Thanks will try, how temp sensitive is Vhit N570
7mm stw with 195 berger eol
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I'm running it in my 338 Edge +P and this STW with near 0 temp sensitivity from 0 F to 75 F. I'm using a correction factor of .17 fps/deg in my AB app that I verified with my Kilo 2400ABS. I haven't shot either in really hot weather however. With both rifles I was able to find a flat spot toward the top that produced great results. For example, I shot a 12 shot group with charge wts. of 80, 80.5, 81, and 81.5 grains that had 1.25" of vertical dispersion at 665 yards. I believe finding these flat spots really negates the temperature swings that occur with other powders.
Jack R Tishue Jr
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willowwolfe1975
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Ya, I have checked there, but there is no data for the 195 EOL yet. At least that I can find.
I have now received data from Berger for Retumbo and IMR 7828
this is the data given to me:
Retumbo
Start 74.5
Max - 78.2 (2866 f/s)
98% capacity
IMR 7828
Start - 67.0
Max - 70.3 (2849 f/s)
92% capacity.
COAL - 3.759
However, there is still no data for the 7977. I am really hoping to get this as where I live the temperature varies considerably and using a temperature insensitive powder is beneficial.
I was provided an email address for a fellow who should have data for the 7977 (contact provided by Berger). However, I still have not heard back from him. If/when I do I will post.
I have now received data from Berger for Retumbo and IMR 7828
this is the data given to me:
Retumbo
Start 74.5
Max - 78.2 (2866 f/s)
98% capacity
IMR 7828
Start - 67.0
Max - 70.3 (2849 f/s)
92% capacity.
COAL - 3.759
However, there is still no data for the 7977. I am really hoping to get this as where I live the temperature varies considerably and using a temperature insensitive powder is beneficial.
I was provided an email address for a fellow who should have data for the 7977 (contact provided by Berger). However, I still have not heard back from him. If/when I do I will post.
willowwolfe1975
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Okay, thanks.
I have heard other people say they are not too impressed with the 195 EOL in 7mm. I was excited to try this bullet and now have 500 bullets so I guess I'd better get to like it.
Hopefully I'll find a sweet load.
willowwolfe1975
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Thats good to hear about the 7828. I was worried about that as here in Northern Saskatchewan the temp swings are pretty substantial. I was hesitant on getting the 7828, but with the limited types of powder I can readily get my hands on I had to go with what was available.
Still need data for the 7977 in the STW with 195 EOL......
willowwolfe1975
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For anyone interested....
I received a call from Berger today with brand new data for 7mm STW using 195 berger EOL and IMR 7977.
26" barrel
1:8 twist
C.O.A.L = 3.753 (shorter than COAL given for retumbo and 7828 [3.759])
START - 69.5 IMR 7977 (2629 f/s)
MAX - 73.0 IMR 7977 (2754 f/s) 94% capacity
Tomorrow I start my testing with Retumbo, IMR 7828, and IMR 7977.
Ill post results.
I received a call from Berger today with brand new data for 7mm STW using 195 berger EOL and IMR 7977.
26" barrel
1:8 twist
C.O.A.L = 3.753 (shorter than COAL given for retumbo and 7828 [3.759])
START - 69.5 IMR 7977 (2629 f/s)
MAX - 73.0 IMR 7977 (2754 f/s) 94% capacity
Tomorrow I start my testing with Retumbo, IMR 7828, and IMR 7977.
Ill post results.
MudRunner2005
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That seems incredibly low in both charge and velocity... I'm using 71gr of 7828 SSC with a 180 Hybrid and getting right at 3K. The 7mm STW has a very similar case capacity to the .300 Weatherby (only 7gr difference). And with a 210 Berger, my .300 Ackley (.300 Wby Imp.) is showing pressure signs around 83-84 grains of 7977 pushing it at right at 3,000 FPS MV.
willowwolfe1975
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Thanks for the information.
I only have to go on what I was given by Berger. With that said, tomorrow I hope to start developing loads. I prepared loads in 0.5g increments from min to max on the data given for all 3 powders (Retumbo, 7977, and 7828).
Do you run your bullets long?
I was wondering about the increased powder that you use, and I took some measurements of the COAL compared to the Olgive measurement using the Hornady COAL tool. I found that the 3.760 COAL with the olgive to base measurement of 2.999 using the Berger 195 EOL is the same jump from olgive to lands as my old loads at 3.600" (168g Berger) I used in an old STW. I am thinking that the COAL from Berger represents the typical COAL of 3.600. So this is where I have started, but in my rifle the olgive touches the lands at a COAL of 3.950" and an olgive measurement of 3.188 (on my tools). I believe this added length would give significantly less pressure due to the internal ballistic changes and therefore allow for more powder to be used to create higher velocities at lesser or equal pressure.
