175gr BTHPs/.308 with 1 in 12" twist

This is a discussion on 175gr BTHPs/.308 with 1 in 12" twist within the Cartridges & Calibers forums, part of the Sniping Related category; I know that the slower twist rates work better with lighter bullets, but can I shoot a 175gr. bthp out of my 700P which has ...

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  1. #1
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    175gr BTHPs/.308 with 1 in 12" twist

    I know that the slower twist rates work better with lighter bullets, but can I shoot a 175gr. bthp out of my 700P which has a 20" barrel and a 1 in 12" twist? What type of performance can be expected? I'm trying to milk a little more range out of my setup.

  2. #2
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    You will be able to push 155 scenars out to 1200 yards with a 20" barrel.
    You could have been able to push 155 scenars out to 1300 yards with a 24" barrel.
    {I don't remember anything about 175s.....}

    175s prefer 11.25 twist rate, but in realistic terms, a 1:12 is just fine as long as you are not shooting at sea level under high pressure in 0dF conditions. Add altitude, temperature, or more typical atmospherics, and you will be fine.

  3. #3
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    ...... you really should give 155 Lapua Scenars a try animalspooker ..... unless you are wanting a projectile for hunting only.

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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    Have not heard of the Scenars. I've always shot and hunted with 150 gr. shelf ammo. Now that FGGM 165s are getting cheaper I've started buying them. I've always read and heard that the 165s don't have the range of the 175s. Going to a 155 sounds backwards. What can you all tell me about the Scenars? Who makes 'em? I'll do some research.

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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    They are made by Lapua in Finland.

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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    Quote Originally Posted by animalspooker
    Have not heard of the Scenars. I've always shot and hunted with 150 gr. shelf ammo. Now that FGGM 165s are getting cheaper I've started buying them. I've always read and heard that the 165s don't have the range of the 175s. Going to a 155 sounds backwards.
    Imagine a 155 bullet that has the ballistics of the 175 SMK, and the weight of (ahem) a 155. This means that one can push them to 2925-2950 fps reliably and without exceeding pressure limits in the little 308 case. So, we have a 175 SMK set of ballistics flying 250-300 fps faster than the 175 SMK. So, instead of 40 MoA drop to 1000 yards, one only has 30 MoA drop.

    Now to be fair, the 155 Scenar (Lapua), the 155.5 Full Bore (Berger), and the 155 SMK (2156::Sierra) are all nip and tuck in the high BC game, as the bullet manufactures turn their modern bullet efforts toward the PALMA shooters.

  7. #7
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    Have you found any one of the three 155(.5) projectiles you mention to have an advantage over the other two Mitch?

  8. #8
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    I've spent a fair amount of time researching this and am still somewhat in the fog, but I'll give you what I've got.

    The 175's will shoot OK out of a 20" barrel, but they seem to be much more suited to a 24" or 26" barrel, where you can burn a slight slower powder completely behind them. As to twist, 1:12 seems to be just barely enough.

    There are some Berger VLD 175's that have a higher BC than some of the others, but they are long and not well suited to something like a 700P which has a long throat and is magazine fed.

    Some time back, the 155's showed up on the Palma scene and are the heaviest bullet allowed for that. The Lapua and Berger are the clear front runners in the BC game but the Sierra are not far behind. The interesting thing is that, from everything I have read and all the numbers I have run, the Sierra should be just as good as the other two in a stock rifle (particularly a 20" barrel). If you want to try the Sierra, just be sure you get the newer 2156 part nbr as there is an older 155.

    FWIW, I'm waiting on supplies and the weather, but I'm going to try Nosler 155's over H4895. The published BC is not quite as high as the Sierra but they are cheaper to play with (plus I bought a bunch from a fellow I know at a discount) and the numbers don't seem to be that much different (about 2" more drop at 500yds). I'm using that powder because it's faster than something like Varget which should allow for a complete burn in a 20" barrel.

    Disclaimer: I'm not an expert and don't play one on TV. Offer not valid in all states.
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    The 175s/178s work just fine in a 20" barrel. I have been using them for years. Get around 2690fps from them pushed by Varget.

    Also there are quite afew people shooting the 208 AMAX out of 12 twist rifles.

    Another bullet to look at is the new Hornady 178 BTHP which has a .530 BC. Not overly long so it should be able to be loaded to factory mag length of around 2.820" and be pushed to good speeds.

    I have never shot 155 bullets so can't comment on them.

  10. #10
    Senior Member gsmithplm's Avatar
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    Re: 175gr BTHPs/.308 with 1 in 12" twist

    [quote="Rob01"the new Hornady 178 BTHP which has a .530 BC.[/quote]
    I found the bullets at Hornady, but the page at Hornady that searches take me to seems to be primarily sales and has very little info. I'm sure that they have a page somewhere with ballistics info on their bullets, but I don't know where. It's very annoying.
    Graham Smith, SFC, US Army (Ret)
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