Short Dot questions...

[Derek_Connor]

Seems like following in the trend an ideas behind the short dot, zeroing out the scope @ 50yards to follow the 50/200 bzo is the standard practice? Any thoughts/suggestions?

Second question, i haven't seen an official reticle schemtic on the CQB. I assume that the larger hash marks are 1.0mil and the inbetween, smaller hash marks are 0.5mil?

[Jay Cunningham]

Have you checked out this tacked thread:

S&B Short Dot Models Explained. (https://www.m4carbine.net/showthread.php?t=5872)

[Derek_Connor]

Yes, I have. Have you? It is the individual nomenclature explanations, no reticles explained.

[Jay Cunningham]

Yes, I have. Have you?

You can stow the attitude, bro. Good luck with your quest for knowledge.

[Derek_Connor]

You can stow the attitude, bro. Good luck with your quest for knowledge.

Attitude? no attitude here...wanted to make sure we are all on the same page since I was recommended to a generic thread regarding my question that had no information that was releveant to my original post.

[USMC03]

Derek,

With optics like the Short Dot and the Leupold MR/T 1.5-5x M2, I initally zero the optics at 100 yards and adjust the elevation / bullet drop comp knob to the 100 yard mark.

With my Aimpoints, irons sights, etc. I zero at 50 yards.


So I don't have to worry about point of aim / point of impact being different from gun to gun, with the Short Dots / Leupold MR/T M2, etc. after they are zeroed at 100 yards, I turn the elevation knob to the 200 yard setting and then go 1 click past (this is approximately 220 yards ..... for most 16" barrels shooting 55 grain 5.56 ammo point of aim / point of impact is the same at 50 yards and approximately 220 yards). This gives me basically a 50 yard zero on the gun (point of aim / point of impact being the same at 50 yards / 220 yards).


At a match I'll change the elevation knob to whatever is needed on the Short Dots / Leupold. But for carry it at work, I leave it set for 220 yards (improvised 50 yard zero). So the point of aim / point of impact is the same no matter if I'm carrying a gun with an Aimpoint or a Short Dot.



Hope this was the info you were after.



Semper Fi,
Jeff

[Derek_Connor]

Derek,

With optics like the Short Dot and the Leupold MR/T 1.5-5x M2, I initally zero the optics at 100 yards and adjust the elevation / bullet drop comp knob to the 100 yard mark.

With my Aimpoints, irons sights, etc. I zero at 50 yards.


So I don't have to worry about point of aim / point of impact being different from gun to gun, with the Short Dots / Leupold MR/T M2, etc. after they are zeroed at 100 yards, I turn the elevation knob to the 200 yard setting and then go 1 click past (this is approximately 220 yards ..... for most 16" barrels shooting 55 grain 5.56 ammo point of aim / point of impact is the same at 50 yards and approximately 220 yards). This gives me basically a 50 yard zero on the gun (point of aim / point of impact being the same at 50 yards / 220 yards).


At a match I'll change the elevation knob to whatever is needed on the Short Dots / Leupold. But for carry it at work, I leave it set for 220 yards (improvised 50 yard zero). So the point of aim / point of impact is the same no matter if I'm carrying a gun with an Aimpoint or a Short Dot.



Hope this was the info you were after.



Semper Fi,
Jeff

Jeff, very informative. Thanks..

A summary of your post to make sure I am following:

you find the adjustments needed to zero your short dot at 100 yards, then adjust your BDC to make that your 100 yard dope.

You then dial in more elevation per se, to 220 yard mark on the BDC to simulate the 50yard/200 yard zero (for the 16inch barrel velocity)

Only thing I'd have to do different is compensate for a short barrel...

I emailed Premiere earlier this week, but I figured they were @ Shot. I haven't been able to find any info to confirm the retilcle values...

thanks again

[jtb1967]

The SB have fantastic optics, but I've decided to sell mine. I think the eotech might give me the edge for up close quick shooting.

[USMC03]

Derek,



Correct: Zero at 100 yards initially, and then move the elevation knob to 220 yards (for 14.5" - 16" barrels using 55 gr. 5.56 ammo).

If you are using a SBR, you may want to crono the round you are using and use a ballistic calculator to figure out where the bullet will impact if using a 50 yard zero.

With the Short Dot and most low powered variable optics that use the elevation knob as a bullet drop comp, most don't have enough negative clicks of elevation at the 100 yard setting to get you back to a true 50 yard zero. Most stop at 1 - 2 clicks under the 100 yard designation.