Even with the olgive touching the lands the Berger 195 EOL leaves enough contact surface inside the neck of the cartridge that I have read is recommended for stability and accuracy (at least equal to the calibre).
With this in mind I had expected that when I get an initially accurate charge and then start moving the bullet length toward the lands I will likely find that I can use heavier charges and gain velocity safely.
So I think that the powder charges and velocities that you have are very reasonable to expect as I move toward the upper ends of load development; at least I really hope so. At this time I don't have a chronograph so my eventual max loads will be based on pressure signs alone.
However, I also tend to back off the max loads I develop in the winter due to increased pressures in the summer. Currently we are in the -35C range outside. Summer of course is the typical 20-30+C giving a temp swing of around 60 degrees. I still haven't had the nerve to pull the trigger on a winter load in the summertime! Not sure I ever will!
Thanks again for the info, and please any other info/advice would be greatly appreciated.
MudRunner2005
Well-Known Member
I would start with the info they gave, but work up slowly from there to see if you can get more out of it. That's what I would do, but if you do, do it carefully. I am interested to hear your results.
Also, what brass and primers are you using? I use Nosler brass and Fed 215M primers.
Yes, I run my bullets long in ALL of my rifles. Typically always 0.015" off the lands (but certain guns are exceptions). With the STW and .300 Ackley it is a single-shot rifle at that that COAL, they are WAY too long to fit in the factory mag box.
Also, what brass and primers are you using? I use Nosler brass and Fed 215M primers.
Yes, I run my bullets long in ALL of my rifles. Typically always 0.015" off the lands (but certain guns are exceptions). With the STW and .300 Ackley it is a single-shot rifle at that that COAL, they are WAY too long to fit in the factory mag box.
willowwolfe1975
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Okay, that makes sense to me.
I am using Federal 215M primers and Hornady brass.
However, I am thinking about changing brass as I find a fair amount of inconsistency between the weight of cases. Yesterday I open 2 new boxes of brass from Hornady and there were weight inconsistencies of up to 20 grains. My understanding is that this can result in differences in pressure and therefore inconsistent accuracy. So I am going to try another brand next go 'round. What I find interesting in terms of brass is that when I loaded for my 7 RM I reloaded factory Federal brass and I found the weights to be more consistent than the Hornady I have now.
MudRunner2005
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If you are having weight inconsistencies, you should really try the Nosler brass. It's night & day compared to other brands as far as quality and already being pre weight-sorted before packaging. It's worth the extra money to me.
willowwolfe1975
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So, I think I bit off a bit more than I could chew today. I made far too many test loads to try in the time I had today. My original plan was to test all powders at 0.5 grain steps of Min/Max recommendations. That was 180 rounds, so I had to change to 1.0 grain increments to help narrow things down. Also, I've never fired long batches like that, so barrel heat became an issue creating mirage after every 4-5 rounds.
Otherwise, I had an exceptional day for shooting. It was quite warm (-22C), wind was NIL and I was able to get a good set up with the wind at my back. Elevation is 224 meters, pressure 100.8 kpa, humidity 76%
My method was simple. Each powder had 5 extra rounds made at the minimum charge. These were used to bring temperature up to a running temp. 10 minutes between 5 shot groups, then 20 minutes cool down completely before moving to the next powder.
All ammunition and rifle was left outside prior to shooting to ensure everything was at a consistent temperature.
Rifle cleaned between each powder.
Shooting was prone in the snow using bipod and and rear bag.
Distance was 100y from muzzle to target.
This is what I got...
Out of all 5 shot groups, all but one group were sub MOA the largest being 1.029" using the 7828 at 68 grain. The retumbo was nicer to shoot giving a "shove" opposed to a "kick" the 7828 had the sharpest kick. Top loads show no indication of over pressure. I question the final group using the 7977 as a snowmobiler came by and decided to be a spectator. I typically don't have anyone else around when I'm shooting and the guy wouldn't stop talking...With that said I think this load deserves a redo.
COAL for all rounds is 3.600 (Olgive 2.999).
Hornady Brass - New, resized, trimmed to perfect length.
Primer - Federal 215m
Bullet - Berger 195 EOL
Retumbo - best group with 76.5 grains yielding a 5 shot group of 0.539"
IMR 7828 - best group with 68.0 grains yielding a five shot group of 0.619".
IMR 7977 - produced the best group today with 72.5 grains yielding a 5 shot group of 0.261 (one nice hole).
Despite the best group coming from the 7977, Retumbo's groups were all close in size despite the change in charge.
So, from here I guess I'll take the best of each and try to reproduce the results. If I can do that then I'll test either side of the load at 0.1 grain increments then move to testing distance from lands. Then increase charge to find my max.
Pretty excited with the results so far.
Satterlee Scott
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this technique works like a champ to get a good starting load for anything. Especially magnums 10 rounds gets you in the ball park.
