190gr 7mm Berger Long-range hybrids for SAUM?

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John Weigel
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Joined: Sat Dec 26, 2020 8:51 am

190gr 7mm Berger Long-range hybrids for SAUM?

#1 Postby John Weigel » Wed Apr 21, 2021 12:33 pm

Has anyone worked with these fairly new projectiles in 7mm SAUM (or WSM) yet? My guess is that the shift from 2209 to 2213sc is warranted? Due to the short life of SAUM barrels, I'd prefer to know of the experience of others to gain a starting point before embarking on load development. Cheers,
John

Hybrid284
Posts: 6
Joined: Tue Mar 28, 2023 11:08 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#2 Postby Hybrid284 » Tue May 02, 2023 2:51 am

Although an old thread does anyone have any advice? Thanks

Bretto77
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Joined: Thu Sep 09, 2021 2:47 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#3 Postby Bretto77 » Tue May 02, 2023 1:57 pm

I’m about to embark on this very soon as I have a few and want to get them running in my RSAUM have read a few posts about them being good and bad on the accurate shooter forum so maybe if there’s a few of us would take less working out.
Maybe just load some up 30 thou jump and see how they go will load some up and see this weekend.

Hybrid284
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Joined: Tue Mar 28, 2023 11:08 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#4 Postby Hybrid284 » Tue May 02, 2023 2:49 pm

I'll update when I can get some testing done. My guess is about 2900fps max but I could be wrong. Hopefully someone can give us a head start. Cheers.

Bretto77
Posts: 22
Joined: Thu Sep 09, 2021 2:47 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#5 Postby Bretto77 » Tue May 02, 2023 3:53 pm

Yeah I’ll do the same but I’m thinking les speed than that with the 190’s but time will tell.

willow
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Joined: Sat Aug 15, 2015 9:51 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#6 Postby willow » Tue May 02, 2023 9:11 pm

Tried them in a 7mm SAUM improved, barrel was a 32" 8 twist and ran them at speeds up to 2900fps. It was easy to get great ES and SD figures with them but ultimately I couldn't get them to shoot with a variety of powders, primers and seating depths.

BRETT B
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Location: PERTH

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#7 Postby BRETT B » Wed May 03, 2023 12:59 am

I used them in my 7 Saum IMP with 2209 at 2840 and they hammered. Shot as good as 180 class bullets .
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

williada
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Joined: Wed Jul 22, 2009 12:37 am

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#8 Postby williada » Sat May 06, 2023 5:25 pm

We can get rifles to shoot at specific ranges. We can get the low SD's and extreme spread and they shoot well up to middle distance. At long range, it is vital to get low extreme spreads and low SD's to reduce vertical. This has more to do with reducing variable ignition which causes the bullet to exit when the muzzle is in a different position. The seating depth also has an effect variable ignition, but its influence extends to the barrel harmonics which is an important element of tuning at long range in the sense that it influences the size of the bore at the muzzle with the goal to minimise bore expansion on projectile exit which reduces group size. Shockwaves prior to bullet exit change bore size. Seating depth affects the timing. The fundamental whip also influences the vertical position of the muzzle and this is influenced by the combination of shooter mass if not free recoiling, the centre of gravity of the rifle in relation to bore and so at a specific range a rifle may positively compensate some variable ignition. So tuning, involves looking for optimum performance across three broad factors. One swallow is not predictive of a summer coming.

The quest to use heavier bullets to increase BC to reduce wind drift becomes marginal for an all round rifle in my opinion because of the bullet stability factor in different atmospheres of barometric pressure. By this I mean, the optimum twist rate becomes finicky.

It becomes more finicky at 1000 yards when the projectile is on the downward trajectory. I commented about this phenomenon over 20 years ago when doing ballistic testing for the NRAA from a machine rest at 1000 yards at Rosedale having sent hundreds of rounds down the range with different paired barrels of different twist rates and different internal dimensions of bore and groove.

Previous studies by bench rest shooters at short range have advocated a minimum twist to minimise the effect of jacket and core imperfections because in an overstabilzed bullet, there was a tendency to yaw off if the jacket was thicker on once side or perhaps the core was misaligned. Over long range and shooting for score that is not an issue unless you only shoot up to 500 yards because yaw at the other end of the trajectory poses a greater problem with insufficient stabilzation.

Bullet quality and meticulous sorting can reduce some imperfections for long range. Litz demonstrated a minimum stability factor of 1.5 was more reliable. I certainly think so where much of the bullet momentum can be maintained, but at 1000 yards, the angle of attack is steep and the the bullet is losing a lot of energy even if it remains above the transonic speed. As a bullet slows, its comparative BC also reduces along with a greater tendency to tendency to yaw and enlarge groups which can be recognized by their elliptical shape. A round group is what you should be looking for even if it is a tad larger at long range.

There may be a compromise with a lighter bullet driven harder but of critical length to match the best stability factor. I check different bullet lengths against the predicted outcomes. Also there is a reduced time of flight which reduces wind variables, particularly over long range. It is group size that matters. Otherwise the stability factor has to be increased with a faster twist rate to maintain group size across different atmospheric conditions. The stability factor required maybe closer to 1.75 for heavier bullets as a maximum for long range due to the downward trajectory.

If we look at Willow's figures, this could explain his results. Have a look at the tables below which highlights how a small change in twist rate has a big effect on stability. To match your heavy projectile with an optimum twist rate, you have to get a barrel made in tiny 0.1 increments. Only a custom barrel maker can do this. I did not publish these, but I can assure you this is why I think heavy bullets are not everything. When you also consider recoil, time of flight and getting a barrel to match the best bullet stability factor. A lighter bullet will perform well in a variety of atmospheric conditions across more distances. I shoot a 7mm SAUM. There have been a lot of fads over the years, but you can't beat learning to read conditions and knowing your gear.
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williada
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Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#9 Postby williada » Sat May 06, 2023 5:45 pm

Trying again to upload the stability file again.
Stability of 190 Berger.jpg
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Bretto77
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Joined: Thu Sep 09, 2021 2:47 pm

Re: 190gr 7mm Berger Long-range hybrids for SAUM?

#10 Postby Bretto77 » Sat May 06, 2023 8:27 pm

It’s more of a point of trying to get projectiles to work what we can actually get hold of as with the diminishing amount we have all got to allocate between us now days it’s hard to get hold of anything let alone what we would really like to use so for me I could get hold of some 190s so got them and I will get them to work maybe not as great as a 180 hybrid but it’s all we can do is use what we can get hold of I guess.


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