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Thread: What Makes 175gr SMK better than 168gr?

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    What Makes 175gr SMK better than 168gr?

    Im shooting 168gr SMKs right now at 2625fps and finding that theyre dying out ~800m (agrees with what JBM says). I plug in data for 175gr SMKs with MVs posted by other members here and its saying that the bullets will go sub-sonic at around 900m.

    Im looking at pushing out to 1000m with my 308, and while I know 175 is a better choice, the calculations dont seem to support that.

    So what am I missing? what makes 175gr that much better than 168?

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    Its higher ballistic coefficient.
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    The higher X count at the end of the match ha! It's the angle of the boat tail that makes it fly better, Berger hybrid 168 are the exception. Those smoke all the other 168g bullets (308)

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    This^^^. The 168 SMK has terrible dynamic stability. Once it approaches transonic it's a crap shoot.
    You must be shooting out of a short barrel and near sea level to see the 175smk peeter out at 900m.
    I launch them at 2725 out of a 24"bbl and last i checked they didn't approach transonic until about 1300 yards at about 5,000ft DA
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    Quote Originally Posted by bodywerks View Post
    You must be shooting out of a short barrel and near sea level to see the 175smk peeter out at 900m.
    This is the issue...im only ~440ft above sea level. plugging in a higher altitude gave me similar results to yours. thanks!

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    Quote Originally Posted by chrisward3 View Post
    This is the issue...im only ~440ft above sea level. plugging in a higher altitude gave me similar results to yours. thanks!
    What is your barrel length? and twist rate?

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    I earnestly believe that the 13* boat tail on the 168gr class of .30 cal bullets is a marketing ploy to keep those rounds out of 1000y contention. Sierra is not the only company to manufacture dynamic instability as a means of forcing product line diversity.

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    Quote Originally Posted by bcrich View Post
    The higher X count at the end of the match ha! It's the angle of the boat tail that makes it fly better, Berger hybrid 168 are the exception. Those smoke all the other 168g bullets (308)
    They are better than the 175 as well .505 for sierra .515 for berger

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    Before the 175s came out, I did pretty well at 1000 yards (914 M) with Sierra 168s at 2700fps at about sea level. I don't know why everyone else has issues. Sure, they were keyholing on the target, but I shot some pretty decent scores shooting my .308 and 168s against the guys shooting heavy bullets in .300 Win.Mags. Has the boattail angle on the Sierra 168s always been the same?

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    Quote Originally Posted by MarineMD View Post
    What is your barrel length? and twist rate?
    20" 1-10 twist (Rem AAC-SD factory barrel)

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    The new berger 168 hybrid have even better bc than the 175 i think.

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    In my experience...800 yards is the max repeatable range with the 168's out of a .308 W.
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    Quote Originally Posted by chrisward3 View Post
    20" 1-10 twist (Rem AAC-SD factory barrel)
    Shoot 175's past 700, shoot 168's 700 and in...

    Your short barrel doesn't help you on speed.
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    the 175 shoot better.... because of better BC... the 175 will shoot 2 to 3 moa flatter at 1000 yards...

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    The 168 Sierra Match King was originally called the International was designed for 300m ISU competition, and was introduced in 1959. It wasn't designed to be a long range match bullet, but out to 800 yards, it does an excellent job at that. That was a long time ago the bullet has not been changed since then. Back then if you were shooting long range you were probably using a long action magnum round like the .300 H&H Magnum. The .300 Win. Mag. wasn't introduced until 1963 and long range rifle technology has advanced a lot since then. The 168 SMK is a great bullet and gives great accuracy until it starts to go transonic, which is why it's still around after 54 years. I believe the 175 Match King was designed as a replacement for the 173 gr. FMJBT match bullets made by Lake City and it was designed to stay supersonic in the 308 round to 1000 yards.

    In my experience at my range at about 500 ft elevation, the 168s begin to get unpredictable around 850 to 900 yards. At the last tactical match I shot at my club, which usually doesn't have shots in this match beyond 675 yards, the first three shots were from the back of the parking lot at targets at 955 and 925 yards. I missed the first shot a full mil high, corrected then hit the second shot. The third shot was at 925 and again I missed high by a mil. The ballistic solution from Ballistic FTE and Shooter was a full mil high, which means that the bullets true ballistic coefficient at transonic and subsonic velocities was way different than what my software predicted. The accuracy was good enough that I hit on the 2nd shot, but this was probably because in my rifle, with a 24" 1:11.25 Rock barrel, the bullet was optimally stabilized and was still accurate. If I had been shooting my 175 SMK load, the ballistic solution wouldn't have been off and I think I would have made hits on all three of those shots.

    When I run out of my stash of 168 SMKs, I'm going to shoot only 175 SMKs from here on.
    Last edited by m1match; 05-23-2013 at 10:13 PM.

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    Another alternative to the 168s are the various 155 grain bullets developed to follow the Palma/Fullbore rules.

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    I really don't know why folk are so set on the 175 SMK's for target shooting.

    The new 155 SMK part 2156 has a B.C of .505 matching that of the 175 SMK and you will achieve a much higher velocity out of your short barrel. They will also be lighter on recoil.

