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In 1988 Robert McCoy of the US Army Ballistics Research Lab reported on flight characteristics of the 173 gr GI match bullet and the 168 and 190 gr SMK. Based on test results recommended twist rates for the bullets were made.

A lot of complicated aerodynamic stuff in the report.

To me it is interesting how far the military shooting teams would go to optimize performance.

McCoy and the BRL even did research on the flight characteristics of .22 rimfire ammo for the USAMTU smallbore team.

Here is a link to the 173 gr test report:

http://www.dtic.mil/dtic/tr/fulltext/u2/a205633.pdf
 

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Interesting data to say the least. Thought I might print it, but 173 pages?? Have not read it all, but will and brings back memories for me when active shooting NRA Long Range, Palma, etc. Had a Rem. 40X w/ Krieger 30" Palma barrel-12 twist, Alex Sitman custom stock, Warner rear/Anshutz globe front-post-lens, and used for all Long Range matches. Found the most reliable accurate load was the Sierra MK 190gr over 42.2 of IMR4064, Fed.GM primers, Lapua brass and bullet seated some .002-3" from lands and grooves. All my shooting buddies warned me that the bullet would be sub sonic at the 1K mark and it may well have been so, but scores went up and then the others wanted to know "just how hot are you loading that thing...?" I had already tested warmer loads but accuracy decreased for me and my particular rifle so left the velocity as is. Later on re barreled with Douglas(same specs.) and gave same good performance.
The 600yd matches were pretty much "duck soup" with this rifle/load and helped me gain higher classification in one season. Don't know the rules today, but back then a true 600yd. match, 3x20, qualified as a Long Range match. I never could get the same results with the 155's or the 175's from either barrel so stuck with the 190's balance of my shooting match days. Best scores for me at the 600yd matches was 596 w/about 50% X's. Best at 1000yds. was a 195 w/ again 50% X's and for me that was as good as it ever got. As for Palma the 800 could be cleaned, not a problem, but that 900 always dropped some points and again at the 1K mark and best I ever did was something like 436 out of 450 possible. At Quantico Base spoke with very qualified shooter and told him I could never seem to clean that 1000yd. target and when asked what caliber I was using told him 308 and he smiled and said to do so was not common. I felt relieved. Much appreciate you pointing this article out and always wondered about the science of the fight of the bullet.
 

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German Salazar is a triple distinguished marksman. Shoots long range prone and has (or had) a real interesting blog which seems to have been mothballed.

Even in this day of VLD and Palma bullets, Salazar considers the 190 SMK to be the gold standard for long range.

I enjoy stuff like this BRL report. I'm fascinated by but in no way understand the science behind bullet flight. Things like the spark photography in which the shock waves and turbulence coming off the bullet are visible. Amazing stuff.

I've been out of the game for a long time. Trying to ease into mid range prone. If I can still keep them somewhere near the middle at 600, maybe I'll work up the nerve to try long range. I've never shot a 1,000 yd match.
 

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Here are some facts I gleaned during my almost 40 years of competing with the M14 and collected from other sources.

At 1000 yards I shot my best scores using Sierra 180 grain MK bullets in a Krieger 1:10 heavy barrel. (Not all M14 rifles shoot 180 grain bullets well, but mine did).

The 168 grain SMK will not go 1000 yards without going subsonic and tumbling.

The 175 SMK will shoot 1000 yards just fine. Sierra designed the 175 to replace the M118 173 grain match bullet and be shot in a 1:12 twist.

Krieger told me that a 1:14 twist is optimal for .308, but I'm sure they were thinking of the 155 grain Palma in a bolt rifle.

I have always shot a 1:10 twist in my personal NM rifles. However, I have also shot 1:12 out to 1000 yards and I didn't detect any significant difference in performance.

The 1:11 twist is a good compromise for those who cannot make up their mind.

I've fired excellent scores at 600 yards with 168 grain bullets in spite of the fact that Sierra told me the 168 was only designed to shoot 300 meters.

I think the 175 SMK is probably the best all around bullet for the M14 and better than the 168 at 600 yards. It is the best choice for those using one load at all ranges.

Hornady A-MAX bullets are a good choice too.
 

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The 168 grain SMK will not go 1000 yards without going subsonic and tumbling.
Ted, Thanks! You provided some great information. However, the 168 grain SMK does not tumble (which implies that it goes end over end) - it yaws in flight once it reaches trans-sonic velocities. The yawing motion causes the projectile to become unstable and accuracy suffers. Rick
 

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Here are some facts I gleaned during my almost 40 years of competing with the M14 and collected from other sources.

At 1000 yards I shot my best scores using Sierra 180 grain MK bullets in a Krieger 1:10 heavy barrel. (Not all M14 rifles shoot 180 grain bullets well, but mine did).
Ted, I think its safe too say the 180's that you fired back in the day was long before Sierra changed the design of the 180SMK and not for the better. The old 180SMK had a 9* boat tail angle with a shorter bearing length, the current 180SMK has a longer bearing surface with a horrible BT angle.
 
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