bluebayou.
Neither the 243 nor the 25-06 are the greatest handloading cartridges, one has a too short a neck and the other holds more powder than needed.
Please remember we are talking about Handi rifles. The 243 with its short neck will give concentricity troubles unless you outside neck turn the case necks.
2. Due to its long sloping shoulder it creates a lot of forward brasss flow.
3. Case life is short because of action stretch and each reload needs the shoulder set back .003" to make sure the Handi action will fully close.
The same applies to the 25-06 but with its longer neck bullets are easier to hold straight with minimal outside neck turning.
With all high intensity loadings no more than 8 reloads can be expected.
Lower velocities will enhance case life and accuracy.
If you want a good deer rifle in a Handi the 7mm-08 is a good one. With it you still need to watch your fired cases to make sure you have your .003 head space. That I believe applies to all Handi's.
Unless your action is fully closed and with out compressed tension from the cartridge against the standing breech, only sporadic accuracy will prevail or non at all.