Questions about ES

[270WSM]

Hello to everyone,

I've been playing with some different loads for my 270WSM and noticed how large my ES's are using 140grn Accubonds and Magpro. I was trying to get into the 3200 fps range while keeping good accuracy and was unsuccesful. My groups are ~1.0 @ 3250, but they're constantly less than .5" @ 3065. My ES's have consistantly been 50-100 with this combo. Sometimes lower at the slower velocities.

I then loaded up some 169.5grn Wildcat RBBT's with Retumbo and the same batch of prepped cases. My ES's were less than 10 and they shot pretty good (2 loads ~2/3MOA). I was suprised these shot so well with a 1-10 twist.

My question is, What causes large ES's? Is it the powder? Rifle? Bullet? Combo of all? Does ES change with velocity nodes? Seating depths? Any info would be great. Thanks.

 

[davewilson]

i'm just waitin to see how much 50 writes on this one!

 

[270WSM]

The more info the better /ubbthreads/images/graemlins/grin.gif

 

[wapiti13]

ES shows that your pressure is not consistent. Type of powder, amount of powder, primer, etc. can all lend themselves to ES. Obviously, we are all looking for a small ES. Especially with a fat case like the WSM series, I have found that the cartridge works better hotrodded. Also, several discussions with tech support at the various powder/bullet/bullet companies have agreed that the WSM work best at the top end. Therefore, it is important to match the powder to the case. Also, I have found that primer choice is important with the WSM cases. Regular primers like the Fed210, Fed 210M, WLR, etc. seem to work better than mag primers! ES gets smaller and SD gets tighter as it should as you start approaching the max for that powder/primer combination. You should be able to get ES down to 20-30 FPS range with the WSM. If you are not making velocity, you are using the wrong powder. I haven't reloaded the 270WSM personally, but a lot of experience with the 300WSM. What works in the 300 might not work in the 270 as well because of different expansion ratios. Find a powder (reference reloading manuals & magazine articles) and you will usually find a common powder that is making the velocity you want. Then load it up until you start getting the ES you are looking for. With the WSM case, your best groups and ES will usually be very close to max load. The case just works better when pushed. Watch your ES & SD if your chrono shows it. You will see a shrinking SD as you approach pressue max. You will see a rise in SD and often a drop in velocity and/or less velocity gain for the powder increase if you pass the powder max. This means the powder has run out of power. Then, you need to try another powder since pressure can go high real fast. Good luck, but watch your head expansion, primers, etc. for too much pressure. /ubbthreads/images/graemlins/smile.gif