The first picture looks like a rifle of manageable length (an R8 buys you 3.5 inches or so), but the lower one looks like a boat rod. I have a suppressor on a 6.5x54 R8 Barrel for stand hunting deer and it is manageable. But I recently used a suppressed .300 Win Mag in Hungary for roe deer. Yes it was "pleasant" to shoot, but it was also like trying to maneuver a revolutionary war musket through the thick stuff. I can't imagine using one on a DG rifle.Two ways to go when suppressing a rifle.
The traditional thread on the end of the barrel.
The Reflex or back over the barrel method.
Both most likely require removing thr front sight to have the barrel threaded. Unless you are using a Ruger Hawkeye, Blasser or another factory threaded barrel.
The back over the barrel requires no front sight or a removable front sight.
1st picture.
My buddy used an AB suppressor Raptor 10 on his Blasser in 375 H&H. This was a reflex suppressor.
2nd picture.
Another friend used a Hybrid 46M on his Ruger in 375 Ruger. A traditional thread on the end of the barrel.
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With respect to DG, I also like access to my open sights if things go sideways on a follow-up.