.458 muzzle threads

[generalzip]

planning to chop and thread my m70 safari to 19 or 20” and thread for a suppressor. Anyone know the proper thread pitch? My 375 ruger is 11/16x24 and there’s plenty of shoulder to mount my suppressor and it’s doesn’t loosen anyone know the muzzle diameter of this rifle in 458wm at 29”?

I’d imagine 5/8x24 is too small. 3/4x24 may work but not sure if enough shoulder would be left. Would be conveinent if 11/16x24 was the proper thread pitch as that’s what’s on the suppressor for my 375 now so would be an easy swap.

 

[generalzip]

I read the muzzle is 18.4mm, or .7244" diameter @ 24 inches. This leads me to believe it may not even be possible to thread for a suppressor as 3/4" is not even physically possible and 11/16" threads would not leave the require .100" major thread diameter to barrel wall distance required. 5/8x24 likely would not leave enough wall thickness for a round of this pressure and recoil and would likely snap off at some point....hmmm

Really curious if anyone threaded a m70 safari express 458 win mag successfully for a suppressor and if so how was this accomplished. Only idea I could thick of is perhaps threading a muzzle brake on 11/16" threads and torquing it down and rocksett. Then use a ASR or other QD mount on a suppressor to attach the suppressor and verify alignment. Downside is this adds length and weight to the setup. However, this may solve the issue with shoulder possibly, especially if shims are used.

 

[Riflecrank]

What are the outside diameters of the barrel at 20" and 19" from the breech face ?
I have several .458 WIN MAG, one .458 B&M+ and even one .458 Lott rifle (Like Jack Built not SAAMI) that have been threaded 5/8"x24 tpi for muzzle brakes and thread protectors.

Others I have are 11/16"x24tpi in .45-70, .454 Casull, 45LC, 44RM and 357RM.
Meant for suppressor use.

I just measured a barrel from a factory contoured M70 Classic Stainless (.375 H&H) that has same muzzle diameter as you state above. Mine is a JES rebore to .458 WIN MAG.
I was fondling it just now so easiest to reach with calipers.
I think same contour was used on the .458 WIN MAG factory M70 Classics.
20" diameter is 0.775".
19" diameter is 0.790".
18" diameter is 0.805".

11/16" = 0.6875"

Cut it to 19" and thread it 11/16"x24tpi.
Thread protector cap for it does not have to be a "slim line."

I have a Griffin Bushwacker 46 and adapters ("Taper Mount Silencer Mount") for both 5/8"x24tpi and 11/16"x24tpi.
Those adapters screw onto muzzle and work as a "minimalist muzzle brake" (better than porting)
without the suppressor screwed onto them.

I never gave a thought to the can breaking off the end of my barrel. But I will now.
11/16"x24tpi is better.