Oldbloke wrote:The effect is called detonation or the Secondary Explosion Effect and there are a few theories around if you do the google.
"Depends on the cartridge.
I've loaded 8x57mm down to 20gns of 2206H at 1050fps with 180's with no problems.
A maximum charge is around 46gns of 2206H.
I used to load my .222 subsonic with 40gn bullets and IMR4198 but I have no idea what the charge weights were now."
20gr of 2206H is well under 50% of a medium to slow powder so could be a contender for an SEE. ADI recommends no less that 75% of case capacity as I posted last night.
Ive just dropped in a pic and a link to some further info below.
http://reloadammo.com/liteload.htmExplosive detonation.jpeg
I am well aware of the potential problem thanks OldBloke
As I said, I don't shoot this as a regular load since Trailboss works so much better with even less powder.
But unless you try it yourself you're not going to learn much just going with the accepted flow.
If you want to try lighter loads take the same precautions as you do pushing maximum loads. I can't think of any cartridge that I haven't managed to load above the "maximums listed" without major problems. Most start to lose accuracy approaching the maximums though so there's no reason to run them that hot. Except the .204 with the 24gn NTX - it just seems to get more and more accurate the faster I push it. The 32's, 39's and 40's don't need to run hot for best accuracy.
In the .204, ADI lists the maximum for AR2206H behind the 24gn NTX is a compressed 29.5gn charge. My standard load is 30.0gn and I have had no problems with pressures at all, the brass only needing trimming after six loads or more. 30.0gn actually piles _above_ the case mouth unless I trickle it into the brass from a few inches height. I've shot approximately 210 of these hot loads so far with the same brass, primers are still tight and unflattened, and the new Norma brass has never been full-length sized or cleaned. The same brass has also fired heaps of 32gn, 39gn and 40gn loads.
Load data is only recommendations based on somebody else's testing.
The only way to know what your specific firearm is capable of is by your own testing.
I would not recommend anybody start their load development at 30gns, but I also don't think people should look at the maximums as a concrete wall that can't be crossed.
If you're really concerned about light charges you also have the option of using a case filler.