Can I feed a .243 reliability through a "long action" AICS 3.56 magazine?

[GingerNinja1776]

Hey, everybody. I need help!

TLDR: I would like to put my Tikka .243 in a long-action chassis (3.56 AICS) so that I have options if I want to change cartridges later.

So, the reason I'm asking this....
I am putting together a rifle to be my son's first deer rifle. I want it to be something that is a very accurate rifle for hunting, but will also double as a Precision Long range gun as well.

I decided to get him a Tikka t3x in .243. Got an Arken EP-4 on it with some RPM rings. And in a few weeks, I plan to order the new "Backlight" Chassis from Backfire.
THAT is where my conundrum appears. I know the Tikka has just the one action length, with different bolt stops and magazine spacers to swap out when you change calibers.... But the backlight chassis is laid out to take either short action AICS magazines, or long action (3.56") AICS magazines.

What I would LIKE? I would like to let this rifle grow with him. I'm sure he will be fine to use a .243 until he's at least 12, maybe 14 or so. But if he decides he wants a bit more power, I want him to be able to keep everything and just re-barrel this rifle if he wants.
If he wants to go .25-06? .270? .280 Ackley Imp? 30-06? 7SAUM? I don't want to have to put it in a different chassis if I can help it.

So, friends....is there a way I can get the Long Action chassis right now and still have a .243 feed out of the 3.56 AICS Magazine?

 

[The Guide]

I don't have a 30-06 size AICS mag, only a magnum sized that I run my 7mm PRC in. I've put 6.5 PRC in it and it will feed them easily. You will need to change to a LA or XLA bolt stop to use the LA magazines though as the rear portion of the magazine is further back than the SA bolt stop will reach.

Jay