375 Winchester Pistol: Cast Loads and other info

[Blackhawker]

I have been searching for a T/C pistol barrel in 38-55 to "go along" with my W&H Target Classic and Thompson Contender 20 inch carbine barrel.  I really like this caliber and have found it to be one of my most accurate rounds I load/shoot.  After a year or so of searching the auctions sites etc for a used pistol barrel in this caliber I had given thought to the .375 Winchester.  Well, I came across a very good deal on a 10 inch barrel with sights and a muzzle break (overall length with brake is 12 inches) and I couldn't pass it up.  As a matter of fact, I just got the e-mail for the UPS tracking and I should have it in hand in the next day or so. 
 
Enough of the history.  Here is what I was thinking when I bought the barrel:
"Maybe I could shoot my 38-55 loads through it?" 
"If the 38-55's don't chamber, then I'll have it reemed to chamber the longer 38-55."   
"Maybe I'll just trim a hundred of my 38-55 cartridges to .375 Win length." 
 
Since I had seen barrels with a good price disappear quickly on auction sites, I acted before educating myself on these two similar yet very different calibers.  Now that a couple of days have gone buy, I have spent some time reading about how these two calibers differ, I realize that I have to treat them as two entrirely different rounds when loading for them....or do I?  The "or do I" is basically where my questions for this post begin.
 
I don't know how long the chambers are on Contenders but I had read that If I flare an empty 38-55 cartridge a bit and drop it in the chamber of the 375 barrel and it fully fits flush, I could more than likely shoot my 38-55's from this barrel.  (provided, of course, that the barrel slugs out to the same diameter)  What do you guys think?  Is this a fair line of thinking?  My Thompson Contender 38-55 barrel (a David Van Horn barrel) slugs out at .375" and I'd imagine that the T/C will be the same.
 
A second question comes to mind if the answer to the above question is "yes" of if I end up trmming the brass down to proper length of the .375 chambering.  Is 38-55 brass a good choice to use if loading .375 loads in it?  Is the brass too thin?
 
Third question:  I don't intend to hunt deer or any large game with this barrel.  At best I may tinker with some prairie dogs but for the most part I just target shoot.  With that, I tend to go the cheaper route when shooting and I shoot LOTS of cast bullets.  So, I have pretty much decided that be it 38-55 loads or .375 Winchester loads, I am probably going to shoot 240 to 250 grain cast bullets from this barrel.  I don't think I'll go all the way up to the 265 grain bullets as I shoot through my Target Classic and Van Horn barrel though.  Do any of you shoot cast bullets in the .375, particularly from a pistol barrel?  Do cast bullets lend themselves to decent accuracy in this caliber and configuration?
 
If some of you don't mind, may I pick your brain for any other info with this caliber and/or your thoughts on what my train of thought has been with this barrel that is soon to arrive?  Any advice or thoughts are much appreciated.
Thanks in advance!
Blackhawker

[Blackhawker]

Well, the barrel arrived.  I took one of my trimmed 38-55 cartridges and flared it quite a bit and then dropped it in the chamber of the barrel.  As it turns out, it fit flush and I don't believe the front headspace of the cartridge had hit the end of the chamber.  With that, I'm thinking that it might be OK to shoot my 38-55 loads from this barrel.  Does anyone have any feelings either way about this?

I see some people have read the link but no one has commented.  I'm sure there has to be someone out there with experience with these calibers.   

[BBF]

I've had and shot a 375 Win with a Ruger#3 and all rounds were with jacket bullets the 220 and 235 gr Speer Semi Spitzer with RL-7.
Looking at Lyman #48 Page 271 there is a warning to NEVER put a 375 Win into a 38-55 nor the opposite, calling the 375 a higher pressure rebirth of the38-55.
Incompatible neck dia. can cause serious hazard.
 
Loading Data for a 249 gr cast(alloy#2) is given with powders from 2400 to IMR 3031 with suggested best accurate loads from SR-4759 and IMR 4227. Starting MV from 1500 fps out of a 20" barrel.

