Rifle Scopes US Optics MST-100 BDC

[ArmedGinger]

I have one of the MST-100 scopes on my M40A1 build. Now I am currently not set up for reloading so I've been forced to use Factory ammunition.

I've been using the Federal Gold Medal Match 175gr Sierra Match Kings. The muzzle velocity is listed at 2600 fps.

I've been finding though that the BDC on the scope doesn't line up. At 500 yards (ranged), instead of putting the dial on 5, I'm having to put it to 4 and the fine dial to about up 2 or 3.

I had read that the BDC was for the 175gr at 2600fps so I'm not sure what is causing to be out. At 700 yards I was dialing 6 and the fine tune up 3.

Does this mean that when I finally do start reloading my own I will need to dial the speed down a little until it matches the BDC?

 

[918v]

FGMM is often a lot faster than 2600 FPS.

When you start reloading you’ll be able to control the velocity to match your bdc.

You’ll prolly end up using 41.7grs of IMR4064.

 

[pmclaine]

Get a blank sheet of paper.

Write down what number corresponds to what yard.

Keep newly filled information readily available for future reference.

There are charts that show corresponding MOA adjustments for settings on the MST-100.

Disregard the numbers and know that the 2 mark is 2 MOA up from the 1 mark.

Than you have 3 MOA of adjustment on the fine adjust in 1/2 MOA increments for further adjustments.

Dope out your rifle based on MOA adjustments for range shot.

Sometimes you will "over dial" and fine adjust down.

Sometimes you will "under dial" and fine adjust down.

When you get it all figured out you will be at a different elevation. a storm will be coming or going and your known lot of ammunition will have changed.

 

[ArmedGinger]

FGMM is often a lot faster than 2600 FPS.

I am just going by what is on the box itself. Granted it's not a precise measurement but I did borrow a chrono to get a better reading of the speeds.

Get a blank sheet of paper.

Write down what number corresponds to what yard.

Keep newly filled information readily available for future reference.

There are charts that show corresponding MOA adjustments for settings on the MST-100.

Disregard the numbers and know that the 2 mark is 2 MOA up from the 1 mark.

Than you have 3 MOA of adjustment on the fine adjust in 1/2 MOA increments for further adjustments.

Dope out your rifle based on MOA adjustments for range shot.

Sometimes you will "over dial" and fine adjust down.

Sometimes you will "under dial" and fine adjust down.

When you get it all figured out you will be at a different elevation. a storm will be coming or going and your known lot of ammunition will have changed.

I do have the dope sheet that the scope should be set at with spaces for me to make corrections. So far 1=100 yards, 2=200 yards, and 3=300 yards. I never tried shooting at 400 yards. At 500 yards I dial to 4 and at 700 yards I had to dial at 6. Haven't tried past the 700 yard mark yet.

I may look into grabbing a couple boxes of Hornady ELD-X 178gr to see if the slightly heavier bullet will match up a little better to the BDC since I am also looking for a proper hunting round for it (the SMK don't really cut it well enough for hunting IMO).

I've created more than a couple dope charts for my other rifles. Just wanted to get the BDC on the MST-100 proper though since it makes it real easy when hunting

 

[onetopgun]

These are the Come Ups for the Main Elevation Turret of the US Optics MST-100:

100 - 0
200 - 2 MOA
300 - 5 MOA
400 - 8 MOA
500 - 12 MOA
600 - 16 MOA
700 - 20.5 MOA
800 - 25 MOA
900 - 31 MOA
1000 - 37.5 MOA

Set the Ocular first to bring the Reticle to a sharp focus against a blank background.

Adjust the objective so the scope is parallax free at 300 yards

Rough Zero the scope at 100 yards with the Main Elevation Turret set at “1”

If possible, Refine your Zero at 300 yards with the main elevation turret set at “3” with “0” on or off the vernier (Fine Tune) with whatever apparent windage is necessary.

Ping the following thread for additional detail: https://www.snipershide.com/shooting/threads/using-the-mst-100.23517/

Regards
JHC

 

[pmclaine]

Using @onetopgun ballistic chart you can get within 1/2 MOA of any elevation adjustment you need.

It messes with our anal sensibilities to not have the BDC work perfectly for the chosen ammo but that is the weakness of BDC.