7mm-300 Weatherby

[MRogersII]

When I built my 7mm-300 Wby last year, I had a heck of a time finding useful data. Mostly just random commentary here and there. Not a lot of meat data. That being the case I thought I would start a thread and record what data I've generated thus far. May shorten somebody else's curve later.

As is always the case, this is data from my rifle, not yours. Start low and adjust accordingly.

Basic info:
7mm-300 Weatherby Mag
Rem 700
28" 1:8, Vais break, Jewel, Leupold LRP
Norma 300 Wby brass, 215 GMM
Labradar

 

[MRogersII]

When I started, I was curious about how many firings I could expect to get on a given case. So I fireformed a single case and then reworked and re-fired the same case to see how the case changed over repeated firings. Here's that data:
FF, 175 Sierra, +0.011, 66.0gr RL-22, 2888
2x, 195 EOL, -0.040, 70.0gr Retumbo, 2911
3x, 195 EOL, -0.040, 70.0gr Retumbo, 2908
4x, 195 EOL, -0.040, 70.0gr Retumbo, 2882
5x, 195 EOL, -0.040, 70.0gr Retumbo, 2900
6x, 195 EOL, -0.040, 70.0gr Retumbo, 2891
7x, 195 EOL, -0.040, 70.0gr Retumbo, x
8x, 195 EOL, -0.040, 70.0gr Retumbo, x

I've fired this case 8x and it still holds a primer. Not as tight as it was at day one but still very serviceable. I'll update later as I get additional firings on it. For 7x and 8x I was working through an issue with my Labradar battery.

 

[MRogersII]

Various ladders:
183 Sierra, -0.038, RL-25
74.0 3020
73.0 2950
72.0 2932
71.0 2904
70.0 2885

183 Sierra, -0.038, MRP
71.5 2997
70.5 2956
69.5 2918
68.5 2895

183 Sierra, -0.025, N217
78.2 3083 (+P) pressure signs
77.6 3074
77.0 3060
76.4 3037
75.8 3016
75.2 3008
74.6 2971

180 ELDM, -0.030, MRP
71.0 2994
70.5 2991
70.0 2966
69.5 2958
69.0 2937

180 ELDM, -0.030, N217
77.6 3042
77.0 3050
76.4 3034
75.8 3010
75.2 2983
74.6 2972
74.0 2944

 

[MRogersII]

Ladders:

180 ELDM, -0.030, H1000
77.0 xx
76.4 xx
75.8 3090 +P
75.2 3056 +P
74.6 3049
74.0 3039

180 ELDM, -0.030, RL-33
83.0 3119
82.0 3099
81.0 3078
80.0 3058
79.0 3027

180 ELDM, -0.030, VV165
73.0 XX
72.0 2991 +P
71.0 2958 +P
70.0 2946
69.0 2916
68.0 2887

195 EOL, -0.040, Retumbo
78.0 2900
77.0 2869
76.0 2862
75.0 2830
74.0 2758

 

[MRogersII]

At some point I stopped shooting the 180 ELDM's. The range I shoot at is 760yd. I began having shots miss the target, in a very random fashion. Coloring bullets I was shooting multiple, overlapping groups into the same 4x4 target. Occasionally, and because of different loads, groups would print all over the target. The first few times I noticed this, the groups were out towards the edge and I chalked it up to losing a shot off the edge. Took me awhile to figure out that bullets were coming apart. I had them come apart from 2900 and up. I would guess the frequency would have been 1 out of 25 or 30. I read about a few others who had experienced the same. Shame really, they tended to group very well, when they all got there.

 

[MRogersII]

This data represents testing I did to establish pressure limits with two different bullets (prior to ladder testing): 195 Berger and 197 Sierra. +P is of course visible pressure signs. 4x indicates 4th firing on that particular case, and so on.

195 Berger, -0.040, 4x
69.5 Retumbo 2842
70.5 Retumbo 2866 -P
75.0 N570 3017 +P
74.0 N570 2983 -P
78.0 RL-33 3058 ++P LOCKED BOLT
75.0 RL-33 2927
76.0 N217 3007 -P

197 Sierra, -0.040, 5x
69.0 Retumbo 2787
70.5 Retumbo 2829 -P
75.0 RL-33 2858
76.0 RL-33 2884
74.0 N570 2941
75.0 N217 2957
73.0 AA8700 2594
77.0 AA8700 2687

 

[Murray Brook]

Good info. Thanks for posting

 

[500yards]

My dad had one built about 17-18 yrs ago. He had a Wby MkV 257mag that never shot to his liking so he sent it off to Howard Wolfe in PA. and he rebarreled it into a 7-300Wby mag. If I recall the 7-300Wby was kind of one of Howard Wolfe's specialties. I remember it shot really well. The 7-300wby is basically a twin to the 7STW.

 

[drags]

We used h870 and imr 7828 with 168 gr. SMK with 30" barrels when we had 7/300 wby's. We had many kills on Pa. whitetails at 800 yard plus, I also saw a whitetail shot at just over a 1000 yards with the 7/300 using the old Hornady 162 BTHP and the exit wound was impressive. Howard Wolfe (now deceased) invented the 7/300 but his son Bob is now working the shop and could give lots of info on this cartridge, I will PM you his phone # talking to him would be very usefull.
Drags

 

[MRogersII]

Beginner ELR revelations - So, I built the 7mm-300 Wby for informal LR shooting. Not necessarily for a specific range number but just to see what could be done. Had the first opportunity to shoot at 1,960 and learned quite a lot from that experience. Shooting at milk jugs with colored water. I won't say how many jugs were optimistically placed...but I will say that @ 1,960 the survival rate for milk jugs was very high.

Shooting from the top of a ridge, shooting over hill A at 1100, over hill B at 1600 and into the gently sloping sod ground side of hill C at 1960. 300 Win Mag with 215's, 7mm-300 Wby with 195's and 260 AI with 142's. Impacts were plainly visible with all three at 1100. 1600 was not as simple. 7mm impacts were very light, and required very careful viewing so as not to miss them. At 1960 we didn't see any impacts, at all. Secondarily, the steep angle of travel made watching the vapor trail hit or miss at best.

Driving over to the targets we did not make a positive ID on any of the impacts. This was in pasture ground with grass that varied from an inch or two tall to clumps of grass that were 6-8 inches or higher. Nothing stood out as a distinct impact "crater".

Two different ballistic programs suggest that we were very much in the proximity of the target but the 500lb or less energy apparently was not sufficient to "leave a mark" on the sod ground that was plainly visible.

For what it's worth, there that is. Will go forth next time a little smarter, and a little better prepared.

 

[Zero333]

Very Kool... Thanks for posting.

At the end of summer when the ground is dry you should see some of the ground impacts.

 

[slm9s]

Some type of dirt at the target area is key. Very frustrating to shoot LR at targets on grass.