powder/load recommendation 338lm/berger 250otm

[Bodywerks]

I really haven't found a wealth of info on successful real world load data for this combo and I'm hoping I didn't waste my money on these. Ballistically, they are WAY flatter flying than the 300gr otm out to 1200 or less when compared to my current load of 300s under 90gr retumbo, flying at about 2700. From what little I read I should be able to get 3000fps pretty easy on the 250s out of my 29" barrel. Question is, what powder should I use and how many grains to start? I have retumbo, h1000, h4831sc, and h4350 on hand. I will consider other powder options but I prefer extreme powders for the desert environment I live in.

 

[angus-5024]

I have a .338 RUM, not the Lapua but it can give you an idea. I shoot the OTM with 90.5 grain 7828ssc for 3050fps.

 

[Bodywerks]

Thanks for the info. I wish it helped, but it doesn't. I looked at hodgdons website and they showed the 338RUM launching a 300smk faster at 90.5 grains of retumbo than the 338lm does with 94grains.
But what length barrel are you running? That would help. I'm hoping to get 3000-3200 to realize the benefits of a lighter bullet flying faster. My ballistics app shows almost a full mil improvement at 1000 yards.

 

[bigngreen]

It's odd that your running so slow, I also shoot a RUM with a 28in barrel and 90gr of Retumbo gets me 2800fps and 97gr of H1000 gets me 3100 fps with the 250 OTM and generally the Lapua just runs a couple gains more. Your running slower than a 338 Norma with a mild load!!

 

[MMERSS]

I'm hoping to get 3000-3200 to realize the benefits of a lighter bullet flying faster.

What do you mean by or what are you trying to achieve by this comment? Can you please provide some data for examples and explanation?

 

[Bodywerks]

What do you mean by or what are you trying to achieve by this comment? Can you please provide some data for examples and explanation?

I'm going off of what my ballistics tables are telling me(shooter ballistics for android). So far, while accurate, the 300s aren't performing like I hoped. I'm pretty confident in my measured muzzle velocity of around 2700fps through a magnetospeed chrony. And even plugging in that velocity my ballistics tables don't jive with my actual dopes at various distances with the advertised g7 BC of .419. There was an event last year where a bunch of 338 shooters got together to test and compare various bullets. One of them was the Berger 300otm. They measured the g7 to .389. Plugging that BC in lines my dopes up much closer.
The fluffed/advertised BC calls for 7.3 mils to 1000. Cold bore takes me 7.5 mils to get there and plugging .389g7 gives me that solution. It actually takes me 7.6mils on a warm barrel.
Now, to better answer your question, ballistics call for 7.5 mils and 1.35seconds TOF for the 300s with a MV of 2700. The 250s at a 3050fps call for only 5.7 mils and 1.21 seconds TOF. I haven't calculated lag time and I'm sure there's more in the 250s, but the flatter trajectory is a clear advantagefor me. Since most of my shooting is 1200yds or less I think the 250s have the advantage if I can call the wind well enough.
Of course, this all assumes that I don't have a slow barrel in general and that I can get 3000fps or better.
FWIW, its a 29" bartlein barrel on a tac338 action 9.5twist 5r and its accurate. I got 1/4" groups or better at 100, a 3 shot 1.1" group at 545, and an 8" 5 shot group my first time out to 1k with it in heavy mirage and varying winds. Its the rifle in my signature.

 

[Bodywerks]

I read somewhere that someone had success running these under 4831sc? Is there a velocity or consistency advantage to that powder? I'm thinking that or a lot of h1000 is what its gonna take to get my target velocity of 3k+.

 

[MMERSS]

FWIW, its a 29" bartlein barrel on a tac338 action 9.5twist 5r and its accurate. I got 1/4" groups or better at 100, a 3 shot 1.1" group at 545, and an 8" 5 shot group my first time out to 1k with it in heavy mirage and varying winds.

From the numbers you provided the lag time between the 250 and 300 are almost identical. I'm not sure what more you will gain besides a little less time of flight with the 250s over the already established success with the 300 groups. You're call but if me I wouldn't mess with the 250s based on the data you provided. If you must stick to Retumbo or H1000 and leave the H4831sc to those cases below 90gr capacity.

 

[Bodywerks]

Lag time might be the same, but trajectory WAY flatter. Ballistics tell me nearly 2mil difference at 1k. Less drop means flatter trajectory and less vertical spread for variances in velocity. In fact, according to Shooter, the 250s have slightly less wind drift at 1k. So at shorter distances the 250s have the advantage IMO.
What other powders do you recommend? If I knew the MV/°f for a given powder without having to send a hundred rounds down range I'd have less problem with non extreme powders.

 

[angus-5024]

If bigngreen is using h1000 with success I would try that..338 RUM and Lapua load data is ALMOST interchangeable, usually if it works for one it will work for the other within a few grains.

I don't really shoot over 1k very often, have switched over to the 250's and really like them. I really like how much flatter thy are too 400 yards on the quicker shots.