Brisbane

I am not sure whether there is still any interest in this thread/subject? I have recently had exactly the same issues with protruding primers using Lil' Gun powder and found this thread very interesting. I had previously been using the ADI (Australian Defense Industries) 2205 Powder for my 22 Hornet reloading and experienced no issues with primers or pressure. As soon as i switched to Lil' Gun the primers started protruding. I was using 40gr Winchester bullets, Lil' Gun start load of 12gr, ICI (Imperial Chemical Industries) cases and CCI Small Rifle Primers. I loaded several rounds starting below the start load (11.5gr) and worked up to below the maximum load (12.7gr) - all primers protruded, however there were no signs of high pressure i.e. flat primer, stiff bolt lift etc. I thought this may be a headspace problem but the rifle was checked by a gunsmith who confirmed this was not so. I have researched this issue further and i believe the protruding primers are a result of low pressure. This is why: The SAAMI Voluntary Performance Standards lists the Maximum Average Pressure (MAP) for the 22 Hornet as 43,000 CUP. The ADI Powders Handloaders' Guide gives a pressure of 39,900 CUP for the start load (9gr) and 43,000 CUP for the max load (10.2gr) of AR2205 with a 40 gr bullet. The maximum aligning with the SAAMI maximum above. The Hodgdon Reloading Data Center lists the following pressures for the Hornet with Lil' Gun powder and a 40gr bullet: 24,900 CUP for the start load (12gr) and 28,400 CUP for the maximum load (13gr). It can be seen from the figures above that the maximum load pressure for the Lil' Gun is nowhere near the SAAMI Maximum Average Pressure. In addition the maximum load pressure for Lil' Gun is substantially lower than the AR 2205 start load pressure. As a result, it would appear that lack of case capacity for the 22 Hornet/Lil' Gun combination becomes the issue long before the maximum load pressure is reached - hence the compressed loads. I did as Daveo26 did and changed cases, noting that his primers were okay using Winchester and Remington cases. I switched to WW Super (Winchester-Western) cases and again loaded up some cartridges starting below the start load and finishing below the maximum load. There was no primer protrusion for any of the loads. I have no idea why primers don't protrude in the Winchester cases while they do in ICI cases (and others), but my 'theory' on why they do protrude is that the pressure generated by Lil' Gun is too low to 'seal' the cartridge case in the chamber during firing and prevent movement - hence the primers are able to move back out of the case and remain protruding once ejected. For what it's worth! Regards