It is pretty clear that radioactivity in actinids improves their combustion rate. This comes from a simple effect : an increase in 10°C in the temperature multiplicates the cinetics of a chemical reaction by a factor 2 or 4. So if the metal used is naturally warmer, its combustion would be accelerated.
Even though it is always difficult to compare two different chemical elements, uranium and plutonium are both actinids, and plutonium is more reactive than uranium (see Why is weapons grade plutonium more hazardous to work with than highly enriched uranium? Journal of Chemical Health and Safety, Volume 22, Issue 4, July–August 2015, Pages 2-9, Michael E. Cournoyer, Stephen A. Costigan, Bradley S. Schake : it says massive pieces of uranium self ignite at 700°C, while the temperature is 500°C for plutonium, and it also confirms that whereas uranium is stable when stored under oil, plutonium is still able to self ignite when stored in the same conditions). The suspected production of plutonium bullets (subcritical of course) can be linked with that.
It is also actually difficult to find research about DEPLETED uranium pyrophoricity, on Google and on Science Direct. See for instance this :
If I change my request and type “uranium pyrophoricity” (with the commas) instead I get more than 480 results, including several academic articles.
I also get only 50 results on a sciencedirect research on depleted uranium pyrophoricity and none have “pyrophoricity” as their topic (so it is dubious that they would include actual experiments about depleted uranium pyrophoricity).
We have also one weapon patent which implicitely separates : “depleted uranium” used for kinetic purposes and “uranium” used for reactive (incendiary) purposes (here).
Lastly, two chemists have confirmed to me that higher radioactivity improves the combustion rate of the metal.
So one very simple question : if depleted uranium is so pyrophoric, why is there a need to add one incendiary round (HEI) every 4-5 DU bullets in the A10 Warthog combat mix ? See this video of A10 strafing rounds : at 1:05 I only see a few incendiary bullets. The uranium should be in part pulverised and react as it is in fine dust and the temperature is strongly increased by the impacts on the dirt floor. The usual firing rate of the A10 is 65 rounds/second. In principle we should see much more fire. Same in this other video. I’d say there is a bit less than 20 flammable rounds per second, matching pretty much the DU / HEI ratio in the GAU 8 of the A10. Both bullets are called “incendiary”(DU = “armor piercing incendiary”, API) but the only incendiary bullets I see here are the HEI.