Terminal velocity

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All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should treated as suspect and not used.

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Forum rules
All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should be treated as suspect and not used.

Use reloading information posted here at your own risk. This forum (http://www.full-bore.co.uk) is not responsible for any property damage or personal injury as a consequence of using reloading data posted here, the information is individual members findings and observations only. Always verify the load data and be absolutely sure your firearm can handle the load, especially older ones. If in doubt start low and work your way up.
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johngarnett
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Terminal velocity

#1 Post by johngarnett »

This is a question for FTR'ers and TR'ers!

What muzzle velocity will still be supersonic and stable at 1000yds in 308 using 190 SMK please?


I have an idea from the various calculators available but I wonder if anyone has real info and data please?


(12T 30" barrel, Powder prob Vit150)

Thank you

JohnG :cornwall:
Racalman
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Re: Terminal velocity

#2 Post by Racalman »

How far above supersonic do you want to be?

I don't have any real data, but according to the Shooter app and Bryan Litz's data for that bullet, an MV of 2600fps will give a terminal velocity of 1200fps.

Does that match your estimates?
johngarnett
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Re: Terminal velocity

#3 Post by johngarnett »

Just want to be out of the transonic zone. I had found 2700fps should clear it. I just wanted confirmation from 'the real world'!!
Thank you
JohnG
Racalman
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Re: Terminal velocity

#4 Post by Racalman »

I use 185gn Bergers with N150 and an MV of 2660fps. The shooter app predicts a 1,000 yard velocity of 1293fps.

The Berger has a G7 BC of 0.283 while the 190gn SMK is 0.268 so they're not worlds apart.
Laurie
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Re: Terminal velocity

#5 Post by Laurie »

It shoots well at 1,000 at around 2,600 fps MV. This will be transsonic, but the old 190, 200 and 220 Sierra MKs, especially the 190 version, were well known for their excellent manners in trans and even subsonic flights. The 'Match Rifle' people used them for their 1,000/1,100/1,200 matches until the current generation of 210gn, later uber-high BC 200gn, long-range bullets came into use maybe 10 years ago. The 185gn Berger Juggernaut is a better bullet though in this weight class and easier to attain respectable terminal velocities.

Work done by the US Army in the early days of 7.62 match and sniper ammo development with the old 173gn FA Match FMJBT variant of the inter-wars M1 service ball ammo bullet found that a terminal speed around 100 fps higher than the pertaining speed of sound, ie ~1,225 fps, was critical. Drop below that and groups sizes and wind induced movement grew by over 50%. That may be bullet design specific, but I suspect it applies to most longer boat-tailed designs. That is borne out by user feedback on the US M118LR sniper round loaded with the 175gn SMK which has an nominal MV around 2,650 fps IIRC, but many rifles in service probably produce less depending on usage. Despite it being a claimed 1,000 yard-accurate round, the US Marine Corps which takes its sniping very seriously says performance drops off a cliff beyond 800 metres, or getting on for 900 yards. At 2,650 fps MV it's calculated to be doing around 1,235 fps at 900 in standard ballistic conditions.
johngarnett
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Re: Terminal velocity

#6 Post by johngarnett »

Gentlemen, thank you for your replies. Much appreciated.
For years I have sworn by 155 Lapuas over N140/TR140/RS50 but having just tried N150 and 190SMK together ('cos I had some!) I'm getting one hole groups at 100yds which can only be good at 1k yds!!
1k is not very often but if I do I would like to think my ammo will make it.
Back to the reloading bench!! Just going to check the FTR rules re 'heavier than 155'
Thank you again
JohnG
Laurie
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Re: Terminal velocity

#7 Post by Laurie »

There are no restrictions on bullet weight in F/TR. (There are in some countries, but not here or the USA.) So unless your club has a 'local' restriction, you can use any bullet that takes your fancy.
johngarnett
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Re: Terminal velocity

#8 Post by johngarnett »

Thank you Laurie and thank you for all your information on various forums (fora - plural?!) over the years. I've been searching for various subjects and your replies are most educating.

JohnG
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