Long time 6.5 project almost done

[RockyMtnMT]

Ok, I think we may have this thin figured out. We had to scrap the US-869, it was giving huge pressure swings with small temp increases. Settled today on Retumbo. Have burnt a lot of powder the last couple of weeks to figure this girl out. Running 90g to push the 130 to 3850fps. Not nearly as sexy sounding as before but still pretty impressive. At that speed the .63bc still looks good to 1070yrds. Will be able to work that out a little better at the next session. Wind was a bit tricky today but was able to shoot consistent 4" groups at 635yrds and shot about 8" at 1070yrds. No more powders this year, but would really like to try Ramshot Magnum if it ever comes available.

Over all feeling pretty good about how the day went. Should be able to go out next time and just fine tune drops and get ready for the soon to come hunting season.

Steve

Have to make a correction. Looked back at the notes this morning and I was wrong on the velocity. We went up to 93g Retumbo @ 3850fps. This was too hard on the brass. 90g got 3790fps no ejector mark and easy ejection. It seems that in the huge over bore when the pressure shows it shows quickly. It may also be due to the drive band style bullet we are using. Very little needed to get it started into the bore.

 

[RockyMtnMT]

Ok, I think we may have this thin figured out. We had to scrap the US-869, it was giving huge pressure swings with small temp increases. Settled today on Retumbo. Have burnt a lot of powder the last couple of weeks to figure this girl out. Running 90g to push the 130 to 3850fps. Not nearly as sexy sounding as before but still pretty impressive. At that speed the .63bc still looks good to 1070yrds. Will be able to work that out a little better at the next session. Wind was a bit tricky today but was able to shoot consistent 4" groups at 635yrds and shot about 8" at 1070yrds. No more powders this year, but would really like to try Ramshot Magnum if it ever comes available.

Over all feeling pretty good about how the day went. Should be able to go out next time and just fine tune drops and get ready for the soon to come hunting season.

Steve

Have to make a correction. Looked back at the notes this morning and I was wrong on the velocity. We went up to 93g Retumbo @ 3850fps. This was too hard on the brass. 90g got 3790fps no ejector mark and easy ejection. It seems that in the huge over bore when the pressure shows it shows quickly. It may also be due to the drive band style bullet we are using. Very little needed to get it started into the bore.

Steve

 

[RockyMtnMT]

Ooops not sure how that happened.

Steve

 

[IdahoCTD]

Seems to me you should be looking at R-33, R-50, 50BMG, etc if your looking for velocity away from 869 or 872. You could probably pick up some of the 150fps you lost switching powders to Retumbo.

 

[RockyMtnMT]

Seems to me you should be looking at R-33, R-50, 50BMG, etc if your looking for velocity away from 869 or 872. You could probably pick up some of the 150fps you lost switching powders to Retumbo.

We tried those and stopped at the same spot. (roughly) I have some 872 on its way. The Retumbo seems to be working predictably, and being part of the extreme line the hope is that we won't see large changes if it gets warmer like we saw with the 869. Little nervous about the ball powder because of that. I think that the 872 may be better in the over bore case than the 869. Don't know if we will try it this season or not. Running out of time before hunting season, and have to get it dialed in. It is now about testing the bullet on game. We will probably visit the rifle performance again later. May go back and try the rl-33 again. Rumor is that it is temp sensitive too. Right now on paper the ramshot magnum looks perfect, but can't find any.

Steve