7mm Rem mag, 168gr vld & retumbo load data?
- Thread starter Grizz25
- Start date
Help Support Long Range Hunting Forum
tomt
Well-Known Member
Have you chronograph your loads?
mkmccutchen
New Member
Hi TomT - Yes, I did get out over the weekend. Five rounds 168 VLD over 72 grains of Retumbo with BR2 primers in 233grain brass. Magneto Speed V3 
Hope the data helps.
3056, 3063, 3046, 3058, 3074
Average 3059, SD 10.2, Extreme Spread 28
Also shot eight rounds with turned necks, all other variables are the same.
3042, 3055,3043,3056, 3031, 3027, 3028, 3059
Average 3042, SD 13.0, Extreme Spread 32
Also shot 2 groups of 4 rounds each. One group was 230 grains the second was 238 grains.
Group1 - 230 grain brass Hornady
2994, 2994, 2987, 2988
Average 2990, SD 3.8, Extreme Spread 7
Group2 - 238 grain brass, Mixed Manufacturers
3088, 3057, 3032, 3018
Average 3046, SD 27.4, Extreme Spread 62
Hope the data helps.3056, 3063, 3046, 3058, 3074
Average 3059, SD 10.2, Extreme Spread 28
Also shot eight rounds with turned necks, all other variables are the same.
3042, 3055,3043,3056, 3031, 3027, 3028, 3059
Average 3042, SD 13.0, Extreme Spread 32
Also shot 2 groups of 4 rounds each. One group was 230 grains the second was 238 grains.
Group1 - 230 grain brass Hornady
2994, 2994, 2987, 2988
Average 2990, SD 3.8, Extreme Spread 7
Group2 - 238 grain brass, Mixed Manufacturers
3088, 3057, 3032, 3018
Average 3046, SD 27.4, Extreme Spread 62
Attachments
I had great groups with retumbo in my 7 mag with both 175lrab and the berger 180 hybrid, including some in the .2s. It just flat out shot well. The problem was I could never get the ES down to less than 30. I shot a 100 yard group with the 180s that was .3 moa, and the ES was 80! Also I started seeing pressure when it was hot outside.
H1000 has proved more consistent, high 20s in ES, SD around 10, about 50-60 fps slower, although groups hover around .5 or so.
If you are using 3 shot strings for ES data then you arent getting a real picture of the true performance. You really need 10-15 shots to have an inkling of real life performance.
For long range, I think focusing on group size more than ES is a mistake, velocity consistency is at least as important. Getting SD into the single digits ought to be the goal. Remember what these numbers are telling you...that 95% of your shots will be within two standad deviations. if you have an SD of 10, then 95% of your rounds will be + or - 20fps of the average. Thats a true extreme spread of 40 fps, and 5% will even be outside of that!
H1000 has proved more consistent, high 20s in ES, SD around 10, about 50-60 fps slower, although groups hover around .5 or so.
If you are using 3 shot strings for ES data then you arent getting a real picture of the true performance. You really need 10-15 shots to have an inkling of real life performance.
For long range, I think focusing on group size more than ES is a mistake, velocity consistency is at least as important. Getting SD into the single digits ought to be the goal. Remember what these numbers are telling you...that 95% of your shots will be within two standad deviations. if you have an SD of 10, then 95% of your rounds will be + or - 20fps of the average. Thats a true extreme spread of 40 fps, and 5% will even be outside of that!
Its not ES and SD MAY matter, they absolutely DO matter, and can matter as much as groups do if you are shooting long range.
If I implied groups dont matter, i dudnt mean to, of course they do.
I was pointing out that it can be tempting to ignore the chrony data and go for the .3 inch group instead of the .6 group. In cases where the ES is significantly better, it may not be wise. That was my experience...slightly better groups with retumbo, but much better ES with H1000. Long range results on target bore out what i already knew from the chrony data.
Consider a 338lapua, with a 300 grain SMK. A formidable long range setup. At 2800 fps it drops 274inches in the conditions last in my ballistic calculator. At 2750 it is 286inches. Roughly 1.2 moa. Its not difficult at all to see 50fps spreads in large cases of slow powder if you arent paying attention to it. I am a meticulous reloader, weighing to the kernal, little to no runout and ogive to lands consistent within .001, and i saw as much as 80 with retumbo.
Im just saying that group size is only half the equation unless you only shoot at closer ranges. Its also surprising how much velocity spread you can have in an otherwise excellent short range group. You would think that good groups would also have consistent velocities, but often that isnt true. It makes no sense to tune a group to sub moa precision and then accept velocity spreads that will definitely result in over moa groups at range.
It is also maddening to get small ES sometimes. I think it is much easier to tune for groups than it is velocity consistency.
If I implied groups dont matter, i dudnt mean to, of course they do.
I was pointing out that it can be tempting to ignore the chrony data and go for the .3 inch group instead of the .6 group. In cases where the ES is significantly better, it may not be wise. That was my experience...slightly better groups with retumbo, but much better ES with H1000. Long range results on target bore out what i already knew from the chrony data.
