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458x2 American SBR Thumper

S

st1650

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Minuteman
Aug 13, 2009
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So a gunsmith good friend of mine wants to work on a fun 458 dedicated subsonic thumper.

He's already setting up a WTO Switchlug Tikka off the mag bolt face for his 7-6.5PRC and would like to switch barrel to a 12.5in thumper

We're thinking .458×2-inch American in a 1:10 twist for the Hornady 410 SubX or the Barnes 450-500gr.

I think it could be a good idea because:
- He's got a lathe so making the brass should be relatively easy
- Dies and reamer easily found
- Headspaces off the belt
- Uses his Tikka mag bolt face and could simply swap the bolt stop to go from long to short action
- Almost perfect case fill with VV TinStar which is very similar to Trailboss but less dense but N105 or N110 could also be used.



not a whole lot of information available, it also seems like .458×1.5 would work as well for a dedicated subsonic thumper since it seems like they built these in vietnam but haven't found as much info for sub loads as .458×2

This is what I'm getting from quickload using Barnes 450gr

So my question is would there be a better 458 subsonic caliber more suitable than .458x2 ?

I'm not sure .458×2 would feed from an AICS without modification but it's more of a fun project. Most of the heavy subs are based off the 308 bolt
 

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may he get what he wants me I just wanna winning mega million lottery ticket mostly so I can then buy hookers and blow ... lol:ROFLMAO: powder and primers
 
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Wish someone would try the 45-70 with 500+ grn bullets and report back. Most loads are already close to sub in the heavies. Had this idea for a while,just dont have time or $$ to do it
 
paulrem308 said:
Wish someone would try the 45-70 with 500+ grn bullets and report back. Most loads are already close to sub in the heavies. Had this idea for a while,just dont have time or $$ to do it
Click to expand...
It would work fine with trailboss I’m sure I’d just be worried about the twist rate
 
paulrem308 said:
Wish someone would try the 45-70 with 500+ grn bullets and report back. Most loads are already close to sub in the heavies. Had this idea for a while,just dont have time or $$ to do it
Click to expand...
Came across the post in a search. I currently shoot a fast twist 45/70 TC Encore and I’ve shot anything from ~225gr up to 730gr subs out of it. But I mostly shoot a lot of my own cast bullets with a deep hollow point. It works very good on deer inside 100yds.
 
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Where did you get the fast twist barrel? Been a while since I looked around. Didn't come up with much. Your setup sounds like what I have been thinking about.
 
paulrem308 said:
Where did you get the fast twist barrel? Been a while since I looked around. Didn't come up with much. Your setup sounds like what I have been thinking about.
Click to expand...
MGM (Match Grade Machine). Beware, for whatever reason they wouldn’t let me get it threaded 5/8x24 so I had to get an abnormal 3/4 thread. Ended up sending it off to get rethreaded to 5/8x24 anyway. But it’s been a hammer.
 
st1650 said:
So a gunsmith good friend of mine wants to work on a fun 458 dedicated subsonic thumper.

He's already setting up a WTO Switchlug Tikka off the mag bolt face for his 7-6.5PRC and would like to switch barrel to a 12.5in thumper

We're thinking .458×2-inch American in a 1:10 twist for the Hornady 410 SubX or the Barnes 450-500gr.

I think it could be a good idea because:
- He's got a lathe so making the brass should be relatively easy
- Dies and reamer easily found
- Headspaces off the belt
- Uses his Tikka mag bolt face and could simply swap the bolt stop to go from long to short action
- Almost perfect case fill with VV TinStar which is very similar to Trailboss but less dense but N105 or N110 could also be used.



not a whole lot of information available, it also seems like .458×1.5 would work as well for a dedicated subsonic thumper since it seems like they built these in vietnam but haven't found as much info for sub loads as .458×2

This is what I'm getting from quickload using Barnes 450gr

So my question is would there be a better 458 subsonic caliber more suitable than .458x2 ?

I'm not sure .458×2 would feed from an AICS without modification but it's more of a fun project. Most of the heavy subs are based off the 308 bolt
Click to expand...
You making brass from .458 Win mag or .450 Marlin?

Mike

Less trimming with the .450 Marlin. Different belt thickness than the .458WM

1674123716617.png
 
paulrem308 said:
Wish someone would try the 45-70 with 500+ grn bullets and report back. Most loads are already close to sub in the heavies. Had this idea for a while,just dont have time or $$ to do it
Click to expand...
A good friend of mine made a 45/70 bolt gun on 700 receiver that feeds from Magpul AICS mags. He cut the rim off and put an extractor groove
on the brass with a mini lathe. I'm not going to spend that much time on something, but he's retired, so he's got a lot of free time on his hands.
 
Very nice! Been considering it myself, something similar.

I have had good luck with normal 4570 loaded with 625g pc cast bullets. Had to make them since not much like that for sale. Noe, cbe, or accurate molds has options. Kinda look like the classic postell bullet, just a bit longer. Would suggest your short case approach for sure if you arent interested in mesing around casting your own.

Pretty good case fill and accuracy from an encore, ssk barrel and a bowers vers 50 can. My buddy has a hybrid 46 that was nice, but not as quiet.
 
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