I have also found that when re-confirming the "50 - 200 yard zero" at both 50 yards and 200 yards, that when zeroing at 50 yards the zero is high at 200 yards. The point of impact actually intersects with most carbines at 220 - 235 yards. This is why I use the 200 yard bullet drop comp on the elevation knob and go one more click (toward the 300 yard mark). Take into consideration that I'm at 5,000' elevation.

Sounds complicated here, but zero at 100 yards, readjust your elevation knob to the 100 yard setting. Then move the elevation knob to the 220 yard setting (200 yard + 1 click) and shoot a group at 50 yards and again at 220 yards. Should be good to go, or need a click or two minor adjustment at most to get your zero squared away. Now leave your Short Dot at this setting and you have a 50 yard zero. And if you have a target at 400 yards, move the elevation knob to the 400 yar setting and you will be on target. When you want to go back to a 50 yard zero, move the elevation knob back to the 200 yard + 1 click setting.






S/F,
Jeff

[Nick S]

I diverge a bit from Jeff in how I zero/compensate for range. I figured this out the hard way. As David pointed out the BDC on the SB is in meters not yds. Up close its not an issue but t the ranges you might actually use your BDC (>300 yds) and especially past 400 yds it is significant. In addition, the cams are calibrated for a specific bullet weight/MV that your barrel may or may not deliver.

Whether you use a 50/200, 100 or 200 yd zero is up to you and really moot. They all work if you know how to apply them. I think a better method for doping in range is in MOA vs distance. If you use this method the cam does not matter in regards to bullet as all the SB cams have MOA marks as well as range.

You will need to chrono your respective bullet and run that data as well as weight, BC, environmental conditions etc through a ballistic computer.

http://www.eskimo.com/~jbm/calculations/traj_card/traj_card.html

Then output your drop in MOA vs inches for the respective load. Obviously you need to verify the dope by actually shooting it. So far it's worked well for me.

BTW i'm open to criticism on this method if anyone has any. My SB has a #7 reticle so no reference points for holdover/hold-offs.

Take care.

Nick

[USMC03]

David,



Thanks for the info. I had forgotten about the Short Dot being in Meters vs. Yards.

What is posted above is what works for me for a 50 yard zero with the Short Dot with the 62grn cam with a Colt or LMT 14.5", 1/7" twist barrel, using 55grn 5.56 ammo.

I have noticed using 14.5" and 16" barrels (both 1/7 and 1/9) and 55gr 5.56 ammo (Fed xm193, Win Q3131A, etc) and low powered scopes is that if I zero the scope at 50 yards, the point of impact is high at 200 yards and have found that on the Short Dot, Leupold MKIV 1.5-5x M2, Leupold Vari-X III 1.5-5x, etc. that if I zero at 50 yards and move the target back to 200 yards, the strike of the round is always high. I have found that the point of aim / point of impact with a 50 yard zero is usually between 220 yards and 240 yards (ie. zero the gun at 50 yards and move the target back without touching the elevation knob).

I don't know if this is due to the elevation I'm at (5,000'), or if the 50 / 200 yard zero is based on a heavier bullet, or another factor.



Nick,

Using the zero method above, I shoot run and gun rifle competiton out to 425 yards on a regular basis. When shooting the 425 yard stage (Short Dot set at the 100 meter zero, but zeroed at 100 yards), if I move the elevation knob to 400 meters plus 1 click, I have no problems hitting steel gongs, steel pepper poppers, small LaRues, etc at 425 yards.

On 1/2 size human targets I don't have a problem, if I were shooting 8" steel plates at 425 yards, that may be a different story. But in reality, I probably couldn't see a 8" steel plate real well with a 4x optic at 425 yards anyway.

Engaging targets at 425 yard with the Short Dot:

http://demigod.org/~zak/DigiCam/PRM-2007.02/smaller/D101_1422_img.jpg



Just my personal experiences

S/F,
Jeff

[Derek_Connor]

All good stuff, good to see things outside the box....

For those of you who were looking like I, another member helped me out and sent me a reticle schematic for the CQB Reticle, FYI:


http://img168.imageshack.us/img168/6167/cqbreticlegp8.png

[davemcdonald]

Thanks guys. This has been one of the most informative threads that I have read in quite some time.

Dave

[IrishDevil]

Great info here, I'm slowly but surely saving for a Short Dot.

[Nathan_Bell]

Great info here, I'm slowly but surely saving for a Short Dot.

Aye 18 months till I had the money and found the price I wanted to pay for one, great optic.

