Drill bit boolits

[daschnoz]

The next thing for my locker is going to be a CZ527 in 7.62x39. My plan is to do some serious sub-sonic development with it. I'm thinking REALLY heavy boolit and either Unique or Red Dot.

Bullet diameter is technically 0.311. A 5/16" drill bit is 0.3125". I'm thinking that I can buy a set of mold blanks from Lee and drill & ream my own in about 10 minutes. I should be able to shoot them as cast - no resizing needed.


I'm thinking something in the 250gr area. If I did the math below correctly, my boolit needs to be about 1.13" long to get me 250gr.

Lead density:
0.41# per cubic inch
0.41 * 7000 = 2870gr per cubic inch
@ 0.3125" dia, 0.0767cubic inches per inch of boolit
0.0767 * 2870 = 220gr per inch of boolit length

Does your math work out the same as mine?


Since I'll be throwing them slowly (sub 1000fps), I don't need a GC. If I use LLA to lube them, do they need grooves, or can the whole boolit be the bearing surface?

[Ben]

You may have great success with all this.....but..... I find it interesting that if a long bullet with no lube ring was " the thing " in the cast bullet fraternity , makes you wonder why at least 1 mold manufacturer isn't making them ?

I've seen core molds, which seem to be very similar to what you've described, but these were designed to by used in the Swaging process.

Ben

[Rangefinder]

I'd suggest under-drilling it initially then using a course-thread 5/16 tap to cut your grooves partially down the length. Using the entire boolit as a bearing surface is going to make the thing really difficult to stabilize, especially at low velocities, and no grooves at all will run out of lube very quickly in your bore.

[waksupi]

Bobby, I would go undersize, and paper patch them.

[Rangefinder]

^^^ That's a big +1 on patching. ;) I'm almost ashamed I didn't think of it... ALMOST. That's why I dwell here--someone is always thinking when I'm not. ;)

[badbob454]

is a lee blank cheaper than a mold?, or is this something you just want to do ..

[JonB_in_Glencoe]

I'm not sure what Lee charges for blank molds,
but if your looking to get 1+ inches, your not going to
get it from there standard size 2 cavity.
Maybe the Swede CM from Midsouth...that's on a deeper block,
I don't have mine handy to measure for you.

Plus if you start with a machined mold, and just
enlarge the cavities, chances are better they will be straight.

I like the idea of using a tap to make spiral tumble lube grooves,
I wonder if the spiral will make some wind noise if you going subsonic ?
good luck,
Jon

another thought...
making redneck concentric tumble lube grooves...
maybe using a drill press like a mill and using a smaller drill bit
installed backwards using one that has a Burr...I see burred up
drill shanks all the time at work, people never tighten a chuck tight enough.

[Baryngyl]

I like the idea of using a tap to make spiral tumble lube grooves,

Then get you a barrel that is tapped with threads the full length inside and you can have the first 20:1 riffling (or is that 1:1/20). :kidding:

Plus the Boolit will be pre-engraved. LOL

Michael Grace

[Bret4207]

Unless you are incredibly lucky your 5/16 drill bit will probably produce an oversized and not so round hole. If you really want to try this, better to drill it undersized and ream the hole to your finished size, and don't forget to allow for boolit shrinkage. I don't know how many thousands that is, maybe .002? Maybe more, maybe less. Either way you're going to want something a little bigger than you planned.

[daschnoz]

Using a tap to cut lube grooves - BRILLIANT!!!

I've never paper patched. Are there any good links on the subject?

As for the why - read some of this
http://members.shaw.ca/cronhelm/762ProjectRifle.html
It's quite interesting. Things you would never have thought of...




Here is what I have come up with.

- Start with a 1/4" hole, 1.5" deep.

- Open up the top 1/8" with a 5/16 drill bit - driving band and gas seal. If I need to increase it, there are a couple of letter and number drill sizes that get me as far as 0.316" (letter size "O") before the next jump to 0.323" (letter size "P"). It's easier to remove metal than it is to add it back.

- Bottom out a 5/16-18 starter tap in the hole to make lube grooves.

Thoughts?

[waksupi]

Bobby, there is a full section on paper patching here! You need to get out more! ;o)

[JSnover]

I'd consider using a 1/4" ball mill to finish the hole. You'll get a round nose boolit.

[daschnoz]

Paper patching - using paper to make a sabot for your undersized boolit. I see. I need to research this some more.


I'm not sure I want a round nose on this. Blunt nose projectiles have better terminal performance at sub-sonic speeds.

[nanuk]

GoodSteel did this

Hope he finds this and explains his experiences.

[daschnoz]

Upon further thought - Fk it. I'll try to get one of the 247gr whisper molds.

[Ben]

I do believe in the long term haul that you'd be about 300% happier with your decision.

Ben

[Idaho Sharpshooter]

I got a visual on the threaded boolet. I wonder how much fun it would be to try and drop that one from the mould blocks...

Rich

[Bret4207]

Upon further thought -. I'll try to get one of the 247gr whisper molds.

