7/300WSM Load Development

[Kyle Schultz]

I'm having a 7/300WSM chamber cut in a new 32" Krieger 8.5:1 tw barrel. Berger 180g Hybrid. Playing with QuickLoad while I wait. Many questions.

Anticipate COAL of 3.190". (Yes- I spec'd a long reamer freebore hoping for the promised 195 EOL.) While I will measure the actual water capacity of a fired case when I have some, for now, I'm using a calculated case capacity of 79.26 gr H2O. The only other non-default parameter I'm using is bore cross sectional area which I calculated to be 0.06244 sq in.

I've read with much interest Chris Long's work on OBT and want to marry that theory with the QL predictions.

Here are some QL predictions using RL-25.

62.9g
94.1% case fill
48,690# case pressure (Max of 63,817#)
1.632 ms barrel time (Chris' Node 5)
2904 fps muzzle velocity

68.2g
102.0% case fill
63,402# case pressure (VERY close to max)
1.459 ms (Node 4)
3107 fps muzzle velocity

Questions...

1) Do these numbers seem reasonable?
2) I'm thinking the smart (and safe) way to validate these predictions is run a 3-shot ladder from 62 to 68 grains in 0.5g increments while watching for pressure signs and accuracy nodes. Agreed?

So far, the best powder I've found is N560. Here's how it looks.

60.8g
88.5% fill
48,904#
1.634 ms
2908 fps

66.2g
96.4% fill
63,452#
1.457 ms
3138 fps

Again, would confirm with ladder testing.

Thanks in advance for your help and advice!

 

[jeepcj6]

I have the same setup krieger 1in 8,5 twist 32 inch
ladder test is the best and safest way to do it
so far the best load for my rifle and max load is 66 gr N 165 180 berg vld hunt 5 shot 0,464 at 200 yards. 66,2 n 560 was to hot for my rifle at 3090 fps

 

[Kyle Schultz]

Another good looking load from QL is IMR7828SSC.

65.6g
95.0% fill
62,794# (lowest of all the higher velocity node loads)
1.454 ms
3113 fps muzzle velocity

I know this is one of TonyR's favorite powders and I do have a bottle.

 

[prairieguy]

Hi Kyle,

I have been running a 7-300wsm for close to three years now primarily using RL-25 and Berger 180 vlds.

Your quickload data is pretty close at the low end. I found a node at 62.5 gr RL25 which gives me ~2950fps.

My competition load has been 64.0 gr RL-25. It on the hot side and runs at 3080 fps.

68 gr of RL-25 is way too hot. I was blowing primers in the 66 gr range.

I have found that I was getting pressure signs very early with the 180 hybrids about could not use the above powder charges of RL-25. I had to step it back so far I was in the 2700 fps range when I finally got rid of the pressure signs.

I have been playing with N560 for the past two months and getting fantastic results but am also now using the 190 gr Matrix Ballistics VLD.

Getting very nice groups at both 57.0 (2870 fps) and 60.0 gr (2980). I blew a primer at 63 grains. So your top end QL calculations might be a bit optimistic too.

 

[Broncazonk]

Please pardon the tangent, but what are the advantages of a 7/300 WSM over the Remington 7mm SAUM? Also, didn't Winchester develop the 7mm WSM as well? (Did Winchester abandon the 7mm WSM and are not making cases for it?)

Thanks

Bronc

 

[Nomad47]

I'm sure you will get some better answers but basically the 7mmWSM has a longer body and shorter neck to prevent it from being chambered in a 270 WSM. By using the 300 WSM case, there is a better selection of brass. Also slightly less case capacity that is not really needed anyway.

 

[Kyle Schultz]

Update to earlier post.

My fired case capacity is 79.46 grs H2O. Pretty close to the theoretical volume.

Started seeing pressure signs with RL-25 at around 67 grs. Clocked 3008 fps using my PVM-21. H1000 gave me pressure signs around 66 grs which clocked 2958 fps. I believe both these powders are too slow for my setup.

Ran all the way up to 66 grs N560 with no pressure signs. Highest speed clocked was 3113 fps. Tested 7828SSC up to 66 grs (3074 fps) and started feeling heavy bolt lift at 65 grs. Both these powders a little faster burning than either RL-25 or H1000.

On the other end, tested H4350 and H4831SC. Was not able to clock these rounds. Started feeling heavy bolt lift with 58.5 grs of H4350. H4831SC started giving pressure signs at 62 grs. I fired one more rung at 62.5 grs before stopping. Did not finish intended ladder with either of these 2 powders. I know the 7SAUM guys are raving about H4350 in their guns. Maybe it's the smaller case capacity or maybe the slightly higher pressure rating, but I just don't feel it's a good powder for me. Both it and H4831SC appear to burn a little fast for my setup.

Most recently, I've done some testting with RL-22. It's in that middle region around N560 and, as another poster noted, N165. So far I'm having good results. Ran a single shot ladder from 61 to 65 grs in 0.5 gr increments. No pressure signs. Saw some grouping as described by Jason Baney in his ladder testing article. Ran a multi-shot ladder from 62 to 64.4 grs at 0.3 gr increment and am clearly seeing a sweet spot in the 63.2 to 63.8 gr range. Clocking between 2980 and 3020 fps with easy bolt lift.

Will do more testing (as soon as I locate some more RL-22 powder) inside this range to hopefully pin point the optimum.

 

[Yellow11]

For what is might be worth, below is straight from my loading notes and I have been using this mix since 2010.

Hope it is of some help...

7/300 WSM
Case capacity H2O. 79.6
Bullet Berger 180s length/1.532
Seating depth above brass/1.118
Thus below brass/0.414

Chrono for 66g x RL 25 32" barrel to bolt 32" 2920 fps
Quickload adjusted suggests. 2929 fps, 1.63 node @ 66 g RL25
Gives node 1.631 target 1.633 (65.9g is closer node)

 

[Steve Blair]

You will likely find that the single base powders (N165, H1000, IMR 7828 SSC, etc.) will produce more consistent results and hold better vertical at 1000. Taking into account morning to afternoon temperature differentials, barrel heating, etc.; double base powders are at a disadvantage and also generally show a narrower tuning window. I have always been able to get better velocity with double base powders but they will not hold vertical as well. [br]
BTW, this cartridge is also known as the 7/270 WSM. I guess it just depends upon where you start.

 

[savagedasher]

Happy New Year Check Norma MRP 2 in our 260 AI it was one of the best. Your gun
69.5gr 102%fill 100% burn 60804 psi 3146 fps and the z1 and p1 are almost together.
Good Shooting Larry