Proper sizing of bore-riding portion of a cast bullet?

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Gents,

In an effort to work out which lube sizing dies to buy I cast a couple of soft slugs from a Lee mold and gently forced them into the muzzle end of my two 30 cal rifles, a tikka 3006 and a sako 308.

The tikka bullet is on the left and as this was my first rifle and I have put around me 3500 rounds through it since I have owned it, I don't know how many the previous owner had fired before I got it, it is well worn.

The groove measurement taken from the bullet is 0.3092" and the nose portion (which was not engraved at all in this rifle but was in the sako ) measured 0.3010".

The bullet from the sako is on the right and measured 0.3082" across the grooves and showed engraving on the bore riding nose portion. Not having a blade micrometer made precise measurement of this last difficult but I think it's almost exactly 0.3000" from what I have been able to tell with wires and micrometer.

My first question is that assuming the throat tikka is similarly larger than the sako would I need to have two "different" bullets ( as in sized differently), one for each rifle, or can I get away with just buying the larger diameter sizing dies ( to suit the enlarged bore) and use that for both?

The second question is whether or not the bore riding nose portion of the bullet needs to be sized to the bore as I understand the groove riding portion needs to be sized to the throat and groove? The forward portion engraves the rifling on the 308 and I am wondering if this might promote leading?

With thanks,

Looks like you may have accidentally uploaded the same pic twice. Based on your description and the picture above, the engraved nose is a very good thing so long as you can chamber a loaded round without undue effort. Accuracy will be better with the supported nose and it won't be a cause of leading. I prefer light engraving on bore rider noses. In my book .0005-.001" over land diameter is about perfect for bore riding noses. Bigger than that and they can be difficult to chamber and may set back or pull depending on neck tension. One school of thought is to size the body as large as will chamber since they all get sized by the throat upon firing. Once you have a decent load, trying varying body sizes may show you some improvement in accuracy. That loosey goose nose on your Tikka won't help with accuracy, but it can't hurt to try a few.

size to 310 shoot in sako.
you need something else for the tikka.

Thanks chaps.

The Tikka has a pretty rough bore, coppers up quite significantly especially towards the chamber.

The bullets as dropped from the mold measure 0.312", would this work in the slacker throat and barrel of the 3006 or am I better off trying to find a .303 mold?

The sako bore is like a mirror by comparison.

Out of interest, why a .310" dies rather than (what seems to be the more commonly available) .309" die?

Is there a formula based on bore measurement?

your ball seat [leade into the throat] area is 310.

get some loads under your belt then look the other rifle over again a rough worn barrel can shoot okay or be such a pain to deal with.
having something successful to look at and compare will help you make the decision how to handle it better. [when combined with more reading here]

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Originally Posted by runfiverun

your ball seat [leade into the throat] area is 310.

get some loads under your belt then look the other rifle over again a rough worn barrel can shoot okay or be such a pain to deal with.
having something successful to look at and compare will help you make the decision how to handle it better. [when combined with more reading here]

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Ah right, thanks Run' I was going to measure the leade and throat using the method where a soft bullet is seated into a case of lead and pounded down but was waiting for a day without rain ( I am in the UK remember... :D ) to melt down some lead to fill the case with which to do so.

I take the wisdom of your advice on starting with the Sako and am in fact doing so. The Tikka i am interested in simply because I have it and it is (nominally ;) :D) the same calibre as the Sako. Will leave it for now.

As an experiement I seated a bullet into a sized and flared case and then tapped it out with the kinetic hammer.

The driving bands were squashed down by the case to almost exactly 0.310", can I shoot it like this whilst I am waiting for the correct sizing die to arrive?

In short, yes. Get all the copper out of the barrel of the Tikka before you try lead in it, too.

Cheers Wayne, will load a few and give them a try.

I assume I can just lube them by hand while waiting for the die to arrive, just smear some 50/50 lube from the stick into the grooves?

I have had good success sizing the drive bands to fit the chamber throat and then sizing the bore ride section to fit the bore. In my 7mm guns that nose gets sized .277" and the 30 cal gets sized to .300". This gives me more leeway to seat the bullets out more without an oversized nose section impeding the overall length. Accuracy was greatly improved by doing this and I experience no leading at all.

I want the nose to have engraving marks when the round is chambered.

I take it your going to try shooting these without the gas check?
I would remove the gas check shank from the mold making it a pure plain base if so.
if not you will need the sizing die to press the check into place.

now you can shoot them as is but your speed will be even lower than a plain base to maintain reasonable accuracy.

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Originally Posted by runfiverun

I want the nose to have engraving marks when the round is chambered.

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That's what I strive for but not so tight of a fit that a bullet stays in the rifling if you try to eject a loaded cartridge.