175 SMK vs 175 TMK

[390fe]

For what it's worth, my rifle has shown pressure signs early with three different powders. This is why responsible reloaders always start low and work up.

An update to my post on 5/3/15

I have settled on seating my 175 grain TMK's at 2.910 coal. These are jumping into the lands by a healthy amount...

I'm using 42.2 grains of IMR4064, Remington brass, and Remington 9 1/2 primers.

Velocity from my 20 inch Hog Hunter is 2590 according to my FDAC and JBM ballistics.

[darkker]

which will push it right at 2700 FPS and allow me to stay supersonic till almost 1200 yards... .


I've never understood why this is such a concern to people? The 175 SMK will flawlessly cross trans-sonic, Sierra specifically built it that way for the army; with the military testing and watching....

[cowtownup]

That is good to hear.. The only experience I've had with projectiles tumbling was with some 165 SGK's that I was shooting at 1000 yards and got some sideways hits on the steel. I assumed that was due to crossing the trans-sonic. I just assumed the SMK would likely do the same thing.

[darkker]

No. After the debacle at Camp Perry, where the original 168gr MK wouldn't cross past @ 800; and the civilians started whupping on the Army's chosen few, they called Sierra. The army didn't ever want that to happen again, and did mountains of testing along side Sierra's development.
Dr. McCoy did mountains of work on this separately, and it comes down mostly to tail angle. 8.5° is the the best compromise between survival and BC. The original 168 had a 13°. Gives a sexy BC, but guarantees destabilization.

[cowtownup]

I was not aware of that information.. Thanks for letting me know..

[pda4de]

Hello, I'm new here. I wanted to comment on the 175 TMK. I just received a 500 count box from OK Weber and now I'm not sure what I'm going to do with them. My plan was to load them with RL-15 for my Sig 716 3 Gun Heavy, but they are super long and skinny. At the lands, in the Sig, they are 2.966" OAL and a 175 SMK is 2.761" OAL. The 175 TMK will not even fit in the Magpul LR/SR magazine which offers a max OAL of 2.830". I don't think the 175 TMK can be compared the the 175 SMK. I believe the 175 TMK is really a lightened 190 SMK. The Sierra MK 190 gr. #2200 with a BC of .533 and the TMK 175 gr. #7775 with a BC of .545 have a different shape but a similar length and BC. I think I'm going to have to load the 175 TMK for my Savage 10 FCP McMillan as an alternative to the SMK 190, that I run at just under 2700 fps. with RL-17 or Varget. The more I think about it the more confused I get about how to approach the 175 TMK. I usually run SMK 175 with RL-15 in the Sig at just under 2500 fps. Anything more than 2500 fps. will tear up the base of the brass and really beats on the action. I don't usually run 175 gr. bullets through my Savage 10, but if I must, I think I'll use RL-17 with a little lighter load than my normal SMK 190. After several months of trying to get Sig 716 and the Savage 10 dialed, Sierra had to go screw everything up. Just what I need, more change.

[390fe]

I've been loading my 175 grain tmks over 42.2 grains of IMR4064 in Remington brass and using Remington primers. I've been seating my tmk's to 2.910 overall length and they function in my magazine. Velocity averages 2.589 fps from my 20" Savage barrel.

Accuracy is outstanding - I was dialing 13.5 minutes for drop, 3.5 minutes for wind, and destroying clay pidgeons on the berm at 500 meters.

Temp was 73, overcast skies with variable winds east to west 7mph early to nearly 20mph later, full value.

[pda4de]

Today I was able to test 50 rounds. I tried to load the 175 TMK pills into cases with necks that were too tight, using the incorrect seating stem, and the results were sloppy. My best results were 2646 fps with 42.5 grains of IMR 4895 from a 24" Savage 10. After I returned from the range I re-sized all the brass (Hornady Match) from today with a Redding neck die (.335 and no expander ball) and sorted it with a Ballistic Tools case mouth neck tension gauge after giving the inside of each neck a couple turns with Sinclair Carbide Vld Case Mouth Chamfering Tool - Carbide 28 Degree Cutter. I bought a new VLD seating stem for my Wilson seating die which I will use to load the next batch of 175 TMK pills into the loose neck cases that I sorted today. I need to be at 2.829" OAL or 2.112" OG with the Hornady gauge.

[cerralvo78]

Hello...I am new to this forum
I was looking also info online on the .308 win 175 TMK
I got a box at my local shop
RIFLE DPMS LR308 24" BARREL

I loaded them with my 175 SMK load:(lapua 2.005, Varget 43.6, 175 SMK, 2.230 CBTO or 2.815 COAL)
on the TMK I use 2.800" coal and pour 43.6V........When I load the first round i heard the crushing sound...........
I stop
Then I decide to test on the capacity of my ammo,
Lapua brass 2.005", 175 TMK(base to ogive .656"), varget powder, 2.800" coal

40.0gr varget did not compress(I hear the powder shaking)
41.5gr varget did not compress(I hear the powder shaking)
42.0gr varget IT DID COMPRESS(I couldn't hear the powder shaking)


Max COAL on my DPMS is 2.825 with a 1.380"(base to tip) 175 TMK bullet
My max COAL will be 2.820" to cover for length imperfections(1.375" to 1.384")
My max COAL (DPMS max to lands) is 2.980"

Ladder indoor at 25 yards (no POI info only test for velocities and pressure signs)
175 TMK/fm lapua brass 2.005"/WLR/varget powder/COAL 2.820"/2.100" CBTO

Varget/SPEED
39.4 2371
39.7 2422?????
40.0 2417
40.3 2486
40.6 2444 ?????
40.9 2487
41.2 2517
41.5 2529

I DID NOT SEE ANY PRESSURE SIGNS
I'm single loading
I WILL LOVE TO HAVE A ROUND 2650 FPS ON THIS BULLET

MY QUESTION IS....WOULD IT BE OK TO GO ANY HIGHER THAN 41.5??
I WILL DO A POI LADDER TEST LATER AT 400YDS

THANKS

[pda4de]

Hello cerralvo78, I think you need a faster powder that has a lower volume. Try RL-15 or IMR 4895. Save the Varget for 190 SMK.

[cerralvo78]

Thanks pda4de, you are right maybe I was thinking 4064 or 4895. Now that I ran some numbers on the Ballistic AE app I decide that I want to get around 2450 fps to 2500 fps and I do not need to push it harder up to 2660 fps like on my 175 SMK load so I can stay supersonic up to 1000 yards

According Sierra they claim that the new .308 175 TMK will stay supersonic to 1000 yards at a 2400 fps muzzle velocity

I ran some numbers on my Ballistic AE app using Sierra's BC G1 .545.
At the Sierra testing facility in Sedalia, MO the altitude is about 909ft, so @ 2400 fps it will stay supersonic up to 1130 yards

I also ran some numbers on my Ballistic AE app using Bryan's Litz Field-Tests BCs of Sierra Tipped MatchKings
I use Bryan's .267 G7 for ballistic coefficient
I am big fan of Bryan's testing so I decide to use his BC
At the Shooting range were I test in Houston Texas, altitude is around 100ft, so @ 2400 fps it will stay supersonic up to 955 yards
I will have to go to around 2475 to stay supersonic up to 1110 yards