Cutting down 308

[Pipthedog]

My concern was that of impact velocity. If I am not doing 1,800fps when I hit the deer with a Barnes ttsx 130gn I understand that it potentially will not open. So I need to work out what is the maximum range I can shoot at.
That’s when I wonder if my 18” 308 barrel with a 1:11 twist was a mistake.

 

[MarinePMI]

AI used to offer the AX "Covert" rifle that had a 16.5" 308 barrel, if that tells you anything.

 

[scotch_egg]

My concern was that of impact velocity. If I am not doing 1,800fps when I hit the deer with a Barnes ttsx 130gn I understand that it potentially will not open. So I need to work out what is the maximum range I can shoot at.
That’s when I wonder if my 18” 308 barrel with a 1:11 twist was a mistake.

Even at 2300fps at the muzzle according to Ballistic AE you would be achieving 1800fps at 200m

I should imagine you will be achieving well above 2300fps at the muzzle. Depending on time I might swap back to the 16” .308 barrel next week when at the range and check my MV with the 130gr TTSX.

 

[Jamie020]

You should be fine.

With 45.5gr of N140 I'm getting 2750fps at the muzzle from a 20.5inch barrel with 150gr Nosler BT's.

At 500yards the bullet is still travelling at 1800fps (enough to mushroom) with over 1,000ft/lb of energy. Which is beyond the distance I'd personally want to shoot deer. What's the max distance you intend to shoot at?

Say you were achieving 2600fps at the muzzle out of an 18inch barrel with factory ammo, the bullet would still be doing more than 1800fps at 400yards with over 1,000ft.lb of energy. Plenty!

 

[Pipthedog]

Thanks for your thoughts.
Most of my shooting is at the 75-150m range.
It’s more about knowing what the maximum range is that I could take a shot at and be confident that the bullet would mushroom.
I have bought some N133 and was planning on using that to build a load that I could be confident that the bullet would still be doing more than 1800 fps out to say 300m.

 

[Jamie020]

Thanks for your thoughts.
Most of my shooting is at the 75-150m range.
It’s more about knowing what the maximum range is that I could take a shot at and be confident that the bullet would mushroom.
I have bought some N133 and was planning on using that to build a load that I could be confident that the bullet would still be doing more than 1800 fps out to say 300m.

With N133 vit's data (min/max) indicates approx. 2700 to 2900fps out of a 24" barrel. If we estimate a worst case reduction of 200fps due to 18inch barrel compared with their tested 24inch, you should still be able to achieve 2500 to 2700fps.

Again worst case, if 2,500fps is achieved at the muzzle, .35 BC of the 130gr TTSX, would give 1,800fps at 275m (just under 1,000ft/lb energy).

So yeah, I think you could be confident you'll be able to work up a load that'll suit your needs out to 300m.

 

[PhilRS03]

You’ll be seeing around 2350 fps using something like a 185gr bullet. Shooting something like 168gr Gold medal match maybe 2370 from a 16” .308. The only limiting factor for .308 length really is the law. For anything out to 400m you’d be absolutely fine with a 12.5”!

 

[Pipthedog]

That’s very useful. Thank you.

Does that factor in the 1:11 twist?

Could you still achieve 1800 fps at 300m with a 16” barrel?

 

[johnboy57]

Try the Search feature on here and it will show lots of info you are looking for.
Cheers, Ken.

The deer won't know the difference when you pull the trigger they still going to fall over dead just make sure the barrel has been recrowned properly
I have 2 x308s a Forbes UltraLite51/4 pound rifle with a 21" barrel and a Tikka t3x that has been cut to18" from 22" and it is accurate as. makes it easy to get through the thick scrub when on my back. one of my mates has cut his barrel to 16" for the same reason and I would call that a true bushpig rifle and it still works fine so don,t panic just do it

 

[scotch_egg]

That’s very useful. Thank you.

Does that factor in the 1:11 twist?

Could you still achieve 1800 fps at 300m with a 16” barrel?

Twist rate isn’t an issue with such a light weight bullet. The bullet will be stabilised.

Admittedly it has been found that spinning a lower velocity bullet does assist with expansion, this really only means anything when applying it to subsonic loads.