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    + 1 on what m1match said

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    Quote Originally Posted by m1match View Post
    When I run out of my stash of 168 SMKs, I'm going to shoot only 175 SMKs from here on.
    Hornady is more readily available in my part of Canada than SMK and costs me about 10 bucks less per box.....and I'm really not that good of a shot just yet to justify getting into Norma or Lapua Brass, SMK etc. etc. At this stage of my game I wouldn't know the difference. My main goal is to find the right recipe and produce in mass to work on my technique. The US gunpowder issue is prevalent a bit in Canada so most guys here buy whatever they can buy and do multiple load tests.

    That being said, for now I am running 168gr Hornady Match or A-Max (again based on availability) out of my Rem700AACSD. I know its capable of firing heavier rounds so I want to get up to 175-178-180gr neighbourhood.

    What would the differences be between 168-175-178-180 in terms of overall performance? (I'm new to reloading, sorry for beating a dead horse) Anything lighter than 165, to me anyways looks like I may as well be firing an SKS off hand upside down with my dominant eye closed, this is because of the 1:10 rifling that my stick has versus the usual 1:12 that most 700's in 308 come in.... am I right or am I wrong?

    Thanks in advance!

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    Quote Originally Posted by Scotch_egg View Post
    I really don't know why folk are so set on the 175 SMK's for target shooting.

    For me, it's the bullet my rifle barrel/chamber was built around and I'm too cheap to change it.
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    Quote Originally Posted by usafabrad View Post
    I earnestly believe that the 13* boat tail on the 168gr class of .30 cal bullets is a marketing ploy to keep those rounds out of 1000y contention. Sierra is not the only company to manufacture dynamic instability as a means of forcing product line diversity.
    The 168 SMK was designed in the 1950's specifically 300 meter shooting. It was never intended to be an LR bullet. However, at short-mid range they shoot lights out. When one is shooting competitively, it is best to get a bullet specifically suited to his needs. FWIW, the 175 ain't so hot for 1k either. It works, but it leaves a lot on the table when compared to the 185 Berger Juggernaut. I have only been to s few 1k matches, but none of the people that were in contention were shooting 175 SMK's at any of them...

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    Quote Originally Posted by Scotch_egg View Post
    I really don't know why folk are so set on the 175 SMK's for target shooting.

    The new 155 SMK part 2156 has a B.C of .505 matching that of the 175 SMK and you will achieve a much higher velocity out of your short barrel. They will also be lighter on recoil.
    The BC on the 2156 is .450. (this is an approximate average. you will not be traveling anywhere near 2700 fps at 1k yards in a 308) The only people that shoot those things at long range are the people who HAVE to (international Palma)

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    I'm curious on the 2156 - since I just bought some...

    running JBM with Litz G7 for both the 2156 and the 175 I get the following @ 1000 yds 10mph full value wind

    2156 - 2850 muzzle vel - 9.8 drop 2.8 wind
    175 - 2650 muzzle vel - 11.0 drop 2.9 wind

    Those both seem like reasonable muzzle velocities, and the clear winner is the 2156 - both are still supersonic at 1000.

    I guess I'll find out soon how they work for me.

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    Just for clarification, the 175 was designed at the request of LCAAP when they were developing the M118LR ammo some years back. The weight was set by them, with (as I recall) a limitation of the finished bullet to be between 150-175 grains. The old style 180SMK was an excellent Long Range bullet that was much favored by USAMU when their teams were still shooting M14s in 1,000 yard competition. Since it was redesigned with the short boat tail (same one used on the 168), it became essentially useless. The AMU continued to use the old style 180 SMK for some time afterwards, and there were special runs of the old style bullets run specifically for AMU contract orders. The 175 was basically an attempt to match the ballistic properties of the original M72/M118 bullet, the 173 grain FMJBT. Very good bullet out to 1,000 yards, but didn't have the accuracy of the OTM designs. The finished product pretty well accomplished that goal, and has been the standard bullet in the M118LR bullet ever since.

    While the 155 Palmas do have a similar BC, they can be a bit more problematic than the 175s. They (Sierra) had to violate several of their basic guidelines of bullet design to arrive at this bullet. The bearing surface of less than 1 caliber is a primary example. These bullets shoot very well in barrels, chambers and throats that are specifically set up for them. This usually entails a tight bored (.2985" is common) barrel, with a short throat and a 1x13" twist, normally finished at about 29"-30". They need this to achieve the 2950 fps that is required to reliably keep these bullets supersonic at 1K. In shorter barrels, or conventional .300" bore guns with somewhat faster twists, they may, or may not shoot as well as the heavier bullets. But chefcam864 is perfectly correct here; we don't use 155s because they're the best bullets for this job (they aren't) but because that's what the rules require for this game. Note that most US shooters who build "Palma" guns that they don't intend to use in matches governed by International Palma rules, usually go with faster twists, and use heavier, higher BC projectiles. Like I said, they're what the rules require, but not what is necessarily best.
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    Quote Originally Posted by ksthomas View Post
    Just for clarification, the 175 was designed at the request of LCAAP when they were developing the M118LR ammo some years back. The weight was set by them, with (as I recall) a limitation of the finished bullet to be between 150-175 grains. The old style 180SMK was an excellent Long Range bullet that was much favored by USAMU when their teams were still shooting M14s in 1,000 yard competition. Since it was redesigned with the short boat tail (same one used on the 168), it became essentially useless. The AMU continued to use the old style 180 SMK for some time afterwards, and there were special runs of the old style bullets run specifically for AMU contract orders. The 175 was basically an attempt to match the ballistic properties of the original M72/M118 bullet, the 173 grain FMJBT. Very good bullet out to 1,000 yards, but didn't have the accuracy of the OTM designs. The finished product pretty well accomplished that goal, and has been the standard bullet in the M118LR bullet ever since.

