Light or heavy bullets for 20” 338 win mag

200-225 gr projectiles should be a great all around option for you. If you were shooting Brown Bears 200 yards and in, I'd vote 250's. It's not necessary for Moose in my opinion though. Might as well benefit from the lowered recoil using 200-225's, especially for suppressed, as well as maintaining fair speeds. I just built one similar and wouldn't change a thing man.
 
I would push for a 200g class of mono personally for moose.
I am a huge fan of Accubonds and Partitions, but since getting my REM 700 SPS in 300RUM (2015 build) all I have used are 165g TTSX & 180g TTSX in it to date, have taken 5 deer (Sambar) with the 180g TTSX and my Dad took 1 Sambar with the 165g TTSX. These Barnes bullets are a lot different to the TSX I tried 10+ years ago, these group really well and perform beautifully on game.
Another awesome bullet that I have had shoot really well in 3 338WM's and my custom wildcat 338-416 Rigby Improved 45° is the 225g & 250g Accubond, exceptionally accurate.

Cheers.
 
I just got done cutting down the barrel for my Winchester m70 in 338 win mag

Did you manage to get the new crown perfect? Without a perfect crown, you'll be behind the curve no matter what bullet you choose.

Should I go a lighter bullet because of the shorter barrel?

The weight of the bullet really doesn't matter since you will be developing a load which will burn efficiently in that barrel. The barrel will usually determine which bullet(s) it likes and that should guide your decision. The bullet composition can affect which way you go since solids don't shoot the same as cup and core. Solids are longer per weigh when compared to the cup and core so twist rate is important.

I've used quite a few .338 bullets on a couple of depredation hunts just for the opportunity of testing from 160 TTSX to 285 AMAX (leftovers).

My suggestion is to use any of the 250 grain bullets since there is a big supply available. 225 grain is nearly as good a selection. Powder choice is reflected in the amount of powder burned in your 20" barrel. Even with faster powders, be prepared to have some form of 'fireball' (super heated plasma) exiting the muzzle. Harvesting your bull at near dawn or dusk can be a new experience.

We are all envious of your hunt opportunity! Enjoy every minute and please try to remember to have some pictures to show us when you return!

:)
 
I would push for a 200g class of mono personally for moose.
I am a huge fan of Accubonds and Partitions, but since getting my REM 700 SPS in 300RUM (2015 build) all I have used are 165g TTSX & 180g TTSX in it to date, have taken 5 deer (Sambar) with the 180g TTSX and my Dad took 1 Sambar with the 165g TTSX. These Barnes bullets are a lot different to the TSX I tried 10+ years ago, these group really well and perform beautifully on game.
Another awesome bullet that I have had shoot really well in 3 338WM's and my custom wildcat 338-416 Rigby Improved 45° is the 225g & 250g Accubond, exceptionally accurate.

Cheers.
I went from tsx to ttsx to lrx barnes bullets. All have been good performers on game for me and my friends that I load for. We have taken well over 50 head of various game animals with them.
 
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