Anyone have a good source for .44 magnum barrel blanks or finished

Green mountain is the only source i've found. You may be able to make a Handi rifle barrel work.

You will need to know the Barrel shank Diameter
Thread pitch and angle

How similar is .303 and .44 mag in OAL and case head diameter?
How similar are the rim thicknesses?
Does the ejector need to be moved

I'm extremely curious about this, give us more details.

What are you doing for a magazine? Would probably actually be easier to set it up to run deagle brand deagle mags than to mod a 303 mag.

>>33169560
303 is way longer than 44mag but that shouldn't be a problem with deagle mags. Base diameter is identical, 303 rim is .530 and 44 rim dia is .514in, extractor may even work as is if not it would only need minor modification.

>>33169560
Apparently not too many modifications need to be made to pressure components:

https://www.youtube.com/watch?v=h0mL2go92N8
http://www.sporterizing.com/index.php?showtopic=7496

Mag needs to be swapped out anyways and an adapter using a pre-existing pistol mag seems to be possible to make.

.303 Rim diameter: 13.72 mm (0.540 in)
.44 magnum Rim diameterL 13.1 mm (.514 in)

.303 Rim thickness: 1.63 mm (0.064 in)
.44 magnum Rim diameter: 1.5 mm (0.060 in)

>>33169066
>>44 Mag SMLE
mate that's a fucking neat idea

>>33170652
This thread made my weiner wiggle in a very good way

It'd be like a Ruger M77/44 except British, I dig the idea.

Make sure to post pics if you ever finish it, maybe send some to TFB, I'm sure they'll get a kick out of it.