100-300
yes
You need to contact Ruger for the answer to make sure the warranty isn't voided.
100-300 USD
$250-$300
100-300 or so
Zero. Ruger never made the P38.
.38 Special cartridges of any make can safety be fired from any .357 Magnum. However, there is another, older .38, which is the .38 S&W (no special) It is larger in diameter than .38 Special, and will not chamber in a .38 Special nor a .357 Magnum. NOTE: If you DO shoot .38 Special cartridges in a .357 Magnum revolver, be sure to clean the gun properly. Tends to build up a ring of carbon at the case mouth that will interfere with loading .357 cartridges.
There is no such thing as a ".38 Special +P" firearm - it's still a .38 Special, with some indication from the manufacturer that it is capable of handling the higher chamber pressures of the more heavily loaded +P cartridges. That's the only difference between a regular and a +P cartridge - more powder.
38 special
500 or so
The range varies but for new 38 Special revolvers the cheapest are around $225 to upwards of several hundred dollars for high quality 38 Specials. There are very expensive collector's editions that can cost $1000+. There are several good quality revolvers between the $225-$300 made by Rossi, Comanche, Ruger, etc.
Ruger did not make firearms in 1934