You mention that the front sight has a dove tail insert?
As far I remember, all MLM and MLE long rifles have a fixed front barley corn on their sight ramp. Maybe some late models had different sight ramps?, but what I am suggesting without seeing pics, is that if this is not a custom made sight, the other possibility is that it is the front sight set up for a Charger Loading Lee Enfield. They had a dove tail to accept a considerably taller front sight insert to match with the taller windage adjustable rear.
I have a naval marked MLM that has a HV SC marked barrel and the rear sight cap is considerably taller, I figured sighted for the Mk.VII round. Some Naval long rifles were resighted. Away from my library, but I'm thinking that there was a conversion program around 1914
Does your rear leaf have graduations to 1900 yards? Does it have CL stamped at bottom right of leaf?
If the front sight is too tall, your aim will be too low. Even more so if you have a regular rear sight bed and leaf, which is lower than CLLE. That would compound your problem.
Charger loading leaf on left, regular leaf shown aginst regular leaf.
Does your blade insert have numbers and letter marked? eg. 878E which denotes blade tip 0.878 inches above the centerline of the bore and for Enfield riflng.
Does the front sight ramp have a drilled hole to accept the screw for the sight protector bunny ears?