[threebanger]

I zero mine @ 100 yrds & just use the elevation turret MOA adjustments @ greater distances. I don't even fool with the BDC since it's in meters (collecting dope is more fun anyways)

[Derek_Connor]

Derek,



Correct: Zero at 100 yards initially, and then move the elevation knob to 220 yards (for 14.5" - 16" barrels using 55 gr. 5.56 ammo).

If you are using a SBR, you may want to crono the round you are using and use a ballistic calculator to figure out where the bullet will impact if using a 50 yard zero.

With the Short Dot and most low powered variable optics that use the elevation knob as a bullet drop comp, most don't have enough negative clicks of elevation at the 100 yard setting to get you back to a true 50 yard zero. Most stop at 1 - 2 clicks under the 100 yard designation.

I have also found that when re-confirming the "50 - 200 yard zero" at both 50 yards and 200 yards, that when zeroing at 50 yards the zero is high at 200 yards. The point of impact actually intersects with most carbines at 220 - 235 yards. This is why I use the 200 yard bullet drop comp on the elevation knob and go one more click (toward the 300 yard mark). Take into consideration that I'm at 5,000' elevation.

Sounds complicated here, but zero at 100 yards, readjust your elevation knob to the 100 yard setting. Then move the elevation knob to the 220 yard setting (200 yard + 1 click) and shoot a group at 50 yards and again at 220 yards. Should be good to go, or need a click or two minor adjustment at most to get your zero squared away. Now leave your Short Dot at this setting and you have a 50 yard zero. And if you have a target at 400 yards, move the elevation knob to the 400 yar setting and you will be on target. When you want to go back to a 50 yard zero, move the elevation knob back to the 200 yard + 1 click setting.






S/F,
Jeff


FWIW, i did this method today Jeff and it did very well. I zero'd @ 100, reset the dial.

Guestimated dope out to 250yards, shot, adjusted, and starting hitting the center of my target consistently.

Then immediately shot @50 yards, and it was just a tad bit high. So i brought it down one click and that will be my go to zero..

thanks jeff, good stuff

ETA: ammo was 55grain FMJ

[caporider]

FWIW, i did this method today Jeff and it did very well. I zero'd @ 100, reset the dial.

Guestimated dope out to 250yards, shot, adjusted, and starting hitting the center of my target consistently.

Then immediately shot @50 yards, and it was just a tad bit high. So i brought it down one click and that will be my go to zero..

thanks jeff, good stuff

ETA: ammo was 55grain FMJ

Are you shooting the cheap PMC stuff from Outdoor Marksman using the M855 BDC cam? I just had a couple of Short Dots show up today and will be shooting the PMC with one of them for training and practice.

[Derek_Connor]

Are you shooting the cheap PMC stuff from Outdoor Marksman using the M855 BDC cam? I just had a couple of Short Dots show up today and will be shooting the PMC with one of them for training and practice.


Federal FMJ Ball 55grain, with the M855 turrents..

[flyfishdave]

DIY ballistic dope stick’ums:

First off, credit for this should go to Ned Christiansen as he posted on this site sometime last year about some professionally made ‘Ballistickers’ with dope information for various loads. You can see his post here at:

https://www.m4carbine.net/showthread.php?t=8585

I thought this was a great idea and attempted to make a crude homemade DIY version, customized for my loads and data needed. After testing various media and methods, I found that printing on photo sticker stock using a dye sublimation photo printer yielded a pretty good weather resistant product that wouldn’t smear or fade easily, but cheap enough to allow me to make multiple attempts at printing for whatever reason.

Anyway, getting back to the original theme of this post, I found that METERS and MOA don’t mix very well together and the BDC for M855 was not very useful to me, as I currently shoot mostly 55 grain M193, PRVI. Anyway, I searched the internet and various forums and came up with some numbers and averages to use with a ballistic calculator to come up with various tables, to help me decide which zeros would work best for the type of shooting I was primarily doing. Here’s the link to an online ballistic calculator that’s pretty basic and simple:

http://www.handloads.com/calc/

I used the following constants:

55 grain
BC = 0.243

Estimated muzzle velocities:

16” – 30 97 fps
14.5” - 2984 fps
11.5” – 2872 fps
10.5” – 2750 fps

***I don’t own a chronograph so I have no clue what the actual MV’s are. I just took the average of all the MV’s I could find for M193 out of various length barrels

Height over bore (HOB) for M4 flat-top – 1.215”

Mount height:

Larue Aimpoint M4 mount – 1.725”
Larue 1.93 mount – 1.93”

***remember to add the M4 flat-top HOB to the mount height for your particular mount.

Attached below or somewhere in this post, should be a link to an Excel spreadsheet file I made showing some various drops at various zeros.

