PDA

View Full Version : When a plan comes together, SBR and ACOG


308sako
08-23-12, 17:30
http://www.trijicon.com/images/product_reticles/TA01NSN_reticle_popup.jpg

http://i181.photobucket.com/albums/x160/308sako/115inchSBR.jpg

Using the ACOG TAO1NSN 4X optic that has stadia lines at 100 meter intervals poses a challenge for the application of a SBR. The factory ballistic calculations allow for the 62 grain M855 round as fired from a 14.5 inch barrel. The claimed ballistics would be impossible to get from a 11.5 inch barrel so by substituting a 55 grain Nosler Ballistic Tip bullet loaded to 5.56 NATO specification velocities (M193 MV from the 11.5" or 2825 ft/secs) an extremely similar curve over yards not meters appears. That said I have a 100 yard zero of approximately 1/4" high, about the same as best one can tell at 200 yards, and shown here is a composite group fired at both 300 and 400 yards using the "appropriate" stadia. I think this will suffice.

The rounds not included in the composite were fired first as a zero check at 300 yards, an adjustment was made and then the central group(s) were fired. Look close and you will see they were marked with a black marker.

http://i181.photobucket.com/albums/x160/308sako/ShortysBesteffort400and300combined.jpg
WS6
08-24-12, 05:34
Nice work, great results! Planning...usually a precursor to success.
fallenromeo
08-24-12, 10:33
Very nice!
Serpico1985
08-26-12, 15:38
So for the record you were able to get sub-MOA out of a 11.5" barrel at 400yards with hand loads and a ACOG?

That is awesome. Can you give more info on the rifle.

*****Nevermind, found the build specs in your other threads*****
shtf6688
08-26-12, 19:58
congrats
P2000
08-26-12, 20:09
That is one hell of a group. Good work!
308sako
08-27-12, 12:58
So for the record you were able to get sub-MOA out of a 11.5" barrel at 400yards with hand loads and a ACOG?

That is awesome. Can you give more info on the rifle.

*****Nevermind, found the build specs in your other threads*****

Actually the group shown is indeed two groups overlapping each other, one fired at 300 yards and the other at 400 yards, so yeah it works. Frankly the local metro firearms training officer and myself were utterly amazed at this performance. Exactly how repeatable it will be remains to be seen. The rifle does shoot this particular combination into those sized groups with regularity, so I expect it will. I strongly urge others to try this type of setup as the versatility and speed with which one can transition various ranges is amazing.
Serpico1985
08-27-12, 22:56
And from a lightweight chrome lined barrel no less. Not to mention great shootin'!

Makes me want to set up a trust and get a shorty. Thanks for sharing.
sangria7
09-02-12, 17:36
Very Nice!!
uncle money bags
09-04-12, 21:57
Nice setup, gives me a new direction to go.

Have you shot standard m193 with this? I dont expect the same precision as your hand loads but am interested if the trajectories are similar enough to work.
308sako
09-04-12, 23:10
Nice setup, gives me a new direction to go.

Have you shot standard m193 with this?

Yes, and you would be pleased as the 55 FMJ has a BC of approximately .272, while the Nosler has a BC of approximately .267. My load for the Nos BT averages about 25 ft/secs below the LC 193 we chronographed.

I dont expect the same precision as your hand loads but am interested if the trajectories are similar enough to work.

The same initial velocities and virtually the same ballistic coefficients will yield the same flight path. However the observed accuracy difference is dramatic, unfortunately.
308sako
12-06-12, 13:32
Updated: Shooting the Hornady 55 FMJ's as opposed to LC variant, the accuracy/precision of this load would appear to be within 1/2 MOA at 400 yards... Awesome by my standards.
tostado22
12-06-12, 15:30
Awesome work! Shows some dedication and initiative right there.
Sarah
12-09-12, 21:54
I was so amazed at how accurate your 11.5 with the ACOG was at 400yds...I had so much fun shooting it. I have to admit that was my first experince with an ACOG and I loved yours so much I am going to buy one!
308sako
12-09-12, 22:34
I was so amazed at how accurate your 11.5 with the ACOG was at 400yds...I had so much fun shooting it. I have to admit that was my first experince with an ACOG and I loved yours so much I am going to buy one!


Sarah, while there are many models, time well spent at SHOT will help you in the choice of which model would be right for how you see your build come together.

Yes, I am proud of what I created (worked with) and think it is suitable for my perceived purposes.

After you get a chance to use it in close, perhaps you will have a different feeling?
Sarah
12-10-12, 17:31
I agree Dave, before I buy one I will try and shoot close in and see how I like it> Thanks for letting me experiment!
Magic_Salad0892
12-11-12, 11:16
I agree Dave, before I buy one I will try and shoot close in and see how I like it> Thanks for letting me experiment!

The 3X ones have better eye relief, and in my opinion are easier to shoot close up. My experience is similar to others on this site. Most people who run ACOGs tend to favor the 3X ones.