168 vs 175 SMK?
- Thread starter Taco-XL
- Start date
jwrowland77
New member
168's max is around the 900-950 yard range depending on how hot you push them.
175's you can take out to a grand as long as muzzle velocity is 2650fps.
168's less recoil. 175's have more energy to make it to 1000yds.
I personally like the 178gr Hornady BTHP Match bullets. I shoot these from a 1:12 twist and they do pretty good.
175's you can take out to a grand as long as muzzle velocity is 2650fps.
168's less recoil. 175's have more energy to make it to 1000yds.
I personally like the 178gr Hornady BTHP Match bullets. I shoot these from a 1:12 twist and they do pretty good.
There is an rpm rate band that Sierra's 30 caliber 168's do best at.
168's are barely stabilized when shot from 1:12 twist barrels at 2200 fps. That spins them at 132,000 rpm's; minimum for use at 300 meters. The US Army International Team had Sierra make the first ones in 1958 for their free rifles used in the Olympics.
That bullet's is overspun with a 1:10 twist barrel leaving at 2700 fps spinning 194,400 rpm. I tried them in my 26" 1:10 twist .308 Win. barrel with max loads at 300 yards and they didn't shoot as accurate as when I used 10% reduced loads.
I've shot LC M852 7.62 match ammo with Sierra 168's from 24" Garand barrels at 1000 yards. Very accurate. But I think they were starting into the subsonic range at about 1001 yards.
168's are barely stabilized when shot from 1:12 twist barrels at 2200 fps. That spins them at 132,000 rpm's; minimum for use at 300 meters. The US Army International Team had Sierra make the first ones in 1958 for their free rifles used in the Olympics.
That bullet's is overspun with a 1:10 twist barrel leaving at 2700 fps spinning 194,400 rpm. I tried them in my 26" 1:10 twist .308 Win. barrel with max loads at 300 yards and they didn't shoot as accurate as when I used 10% reduced loads.
I've shot LC M852 7.62 match ammo with Sierra 168's from 24" Garand barrels at 1000 yards. Very accurate. But I think they were starting into the subsonic range at about 1001 yards.
That all may be true . How ever I have shot my smallest groups using 168gr Fed GMM at 100.200 & 300yds from a 1-10 24" barrel . The average muzzle velocity of the five I only ever chrono was 2643fps . They seemed to shoot fine from my 1-10 twist . That being said I've never loaded anything that shot as well as GMM as often . I have some loads that shoot really well 70% of the time , GMM seems to shoot really well 90% of the time . I have to assume the new cases of the GMM help that a bit and then there's me helping the other direction
jwrowland77
New member
To hit 1000yds minimum velocities:
168gr-2775fps
175gr-2650fps
Plus you'll need to be accurate.
168gr-2775fps
175gr-2650fps
Plus you'll need to be accurate.
I can't give you any 30 cal gas gun feedback, but I've handloaded a LOT of 168's and 175's through my R700 Varmint 26" bbl and a 1-12" twist. Hands down I get the best consistiency and accuracy out of 168's. I really have yet to see any significant advantage with the 175's (which seems to be everyone's internet pet bullet) out of my rifle. I mostly shoot 200 meters and 600 yds. 4064 , and Win 748 are my go to powders.
jwrowland77
New member
Have you tried that new powder IMR 4166? I use a lot of IMR 4064, but have been fairly impressed with my test I've done using 4166 under 178's.
hooligan1 and jwroland77,
When you use ballistic software calculating downrange bullet velocity, be sure to input your elevation above sea level and air temperature. .308 Win 168-gr. bullets leaving 2600 fps have about 70" more drop at 1000 yards in Miami, FL than in Raton, NM with 90 F temperatures in both places. There's a 6600 foot difference in elevation; much thinner air at the NRA rifle range near Raton. The speed of sound varies with air temperature.
Sierra software says a 168 leaving at 2600 fps goes through the 1000 yard target in Miami at 1123 fps and in Raton at 1328 fps. Speed of sound's 1153 fps at both places.
I don't think bullets change paths exactly at Mach 1 for their environment. It's several fps above Mach 1 that they start; maybe 50 fps above as they slow down to it. That point may change depending on several things.
