Thread: 303 reloading

Be wary of the Lee seating dies, they are good at seating bullets on the piss. I had to lap the seating stem to get bullets straight-ish. Thats where the wacko-mole lee loader is better, perfectly straight loads all day long.

Thanks for all the pooled wisdom! I’ve loaded 416 Rigby, 375 H&H, 9.3x62, 30-06, 308, 270, 243, and have a full set of reloading toys based on a Lyman Orange press, but 303 will be the first rimmed cartridge so all suggestions appreciated.

Originally Posted by HandH

Thanks for all the pooled wisdom! I’ve loaded 416 Rigby, 375 H&H, 9.3x62, 30-06, 308, 270, 243, and have a full set of reloading toys based on a Lyman Orange press, but 303 will be the first rimmed cartridge so all suggestions appreciated.

Ppu brass is about the best available. Their factory ammo shoots well too, so using factory ammo then reusing the brass seems the way to go.

Greetings,
Some of this has been mentioned in previous posts but this is how I go about preparing my light loads for my .303 rifles.
.303 cartridges headspace on the rim and the forward part of the chamber is cut long to allow easy chambering of rounds covered with battlefield crud. The thickness of the rim on most cases is thinner than standard so this allows a bit of slop that we can use to our advantage. When a .303 round is fired the combination of the firing pin strike and the primer firing shunts the case as far forward in the chamber as the rim allows. At this point the primer is backed out of its pocket to touch the bolt face. As pressure rises the front of the case swells to fit the chamber. If the pressure rises to higher levels the case body just in front of the solid head stretches until the case head touches the bolt face and the primer is re seated in it's pocket. It is this stretching that can lead to a crack developing in the case wall as early as the third firing if the case is FL resized with the die down hard on the shell holder.
To get decent case life with a .303 it is necessary to keep this stretching to a minimum. The first way is to use low pressure loads which will show a backed out primer and cases that can be neck sized again and again. The necks will need to be annealed every few loads. For full pressure loads the FL sizing must be kept to a minimum so that the sized case just fits back in the chamber. This requires very careful adjustment to get it right.
My .303 rifles have light loads and for those that wish to the charge can be increased until the primer protrusion on fired cases starts to reduce showing that case stretching is starting to occur. This is likely to be around the listed starting loads for the appropriate projectile. I am using 34 grains of AR2206H behind the 150 grain projectile and 32 grains behind the 174 grain RN. Both of these loads are about 2 grains below book start loads. Cases are neck sized in a Lee Loader.
One caveat is that both of my rifles have near new barrels. Well used barrels can have considerable throat erosion resulting in lower velocity. Probably for this reason there is a wide variation in the velocities in load data depending on the rifle used. My chronographed results are close to the Hodgdons data in a near new two groove barrel.
Regards Grandpamac.

One point. The primers don't alway fully reseat in their pockets. The flatten and spread and develop a flat topped "top hat:. This is not unique to rimless and occurs with rimless as well. Usually due to pushing the shoulder back too far when sizing. Well covered in past threads.
Often mistaken for over pressure.

The last of my #4s, a 1955 Fulton regulated, gave me a big fright when I first fired it. Using S&B ammo virtually every case 3/4 seperated. Called it quits and checked using a friend's head space gauge. Was massively over head spaced. Changed to a more appropriate bolt head (reasonably available back then) and my problems ceased. The previous owner was a target shooter. Maybe he had no problem with club CAC??

@Mikej

Originally Posted by zimmer

One point. The primers don't alway fully reseat in their pockets. The flatten and spread and develop a flat topped "top hat:. This is not unique to rimless and occurs with rimless as well. Usually due to pushing the shoulder back too far when sizing. Well covered in past threads.
Often mistaken for over pressure.

The last of my #4s, a 1955 Fulton regulated, gave me a big fright when I first fired it. Using S&B ammo virtually every case 3/4 seperated. Called it quits and checked using a friend's head space gauge. Was massively over head spaced. Changed to a more appropriate bolt head (reasonably available back then) and my problems ceased. The previous owner was a target shooter. Maybe he had no problem with club CAC??

Greetings @zimmer,
This is why I don't consider primer appearance useful for guessing pressure. The chronograph is much more useful.
A drizzly day in HB today with fine patches just long enough to get your hopes up so I did a bit of measuring with a comparator. I was looking for the extent of stretching common with .303 loads. The .303 does not have much of a shoulder so accuracy of measurements may not be great but here is what I found. New S&B and PPU cases measured around 46.4mm using the .375 chamber with the comparator. New CAC cases were around 46.2mm and DI 42 cases only 46.0mm. Fired cases measured up to 47.0 mm with one outlier going 47.5mm. With the rimmed case the amount of stretching is limited to the free headspace on the rim with the shoulder being fire formed the remainder. With the rifle I have measured this free headspace amounts to about 0.3mm (0.012") of stretching each time you pull the trigger if you full length resize with the die down hard on the shell holder with high pressure loads. Short case life is guaranteed. Granted some rifles will have less free headspace.
Most of my cases have been given to me as once fired brass so the original load is unknown. Some have needed the shoulder bumped back to chamber freely but none are FL resized. For my rifles with full power loads cases are FL sized with the Competition shell holders.
Regards Grandpamac.

Originally Posted by Three O'Three

Be wary of the Lee seating dies, they are good at seating bullets on the piss. I had to lap the seating stem to get bullets straight-ish. Thats where the wacko-mole lee loader is better, perfectly straight loads all day long.

I will second this. I have been loading some 303 recently and checking the loaded rounds on a concentricity gauge is a real eye opener. Would go from perfectly concentric sized cases to wobbly as hell bullets after seating. Definitely caused by the lee seating die.

I like lee collet dies a lot and use them for almost everything I load for. Advice above to keep the loads light enough that the cases dont need shoulder bumping and just neck sizing them with a collet die is good advice for easy brass prep, long case life and accurate loads.

Originally Posted by SixtyTen

I will second this. I have been loading some 303 recently and checking the loaded rounds on a concentricity gauge is a real eye opener. Would go from perfectly concentric sized cases to wobbly as hell bullets after seating. Definitely caused by the lee seating die.

I like lee collet dies a lot and use them for almost everything I load for. Advice above to keep the loads light enough that the cases dont need shoulder bumping and just neck sizing them with a collet die is good advice for easy brass prep, long case life and accurate loads.

Hornady in-line seating dies are a good option if you can't afford a Forster