Chamber Casts and Impact impressions.

[dromia]

If you ever hear me giving advice about cast boolit making you will constantly hear the refrain to take a chamber/throat/lead/groove slug or cast of the rifle you are going to cast and load for. Until you know your chamber/throat/lead/groove dimensions you will never be able to select the right boolit and know what to size it too for top rate accuracy. To me in military rifles that starts at less than 3 1/2" groups at 300 yrds so just around 1 moa to 300 yrds. If you want that accuracy beyond 300 yrds then some other factors need to come into play and we'll leave them be for present.

From my experience the best way to get these dimensions accurately and have a faithful reproduction of your throat/lead/groove is the impact method. Fortunately Wayne Mclerran has written an excellent article on this and other methods, a copy of which I have lodged in The Library forum, link here: http://www.full-bore.co.uk/viewtopic.php?f=36&t=855

So now no one has any excuse not to get all the accuracy potenial from their rifle using cast boolits.

Remember, jacketed bullets are just a passing fad and will never catch on.

[ovenpaa]

How do you slug your barrels Dromia? I know the rough principle is whack a lump of lead down the barrel with a long dowel and measure it when it pops out the other end but having heard a couple of horror stories I have never tried it.

[dromia]

For slugging a barrel as opposed to a throat/lead/groove slug. Get a soft lead ball over size for the bore, for .303" I'd use a 0.375" ball. Oil the bore and the ball, sit the ball on the muzzle, put a bit of cloth over it to stop the oil spraying and give it a good whack with rubber or plastic faced hammer. The ball should seat in flush with the muzzle and leave a ring of shaved lead. Then slowly push the ball through with a taped steel rod of near bore diameter, do not use a dowel. The ball/slug should push through easily and as you do so you can also feel for any tight spots or rough patches in the bore that might need lapping. When the ball/slug drops out wipe the oil of it and measure then roll up in towelling and put in a plastic bag along with the throat/lead/groove slug with all pertinent details written on it and file for future reference.

[Alpha1]

I am a dab hand at this now Adam went through the procedure with me on one of our range days whilst taking a break from shooting to scoff bacon and black pudding butties and supping tea. If I can do it any body can. I went home and slugged all my military rifles easy peasy.

[Sandgroper]

After reading the article, Dromia kindly posted, I decided to slug the barrels of my Ishapore and my Destroyer.

The Ishapore (in front) came in at 7.8mm (0.307). Very nice.

The Destroyer was a disapointing but expected 9.2mm (0.362). I suspect that a previous owner was firing 38 Super in it, given the wear on the rifling and that my suspicions about the bolt being opened up to accept 38 Super/38ACP are correct. Now that I know, I'll run it with cast boolits and keep the presure down.

[ovenpaa]

Where do you get the soft lead balls from, are they something like old fishing weights or do you cast them yourself?

[Sandgroper]

I had some left over from when I was making multi ball loads for the 410.

http://www.buckandslug.webspace.virginm ... /index.htm

[ovenpaa]

That is a thought, I have some hefty 12g cartridges, from memory they have 9mm ball in them (Saved for the Z*mbies) Would they do?

[Sandgroper]

I don't see why not, but would Christel let you chop up the Zombie killers? :lol:

Seriously though, it took me about 20 minutes to slug both barrels. That was with me getting distracted in the shed as well!

[dromia]

Depends, I usually have a stock of lead balls around for BP shooting, shotgun loads and cats sneeze loads in rifle cartridges.

Slugs can be made very easily by getting a suitably thick piece if wood, 1/4" for this purpose and drilling holes through it of the required diameter over groove. Clamp it to a flat surface and pour your melted soft lead in to the holes, let cool and push out with a nail, trim off any sprue and voila a slug.

For throat imapct slugs use a suitably thicker wood say 1", 1 1/4".

A more refined amd permanent version is to get a thicker piece of wood or metal, drill a pilot hole through for each diameter slug you think you will need big enough for a nail to go through. Then open these holes up to your required diameters and depths. Then pour, cool and push out. Trim sprues and away you go. Don't choose too thick a piece of wood or the pilot hole sprue will be to long and make pushing out the slug a struggle.

Obviously for impact slugs they will need to be under bore diameter, bore slugs over groove diameter.