The 30 HRT is essentially a 6.8 SPC, necked out to 30 cal, and loaded using 30 Herrett dies. I do agree with Josh though. ARs are similar to 1911s in some aspects, the farther you get from it's original design envelope, the crankier it becomes. I'll probably have to take John Taffins advice and get both, or rather build them. The 30 HRT wouldn't suppress very well, but would make a dandy deer and pig round.

 

[Hawk]

Outside neck diameter of fired brass measures 0.357"to 0.360".
Loaded rounds measure 0.335".
Mine has a very short throat. I don't know why they cut them that short and tight.
Ruined a case, so I cut it up to show this:

 

[Josh]

Can you take some measurements of the check height vs shank length and compare it to the drawing? That check (I thought) shouod tuck up closer to the bottom band. Also compare your nose measurements to the design, if the nose is too fat you would have to shorten OAL considerably which would give you the perception of a short cut throat. Knowing that this design is so closely fitted to the throat we may have to play with alloy to help shrink that nose a hair

 

[Hawk]

I went back and looked at post#106 again.
Specs call for a .310 dia boolit in the throat area. Reamer diagram shows the throat at 0.3095.
Mine drops at 0.3125 at the front driving band, which makes the ojive radius a little larger. Sizing takes the bands down, but doesn't affect the ojive.
That 0.0025 is going to make me have to seat it a little deeper to clear the throat.
I need to go back an find the thread that talks about what lead composition makes boolits drop smaller.

We were typing at the same time. I type slowly (two finger style).
AOL= 0.8869 Spec is 0.8870.
All the bands seem within 0.010 of what they should be. The rear band is 0.120 instead of 0.110.
Probably looks smaller because I'm having to size it down from 0.3125 to 0.309. Leads gotta go somewhere.
Extra weight is probably because it is so fat????
I need to open up my sizer to .310.
You guys that shoot .311 should like this one.

 

[Josh]

The more pure lead and tin you have in an alloy the smaller it will cast, that being said let me give some small suggestions before we call this mould out of spec.

1) Try using 75/25 pure/WW with no tin but water drop.

2) Get this mould HOT, frosty bullet hot, when you have a hole in a solid block of metal as it heats it will get larger, if that hole is split down the middle the hotter you get the hole the smaller it gets. (This is why people get more consistent bullets using a PID and a mould thermometer)

If this doesn't work then one of the guys may buy it, or it can be sent back to Tom to be cut smaller.

 

[Ian]

Ian,

I have implemented a few of the design changes you asked for. I have taken the grease groove and shortened it, sharpened the groove sides to the minimum 55* for Tom, reduced the waist to 0.270", and lengthened the lead angle by another 0.010" and dropped it to 0.299" thus keeping the same 1.5* angle.

Let me know what you think here (I even named this one for you)

I quoted this to get the drawing up again. Click to expand. We designed this nose to fit better than that, something's wrong here, the mould as ordered is casting way too fat all over, and too fat ruins the entire fitment method because it won't get close enough to the rifling.

HAWK: If this thing is from Accurate and casts .312" or bigger it's likely that you either spec'ed it with pure lead when you ordered it or he made it wrong. This is not acceptable from a mould designed to run WW alloy. Go back and look at your order to make SURE that you spec'ed it with the alloy you're using, or one with similar properties to the one you're using. The alloy spec and desired band diameter are on the order receipt unless Tom has changed something recently.

 

[Hawk]

I just checked the order and I spec'ed it with clip on wheel weights.

 

[Josh]

I agree that something is jakey, if spec'ed at .310 that mould should drop a bullet somewhere between .309 and .311, if that was the case a few ounces +/- of pure would easily fix that thousandth difference.

 

[Ian]

I'd send it back to Tom then. Might be perfect for me casting with 50-50, but if I were going to buy one I'd add a shallow crimp groove.

Awesome that it feeds, I had no doubt on that, it doesn't take much radius on the ogive to make them wiggle right through and AR.

 

[Ian]

I agree that something is jakey, if spec'ed at .310 that bullet should drop a bullet somewhere between .309 and .311, if that was the case a few ounces +/- of pure would easily fix that thousandth difference.

I have a pile of Tom's moulds and spec'ed with COWW they almost always cast .001" larger with MY WW, and .005" over with 50/50. Add a little tin and it adds a couple "tenths" to each of those. This one is casting .0025" too large, which is out of spec for any alloy unless it's something like straight Linotype!

 

[Josh]

I would try 75/25 and 50/50 and get it hot, if none of that works send it back. As a mould maker I was way happier if a mould came back and I was told they tried a few alloys, even if they got the right numbers with a different alloy but wanted it fixed I at least knew they did work with it a hair.

 

[Hawk]

I think I can load it at 2.100" and clear the throat.
I measured 100 bullets and they all measure 0.3125 to 0.3130, measured with a Lyman micrometer.
I'm casting with an alloy of wheel weights that was unsorted as to COWW and SOWW with no tin added, but I don't know an exact composition.

A frosted, water dropped bullet, 48 hours after casting, has a Brinnell Hardness of 15, if that helps. Using an LBT Tester.

 

[Josh]

At .313 that booger is out, cast a batch to play with send 2 with the mould and ship it back.

 

[fiver]

this is what we drew up and specced pretty much, except for the slight angle change on the nose which I was fine with.
http://accuratemolds.com/bullet_detail.php?bullet=31-155W-D.png

now if you spec the mold with a plus designation it will come about .0015 oversized.
the +/- can be cut to zero or to negative .0015 this usually describes the drive bands and not so much the nose diameter.
at 313 that would work in my throated out Argies, and probably be a great fit in the arisaka. [maybe the SKS would like it too]
I wouldn't even give it a go in a 30 cal. with that diameter.
that extra .002 is easy to see when you size them. the uneven swipe down the side will ruin any chance at matching velocity and accuracy.

add some soft lead alloy [nothing else] and get the mold temp up to turning out some grey boolits.

 

[Hawk]

I don't have any soft lead. I'd have to buy some.

 

[Ian]

Might shoot Tom an email and see what he says. It's sizing half the tapered part of the nose instead of leaving a front bearing band narrower than the rear bearing band at .310". I'd think these would need to run around .3095" so sizing in a .309" die after they've firmed up for a week so they bounce back a smidge would be the ticket. In any case, they'll need to be no bigger than throat entrance diameter minus a couple tenths.

Bottom line is this bullet isn't fitting like we intended at all and sizing 3-4 thousandths is going to kill your chances at decent HV accuracy. Time to punt.

 

[Hawk]

Sent Tom an e-mail.
I'm disappointed. I was looking forward to shooting this, but with the boolit so oversized, I feel like it will be a waste of time to try and work up a load, then start over when I get the next mold.

 

[Josh]

You could work up some pressure data with these bullets, fireform some more brass and such, I think I am just as disappointed as you are and this isn't even my project! (Ok I may have adopted it a hair)

Even though this setback is upsetting it is best to have everything correct before setting off, you will be happy with the result when you are shooting hogs with an AR using cast bullets at 2150 fps.

 

[fiver]

I know I am.
yeah keep a couple of handfuls of the boolits around so you can do some load work ups and such while waiting for the second mold.

 

[Hawk]

I heard from Tom.
I blew it. I ordered a 0.311 and failed to notice on the final checklist there is a box that allows for +0.002" over (didn't expect that). That puts my mold in spec per my order.
My bad all the way for being in too much of a hurry and not reading all of his FAQ.
I'll have to decide if I want to give him another $91.00 or just work with this one.
I was going to ship out some bullets, but there will be no point with these.
I'm officially depressed.