Ok fellas, there is a bit of a story to this, so perhaps put the jug on or grab a coldie and your reading glasses.
Rightio, so I was looking for a No 4 action or an old shot out .303 ( No 4) with a good action to use as a project to rechamber to 7x57R. I got offered a Savage No 4 MK1* for a good price to use for the project. When it arrived it was in far better condition than I expected. I expected an old dinged up war horse with spider webs in the barrel
So any thoughts of butchering it went out the window. So I then thought, if it shoots as good as it looks I might use it for Service Match. I bought some S&B 174grn FMJ rounds ( .311 ) and made up some Hornady 174grn RNSP ( .312 ). It has a 2 groove barrel. I took it to the range and it shot the S&B rounds far better than I expected. It also shot the Hornady rounds even better. Someone with younger eyes could do better but all of my shots landed on target say around minute of BBQ paper plate@100yrds
I bought a front sight adjustment tool and a heap of front sight blades from the UK with enthusiasm. I then realised my eyes are just too old to shoot out further than 100 yards with open sights and also that steel butt plate absolutely punishes me with stiff loads after 20 rounds. So what do I do? Well I was reading about shooting cast and I read that the 2 groove barrel .303 lends itself to shoot cast quite well. I get to keep the rifle original and shoot it, win win. Right, I grab a box of HBRC .311 cast bullets and a 1.5kg bottle of TB. I also spent hours cleaning the bore of any copper or other junk. My first loads I seated the cast projectile with the base of the projectile at the juncture of the shoulder and neck. Knowing .303's like neck tension. Applying the ADI formula for TB I filled the case to approximate base of projectile weighed and reduced starting load to 70%. That was around 10.5grns of TB. So I then made batches of 3 rounds in steps of .5 grain increases. 10.5-14.5grns. 10.5grns@50yrds produced perfectly 180grn cast bullet sideways cutouts. 11.0 the same, all the way to14.5grns the same. Some projectiles don't even make it to the target as you would expect. So I had a whinge about this on another post and in2anity sent me some 115grn .313 rounds to try
I started these with 11grns of TB up to 14grns. All sideways if they even hit the target. The last load at 14grns, which should be stepping along not one round hit anywhere on the target@50?. I have more room to add more TB with the 180grn projectile as I have now seated them out to within a p*ssyhair of the lands. So do I just keep adding powder? Can you compress TB? The reason I asked about filler is. When I read the fundamentals of cast bullet shooting on 303british.net for the 303 they state. Use a fast burning powder Tick, Seat the bullet to the lands Tick, Fill any void with filler ????.
A couple points I want to make is - It shoots jacketed projectiles no problems. An increase of TB by 45% from the start load has had no effect whatsoever on the keyholing problem. Cheers and sorry for the ear chewing