I've shot that M852 load in Garands at 580 and 6600 feet elevation in 1000 yard matches. At 580 feet, it wasn't as accurate with the same lot of ammo as it is at 6600 feet at the same temperature in the same rifle. Obviously, to me, sub sonic through the paper at 580 feet elevation.
When you use ballistic software calculating downrange bullet velocity, be sure to input your elevation above sea level and air temperature. .308 Win 168-gr. bullets leaving 2600 fps have about 70" more drop at 1000 yards in Miami, FL than in Raton, NM with 90 F temperatures in both places. There's a 6600 foot difference in elevation; much thinner air at the NRA rifle range near Raton. The speed of sound varies with air temperature.
Sierra software says a 168 leaving at 2600 fps goes through the 1000 yard target in Miami at 1123 fps and in Raton at 1328 fps. Speed of sound's 1153 fps at both places.
I don't think bullets change paths exactly at Mach 1 for their environment. It's several fps above Mach 1 that they start; maybe 50 fps above as they slow down to it. That point may change depending on several things.
I've shot that M852 load in Garands at 580 and 6600 feet elevation in 1000 yard matches. At 580 feet, it wasn't as accurate with the same lot of ammo as it is at 6600 feet at the same temperature in the same rifle. Obviously, to me, sub sonic through the paper at 580 feet elevation.
Last edited:
While i have had excellent results taking the 168 smk out to 600 yds the experts comment that the 168 should not be used beyond mid range. There is a lot of credible feedback that the 168 become unstable and can keyhole beyond 800 yds. Not sure exactly the issue but i believe it has to do with the angle of the boat tail on the 168's
Last edited:
I don't recall shooting 168s at 800, but I've shot tons of them at 600 and 1000. out of M14/M1As.
The shoot great at 600 but not so well at 1000. The often keyhole at that range.
Granted the M14/M1As are 22 inch barrels
In 24 inch barrels the 168s at normal gas gun velocities (M1s) will remain supper sonic at 1000+ but still, in my experience at not as accurate at 1000 as the 175s.
The OP mentioned 500 yards. Both are excellent at that range. But as others said, the 168s are cheaper.
As Bart mentioned, elevation makes a difference, I will add temp. to that.
I lived in Alaska, shooting for the Alaska NG Rifle team. Even summers are cooler when we shot then the lower 48.
An example: The Wilson Matches (NG Championships) were conducted in Little Rock in the late summer.
In AK, the temps were normally about 50* when we were practicing. 42 gr. 4895 gave us an average velocity of 2518, in Little Rock the temps. were closer to 95 which gave us an average velocity of 2578.
The altitude was pretty much the same.
We would go to 29 Palms each year. Weird there, you may find it warmer or colder, depending on which year. But the Altitude was a bit higher so that through your zeros out the window also.
You can use a BC program, but like reloading manuals they are guides and any info gained from them needs to be confirmed at the range.
All re-enforcing what I've preached forever...........you need to use a data/score book and record every change possible. Data gained from actual shooting.
The shoot great at 600 but not so well at 1000. The often keyhole at that range.
Granted the M14/M1As are 22 inch barrels
In 24 inch barrels the 168s at normal gas gun velocities (M1s) will remain supper sonic at 1000+ but still, in my experience at not as accurate at 1000 as the 175s.
The OP mentioned 500 yards. Both are excellent at that range. But as others said, the 168s are cheaper.
As Bart mentioned, elevation makes a difference, I will add temp. to that.
I lived in Alaska, shooting for the Alaska NG Rifle team. Even summers are cooler when we shot then the lower 48.
An example: The Wilson Matches (NG Championships) were conducted in Little Rock in the late summer.
In AK, the temps were normally about 50* when we were practicing. 42 gr. 4895 gave us an average velocity of 2518, in Little Rock the temps. were closer to 95 which gave us an average velocity of 2578.
The altitude was pretty much the same.
We would go to 29 Palms each year. Weird there, you may find it warmer or colder, depending on which year. But the Altitude was a bit higher so that through your zeros out the window also.
You can use a BC program, but like reloading manuals they are guides and any info gained from them needs to be confirmed at the range.
All re-enforcing what I've preached forever...........you need to use a data/score book and record every change possible. Data gained from actual shooting.
