Thread: "Air space" in 303 British and 308 Winchester caseloads...Dangerous?

Originally Posted by Kiwi Sapper

With reloading 303 and 308 I am now looking at reducing the projectile seating depth to reduce the "bullet jump" I currently have with commercial loads. Sadly, there are 3 gray areas of my knowledge.

1...Having entered reloading via black powder, I am very conscious of the danger from air space in BP rounds and with the reduced seating depth of 303 and 308 projectiles, is the increased airspace in the case a danger, as it is for B.P. I am using when using ADI AR2208.

If not, great, if so, would the usual space fillers for B.P. be suitable?

2...Reducing the projectile seating depth, results in less length of the projectile in the case. For safety and pressure, is there a minimum length of projectile required in the case.....or is it that it must just be solidly fixed?

3...Does the answer to 2 also apply to boat tail projectiles as they have a tapering end which, dependent upon the taper, reduces the ability of the case to securely hold the projectile?


Finally does the OAL measurement as given in the appropriate dies have any relevance to the above? i.e not to be exceeded under any circummstances.
Thank You.

Greetings Kiwi Sapper,
Loads down to start loads will be no problem. With AR2206H you can go down to 60% of max loads for the cartridge and projectile. Best performance will be somewhere above that. I have found in the two cartridges you mention you can still get excellent accuracy with the projectiles well short of the lands, especially with flat base projectiles. Boat tails can be a bit wonky. As mentioned above 1 calibre is the accepted minimum but I have loaded down to 6mm in .308 and .303 with good results. Your magazines may dictate your LOA. A longer jump to the lands will generally lower pressure. I have found that the Hornady 174 grain round nose projectiles are excellent in the .303.
Happy loading Grandpamac.