6.5x55SE 140 gr Accubonds - H4831SC - Fed 210 - Lapua

[azsixshooter]

I'm trying to work up a good load with the 140 gr NABs and H4831SC, my hoped-for goal was sub-MOA @ 2800 FPS or better with safe pressure in my rifle. The Nosler book stops at 47.0 gr but with some well-calibrated Quickload data (and max PSI set to 60K) and careful observation for overpressure signs I worked up to 48.8. I also use a .0001" micrometer to track casehead expansion - >.0005" being a hard stop - and watch speed on the chronograph every shot.

I wasn't seeing anything alarming and no casehead expansion up until 48.8. Velocities started ranging pretty wide (75+ fps) and bolt lift was beginning to show a little more resisitance than with typical factory loads, such as Hornady Superformance. I registered one shot at 500+ fps higher velocity than the rest so I stopped there and pulled the rest of my bullets (I had 10 more loaded for 49.0 gr; 5 at .010" off the lands, 5 at .005" off the lands). It may have been a sensor malfunction, my chronograph isn't a very expensive one and the bullet actually impacted lower than one that registered ~2800 fps. Plus, recoil felt normal, bolt lift wasn't extremely sticky and there were no signs of overpressure on the case. Still, with the other evidence and already being so far over the book max I decided to play it safe.

It doesn't look like I will be able to meet my goal in this CZ 550 American with this combination. During the previous round of testing I was seeing accuracy improve steadily from 47.4 --> 47.7 --> 48.0 with COAL of .020" off the lands. At 48.0 grains I tested .020", .015" and .010" off the lands with accuracy further improving steadily with the longer COAL. At 48.0 gr and .010" off the lands there were no pressure signs at all on my cases, normal bolt lift and an average velocity of 2740 FPS. If I can dial that in better I guess I can live with that speed, although I was hoping for 2800. I don't think the deer will notice ;-)

My next round of testing is going to be:

• 47.8 gr @ 3.140" (.010" off lands)
• 48.0 gr @ 3.145" (.005" off lands)
• 48.0 gr @ 3.140" ← (already tested, baseline)
• 48.2 gr @ 3.140"
• 48.2 gr @ 3.145"

I had great luck in the past using the 130 gr Accubonds and 48.0 gr of N560 powder. I'm hoping I can tune this load and get some good sub-MOA performance. My best group so far has been the 48.0 gr @ 3.140", 5 shots in 1.218". At 2740 fps with this bullet I should be able to zero at 240 yards and have a MPBR on a 6" vital zone out to 283 yards. Out to 360 I can settle my horizontal crosshair on a deer's back and still be in the vitals with 1500+ ft/lbs and still have a good 2200+ FPS of speed for the AccuBond to do it's thing. If I get this load worked out this will be my go-to big game load for this rifle. The nicest thing is the recoil is so mild my 14 yr old daughter can enjoy shooting it too and I don't have to worry about her developing a flinch.

EDIT: I meant to mention that the 5 shot groups at 48.4 and 48.8 were not good, over 2 MOA. Based on the Quickload b_time predictions, I was hoping to hit an accuracy node at 49.0 and get the velocity I was looking for. I must have passed it around 48.0, hopefully I'll be able to find something promising next time out, maybe a little over 2750 if 48.2 comes in.

 

[wvbuckbuster]

2740fps isn't anything to lose sleep over. That is plenty of speed for what you're wanting to accomplish. I've poked a few deer with somewhat lower velocity and as you said the deer won't know the difference, the oil light will still come on. If you can get or have some, try Winchester Stabal6.5 as it gives good velocity and groups for me in my 6.5x55s. Couple of others are RL19 and 22 if you can find them. Glad you are using the Swede and keep after it. Hope your daughter enjoys hunting with it as well.