Gday Stix,
I have just been through the same process with a .310 last year and can likely provide a bit of info.
See my own post on the topic:
viewtopic.php?f=12&t=10334In the end I have an accurate and effective loading regime that works very well, although a little unconventional.
Firstly, the Lee dies. The FLS die and flaring die work perfectly. The seating die on the other hand only works as either a seater, or a crimper, not both at the same time. This is odd, as if the set includes a case mouth flaring die, then you would think that the next step would be seating and crimping that flared mouth. To be able to crimp the case with a seated bullet, you need to remove the seating stem altogether, and then readjust the die for crimping. Not a big deal in the scheme of things really, and more than an acceptable inconvenience if we want the fun of shooting a gem like the cadet. Furthermore, the seating die chamber is only .317", so therefore any projectile greater than .316" wont pass up through to crimp the case anyway.
Secondly, my particular BSA cadet rifle and components.
Bore diameter - .316"
Groove diameter - .321"
ID of Bertram brass case mouth - .310"
ID of fire formed brass from my rifle - .312"
Hawkesbury river 122gr projectile - .316"
Hawkesbury river 128gr heeled projectile - .323" (diameter of the heel -.316")
You can see from those dimensions, that HR projectiles are never going to enter the cases without expanding the mouths, and then some form of crimping is required to get the finished round to chamber.
To achieve this, the following loading steps produce an accurate and consistent load:
1. de-prime using the FL die, but don't push the case up into the die, just enough to punch out the primer (no lube required)
2. normal case prepping including priming
3. flare the case mouth using the flaring die
4. powder charge (4.7 - 5gr ADI AP70N)
5. seat the bullet using the seating die
6. crimp and resize the whole round using the FL sizing die (lube as normal)
My rifle will fire both the Hawkesbury River projectiles, but I find I get a flyer about 1/10 using the smaller .316" projectiles. The .323" seem to be a little more reliable.
The only other thing to watch is the primer depth using the Bertram brass. The primer pockets may be a little small for CCI Small rifle primers and you need to ensure they are pushed in hard to avoid light primer strikes. I have not experimented with another brand of primers which may fix this problem without issues.
I see that a lot of more experienced people than myself recommend the Simplex dies. Maybe a couple of people using those dies could explain exactly why that brand is better and how they function differently.
Of course, if you can tailor your own moulded heeled bullet that will simply thumb seat into your fire-formed brass, then the whole process would be simple (except for the moulding of lead part).
Hope that provides something for you to work with,
Cheers, Goldie