***NOTE, this is not an actual spreadsheet where you can add your own parameters and have new data generated. I just used a spreadsheet as a means to easily organize the data for viewing and printing. The ONLY formulas used here are for converting ‘drop in inches’ to ‘MOA values’ at the bottom of the spreadsheet.

Anyway, back to the meat and potatoes, I used Adobe Illustrator to make a table of various distances, drops, MOA and windage (10 mph), then exported it as a jpeg file. The jpeg file was then used as a photo by my printer’s software to print on 4x6 photo sticker stock, which was precut for four 0.9” x 1.35” and two 1.9” x 2.8” stickers. For those interested in a good dye sub photo printer that is cheap and uses affordable consumables, look at the HiTouch Imaging products. BTW, each sheet of 6 stickers (4 small, 2 medium) come out at 60 cents a sheet.

4 x 6 Photo sticker sheet:
http://images34.fotki.com/v1146/photos/1/126714/4600136/stickercard-vi.jpg

Given the limitations of the software, which was optimized for a PC (I use a mac), the fact that I really never used Adobe Illustrator, the sizing and formatting constraints, and that I was just goofing around, I didn’t’ get the perfect black background, so some of the edges have white…..big deal.

Medium sticker on stock: http://images32.fotki.com/v1091/photos/1/126714/4600136/ballisticardlarge-vi.jpg

Now, before you ask me why I used tape when this is supposedly a sticker, this batch of photo stickers was just found at the bottom of a box that had been in storage for two years, and survived a move from VT to PA. It does stick, but just not as good as it used to. Once I buy some new paper, it should stick without the need to use scotch tape.

After some crude testing of the MOA drops, everything seems to be dead on out to 200. Now, I just dial in the correct MOA on the Short Dot and shoot – I just have to remember to adjust when changing distances. Nevertheless, based on the ballistics chart, with a 100 yard zero, I am within 2” from POA from 25 to 200 yards, which is where we shoot the majority of our carbine matches.

Small sticker on scope:
http://images34.fotki.com/v1121/photos/1/126714/4600136/ballisticardsmall-vi.jpg

It also happens that the small itty bitty sticker, which is still legible, fits neatly on the short dot’s tube, and without the need for any scotch tape. This is more for fun, as the sticker on the stock is easier to read.

Just thought I’d share a fun little side project inspired by the collective spirit of this forum.

Dave.

[Derek_Connor]

Dave, good stuff...thanks bro.

I just caculated some data for the CQB reticle...here is a graph showing the drop for 55grain FMJ and 75BTHP out of a 12.5 barrel, numbers vary for the 16inchers.....


55grain:
http://img114.imageshack.us/img114/2340/sb155grainmediumbg9.png


75grain:
http://img114.imageshack.us/img114/1935/sb275grainmediumua2.png

[Nick S]

Derek

Nice diagrams. What BC and velocities are you using for the respective bullets.

Thanks

Nick

[Derek_Connor]

Derek

Nice diagrams. What BC and velocities are you using for the respective bullets.

Thanks

Nick

Hey Nick - I was using some conservative velocity #s, I will have my own specific data chrony'd tomorrow

But for the 55grain I was using a 0.272 BC with 2950fps out of a 12.5 barrel
For the 75grain I was using a 0.395BC with a 2425fps out of a 12.5 barrel

If you plug in data for 77grain, it gives you about 50yards less per 0.5mil in the reticle as compared to 55grain bullet

[flyfishdave]

Derek (and anyone else that may be interested)

I have some extra sheets of the sticker paper that I need to get rid of. My daughter and wife want photo stickers (that stick) for themselves and can't see myself throwing out this batch of paper, just b/c it doesn't stick as well as it used to.

If you want a set of stickers, printed with YOUR dope, PM me for an address to send a SASE (self-addressed stamped envelope) so I can mail you a sheet. Each sheet has 2 LARGE and 8 SMALL stickers - each sticker can be unique if you like. I'll keep printing until I use up my supply.

***using double-sided scotch tape solves the problem - just did mine again. Peel, turn upside down, apply tape, trim with scissors, and then apply to stock or scope. Obviously, you want to remove any oil from surface first - alcohol works well

Guidelines:

1. B&W only, no funny colors. No boldface, no italics, etc.
2. 4 columns max; can leave out MOA if you like (or don't have a BDC)
3. 14 distance points max
4. You are responsible for generating the data (and its accuracy) you wish to be printed, preferably sent as a spreadsheet file, or NEATLY formatted word file.
5. SASE should be big enough to fit a 6" x 6" print w/o folding.

Regards,

Dave.