The Firing Line Forums - View Single Post - 30.06

RogueMontanan · October 17, 2018, 03:12 PM

I am using IMR 4350, and my optics are vintage. 4x Leupold Pioneer on Leupold base/rings. Have to adjust the POA by adjusting the Base/Rings. Considering the rifle has been sighted in since 1956 when my grandfather originally locktited the base/rings in place I am REALLY trying not to touch it. I realize that this is the easiest fix when I find a load that solidly groups.

The Partition SP 150gr has shot well over the years (consistently in the .75 MOA group range), but I was hoping to load an 150 gr accubond that shot a little faster and flatter with the higher BC for less wind drift. The area I hunt is notorious for gusty winds.

That said I think I misspoke when describing my ladder test. I will describe my process below:

My initial Test: I shot 5 loads of 3 rds each at 100 yards. The loads where 0.5 gr difference from 56.2 Gr up to 58.2 gr IMR 4350. I zero'd in on the tightest groups 56.7 gr IMR4350 (0.69MOA) (but 1.68" Left and 1.68" High) the 1.68" high is nearly perfect as the rifle is zero'd at 200yards.

Second Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were 0.1 gr difference centered around 56.7 gr IMR4350. This time I found that ALL groups were between 1.6 and 2" left of center.

Third Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were again 0.1gr difference centered around the 57.2 gr load (2nd best initial group, but closer to center/elevation. This time I found that 57.3 gr IMR4350 had the best group center around the desired POI at 0.13" Left and 2.21" High. (A little high but my next test should help fix this, I hope).

Fourth Test: I am now adjusting my seating depth to decrease the jump distance to my lands. Because it is an older rifle I have extended my seat to max saami (3.340" on the 3 "base" cartridge), seated three at 3.360", and am going to use a OACL guage tonight to make sure that my old school measurement (smoking the bullet in an unprimed case and progressively seating it until there was no contact) was correct. I have 3 seated at 3.390" OACL (tip to base) for the 150 Gr Accubond is what I came up with for max OACL. I have decided to verify before pulling the trigger with the hornady OACL guage system because 0.050 seems little much even for a rifle of this age. I am hoping that the tighter seating tolerance will help bring the group solidly into MOA/sub-MOA range and bring the POI into the 1.6" to 1.8" high range (maintaining the 200 yard zero).

I know this is a LOT of work to avoid adjusting the scope POA, but I guess I have to admit to some sentimental attachment to keeping the rifle "As-Is" from when my grandfather set it up.

Finally, I feel that the max hunting range for this rifle/setup is solidly around 600 yards. If I need to shoot farther than that I know I need to build a different rifle with modern optics. It is on my "To-Do" list. And before I get a bunch of criticism, I took a 5x5 Bull with the Nosler Partition at 558 yards last year. Dropped in it's tracks. After reflecting on that event and thinking about everything that could have gone way wrong (strelok is great for playing games like "what if the wind had gusted as I shot"). I decided I really needed to try to develop a solid BT round with higher BC that was less susceptible to wind drift and drag/speed bleed, or I needed to re-evaluate and limit myself to 400 yard shots.

October 17, 2018, 03:12 PM	#15
RogueMontanan Junior Member Join Date: September 30, 2018 Posts: 3	I am using IMR 4350, and my optics are vintage. 4x Leupold Pioneer on Leupold base/rings. Have to adjust the POA by adjusting the Base/Rings. Considering the rifle has been sighted in since 1956 when my grandfather originally locktited the base/rings in place I am REALLY trying not to touch it. I realize that this is the easiest fix when I find a load that solidly groups. The Partition SP 150gr has shot well over the years (consistently in the .75 MOA group range), but I was hoping to load an 150 gr accubond that shot a little faster and flatter with the higher BC for less wind drift. The area I hunt is notorious for gusty winds. That said I think I misspoke when describing my ladder test. I will describe my process below: My initial Test: I shot 5 loads of 3 rds each at 100 yards. The loads where 0.5 gr difference from 56.2 Gr up to 58.2 gr IMR 4350. I zero'd in on the tightest groups 56.7 gr IMR4350 (0.69MOA) (but 1.68" Left and 1.68" High) the 1.68" high is nearly perfect as the rifle is zero'd at 200yards. Second Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were 0.1 gr difference centered around 56.7 gr IMR4350. This time I found that ALL groups were between 1.6 and 2" left of center. Third Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were again 0.1gr difference centered around the 57.2 gr load (2nd best initial group, but closer to center/elevation. This time I found that 57.3 gr IMR4350 had the best group center around the desired POI at 0.13" Left and 2.21" High. (A little high but my next test should help fix this, I hope). Fourth Test: I am now adjusting my seating depth to decrease the jump distance to my lands. Because it is an older rifle I have extended my seat to max saami (3.340" on the 3 "base" cartridge), seated three at 3.360", and am going to use a OACL guage tonight to make sure that my old school measurement (smoking the bullet in an unprimed case and progressively seating it until there was no contact) was correct. I have 3 seated at 3.390" OACL (tip to base) for the 150 Gr Accubond is what I came up with for max OACL. I have decided to verify before pulling the trigger with the hornady OACL guage system because 0.050 seems little much even for a rifle of this age. I am hoping that the tighter seating tolerance will help bring the group solidly into MOA/sub-MOA range and bring the POI into the 1.6" to 1.8" high range (maintaining the 200 yard zero). I know this is a LOT of work to avoid adjusting the scope POA, but I guess I have to admit to some sentimental attachment to keeping the rifle "As-Is" from when my grandfather set it up. Finally, I feel that the max hunting range for this rifle/setup is solidly around 600 yards. If I need to shoot farther than that I know I need to build a different rifle with modern optics. It is on my "To-Do" list. And before I get a bunch of criticism, I took a 5x5 Bull with the Nosler Partition at 558 yards last year. Dropped in it's tracks. After reflecting on that event and thinking about everything that could have gone way wrong (strelok is great for playing games like "what if the wind had gusted as I shot"). I decided I really needed to try to develop a solid BT round with higher BC that was less susceptible to wind drift and drag/speed bleed, or I needed to re-evaluate and limit myself to 400 yard shots.