Consider a 338lapua, with a 300 grain SMK. A formidable long range setup. At 2800 fps it drops 274inches in the conditions last in my ballistic calculator. At 2750 it is 286inches. Roughly 1.2 moa. Its not difficult at all to see 50fps spreads in large cases of slow powder if you arent paying attention to it. I am a meticulous reloader, weighing to the kernal, little to no runout and ogive to lands consistent within .001, and i saw as much as 80 with retumbo.
Im just saying that group size is only half the equation unless you only shoot at closer ranges. Its also surprising how much velocity spread you can have in an otherwise excellent short range group. You would think that good groups would also have consistent velocities, but often that isnt true. It makes no sense to tune a group to sub moa precision and then accept velocity spreads that will definitely result in over moa groups at range.
It is also maddening to get small ES sometimes. I think it is much easier to tune for groups than it is velocity consistency.
I believe , and have seen that attention to neck thickness variations /neck turning, annealing, case volume sorting, trimming uniformity, flash hole chamfering, primer pocket unforming will do wonders for ES,SD.
Honestly I rarely see ES of 20 or more for 5 shots for the excellent load groups, and yes some of the less than great loads will have verry low ES but I can't consider one of those loads especially if they are throwing vertical dispersion because of bad harmonics the load induces.
Also, I believe it's best to test those great loads at the intended distance, or varying distances for verification.
Honestly I rarely see ES of 20 or more for 5 shots for the excellent load groups, and yes some of the less than great loads will have verry low ES but I can't consider one of those loads especially if they are throwing vertical dispersion because of bad harmonics the load induces.
Also, I believe it's best to test those great loads at the intended distance, or varying distances for verification.
mkmccutchen
New Member
I think Tom was mostly looking for velocity info for 72 grains of Retumbo pushing 168gr VLD's. Agree that reasonable ES's have little impact on 100 yard groups. Both ES and 100yard groups have everything to do with groups at extended ranges. I did a little quick ballistic calculator work and it seems like a good ES goal would be 20 fps or less, comments?
tomt
Well-Known Member
I broke in my 7mm Rem Mag Sendero before Christmas. I shot the 150 Remington Core-Lokt. It shot alright maybe minute of deer at 100 yards. I loaded 10 of mkmccutchen loads of 72 grains of Retumbo, 168 VLD Bergers in Remington brass and Remington large rifle magnum primers. I went to the range today and 9 of 10 shots went into a .8"x.8" square, this even included the fouling shots. The one shot outside was definitely me. This is with a Vortex PST 2.5-10x32. Can't wait to get the Nightforce mounted.
I loaded 10 of mkmccutchen loads of 72 grains of Retumbo, 168 VLD Bergers in Remington brass and Remington large rifle magnum primers. I went to the range today and 9 of 10 shots went into a .8"x.8" square, this even included the fouling shots. The one shot outside was definitely me. This is with a Vortex PST 2.5-10x32. Can't wait to get the Nightforce mounted.
Metzger
Well-Known Member
I broke in my 7mm Rem Mag Sendero before Christmas. I shot the 150 Remington Core-Lokt. It shot alright maybe minute of deer at 100 yards.
Tim,
Are you looking to get rid of the pst? LMK
mkmccutchen
New Member
Tomt,
Not sure I mentioned it, I had the 168 VLD's 0.010" off the lands in my Sendero.
Not sure I mentioned it, I had the 168 VLD's 0.010" off the lands in my Sendero.
I found post on here stating 69.5 grains of H1000 with the 168 Berger Hunting VLD. This load shoots great in my 7Mag. Quickload shows this as being a moderate pressure load, like 54.5Kpsi at 100% load density. From what I have seen using Quickload, most magnums have an accuracy node around 61Kpsi. I am quite sure I could go higher and find a faster accuracy node, it may be hard on brass though. That being said this load is very easy on brass and shoots great, so I am sticking with it.
Retumbo is much slower than H1000, so 70grains of Retumbo seems a little light in comparison. (QL says 47Kpsi, you have to go to 73 grains Retumbo to get to 54Kpsi)
Retumbo is much slower than H1000, so 70grains of Retumbo seems a little light in comparison. (QL says 47Kpsi, you have to go to 73 grains Retumbo to get to 54Kpsi)
Last edited:
tomt
Well-Known Member
Metzger, the Vortex is going on my AR.
mkmccutchen, Thanks for doing the load development, you made it real simple for me. I started .030" off of rifling.
I was originally going to take the Nightforce off of my Mark V 30-378, but a friend talked me out of it. So Saturday night after much hemming and hawing I ordered a Nightforce NXS 5.5-22x56, Zerostop, Moar-T reticle from Midway USA. When I get the new scope mounted, it's off to the 300 yard range.
Once I verify this load at 300 yards, then it's time for IMR 7977 powder.
mkmccutchen, Thanks for doing the load development, you made it real simple for me. I started .030" off of rifling.
I was originally going to take the Nightforce off of my Mark V 30-378, but a friend talked me out of it. So Saturday night after much hemming and hawing I ordered a Nightforce NXS 5.5-22x56, Zerostop, Moar-T reticle from Midway USA. When I get the new scope mounted, it's off to the 300 yard range.
Once I verify this load at 300 yards, then it's time for IMR 7977 powder.
