Mould for 303

  • Last Post 13 November 2014
kevo posted this 02 June 2013

OK, the bore on my P14 has slugged out to .3115. Now do I still go with the 314299 lyman mould, or would I be better off getting a CBE mould. What number mould do you suggest from CBE to make a suitable bullet at around 200 gr. On another tack, would you suggest a lubesizer die in .314?

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onondaga posted this 03 June 2013


What is important is the size your bullets drop from your mold with your casting method and your alloy. You need the bullets just the right size or larger  so you can size them down to what you need. Cast Bullets that are as big as will slide fit into your chamber throat are the right size and they are also usually .002- .005” larger than the Groove to Groove measurement indicated on your slug from slugging your bore.   Lubersizers or any bullet sizing dies do not make bullets bigger than they are cast in any circumstance. Bumping bullets up in diameter is done by some loaders with a hammer or similar tool and is discussed once in a while. I don't go there, but get the right mold or hone what I have to get bigger bullets.

Your bore truly slugging as large as you say will require bullet molds custom made or  bullet molds commonly made for the .303 Brit or the 7.62X39mm. These are 31-32 CAL and some inexpensive ones are available from Lee and very successful for bores your size.


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onondaga posted this 03 June 2013


try the 314299, it should be plenty big. Make  dummy round and see if it chambers,. you may need some sizing.

Chamber slugging is different than bore slugging. Chamber slugging or better yet,  chamber casting with a chamber cast alloy will give you the exact size measurements your bullets need to be.

An inexpensive and excellent chamber casting alloy:

This stuff can be remelted and re-used until it is gone.


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tturner53 posted this 03 June 2013

You want as fat a bullet as will chamber without forcing it shut. Fit the throat, disregard bore measurements. A down and dirty trick is to measure the ID of a fired case neck, that will tell you what will fit back in. Fine tune from there.

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parkerhale1200 posted this 09 June 2013

contact veral smith of lbt molds, he sure does wonders, no its almost magic. i have 3 molds of his hand, they are better than rcbs lyman noe.....

best regards ph

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Dirtybore posted this 30 January 2014

If I were You, I'd start with that Lyman #214299 bullet mould. That bullet perfomes quite well in my #1 MK 3 .303 with a .312” groove bore. I also have a #4 MK 1 with a .315” groove bore for which I have to use a Lee 185 gr bullet that drops from the mould at .315".

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JeffinNZ posted this 30 January 2014

KEVO: Get hold of David at CBE for a mould. When Jim sold up he had about 15 moulds on catalog for the old Brit war horse.

Cheers from New Zealand

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Dirtybore posted this 10 November 2014

.3115” isn't all that bad.   I have a #4 MK 1 that has a groove diameter of .315".  I have to use the Lee 185 gr, 303 bullet in it.  The mould drops wheel weight bullets .315” in diameter.  

I also use that same bullet in my 7.62X54R since it also has a .315” groove diameter.

   At .3115, you ought to be able to use Lyman's #314299 mould.  I have one and it drops wheel weight bullets at .313".   I don't have any custom moulds and have made do with the magor manufacturers provided stock.   Since no two moulds will ever be exactly alike, meaning that even two different #314299's will not drop a bullet at exactly the same diameter,  you might have to buy a few moulds to find the one that works.  That or order a custome mould at some exorbant price. 

I look at what I'm trying to accompolish and since it's not competition accuracy, I make do with  the more common mould brands.  If I were to want to enter extreme competition, then I'd look into custom moulds.  

What accuracy do you want or need and what are you going to use that rifle and bullet combination for, that is the most important question that you need to ask yourself.   Once those two questions are answered, go on from there with your mould choice.

By the way, I also have a #1 MK 3* that has a groove diameter of .312".  I'm using that Lyman #311299 bullet mould and its .313” bullets in it.  I do not size the bullets and shoot them as cast after I have hand lubed them.

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Ken Campbell Iowa posted this 10 November 2014

every special interest group tends to develop sub-language to describe those interests ; .. whether tuna fishermen or bullet casters ... the CBA has thankfully tried to define certain terms to reflect logically with the unwashed society at large ; ... commuminication with the commune, so to speak.


when a hole is first bored thru a barrel, we call that diameter the * bore * , and so the bore is the lesser diameter of the barrel cross-section.

then to grab the bullet going down the bore to make it rotate, some grooves are created ... thus the larger * groove * diameter.

at the front of the chamber, and in front of the brass case, is a short space intended to help the bullet, upon firing, to transition gently into the bore and grooves. this space is termed the * throat * ...

as more and more is learned .. ( or re-learned ) about better predictability of cast bullet shooting ... it has been helpful to communicate using these agreed-upon conventions.

i realize that rehashing this has been a little .. boring ... but the good news is that our quest for accuracy has progressed to the point that being a bit specific is rewarding .


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John Alexander posted this 10 November 2014

At the risk of saying something “everybody knows” like getting 15% off on car insurance in the TV ad. 

Everybody may know it but I didn't see it mentioned in this thread that bullet nose diameter is also important for a bullet like the 299 design or any other other bore rider. Although a long bore riding bullet like 299 often shoot fairly well with the nose barely touching the lands, it will shoot a lot better if you can see good strong land marks on the nose of an extracted bullet. 

The fit of the driving bands of the bullet is important too; but when I am driven to lapping out a mold it is almost always to enlarge the nose and usually has nothing to do with the rest of the bullet, sizing dies, or the groove diameter of the rifle. 


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gpidaho posted this 10 November 2014

Kevo: It's a little lite of what your looking for, but the Lee C312-185-R would be an inexpensive mould to try. It's my go to bullet for my Mosin Nagant. How's the 303 brass supply holding up in OZ? I traded off my supply for other brass as I no longer owned a 303. Then what should appear in my buddy's Pawn shop but an Enf. I picked up for $125 Hope someone does a new run of brass soon. GP

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Dirtybore posted this 13 November 2014

I see that Lee 185 gr bullet was also used in a 7.62X54R Mosin Nagant in the last Fouling Shot.  See Issue 231, page 12.

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