I am looking at purchasing the Leupold Mark 4 6.5-20x50 and I am unsure of wether I should get the lr/t or ER/t. Can someone please help me and tell me what the difference is? Also, I was wondering if I should get the mil or MOA turret. Is mil more or less accurate than MOA? Thanks for the help.

I forgot one additional question. Ok, so assuming that I am using the Leupold Mark4 with the TMR reticle and a mil turret, if I my poi is 3 mils low, then I would need to adjust my turret up 30 clicks right? Second part of the question, does that calculation only work in a certain focal plane (ffp/sfp)?

I think a lot depends on your intended use, I use both the LRT and ERT MkIV scopes, your on to the difference of which focal plane the reticle is in......in the LRT second focal plane the reticle stays the same size and the target gets bigger as you zoom in, with the ERT in front focal plane (sometimes referred to as first focal) the reticle and target remin the same size and both get bigger as the power is increased......there are benefits to each, I use the ERT's for tactical competitions where I need to calculate holdover and hold wind quickly no matter what power I'm using. The LRT's with the reticle in the second focal plane are used or hunting so as I zoom in the target gets bigger against the reticle for more precise aiming point......the reticle in second focal will substend exactly only on the highest power....if you looked through a LRT at max power and an ERT at max power the view would be the same, as you turn the power down the ERT's reticle will appear to shrink while the LRT's one will stay the same size as the target gets smaller...........I depends on your intended use. As for MIL vs MOA, do a search......MOA is a finer adjustment at .25"@ 100 vs .36"@100 for MIL's........all depends on what your more comfortable with.......ill tell you this, I used to shoot MkIV LRT's with MOA dials and TMR reticles and have since made the switch to ERT's with 1/10 MIL dials FFP and TMR reticles and I'm not going back. I have three Mk IV LRT's TMR 2- 6.5-20 & 1-4.5-14 with MOA dials that I'd be willing to part with, shoot me a PM if your interested....I'll make you a smoking deal. As for your second question, if your LRT was on max power or your ERT is on any power and your bullet impacts were 3 MIL low, then yes 30 clicks up or 3 MIL correction would correct, don't get hung up on clicks, use the numbers on the turrent like a ruler......measure to the number and then break it down to the 1/10 or 1/4 as the case may be.........there are 5 MIL or 15 MOA elevation available per turrent rotation on these scopes.

So if I am using the let and err on max power with the tmr reticle and mil adjustments, then I would only be able to make accurate range calls and adjustments with the err? Or does it matter?

Lets simplify, first focal plane scopes like the ERT's can accurately be used to estimate range at any power selection while second focal plane scopes like the LRT's can only accurately range when turned to the highest power in the case of Leupolds.