270 WSM - 170 gr EOL Berger load development

[VLD Pilot]

The OAL being 2.944 tells me that 30% of case capacity is taken up by bullet. Obviously safety is first and I think with the starting loads being very safe, going up slowly is best. 3125 is what a hunting buddy was getting with very good accuracy. No troubles and still not compressed. .010-.015 off the lands. I try to shoot for 3000 fps with many cartridges that offer good ballistic numbers. Seems to be more than enough for whatever purpose it's used. Accuracy is king.

 

[VLD Pilot]

,^^^

 

[M70280AI]

Great info here!

 

[Lou270]

I'm having a 1-8 Hawk Hill put on a Kimber action. The max OAL in magazine is about 2.95. I was concerned about length of 170 VLD and did some math. Just looking at berger spec sheet, seating the end of 170 VLD bearing surface (i.e. just boat tail in case) to case mouth ends up with OAL of 3.06" for .270 WSM (1.8235 to base of neck + .407 bearing surface + .829 nose length). Every .1 deeper for .277 cal is .099cm^3. Using 14 gr powder/cm3 (H1000 density) that is 1.4gr powder or about 2% for 270WSM case. Rule of thumb is there is 4 to 1 ratio (Barsness Article) of increasing case capacity vs. velocity gain so that is ~.5% change in velocity (2.95 OAL vs 3.05 OAL). Assuming 3000 fps that is about 15 fps. I didn't see it as big deal. In any case for every .1 deeper or longer it is about 2%/15fps. Any case that was my math if somebody finds it useful. 270 WSM OAL is 2.86, not 2.944 by the way so the berger data is for non-saami chamber.

Lou

 

[VLD Pilot]

I'm having a 1-8 Hawk Hill put on a Kimber action. The max OAL in magazine is about 2.95. I was concerned about length of 170 VLD and did some math. Just looking at berger spec sheet, seating the end of 170 VLD bearing surface (i.e. just boat tail in case) to case mouth ends up with OAL of 3.06" for .270 WSM (1.8235 to base of neck + .407 bearing surface + .829 nose length). Every .1 deeper for .277 cal is .099cm^3. Using 14 gr powder/cm3 (H1000 density) that is 1.4gr powder or about 2% for 270WSM case. Rule of thumb is there is 4 to 1 ratio (Barsness Article) of increasing case capacity vs. velocity gain so that is ~.5% change in velocity (2.95 OAL vs 3.05 OAL). Assuming 3000 fps that is about 15 fps. I didn't see it as big deal. In any case for every .1 deeper or longer it is about 2%/15fps. Any case that was my math if somebody finds it useful. 270 WSM OAL is 2.86, not 2.944 by the way so the berger data is for non-saami chamber.

Lou

2.86 IS Saami for the 270 WSM but that is with a much shorter, lighter bullet. Berger's 2.944 OAL is similar to saami dimensions. If they used the exact Saami spec measurement, there would be no reason to use a high bc vld bullet. Achieving better ballistics would be easier with a 140 or 150 grain bullet at 2.86. A COAL of 3.1 minimum is what's needed to achieve the most of the 170 EOL.

 

[Lou270]

3.1+ would give more case capacity. The neck on 270WSM is .2765 (about 1 caliber). For everything you seat beyond about 3.06 you are moving boattail into neck section and reducing amount of bearing surface that is gripped by case neck. May or may not be important to the individual reloader, but 1 caliber is a pretty standard rule of thumb (300 win proved this wrong). I have some 170VLD but not measured them to see how they compare to the data in spec sheets on the website so actual may vary if that info in tech reference sheet is not accurate.

 

[sedancowboy]

Here is a drawing I made to help figure out how much free bore I wanted.

Based on the above drawing we want the juncture of the bullet boat tail 1.236 to be even with the juncture of the case shoulder 1.824. Which would make a COAL of 3.060. This allows the cartridge neck to be trimmed with no effect on COAL.

 

[Lou270]

sedancowboy - this is similar to what I was doing but of course have different limit on COAL. What freebore did you go with given COAL of 3.06 and how close to lands are with 3.06? I dont know how to figure that out based on freebore length. The standard reamer has .16 freebore

 

[VLD Pilot]

I'm having a 1-8 Hawk Hill put on a Kimber action. The max OAL in magazine is about 2.95. I was concerned about length of 170 VLD and did some math. Just looking at berger spec sheet, seating the end of 170 VLD bearing surface (i.e. just boat tail in case) to case mouth ends up with OAL of 3.06" for .270 WSM (1.8235 to base of neck + .407 bearing surface + .829 nose length). Every .1 deeper for .277 cal is .099cm^3. Using 14 gr powder/cm3 (H1000 density) that is 1.4gr powder or about 2% for 270WSM case. Rule of thumb is there is 4 to 1 ratio (Barsness Article) of increasing case capacity vs. velocity gain so that is ~.5% change in velocity (2.95 OAL vs 3.05 OAL). Assuming 3000 fps that is about 15 fps. I didn't see it as big deal. In any case for every .1 deeper or longer it is about 2%/15fps. Any case that was my math if somebody finds it useful. 270 WSM OAL is 2.86, not 2.944 by the way so the berger data is for non-saami chamber.

Lou

If you can make 2975-3000 fps with that OAL, I think it's a good place to be. 3100 is attainable but not necessary. Accuracy means most. My buddy found his best accuracy around 3050+/-. He shoots his at 3125 if going beyond 1000 yards as he found a sweet spot in that velocity range. His best groups were at around 3025-3060. His freebore is .185.

 

[sedancowboy]

sedancowboy - this is similar to what I was doing but of course have different limit on COAL. What freebore did you go with given COAL of 3.06 and how close to lands are with 3.06? I dont know how to figure that out based on freebore length. The standard reamer has .16 freebore

I can figure all that out for you but might be a few days. I will return home on Tuesday and measure my dummy round.
Henry

 

[Lou270]

Thanks!

 

[BigJake91]

Here is a drawing I made to help figure out how much free bore I wanted.

View attachment 203706

View attachment 203712

Based on the above drawing we want the juncture of the bullet boat tail 1.236 to be even with the juncture of the case shoulder 1.824. Which would make a COAL of 3.060. This allows the cartridge neck to be trimmed with no effect on COAL.

not trying top high jack this. but with all the information shared in the last few pages and this. do you know if this would work in a short action at 3.060? sorry if that is a dumb absurd question. just trying to learn about it.

 

[sedancowboy]

Big Jake
No it will not work in a standard Rem or clone short action they are usually about 2.860 Max. There are Baines and Wyatts Mag boxes that will extend that a bit. Some Winchester and clones will have a 3.125 box and they will work great. Also you will need a 1/8 twist for the 170s.

 

[VLD Pilot]

Big Jake
No it will not work in a standard Rem or clone short action they are usually about 2.860 Max. There are Baines and Wyatts Mag boxes that will extend that a bit. Some Winchester and clones will have a 3.125 box and they will work great. Also you will need a 1/8 twist for the 170s.

Savage short actions will handle the 3.1 rounds also