Berger .338 300 grain EH - ballistic coefficient

[D.Camilleri]

Timber,

The last time I went out to shoot, the temps were in the mid 20's, my go to load of H-1000 and the 300 gr Berger OTM, first shot was slightly faster than average and then each shot after dropped about 20 fps for several shots. Rifle and ammo was cold. My thought is that the bore is expanding as the barrel temp comes up and lowers pressure slightly.

All of the reading on rl33 seems to show that it likes high pressure for consistency. In a thread started by Kirby, he had lots of velocity spread when the bullets were away from the lands. I don't load to the lands, so I need to test and see, but this is why I am trying to get a high pressure load to see if it helps. I am not sure that I can get enough rl33 into my case to see a benefit with the berger, but with the accubond longer bearing surface, it seems to help with the pressure. I should be able to find out in a couple of days.

I also bought some of the new imr 7977 powder that is supposed to have a burn rate similar to retumbo, no temp sensitivity and lower pressure higher velocity than retumbo or h-1000.

The last time I shot I wasn't getting my normal good groups and I decided to bed my recoil lug on my bell and carlson alaskan stock and see if the groups shrink again. So I won't really know what helped the most, but hopefully it shoots good again.

 

[Timber338]

Was able to get out and shoot again this morning and I figured out where and how I was 4 inches low last week. Turns out the ballistic coefficient was correct AND the muzzle velocity was correct. So thanks again for the feedback that something else was wrong last week ...

Overall a great lesson in how close you have to pay attention to every single detail. I started out this morning going over every single variable. Starting at 600 yards, I verified the exact distance to be 608 yards... as the shooting benches are 8 yards behind the berm where you lay down prone. Also verified the angle I was shooting at 348 degrees for Coriolis, which confused me at the time since looking at a map which I did in the past said I was shooting somwhere between 6 and 8 degrees. So I turned on Coriolis and spin drift, used 2705 for MV and shot about 2 inches high...

At 1000, it was similar... 1005 yards, 5 yards behind the prone area. I used 2705 MV and 1005 yards, along with 348 degrees for coriolos... and the shots went about 4 inches high...

There's 3.1 inches additional drop at 1005, and it also turns out my phone was set for magnetic north, not true north. And just that little difference in angle is about another inch of drop compared to the 6-8 degrees at true north, and then the shooting solution called for 23.4 MOA so I dialed 23.5. It all added up to shoot a touch over 4 inches high.

Really hammered the lesson that you have to be spot on with every single variable.

I'll spend some more time practicing and hopefully shooting out to 1200 and 1400 and beyond to really get more confident in this load, but as it stands I'm think I'm right where I want to be, splitting hairs at 1000 yards down to the final 1/4 MOA (1-click) that I dial.

 

[D.Camilleri]

Nice shooting Timber! I finally got out to the range this morning and was able to shoot my 101 gr RL33 load with the 300 gr accubond. 2853 was the magneto speed velocity. I only had 5 rounds loaded, and with the magneto speed attached, I hit about 7 inches high at 100 yards. I aimed at the bottom of the target and removed the magneto speed and put two shots at my exact point of aim and touching each other. These hit at the same point of impact as my 300 gr berger load. I save my last two rounds to shoot at 750 yards. My buddy was at the range also and he spotted for me, and I shot the wrong target on my first shot, duh, I shot the 700 yard gong, it was a solid hit and a little high since I dialed for the 750, on my second shot, I pulled the shot a little and hit high and right. I need to load some more rounds now, but I am optimistic.

 

[Timber338]

Nice shooting Timber! I finally got out to the range this morning and was able to shoot my 101 gr RL33 load with the 300 gr accubond. 2853 was the magneto speed velocity. I only had 5 rounds loaded, and with the magneto speed attached, I hit about 7 inches high at 100 yards. I aimed at the bottom of the target and removed the magneto speed and put two shots at my exact point of aim and touching each other. These hit at the same point of impact as my 300 gr berger load. I save my last two rounds to shoot at 750 yards. My buddy was at the range also and he spotted for me, and I shot the wrong target on my first shot, duh, I shot the 700 yard gong, it was a solid hit and a little high since I dialed for the 750, on my second shot, I pulled the shot a little and hit high and right. I need to load some more rounds now, but I am optimistic.

Awesome, I'm really interested to hear how your load ends up. Also think it's odd that my barrel pressures up so much faster than the typical 338Rum barrel. Both my 300 Berger and Accubond loads are at 93 grains of RL33, and I'm over max pressure at 95 grains. Every powder and bullet I've tried, the max/accurate load is always at listed starting loads. I guess not a big deal but it would be nice to get an additional 100 fps !!

 

[D.Camilleri]

Timber,

Aren't you seating your bullets out close to the lands? I am seating to 3.670 OAL and I am still about .140 off the lands with the berger and about .080 off the lands with the accubond. Being a lot closer would spike the pressures and as I found out, being short at saami specs also spiked my pressure. 90 gr of H-1000 with the accubond seated to about 3.6, stuck my bolt. My go to load for my 300 gr berger is 90 gr of H 1000 and I have gone as high as 92, but brass life suffered.