[Dezynco]

You could load your 375 win as if it were a 38-55 for plinking loads. DONT SHOOT 375 loads in an older firearm chambered in 38-55!  Don't use 38-55 brass to make 375 loads. The 375 Winchester is a completely different critter than the 38-55

[Blackhawker]

Well, as I described in the first "book" I wrote at the top, my original intention was to see if I could use my 38-55 loads in this barrel.  This is a lighter load (lower pressure load) in a barrel designed for fairly high pressure.  The only issue with shooting a 38-55 in a 375 chamber is the length of the 38-55 and how it can possibly jam up into the lands of the 375 chamber, causing high pressure issues.  However, if the .375 chamber is long enough to accommodate my 38-55 rounds, I figured it would be OK.  (maybe)

Scatterbrain:  I have the 49th edition of Lyman's load manual and have read those warnings.  This is the same book that no longer lists Ruger Blackhawk loads for the 45 Colt and no longer shows 45-70 loads with fiber wads added to them.  However, if you look in their older edition, they state that a 38-55 can be fired from a 375 Winchester chamber provided it fits, but not a 375 in a 38-55.  This is the same edition that lists higher pressure Ruger Blackhawk loads for the 45 Colt in Ruger Blackhawk revolvers.  This older edition also shows the addition of fiber wads in 45-70 loads as well.  Ironically, I once called Lyman about the deletion of the wads in their later edition of their loading manual and I was told it was a liability thing.  They said that people were literally cramming wads in their loads as if packing a black powder muzzle loader, so with that, they deleted the listing of wads in order to avoid any liability.  I think the note you have referenced from their later edition "MIGHT BE" one of the same for the 38-55 in a 375 chamber.  They simply cannot spell out all of the situations where it may work and may not work.  So, they just say NO to all.  ?  Maybe   Hence, why I asked here where there are some people that have experience with these chamberings in the Thompson Contender.  Nonetheless, I am heeding the warning still.
I suppose if I really want the answer I am in search of, I probably need to do a chamber cast of my David Van Horn 38-55 barrel and this T/C .375 Win barrel and compare the dimensions.

[BBF]

That chamber cast certainly would answer most questions for your barrel.
 
BTW I crosschecked those Lyman warnings with their # 3 Cast Bullet Handbook, they are essentially the same.

[Shortgun]

I have had several Contender and Encore barrels over the years in both calibers. To my knowledge all T/C barrels in those two chamberings have been made in .375 in bores. Most older 38-55 guns had larger bores and as such would not shoot well with factory ammo as that ammo was loaded with .375 in bullets. Some of the older guns had bores as large as .380. Older guns were not as strong as the newer .375 develops to much pressure for them but that is not the case with the T/C platform. They can handle the pressure of the .375 round fired in the 38-55 chamber. If you measure the chamber of either barrel cut by T/C you will find both rounds will chamber and fire in either barrel. It has been so in all 8 of the barrels I have owned and several others as well. My boy has a custom tube chambered in .375 win from MGM and it will chamber and fire a 38-55 as well. The 38-55 Brass is a little thinner and has a bit more case capacity than the .375 brass and as such will not take the pressure of the .375 loadings as well.
 

[Blackhawker]

Ah ha!!  Thank you very much for that info Shortgun.  Last night I slugged my .375 Win barrel at .375" which is exactly the same as my David Van Horn custom 38-55 barrel.  Ironically, the chamber of my David Van Horn 38-55 barrel is actually tighter in diameter than the .375 chamber.  Nonetheless, the 38-55's chamber in both barrels equally in length.  I spent some time measuring the depth of the .375 chamber to ensure that the 38-55 brass does not squeeze into the throat of the barrel and it is clear of doing so. 

I'll be taking the barrel to the range in the next few days.  My 38-55 loads are not heavy by any means and so I will start there with the pistol barrel.  I have no intention of loading heavy in the 38-55 brass as I know that it is thinner than the .375.  What I really wanted was just another barrel (pistol barrel, specifically) to shoot my 38-55's from and I guess I found what I was looking for.

If all goes well, I'll leave a range/firing report after I get to a range.