As a tool maker, I've resorted to drilling the last rammer with a hole in it, all the way through the entire length of the rammer. This greatly helps to prevent composition from packing in the rammer.
The main technique to remember in using such a rammer is to put your thumb over the hole while inserting the rammer into the tube so you don't "pump" powdered composition out, all over the place. Once the rammer is seated on the loose composition, move your thumb out of the way and proceed as usual. Typically, no composition will pack in the rammer at all.
Either find a tool maker/seller willing to modify the last rammer as I described or locate a long drill bit of the same size as the hole and drill it out yourself, using plenty of light oil and drilling in small increments to keep the turnings clear of the hole as you go. Don't forget to chamfer the top hole on the rammer to remove any sharp edges.
Edit: The reason the powder packs in the last "holed" rammer is simple. The loose powder starts above the spindle, especially when filling the last increments before the solid rammer needs to be used. When the last holed rammer is rammed the loose powder gets tightly packed in the hole as the powder around the spindle tip is compacted. It is vital to remove that powder packed into the hole of the shortest holed rammer to prevent damage to the spindle (even if it's made from stainless steel or other hard materials).
The beauty of having the shortest holed rammer have the hole drilled completely through the entire length of the rammer is that the loose powder never gets packed tight into the rammer hole but falls out easily after ramming the rest tight into the rocket casing.
I have used this technique successfully for years.
Edited by WSM, 07 October 2021 - 06:27 AM.