The OP is not shooting 1k and likely will never get there accurately with a 20" 308 AR . His goal is to shoot out to 500yds . From his 20" barrel . I still believe the 168s are the right bullet , 175 will work as well as many other weights out to that range but he only asked about the 168 and 175
Road Clam, you're right about the 168's boattail. It uses a 13 degree heel angle; thought best back in 1958 when that bullet first came out of Sierra's plant for its use in 300 meter international matches.
At the time, Sierra's 180 and 200 grain FMJBT bullets had a 9 degree heel about identical to the military's 172-gr FMJBT match bullet. That worked well for long ranges shot from both the .308 Win and .30-06 rifles. When Sierra hollow pointed those in the early 1960's as well as their new 190 grain version, that same boattail angle was used.
The US Army Rifle Team replaced their 7.62 NATO match ammo's 172-gr. FMJBT bullet with Sierra's new 180-gr. Hollow Point Match King bullet and it shot great; probably the best long range load every used in M14NM rifles with their 22 inch barrel. It remained supersonic to 1000 yards even cold weather at low elevations.
In the early 1980's, in a cost cutting venture, Sierra started using the same heel die on their 180 HPMK's as they did for their 168 HPMK's; the 13 degree angle one. The US Army Team got some of those and they didn't shoot all that well at 1000 yards. They were going subsonic at about 900 yards. So the Army Team contracted Sierra to make them special lots of 180 HPMK's with their original 9 degree boattail. Success again and great scores way down range.
Sierra's new 168 grain tipped Match King looks like its got a 9 degree boattail; much better than its original 13 degree one.
More info on such stuff:
http://bulletin.accurateshooter.com/tag/matchking/
At the time, Sierra's 180 and 200 grain FMJBT bullets had a 9 degree heel about identical to the military's 172-gr FMJBT match bullet. That worked well for long ranges shot from both the .308 Win and .30-06 rifles. When Sierra hollow pointed those in the early 1960's as well as their new 190 grain version, that same boattail angle was used.
The US Army Rifle Team replaced their 7.62 NATO match ammo's 172-gr. FMJBT bullet with Sierra's new 180-gr. Hollow Point Match King bullet and it shot great; probably the best long range load every used in M14NM rifles with their 22 inch barrel. It remained supersonic to 1000 yards even cold weather at low elevations.
In the early 1980's, in a cost cutting venture, Sierra started using the same heel die on their 180 HPMK's as they did for their 168 HPMK's; the 13 degree angle one. The US Army Team got some of those and they didn't shoot all that well at 1000 yards. They were going subsonic at about 900 yards. So the Army Team contracted Sierra to make them special lots of 180 HPMK's with their original 9 degree boattail. Success again and great scores way down range.
Sierra's new 168 grain tipped Match King looks like its got a 9 degree boattail; much better than its original 13 degree one.
More info on such stuff:
http://bulletin.accurateshooter.com/tag/matchking/
Last edited:
I see Bart posted while I was composing, so some of this duplicates his information.
I've had the 168's go unstable before hitting targets at either 748 yards at Gunsite (approximately 4500 ft altitude where we were shooting) and at 800 yards on Viale range at Camp Perry (574 ft altitude at the 800 yard line). I assume that's where Bart fired them at 1000 yards, since the Port Clinton airfield has an altimeter zero of 588 feet. Today this tool makes it easy to find an exact altitude.
I believe the difference is side wind.
The Gunsite shoot was at the old LR1 class where we had permission to fire across a valley at a local rancher's property, as that was longer than any ranges at the school at that time. We had a fairly steady side wind at about 20 mph, with the usual buffetting of momentary turbulent variations of a few mph. Everyone in the classes had PMC match ammo bought through the school that featured the 168 grain SMK. We could hit everything on the valley floor that we were directed to work at in sniper/spotter teams, except that 748 yard popper. I think I and maybe one other person were the only ones to have a shot connect with it, and that was by accident. The rounds from my 24" 10 inch twist Savage 10FP were going left, then right, then up or down. Another student with a European rifle with 300 mm (11.8") twist had the same issue. All correction attempts to correct by hold off our mil-dot sights turned into a bad game of chasing the spotter. If I'd read Jim Owens book on wind doping at that time, I suppose I might have squeezed out a second hit, but it really was unpredictable. Despite the wind being quite steady at our position, we all figured, at the time, that as the shots were firing across the valley to the opposite side, the problem must be gusting changes in wind speed on the way across that we just weren't detecting from our position.