 

[Wedgy]

In regards to the velocity spreads and cold bore I have been reading this thread over at LRO about HBN
hBN bore treatment?

"Take some ammo out you loaded over 6 months ago. Check the ES on it and shoot some past 1000 yards. Or pull some of those bullets and note the difference in how they pull. There are issues with the bullets releasing from the cases, some easy some hard. This greatly effects the ES, and is where I want it to help me."

Interesting

 

[Timber338]

ive read about HBN but never felt the need to try and use it. Maybe I would if I shot the distances that those guys are shooting all the time.

i definitely think it's worth trying to drop ES with lubricants/coatings for all ammo, but I'm skeptical that huge gains will be made in ammo that's been loaded for several months/years. Even if we can prevent cold welding there is nothing we can do to prevent age hardening other than annealing and possibly using the lightest neck tension that we can tolerate. But I'll follow that thread you sent to see what those guys figure out. I certainly won't be proving or disproving anything with a skeptical attitude

I'm going out this afternoon to test my velocity at a higher temperature. This 300 EH is new to me and I've only shot this load in the low 30 degF temps. My 2725 avg fps was recorded at 34 degF and today is supposed to be up in the mid 50's. We'll see how it all goes, I'm hoping to get a good 2nd data point for temp sensitivity.

Any of you guys doing any fancy coatings to drop ES? I've used graphite in the past and more commonly use imperial wax in the necks.

 

[450hunter]

Timber,

What kind of rifle are you shooting? If it's a factory rifle or you using the factory barrel? Thanks for the info and great shooting by the way.

 

[Timber338]

It's a custom 338 RUM built on a Borden Timberine action, 27" Hart barrel #4 contour, McMillan Game Scout Edge and a Jewell trigger. Glass is a Leupold VX6 3-18x50mm. Complete rifle weighs 9 lbs 7 ounces.

 

[450hunter]

Timber,

Thanks and it sounds like a sweet set-up.

 

[338 dude]

Hey guys, thanks for the responses... this is exactly what I was looking for... you are all saying the same thing that the BC should be accurate so look elsewhere.

Doc, thanks for the accurate list of things to look for. Below is the answers to your questions. I was using the Shooter App to calculate all of my drops. I am shooting this bullet using 93 grains of RL33 and seated to a .010" jump. Not sure of my COAL to the tip of the bullet because I always use a comparator, but I think it is right around 4 inches.

1: I checked my MV several times in previous days, but not during the day I shot at 1000 yards. The temperature was luckily the same as my most recent Magnetospeed V3 data of 34 degF.

2. I'm shooting a 27" Hart barrel with 1:10 twist. Shooter app calculates the stability wtih the exact temp and pressure at 1.86. I believe stability says I should be getting the max .417 BC.

3. I have thoroughly tested out my scope and it does have error which I do have a correction factor entered into Shooter. My CF = .97087

4. I am using the Shooter app, and I did not account for Coriolis or Aerodynamic jump (is this just spin drift?). Although, I was shooting nearly due north... 8 degrees to be exact. Even if I turn on Coriolis Jump and Spin Drift, Shooter only changes my vertical impact due to Coriolis by 0.4 inches up (higher).

In fact, my Kestrel measured 4 mph wind at 250 degrees (left to right). without Coriolis or spin drift turned on, Shooter said to dial 1.5 MOA (15.7 inches) for windage, and my group only impacted about 1.5 inches left. When I turn on spin drift and coriolis, Shooter says to increase my windage correction to 2.2 MOA (22.8 inches). If I had adjusted for that I would have shot very far left. And wind flags at 1000 appeared to have about the same effect from wind as the flags right next to me. Not sure how to interpret that data point. Also, I verified pressure to be 25.30 with both my Kestrel and my Leica 1600b.

5. I am as close as i can tell on scope height ... but you say " bore height at the turrets" ... should I be measuring my scope height to something other than the center of the optic? Or am I just totally missing something here?

6. Great article, thanks for the link. It seems Brain's book on ballistics would be a worth while investment.

7. I am not pointing my bullets, and because my goal is to hunt with these bullets, I believe pointing would be a very bad idea.... correct?

So based on everything here especially your experience with this 300 grain Elite Hunter B.C., it sounds like you would recommend adjusting MV rather than B.C. in my application ??

If I drop my MV down to 2705 it brings me right up to where I need to be. I will certainly get more data points shooting at long range. I'm not sure what I will see at shorter distances like 600 yards that won't be easier to see at 1000 or further. I don't have any way to calibrate my Magnetospeed, but it has proven to be very very close to perfect for my 215 berger hybrid out of my 300 win mag. Would be easier for me to accept adjusting MV if that bullet were also impacting similarly low.

you know your BC's correct you know your speed is correct adjust the scope correction factor in Shooter until everything lines up