Really nice, mature language you got there. Grow up, eh?

[melloairman]

I have taken a LEE 32 caliber RN mold that was 98 grains I think and drilled it down or removed the RN and made it a Semi point to about 115-120 grains . Casted about 20 bhn lead in it for my air rifle . Just as a test because the bullets would not group out of the stock mold . At 50 yards 3 shot group 1 fill they did good for me at around 900 fps . Marvin
http://i301.photobucket.com/albums/nn55/melloroadman/IMG_6504A.jpg
http://i301.photobucket.com/albums/nn55/melloroadman/IMG_6501A.jpg
http://i301.photobucket.com/albums/nn55/melloroadman/IMG_6497A.jpg

[excess650]

The CZ-527 is a neat little rifle, but that 247gr is really looooooong. It might work but you are limited to magazine length and a really short neck.

Your thought about all bearing surface seems to neglect that the throat and leade are of limited length unless you're planning on putting a ridiculously long throat in it. Otherwise you're gonna have 1" of boolit in the case.

[geargnasher]

For really low-velocity loads, 45/45/10 Recluse lube is plenty good on a smooth-sided boolit, and I've used Redneck Drill Mould boolits without lube at all, using pure lead and lots of COW filler behind it. NO leading under 800 fps.

Gear

[para45lda]

Saw a picture once. Somebody took their boolit mold, turned it upside down and put new cavities between the old ones from the bottom.. Looked pretty spiffy. And it didn't cost anything.

Wes

[melloairman]

I ran a patch sprayed with dry lube down the barrel after cleaning it . The I sprayed the bullets with a light coat of molly spray . Yes I went over board on the bhn for a reason . But if you use too soft a lead it will shear back to the base of the bullet as well . Marvin

[Buckshot]

...........daschnoz, one of the best things about this place is the number of folks who get an idea for something, and then decides to try it.8-) If you're wanting to use some pre-made blocks, a less expensive route (sometimes) is to aquire a set of used blocks for a round ball. Naturally you'll want them smaller then your proposed cavity's OD.

http://www.fototime.com/8D7CD82788D46E0/standard.jpg

ABOVE: The Lyman 3112847 @ 214 grs in the 7.62x39. It's engraved pretty well, eh :-)! I used a flat nosepunch and 'bumped' the slug in the lube-size die trying to get it short enough to feed from the magazine of the Mauser, and it's JUST a tiny bit too long yet. My rifle is a M94 Small ring Mauser with a .300" x .308" barrel. The big Lyman is very accurate in it's 10" twist. Your idea of a long heavy slug means you're going to need a twist a bit tighter then that to stabilize the slug as IIRC a 240gr 30 cal slug is right on the ragged end of stabilizing.

Also you might want to rethink your powder choices of Unique or Red Dot. As you know, smokless powder becomes more energetic the higher the pressure becomes. At one end of the scale out in the open it merely burns and liberates heat and large quantities of gas. A pound of it will take several seconds to be consumed. At the other end of the scale, in a sealed container you have a bomb, and that does no one any good, that's not EXPECTING a bomb:drinks: Regular published loads for centerfire rifles are already close to the bomb end of the scale. The thing is with such fast powders is they ignite quickly and build pressure darn fast. In the 38 Special with a 148gr WC and 2.7 grs of Bullseye, the powder is consumed and peak pressure is reached before the base of the boolit has cleared the casemouth.

In your situation you have quite a bit of enertia tied up in getting that long heavy boolit sitting there. You're going to want to be looking for a slower powder further down the burn rate chart out of the pistol/shotgun numbers, and a barrel with a twist of probably 8.5" to 9". And if you DO get such a barrel, after it's chambered you could have it throated out for the long slug. Similar to the 7.62x39 I also tried the same Lyman (311284) boolit in the 30-30. In that application I used surplus WC860, which is a 50 BMG powder. It's burn rate is about like chopped notebook paper. Due to the OAL it was a single shot proposition. It was accurate, but searved no purpose I had a use for but it was an interesting experiment.

................Buckshot

[Artful]

What is the twist rate on the 7.63 x 39 is it 1:12, 1:10, 1:9, 1:8 ? That is part of what will determine if your long bullet will stabalize.

[thehouseproduct]

If you check out the Whisper boolit results thread, I'm pretty sure Nobade shot the boolit in a 7.62 527.

[Echo]

Hmmmm. Seems to me that using a tap to make loob grooves would also make a circuitous path around the boolit for combustion gasses.

[Rangefinder]

Hmmmm. Seems to me that using a tap to make loob grooves would also make a circuitous path around the boolit for combustion gasses.

Not if the base was reamed after to a solid rear driving band. ;)

[TRX]

1) paper patch

2) knurl

Corbin sells a knurling tool to roughen the exterior of unjacketed swaged lead bullets.

http://www.corbins.com/hct-2.htm

I've never talked to anyone who has actually used one, but if it works as advertised, it would sure make it easier to DIY molds with a D-bit!