The next year my dad and I took Mid Tompkins' Long Range Firing School, which used to be held at the end of the National Matches before the Iraq war. Marine Scout Sniper volunteers kindly served as our individual firing point coaches. At the first firing session before lunch on day 1 of the school, Mid started the class out at 800 yards. We had a good 10 mph cross-wind that was fairly steady at that time of day, but again with the usual turbulent buffeting. Well, as the sight-in proceeded, there was a lot of loud groaning and cursing up and down the line. It seemed a good 2/3 of the class had come with .30 caliber weapons shooting the 168 grain SMK's and none of us could stay on paper. The pits reported keyholing on the paper that was hit.
Fortunately for us, Kevin Thomas, who then still worked for Sierra, was also shooting in the school that year. He commented that the 168 had been designed as a 300 meter International bullet and that Sierra had been lucky that, as a bonus, it also shot really well at 600 yards, too, but he didn't recommend it beyond that. He said the 175 grain SMK didn't have this problem. So, there we had if from the horse's mouth, so to speak. When the lunch break came, those of use with ammo loaded with the 168's all ran to commercial row and got either Federal or HSM ammo loaded with the 175's to bring back after lunch. Bingo. No more keyholes. My first group on the 800 yard target after sighters was a 99 with a called 9 pulled at 4:30. No more trouble staying in the black, much less on the paper. I've been sold on that bullet ever since.
In his first book, Applied Ballistics for Long Range Shooting, Bryan Litz makes mention of this problem with the 168 grain SMK. He says it is due to a dynamic instability in the transonic range, which is about Mach 0.8-1.25 for that bullet. That translates to about 900-1400 fps at ICAO standard atmospheric conditions. A dynamic instability is one in which disturbances, like buffeting from passing between different velocity zones in air, tend to be over-corrected by the bullet, causing its nose to cone wider than necessary, inviting the overturning and yawing moments to flip it into a spin.
I know both Bart and Hummer70 have fired the 168 successfully at 1000 yards. Hummer70 even did it with a Palma barrel salvaged by setting back and cutting down to 24", so that would have been, I think he said, a 13" twist or a 13½" inch twist. So the problem is not lack of spin. I'd like to know if either of these gentlemen kept notes on wind conditions at the time to very of disprove my theory that its a side wind, or a wind buffeting issue.
The 168 and 175 grain SMK's both have tangent ogives in the vicinity of 7 calibers on the ones I've measured. The main difference is in the boattail angles, which are 13° and 9°, respectively. The combination of a 7 caliber tangent ogive and 9° boattail come from the old military 173 grain M1 bullet design which was done empirically in the post WWI era, IIRC. It's a combination that remains stable through the transonic region and it can be fired a long way. The world record 7.62 sniper shot by Sgt. Jim Gilliland of 1250 m (1367 yards) was made with this bullet.
Anyway, the bottom line is I don't trust the 168 to be stable beyond around and about 700 yards at 24" barrel .308 Win velocities. It obviously can be under some conditions, from Bart's and Hummer70's reports, but I haven't identified those right conditions for certain yet, and won't rely on getting them. So the 175 grain SMK has become my all-around precision bullet for .308 Win and .30-06. I still run the 168's at shorter ranges, though. They seem to be a little easier to get tight groups from at 100 yards.
I've had the 168's go unstable before hitting targets at either 748 yards at Gunsite (approximately 4500 ft altitude where we were shooting) and at 800 yards on Viale range at Camp Perry (574 ft altitude at the 800 yard line). I assume that's where Bart fired them at 1000 yards, since the Port Clinton airfield has an altimeter zero of 588 feet. Today this tool makes it easy to find an exact altitude.
I believe the difference is side wind.
The Gunsite shoot was at the old LR1 class where we had permission to fire across a valley at a local rancher's property, as that was longer than any ranges at the school at that time. We had a fairly steady side wind at about 20 mph, with the usual buffetting of momentary turbulent variations of a few mph. Everyone in the classes had PMC match ammo bought through the school that featured the 168 grain SMK. We could hit everything on the valley floor that we were directed to work at in sniper/spotter teams, except that 748 yard popper. I think I and maybe one other person were the only ones to have a shot connect with it, and that was by accident. The rounds from my 24" 10 inch twist Savage 10FP were going left, then right, then up or down. Another student with a European rifle with 300 mm (11.8") twist had the same issue. All correction attempts to correct by hold off our mil-dot sights turned into a bad game of chasing the spotter. If I'd read Jim Owens book on wind doping at that time, I suppose I might have squeezed out a second hit, but it really was unpredictable. Despite the wind being quite steady at our position, we all figured, at the time, that as the shots were firing across the valley to the opposite side, the problem must be gusting changes in wind speed on the way across that we just weren't detecting from our position.
