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BSA TMD624x44/30SP Tactical Scope


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#1 TxMark

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Posted 25 September 2010 - 11:21 PM

Using mildots and variable scopes can be a problem, so I put my spreadsheet skills to work on figuring the BSA 6x24 out.

Luckily, BSA was nice enough to include a mils to MOA cart for their reticle. Many scope manufacturers don't.

Still, I was a bit confused about a reference in the manual stating that the distance between the mil dots is actually .75 mil, not really one mil. Using my already prepared MOA to inches conversion data, I prepared a line for each magnification to calculate the number of inches between each set of dots at multiple ranges.

Once the calculations were done, I looked for 36 inches in the 1000 yard column. That's what a "miliradian", or mil, is at that range. Sure enough, I found it at 9x, which is the magnification that shows a mildot distance measurement of one mil. The funny thing is that the previously mentioned .75 mil is the value at 12x according to the reference table.

Naturally, I will confirm the math at the range using well defined, measured targets. If anyone sees a problem with the math let me know. Feel free to PM me for a download link for the spreadsheet.

Enjoy.

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#2 Corbin

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Posted 26 September 2010 - 02:32 AM

I'm not sure if this is the case here or not, but sometimes the measurement "between mil dots" is not always talking about center of one dot to the center of the other, but the actual space between them (not including the dots). Depending on the dot size, the measurement "between" them can vary. Most commonly, Mil Dot scopes have the dots themselves at 1/4 Mil, so space between them is 3/4 Mil. 7/8 Mil from crosshair to a dot.

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#3 TxMark

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Posted 26 September 2010 - 07:36 PM

Corbin;

That's a good point, but I think not the case in BSA's statement.

I should have quoted the manual. "One Mil in the reticle is the distance from the center of one dot to the center of the next. Contrary to popular belief, the Mil-Dots on the reticle measure .75 Mil instead of one Mil."

As you can see from my above posting of the measurement diagram from the manual, BSA doesn't even show the actual measurement between dots, only center to center. Their chart and graphic seem to work mathematically, just not the statement. :)

Glad to hear from you. It's nice to see someone else interested in mil-dots.

#4 Corbin

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Posted 27 September 2010 - 10:22 PM

My Mil Dot math, range estimation and general long range dicipline really sucks now. Not that I was ever outstanding at it, but I was a hell of a lot better at it 15 or 20 years ago than I am now. :rolleyes:
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#5 Rhodes1968

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Posted 29 September 2010 - 11:35 PM

Have one of those coming in due to the sale price so thanks for posting this!
Had the Japanese got as far as India, Gandhi's theories of "passive resistance" would have floated down the Ganges River with his bayoneted, beheaded carcass. -- Mike Vanderboegh.

#6 nsdhanoa

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Posted 30 September 2010 - 06:44 AM

You should check out this Flash demo on how to properly range with a mil-dot scope, it really helps drill the formula into your head. This is with a mil/mil scope, I think they also have one for mil/moa scopes.

http://www.shooterre...om/mildemo.html

But yeah, the distance from center to center of the dots should always be one mil or it would be pretty much impossible to range with the scope. It looks like on the BSA the distance from the edge of one dot to the next is .75 mil, so each dot is .25 mils across. So say your target goes from the crosshair to the top edge of the first dot, the mil measurement would be 1.125 mils. I think most manufacturers use either 10x, 12x or the max power to be exactly one mil from center to center, but maybe the BSA is set to 9x? You should definitely check that when you get to the range.

If you look at a yardstick at 100 yards, at the proper power it should take up exactly 10mils, which should be exactly the space between the thick posts of your crosshairs. Depending on your scope it might end up being something odd like halfway between 9x and 10x, so just mark it on the power ring when you find it.

#7 TxMark

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Posted 30 September 2010 - 06:03 PM

Rhodes;

I'm happy to help. I like finding boo-boos and improving vendor stuff, then telling others.

BTW... if you've got the UTG 978, low Picatinny (.25 in) rings will probably work. That gives you a 3.0 sight-line above bore.

Good luck.

#8 TxMark

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Posted 30 September 2010 - 06:52 PM

nsdhanoa;

Hey thanks for the link. That's a cool game.

BTW... even figuring the size of the dots, the BSA numbers don't add up to one mil. At 10x, the chart says center-to-center is 0.90 mil with a dot size of 0.16. That would put the space between the dots at 0.74. Granted, that's close, but it's not 0.75. Besides it's just a screwy statement. Their numbers for 9x match standard mil-dot dimensions, center-to-center, not 10x. :unsure:

Who knows. I'll be sure to calibrate the final numbers when I get a chance.

Since I usually use my MilDot master at true mil size for the scope (probably 9x in this case), I'm planning to just work up a conversion chart for the other ranges. But, I guess if I get tired of playing calculator whiz I could probably just fork over the cash for a quality first focal plane scope. :)

Thanks again.

#9 308saiga

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Posted 30 September 2010 - 07:27 PM

You should check out this Flash demo on how to properly range with a mil-dot scope, it really helps drill the formula into your head. This is with a mil/mil scope, I think they also have one for mil/moa scopes.

http://www.shooterre...om/mildemo.html


The problem with this demo is that it does not tell you the distance of the target, so to adjust for something that you do not have mo info on is just a waist of time..... It is pretty cool....

If I am missing something here please let me know.....
The only thing you have to fear is fear itself, and the American people that the Gov. pisses off......

#10 Gas Giant

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Posted 30 September 2010 - 07:47 PM

Very Cool Simulation
The range is to be determined by the user.
The width and height of the target is given (man Size)
Use this info with the Reticle markings to determine range.


You should check out this Flash demo on how to properly range with a mil-dot scope, it really helps drill the formula into your head. This is with a mil/mil scope, I think they also have one for mil/moa scopes.

http://www.shooterre...om/mildemo.html


The problem with this demo is that it does not tell you the distance of the target, so to adjust for something that you do not have mo info on is just a waist of time..... It is pretty cool....

If I am missing something here please let me know.....


Very Cool Simulation
The range is to be determined by the user.
The width and height of the target is given (man Size)
Use this info with the Reticle markings to determine range.

The Zoom with mil dots is i the lower right corner,..



You should check out this Flash demo on how to properly range with a mil-dot scope, it really helps drill the formula into your head. This is with a mil/mil scope, I think they also have one for mil/moa scopes.

http://www.shooterre...om/mildemo.html


The problem with this demo is that it does not tell you the distance of the target, so to adjust for something that you do not have mo info on is just a waist of time..... It is pretty cool....

If I am missing something here please let me know.....


- GG

#11 Rhodes1968

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Posted 04 October 2010 - 12:57 PM

Just want to say this scope is passing all expectations so far. Two trips to the range and its rock solid. Great scope for $50 no doubt.
Had the Japanese got as far as India, Gandhi's theories of "passive resistance" would have floated down the Ganges River with his bayoneted, beheaded carcass. -- Mike Vanderboegh.




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