7STW 180VLD Retumbo

[jweigel]

Which load would you go with...see attached table of multiple range data for the best to loads???

Thanks for any feedback.

JJW
ND

 

[HarryN]

I don't have enough experience to give advice, but it is interesting that the ES seems to depend more on the date of the test than the powder load.

 

[HarryN]

Just an idea, the 7stw group on the forum is pretty tight. If you post your spreadsheet there, it might get more attention.

 

[dok7mm]

What are the differences in your data? If powder charges are the same exact wt., what was different -- fire forming new brass, primer change, rate of fire, temp. or neck tension. Something is making a difference!

 

[dok7mm]

The 3 SD looks as if you are reaching a node your rifle is liking. Is there a tenth of a gr. not showing up on your data? A longer string would validate that excellent SD in a STW, if the ES is 3.

 

[barefooter56]

Which load would you go with...see attached table of multiple range data for the best to loads???

Thanks for any feedback.

JJW
ND

jweigel,
Do you have any targets to post that are matched up to the loads you posted? Any SD readings? The target tells all sir.

 

[jweigel]

Thanks for the feedback guys. I have made lots of trips to the range with this gun and two others. One thing about this gun is it is consistent. I attached the bullet seating depth test shot at 100 yrds. After testing seating depth three times I verified that .010 OTL is the sweat spot for this gun. I did all my powder testing at that seating depth. I also attached one of the many trips that the groups were pretty representative of other trips but this time out it got to late in the day to get decent chrono readings thus it is not on the table above. Once I narrowed it to 76 and 78 grains, I have shot those two loads three separate times to see which was better. They were both good...one better on one day and one better on the other. I did find this gun likes to be clean after about 30-40 rounds and shots very good clean or with a shot or two to foul.

Again....seat depth shot at 100 yards, powder tests shot at 200 yards.

I put all the data in access, calculated ES, but not SD. I then calculated an overall average ES for 76.0 grains and 78.0 as well as an overall average MOA.

76.0: AV ES=39, AV MOA=.61, AV FPS=2938
78.0: AV ES=24, AV MOA=.56, AV FPS=3022

The MOA was a wash but 78.0 had much better overall lower ES.

I just called Leupold and order a turret for the VX6 4x24 scope. Zero at 250. They said it will go to 950 with one revolution. I scope allows for two revolutions but 950 is enough for me.

Now if I could only get my 7RM to shot this good....and most importantly....this consistent, trip after trip to the range.

jjw
ND

 

[eshorebwhntr]

I would say that the 78gr charge is better but it's hard to tell from the info there. As long as it's not working your pockets too hard I would load up 5 of the 78gr charge and try to move to 600-800 and shoot a 5 shot group on a large paper target. This will prove whether or not your SD/ES is actually good or bad by looking at the vertical dispersion on paper for the 5 shot group.

If it's actually less than 20 as some of your chrono readings suggest, the group will be very tight vertically. If it's almost 100fps like some of your readings say, it will be spread out. Shooting this distance will also get you some info on how close your MV Avg is that you're getting that turret etched for. If it's high/low of your aim point you'll have to adjust. Running the numbers from your chrono will get you ballpark but I would verify before making a turret.

Good luck.