Why You Should NOT Tumble Loaded Ammunition

One of our readers asked: “Is it OK to clean live, loaded ammo in a vibratory tumbler?” The basic answer is NO, do NOT tumble live ammo in a vibratory tumbler. There are serious potential safety hazards that can result from tumbling live ammo. Since it is really NOT necessary to tumble loaded ammo, why take the risk?

Tumbling Can Alter Powder Burn Properties
The main reason to avoid tumbling loaded ammo is that tumbling can break down the powder kernels inside the case and/or alter the burn-rate retarding coatings on the outside of the kernels. This can alter the powder’s burning properties, with dangerous consequences. If you vibrate loaded rounds for a long time, you can both grind or shear the kernels and alter the kernels’ external coatings. Read the warnings on a can of powder, it says do not shake (for that reason).

While we are aware that some hand-loaders, particularly pistol shooters, tumble loaded ammo to remove residual lube or just to make their ammo nice and shiny, this is NOT a sensible procedure. RCBS and most ammo-makers specifically warn against tumbling live ammo in a vibratory tumbler. Hodgdon’s official policy is: “Completed ammo should not be tumbled. The powder will degrade and increase in burn speed.” (From Mike Daly, Customer Satisfaction Manager, Hodgdon/IMR.)

Consider this commentary from the Fr. Frog website:

Q. Is tumbling loaded ammunition dangerous?

Answer: “…Extensive tumbling can cause the breakdown of the powder grains. This would have two major effects. First, smaller grains will ignite more quickly than larger grains, and second the deterrent coating on the outside of the grains may be rubbed off and will be absent from any fractured edges which will cause the powder to burn more quickly raising pressures.

Tests run some years ago by a commercial entity did indicate that potentially dangerous changes in powder charge burning characteristics do take place after PROLONGED periods in either a vibratory or a tumbling cleaner.

The key word here is prolonged. Many manufacturers of ammunition do a final cleaning of their product either by tumbling or a vibratory process before boxing it for shipment. In no case is this allowed to exceed more than just a couple of minutes. The intent is not so much to “polish” but to remove any traces of contaminants which might in time leave marks on the finished product. There seems to be a consensus among the ammunition manufacturing engineers that a minute or two of vibratory cleaning has no discernable effect on burning rates, especially for loads that are compressed, or nearly so. However, all have emphasized the need for EXTREME CAUTION not to overdo the process.

They also pointed out that there is a considerable difference in effect on the powder charge depending on whether the process is by ‘tumbling’ or ‘vibrating’. It would appear that tumbling has less effect on the powder than vibrating, though this is mostly a matter of degree. The admonition to use EXTREME CAUTION to insure that the process never exceeds a couple of minutes applies equally to either process.”