The bullet will be travelling fast enough to expand reliably as per the manufacturers data so this is a non issue.

 

[jthyttin]

Out of the supersonic bullet I've used, only Woodleigh gives reasonable impact velocity ratings. Especially in monolithic bullets manufacturers like Nosler and Barnes quote the lower limit where bullet barely expands. You'd like to add at least 10% to their figures, and 20% if you want the performance not to drop.

Barnes techs usually suggest "few hundred fps over". And the limit is not universal, you have to find it out for every bullet and there's some surprises. Sadly Barnes doesn't list the velocities no longer on their web page.

Nosler is at least open with their claims, showcasing typical bullet expansion at different speed levels, see e.g. (the pic is 30cal 168gr E-Tip at 1800fps)

Expansion Tip® Bullets

Expansion tip bullets provide amazing stopping power and peerless penetration over a broad spectrum of impact velocities, rivaling even the highest quality lead-core bullets.

www.nosler.com

In personal testing, I've found Barnes to expand even less. Here's Barnes 130 TSX shot to wetpack at 1750fps. Barnes quotes the same 1800fps minimum as for the 130 TTSX.

 

[Pipthedog]

Thanks. That’s my concern. I don’t want to pencil through deer. Especially shooting on the edge of plantations.
Looks like I will need to factor in a fair bit of margin.

 

[jthyttin]

Found another, sorry for crappy quality (not focused correctly). This is what to expect about 200fps over advertised minimum. 30cal 110 TSX shot to wetpack at 2090fps, Barnes lists 1900fps as minimum.

Expansion still somewhat uneven, expanded to 13mm (1.7x diameter). About 4mm of expansion cavity intact.

 

[Pipthedog]

Encouraging but not amazing.

Did you test many .30 cal non toxics?

 

[jthyttin]

I haven't done any thorough testing of different manufacturers and weights since there's no personal need. In fact most of the testing has been for someone else.

If you're concerned about the distance, you should really move to better BC bullet. Since it usually means heavier, it also helps at short distance since impact velocity is lower. But in your case, if keep the 300m as maximum it doesn't really matter. I think you can get to 900m/s with 130 TTSX so shorter range impact velocities are reasonable and at 300m the velocity figures are a tie with something like 150gr E-Tip.

IMHO 150gr monos are best match for general use 308. You get nice BC (trajectory and velocity retention), nice velocity, and penetration is enough for larger/tougher game like moose and wild boar. I used to shoot 150gr E-Tip at 870m/s from 20". Went back to previous load (165gr Accubond/BTip) since it happened to match the POI of reduced 125gr AB/BT load I also use.

 

[Pipthedog]

That’s useful. Thank you.

 

[scotch_egg]

Thanks. That’s my concern. I don’t want to pencil through deer. Especially shooting on the edge of plantations.
Looks like I will need to factor in a fair bit of margin.

I would be choosing one of the U.K. made bullets if I’m really honest. If you’re wanting to put animals down fast and to be honest that’s what I want to do. Meat damage is a secondary concern and you need to recover the animal to get the meat in the first place. The English non lead bullets appear to be machined with relief cuts to ensure expansion or even loose petals to ensure vitals are hit should the shot placement be far from ideal. Which some criticise yet is a great feature IMHO.

Yes Tree bullets have huge meplats to ensure expansion and Virtus have the petal that shed.

Found another, sorry for crappy quality (not focused correctly). This is what to expect about 200fps over advertised minimum. 30cal 110 TSX shot to wetpack at 2090fps, Barnes lists 1900fps as minimum.

Expansion still somewhat uneven, expanded to 13mm (1.7x diameter). About 4mm of expansion cavity intact.

View attachment 298838

How were you testing velocity on impact? Labradar?

Realistically no matter how much people want to, the reality is you won’t be shooting Boar in the U.K. so developing a load on the off chance is a waste of some and effort. Have a deer load and stick with it.

 

[jthyttin]

How were you testing velocity on impact? Labradar?

Traditional chronograph in front of wetpack. In the beginning I tested regular loads at distance compared to reduced loads at short range. Since there was no difference (when velocity was same) I've mostly moved to reduced loads at short range. If I need to test something like marginally stable, tumbling bullets at subsonic velocities, I still shoot at distance.