My No. 1, Mk III rifle tends to shoot high at 100 yards. It is my understanding that the presence of a bayonet affects the height accuracy.
Real 1907 pattern bayonets are rather scarce and expensive, but I noticed that Sarco has 1907 bayonets of modern manufacture, not original, for only $75 USD:
https://www.sarcoinc.com/british-enf...with-scabbard/
I went ahead and purchased one these and it appears to fit the rifle quite well:
Both the weight and dimensions look correct. This should be adequate for my experiment. Once the weather improves, off to the range to try this out. Choice of ammo may also make a difference. In contrast to my No. 4 rifles, I achieved better results using 150 grain versus 174 grain bullets.