Short barreled .338LM load help

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jimbo

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Hello all,

I am in need of some help with a hunting load for an 18.5" barreled .338 Lapua Magnum. I have a Desert Tactical Arms Covert in .338LM that I've been trying to develop a good moose load for. I used the rifle last fall and love the way it carries in the bush. I took two moose with it but they were at 83 yards and I'd like the capability to go a lot further with confidence (as in 500-600). (and yes, I shoot almost every week but can only go really long a few days a year)

As it's only a short barrel, I want to use a relatively light 225 grain Accubond and a powder with a faster burn rate in order to get a complete powder burn within the short barrel. Theoretically, a faster powder wouldn't produce a giant fireball at the muzzle and should give a higher muzzle pressure, thereby maximizing the brakes effectiveness. I'm using Lapua brass, Federal GM215m primers, and am partial to Hodgdon power because it's burn rate is supposed to be pretty consistent with respect to temperature.

So far, I've come up with a load of 84.0 grains of H4350 and an OAL of 3.690". Velocity averages about 2750 fps, but herein lies the problem: my ES hovers around 50 to 75 fps. The powder charge doesn't fill the case, which I suspect is behind the ES numbers. Accuracy at 100 metres (unfortunately, the longest I can shoot without driving for three hours) is great, even with the extreme spread.
 
As a generalization, the powders that produce the highest velocity in a long barrel will also produce the highest velocity possible in a short barrel. There is no escaping the advantages of filling the case.

I would experiment with slower powders.
 
I would agree with the above. Don't quote me on this, but I do recall reading an article where they progressively shortened a barrel to observe effects on velocity and how much of the charge was burnt, and it wasn't until sub ~20" that the powder was not fully burnt. Granted this was a 308 being tested, so with a large capacity magnum cartridge, it may be more apparent. Won't hurt to try either way!

I don't have any experience with the .338 Lapua, but I'd have a go with H4831, I4350 (bit slower than the H), or Retumbo if you have any of the 3. I have personally had fantastic success in my limited experience using Retumbo in magnum cartridges, had an SD of 15 in a 5-shot group, slightly compressed charge in 270 WSM.
 
jimbo, you won't be disappointed with Retumbo. It's my "go-to" for just about anything, H1000 is another great one. I use 250gr AB's due to the fast twist in my Savage (26") with 94gr of Retumbo which gets me about 2800fps (I haven't had a chance to chono it yet). Anyways, good luck, I'd like to hear what you settle on and how it shoots.

SL
 
Todd Hodnet (the guy from accuracy first in the magpul movie) is shooting 20" barreled 338's, very far. I have no experience with them but I don't see any reason to avoid the 250's or 300 grain bullets. I'd stick the numbers in a calculator and check em out.
 
"...an 18.5" barreled .338 Lapua Magnum..." Defeats the purpose of that over priced cannon. Magnums really need long barrels to get the velocity.
The muzzle blast and noise out of a wee barrel will be astounding. Be a good fellow and warn anybody shooting anywhere near you before touching off the first shot. Sat next to a guy with a .338 Win one time and was nearly blown of the bench.
 
You might not have to do anything. If you're going to shoot at 600 yards, your ES will have little to no effect on your accuracy.

If you want to shoot farther than that (say 900 yards or more), then you would benefit from reducing your ES (and also from choosing a bullet with better aerodynamics, if that is possible).

With any particular powder you have chosen, you should work your way up to max. Oftentimes loads get more accurate and more consistent (velocity wise) as they get hotter.

Don't forget your earmuffs.
 
Didn't even know that rifle existed. 18" barrel and 338 Lapua doesn't make all that much sense to me without a suppressor, because it's going to give a huge fireball and muzzle blast. The rifle package is sweet, but I don't think you're gaining much in the 338LM that you wouldn't get in a less overbore cartridge, other than epic muzzleblast. Still, that rifle would be a lot of fun taking moose hunting.
 
sunray said:
"...an 18.5" barreled .338 Lapua Magnum..." Defeats the purpose of that over priced cannon. Magnums really need long barrels to get the velocity.
The muzzle blast and noise out of a wee barrel will be astounding. Be a good fellow and warn anybody shooting anywhere near you before touching off the first shot. Sat next to a guy with a .338 Win one time and was nearly blown of the bench.
Click to expand...
BS. It gives 338WM velocities out of a short barrelled handy
rifle. The more velocity you start with the more you have left
after shortening the barrel. I want something similar. Bear
encounters while hunting/butchering under 15yds in thick brush
make me nervous with my 30-06.
 
Thanks, Emerson. I know the short barrel handicaps it somewhat, but I knew that before I dropped $1800.00 on a conversion kit. In the end, I got a great bush rifle, although because of the weight, I wouldn't exactly classify it as a 'handy rifle'.

I loaded up some rounds with Retumbo and will get to the range later this week (although only at 100 yards). I'll let you know how things work out. Thank you all for the advice

Jim
 
Well, I took the overpriced cannon with the wee barrel to the range today to try out the loads using Retumbo. I tried to be a good fellow and warn the guy next to me to wear his ear muffs. Luckily, no one got blown off the benches either. But seriously, I was very pleased with the results. I loaded a few maxing out at102.0 grains of Retumbo which is the maximum load listed in the Hodgdon manual (I was able to exceed it by 2.0grains with the H4350 at 84.0 grains). Velocity averaged out at 2870 fps with the 102gr load and ES was 15, which is less than the margin of error in the chronograph. That's almost 100 fps faster with better consistency and no pressure signs. Accuracy and POI were identical to the loads with H4350 (although this was only at 100m). Thanks guys!
 
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