The next year my dad and I took Mid Tompkins' Long Range Firing School, which used to be held at the end of the National Matches before the Iraq war. Marine Scout Sniper volunteers kindly served as our individual firing point coaches. At the first firing session before lunch on day 1 of the school, Mid started the class out at 800 yards. We had a good 10 mph cross-wind that was fairly steady at that time of day, but again with the usual turbulent buffeting. Well, as the sight-in proceeded, there was a lot of loud groaning and cursing up and down the line. It seemed a good 2/3 of the class had come with .30 caliber weapons shooting the 168 grain SMK's and none of us could stay on paper. The pits reported keyholing on the paper that was hit.
Fortunately for us, Kevin Thomas, who then still worked for Sierra, was also shooting in the school that year. He commented that the 168 had been designed as a 300 meter International bullet and that Sierra had been lucky that, as a bonus, it also shot really well at 600 yards, too, but he didn't recommend it beyond that. He said the 175 grain SMK didn't have this problem. So, there we had if from the horse's mouth, so to speak. When the lunch break came, those of use with ammo loaded with the 168's all ran to commercial row and got either Federal or HSM ammo loaded with the 175's to bring back after lunch. Bingo. No more keyholes. My first group on the 800 yard target after sighters was a 99 with a called 9 pulled at 4:30. No more trouble staying in the black, much less on the paper. I've been sold on that bullet ever since.
In his first book, Applied Ballistics for Long Range Shooting, Bryan Litz makes mention of this problem with the 168 grain SMK. He says it is due to a dynamic instability in the transonic range, which is about Mach 0.8-1.25 for that bullet. That translates to about 900-1400 fps at ICAO standard atmospheric conditions. A dynamic instability is one in which disturbances, like buffeting from passing between different velocity zones in air, tend to be over-corrected by the bullet, causing its nose to cone wider than necessary, inviting the overturning and yawing moments to flip it into a spin.
I know both Bart and Hummer70 have fired the 168 successfully at 1000 yards. Hummer70 even did it with a Palma barrel salvaged by setting back and cutting down to 24", so that would have been, I think he said, a 13" twist or a 13½" inch twist. So the problem is not lack of spin. I'd like to know if either of these gentlemen kept notes on wind conditions at the time to very of disprove my theory that its a side wind, or a wind buffeting issue.
The 168 and 175 grain SMK's both have tangent ogives in the vicinity of 7 calibers on the ones I've measured. The main difference is in the boattail angles, which are 13° and 9°, respectively. The combination of a 7 caliber tangent ogive and 9° boattail come from the old military 173 grain M1 bullet design which was done empirically in the post WWI era, IIRC. It's a combination that remains stable through the transonic region and it can be fired a long way. The world record 7.62 sniper shot by Sgt. Jim Gilliland of 1250 m (1367 yards) was made with this bullet.
Anyway, the bottom line is I don't trust the 168 to be stable beyond around and about 700 yards at 24" barrel .308 Win velocities. It obviously can be under some conditions, from Bart's and Hummer70's reports, but I haven't identified those right conditions for certain yet, and won't rely on getting them. So the 175 grain SMK has become my all-around precision bullet for .308 Win and .30-06. I still run the 168's at shorter ranges, though. They seem to be a little easier to get tight groups from at 100 yards.
My 24" Garand barrel that shot the M852 match ammo's Sierra 168's had a .299" bore and .3077" groove diameter; tight enough to let pressure build up higher and shoot them out a bit faster than normal.
Never shot them in winds more than about 6 or 7 mph at 1000 yards. I usually shot Sierra 180's or 190's from Garands when winds were stronger.
Never shot them in winds more than about 6 or 7 mph at 1000 yards. I usually shot Sierra 180's or 190's from Garands when winds were stronger.