Rifle Scopes Sight Height Q's, Also: 30 MOA Base w/ Falcon 4-14

[PoisonMiller]

When using a canted base, where is it most accurate to measure sight height?

With an uncanted base I tend to measure sight height from bore center to the horizontal split in the rings, but with a canted base the front end will be closer.

Also, what sight height are the M40A3 and M40A5 rifles set at?

 

[kombar]

Re: Couple Sight Height Questions

I'm not entirely sure, but I believe the correct measurement would be from the center of the barrel to the center of the objective lens. It might be something else though.

Either way, even if you were using a 60 MOA base (1 degree), the difference in height between the front and back ring would come to about 0.079" at a 4.5" ring spacing. If you're only using a 20 MOA base, as I suspect you are, that number drops to 0.026". A difference that small won't even be noticeable in your trajectory calculations. Just measure as you always have.

Don't know the answer to your second question.

 

[PoisonMiller]

Re: Couple Sight Height Questions

Thanks for your response...

The difference is only about 1" at 1000 yards based on a 100 yard zero. Which isn't really all that crucial.

However it could be useful to know the exact appropriate point of measurement. Precise is precise, isn't it?

Also, still looking for the M40xx sight heights.

 

[Rob01]

Re: Couple Sight Height Questions

Measure at the windage knob.

 

[PoisonMiller]

Re: Couple Sight Height Questions

Thanks Rob01,

I guess that answers another question, the stock's edge is close enough to bore center?

 

[Rob01]

Re: Couple Sight Height Questions

Yup. Been using it this way for years and it's always worked very well.

 

[PoisonMiller]

Re: Couple Sight Height Questions

I'd still like to know M40A3/5 sight height.

Preferably with the 30MOA base.

Using my <span style="font-style: italic">OK</span> pixel math, based on a 34mm tube, I keep coming up with about 2" in the center of the scope. But I'd like a fairly precise measurement or spec. I suppose any M40A3/5 replicas with appropriate base/ring/scope combo's would be acceptable.

 

[AK10mm]

Re: Couple Sight Height Questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poison Miller</div><div class="ubbcode-body">I'd still like to know M40A3/5 sight height.

Preferably with the 30MOA base.

Using my <span style="font-style: italic">OK</span> pixel math, based on a 34mm tube, I keep coming up with about 2" in the center of the scope. But I'd like a fairly precise measurement or spec. I suppose any M40A3/5 replicas with appropriate base/ring/scope combo's would be acceptable. </div></div>

This precision is necessary for someone,who,in another thread was ready to chop 2" off his barrel with a hacksaw and hand crown it?

 

[PoisonMiller]

Re: Couple Sight Height Questions

Hey, hey... I didn't say I was ready.

I was asking what others experiences were. I wanted real opinions before I just threw away the idea.

I actually found a reputable Class III gunsmith within 40 miles that will do the entire Cut/Crown/Thread job for about $80. I plan to do that.

[Edit]

I thought about putting this in another thread, but I figured it'd compound it into 1 thread.

I bought a Falcon 4-14x44mm FFP mil/mil 3 weeks ago and I am exploring mounting it on my future rifle.

According to RWSnyder and Sniper Central, the MOA version has 75MOA of adjustment (37.5 MOA each way).
According to RWSnyder the Mil/Mil version has 23 Mils of adjustment ( x 3.43775 / 2 = 39.534125 MOA each way). (This is interesting to me because the S&B PM-II Military only has 22 Mils)

I'd like to be able to utilize the complete adjustment range of my scope, so a 30 MOA base seems logical. This would leave me at least 7.5 MOA of up adjustment left to 100 yard zero. Another advantage I see is that longer range targets will be closer to the center of the adjustment range for better clarity. Also, theoretically I'd be able to zero out to 1200 yards or so with M118LR.

Has anyone actually used this combination?

I'm looking at a Seekin's 30MOA base, and I'm considering rings. My first choice was Burris Extreme Tactical, but I fear this may create issues with adjusting eye relief as the ring is 1" thick, and the rear tube is about 1.5" long.
I'd prefer to have a Badger USMC-style set-up so there is a thinner ring in the rear, but I'm not at that budget for rings. I'd like the total of rings to be about $100+/-.
I'm not terribly worried about using different brands of rings as long as the ring heights match up so there isn't any problems (I don't forsee any real problems with this, if there are, feel free to alert me).

 

[AK10mm]

Re: Couple Sight Height Questions

Poison,I can't help being a smart ass.Anyway,in all actuality,make sure you have enough adjustment in the glass you pick,a 20 MOA rail should be plenty,a 30 MOA may give you problems for a 100yd zero,depends on the scope I guess.

 

[PoisonMiller]

Re: Couple Sight Height Questions

Figured since the M40A5 uses a 30 MOA base and a S&B scope with 22 mils of adjustment, whereas I should have at least 22 mils in the Falcon, then it should work out fine.

I'll of course confirm the actual adjustment range once I receive the scope, but I have yet to see them give someone a scope with less than claimed adjustment.

7.5 - 9 MOA should be plenty of <span style="text-decoration: underline">down</span> adjustment for different loads and etc at 100, I think.

(In my other post I mistakingly said UP, sometimes I forget I'm moving the POI not the POA.)

One of the reasons I asked is I was curious about barrel clearance with Burris XTR Lows. I know the clearance is fine with 20 MOA but what about 30?