The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

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:

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?

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

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.

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.

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

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.

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