    While the 155 Palmas do have a similar BC, they can be a bit more problematic than the 175s. They (Sierra) had to violate several of their basic guidelines of bullet design to arrive at this bullet. The bearing surface of less than 1 caliber is a primary example. These bullets shoot very well in barrels, chambers and throats that are specifically set up for them. This usually entails a tight bored (.2985" is common) barrel, with a short throat and a 1x13" twist, normally finished at about 29"-30". They need this to achieve the 2950 fps that is required to reliably keep these bullets supersonic at 1K. In shorter barrels, or conventional .300" bore guns with somewhat faster twists, they may, or may not shoot as well as the heavier bullets. But chefcam864 is perfectly correct here; we don't use 155s because they're the best bullets for this job (they aren't) but because that's what the rules require for this game. Note that most US shooters who build "Palma" guns that they don't intend to use in matches governed by International Palma rules, usually go with faster twists, and use heavier, higher BC projectiles. Like I said, they're what the rules require, but not what is necessarily best.
    You seem to be the expert. For my purposes based on my earlier post am I putting myself ahead with sticking with 168gr? I have Hungarian cheapskate blood in my veins so for now I can't justify to myself to spend the extra coin on SMK while I work on my long range technique and master reloading.

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    I'm not Kevin, and yes he is the expert, but if I were in your shoes, I'd stick with your Hornady 168s since they are less $$ but more importantly you can get them in this environment. Hone your skills within the range limitations of your rifle/ammo combo and once your skills are at a high level then think about what you need to push out further.

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    It's a whole different world when you go from western elevation of 5k to eastern elev. where 700-800 is common. At 5k elevation it's sort of like hitting a golf ball while standing on the moon, the sucker never comes down!! lol. We in the east have to use 185 or better to consistently stay ss @ 1kyds or either send a 175 at around 2750, depending on wind. Even cross wind will rob you of vel.

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    Quote Originally Posted by ksthomas View Post
    Just for clarification, the 175 was designed at the request of LCAAP when they were developing the M118LR ammo some years back. The weight was set by them, with (as I recall) a limitation of the finished bullet to be between 150-175 grains. The old style 180SMK was an excellent Long Range bullet that was much favored by USAMU when their teams were still shooting M14s in 1,000 yard competition. Since it was redesigned with the short boat tail (same one used on the 168), it became essentially useless. The AMU continued to use the old style 180 SMK for some time afterwards, and there were special runs of the old style bullets run specifically for AMU contract orders. The 175 was basically an attempt to match the ballistic properties of the original M72/M118 bullet, the 173 grain FMJBT. Very good bullet out to 1,000 yards, but didn't have the accuracy of the OTM designs. The finished product pretty well accomplished that goal, and has been the standard bullet in the M118LR bullet ever since.

    While the 155 Palmas do have a similar BC, they can be a bit more problematic than the 175s. They (Sierra) had to violate several of their basic guidelines of bullet design to arrive at this bullet. The bearing surface of less than 1 caliber is a primary example. These bullets shoot very well in barrels, chambers and throats that are specifically set up for them. This usually entails a tight bored (.2985" is common) barrel, with a short throat and a 1x13" twist, normally finished at about 29"-30". They need this to achieve the 2950 fps that is required to reliably keep these bullets supersonic at 1K. In shorter barrels, or conventional .300" bore guns with somewhat faster twists, they may, or may not shoot as well as the heavier bullets. But chefcam864 is perfectly correct here; we don't use 155s because they're the best bullets for this job (they aren't) but because that's what the rules require for this game. Note that most US shooters who build "Palma" guns that they don't intend to use in matches governed by International Palma rules, usually go with faster twists, and use heavier, higher BC projectiles. Like I said, they're what the rules require, but not what is necessarily best.
    Kevin, do many Palma shooters still shoot a tight bore? I was under the impression that that came about because of undersized ammo issued by some Commonwealth countries and that since this ammo is no longer issued the need for a tight bore has been negated. Is this the case? I don't really know any Palma shooters, so I'm kind of curious.

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    Quote Originally Posted by Scotch_egg View Post
    I really don't know why folk are so set on the 175 SMK's for target shooting.

    The new 155 SMK part 2156 has a B.C of .505 matching that of the 175 SMK and you will achieve a much higher velocity out of your short barrel. They will also be lighter on recoil.
    Wholeheartedly agree been shooting the 168 and 175 grainers a long time but that 2156 bullet from sierra is outstanding