I plan to start reloading for my model 69. I am going to use Trail Boss. Mild loads to shoot on Cowboy steel. Should I use 44 Special cases or 44 Magnum cases? Thanks!

Either case will work well, but if you use .44 Special cases you should clean out your chambers with a brass bristle brush every 100 rounds or so to avoid carbon build up that could interfere with chambering .44 Magnum rounds. I've used lots of .44 Special in Magnum guns and lots of .38 Special in .357 Magnum guns with no problems if the chambers are kept clean.

I gave up shooting specials in magnum chambers long ago. Just not worth the cleaning issues.

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NRA Cert. Inst. IDPA CSO

2x

Or the duplication of brass inventory effort, or moving the dies...

But you are corect, ring-around-the-chamber is another avoidable hassle.

To OP:
For Trail Boss, just look to the hodgdon site for load data.
Set your sights on pistol reloading data | Hodgdon Reloading

All you will make with Trail Boss are light loads, so that's agreat choice I think. I currently have a few hundres rounds of Xtreme 200gr plated RN over 7.0gr of TB. Very pleasant out of my 3" 629-1. In my 6" 629-1 it feels like .38SPL WC taget loads in a K-Frame.

In my 44 Magnum I load a 240gr LSWC over 5.0gr of Bullseye in Starline,Remington and Hornady cases for range ammo.

In 44spl cases I load the same 240gr LSWC bullet over 4.0gr to 5.0gr of Trail Boss or 5.5gr of Unique.

I use S&B LP primers bought at Cabelas when they are on sale at $19.99/1000

The 240gr LSWC bullets I source from Summers Enterprises $35/500

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NEVER GIVE UP YOUR GUN

Same here. My new 69 has only seen magnum cases, but I don't own a 44 special anymore. For 38spl/357mag I adjust my dies. Rather do that then scrub a cylinder.

I never found running a brush into a cylinder a big deal. 99% of my shooting is with special cases...I also like how they eject easier and clear the cylinder.
Try them and see if you like them...no big deal at all .
Gary

I'm also a fan of shooting 44 special. I use Starline brass, win primer, 240 LSWC, 5.2 Universal, and a COAL of 1.465".

I use Special cases in my Special guns and Magnum cases in my Magnum guns. Larry