Yes, COW is Cream 'O Wheat.

I tend to shoot plain base or ungaschecked gas check bullets because: a) I live in a small area where I cannot easily buy reloading components so less is more; b) I am a minimalist by nature so if I can get away without a gas check why not?; c) gas checks cost money.

The COW filler helps to protect the bullet base and seal the bore.

So far, I am not going to claim match winning accuracy but in general, groups with filler seem to be about the same size as groups without filler.

Also, I like the idea of 100% loading density regardless of powder charge. You can't just go throwing a filler into any old load though, it has to be worked up because the filler not only adds to the mass being expelled from the barrel, the reduced volume in the cartridge will raise pressures.

David Southall has a good article on: .303's and fillers on 303british.com

and there is also a good article here: http://www.surplusrifle.com/shooting...ller/index.asp

I got no leading whatsoever with the loads using filler.

Discussion of fillers seems to result in many polarized opinions. Some people swear they can cause ringed chambers and they may do if not properly used, I have had no problems and will keep using them.

I slugged my barrel and found I had a groove diameter of 0.314"+ and my Lyman 314299 was casting at 0.312" diameter.

I lapped by casting a few bullets, drilling the base and running a wood screw in then cutting off the head. A flat is filed on the lapping bullet and fine valve grinding compound or other abrasive compound put onto the flat then the bullet is clamped in the mould and rotated by hand or slowly in an electric drill. Since I have a two cavity mould I swap the bullet from cavity to cavity frequently to keep things even.

After a bit of lapping I clean up the mould and cast more bullets which are now a little larger then do it all again until the cavities are the right size. In my case 0.305" nose and 0.315" body.

The cavities do tend to get slightly oval ~ bigger at the seams ~ so you have to be careful. The undersized bullets did not shoot well at all while the lapped mould produces bullets that are doing quite nicely now.
Information
Warning: This is a relatively older thread
This discussion is older than 360 days. Some information contained in it may no longer be current.