Which 338 to build?

[jrock]

For those of you who have shot Lapua based cases and RUMs, do you notice any difference in the recoil impulse? I've heard the Lapua cases have more of a shove than a jab.

 

[J E Custom]

For those of you who have shot Lapua based cases and RUMs, do you notice any difference in the recoil impulse? I've heard the Lapua cases have more of a shove than a jab.

Recoil Velocity causes this difference in felt recoil. The lighter the rifle, the higher the recoil velocity and the felt recoil. The 338 Lapua and the 338 rum are very close to the same ballistic performance so in the same type and weight rifle it would be very hard to tell one from the other. The only real difference in the two Is the bolt loading. The bigger the bolt face/case head, the higher the bolt loading for the same pressure and velocity.

Case capacity can also have a bearing on powder burn rate and recoil. the case capacity of each cartridge should also be an indication of the potential recoil and recoil velocity.

Case capacity for the 338 Norma is107 grains H2o.
Case capacity for the338 RUM is 113 grains H2o.
Case capacity for the 338 Lapua is 114 grains h2o.
And the case capacity of the 338 Edge is122 grains H2o.
These volume's are taken at the top of the neck for comparison and actual powder volumes vary depending on the powder used. (actual usable volumes will be around 7 to 10 grains less than these numbers)


J E CUSTOM

 

[Timnterra]

So I'm really slow at getting rifles finished but here it is. This is the rifle I decided to build. It's a 338 RUM with a 4" Wyatt box lilja 28" barrel fat bastard muzzle brake Remington action jewell trigger McMillan game hunter stock. I haven't been able to shoot it yet but thanks to Rum Man I've got brass and bullets to play with. Anyone have a favorite 338 Rum 300gr Berger recipe?

 

[codyadams]

What powder do you have on hand?

 

[Rum Man]

So I'm really slow at getting rifles finished but here it is. This is the rifle I decided to build. It's a 338 RUM with a 4" Wyatt box lilja 28" barrel fat bastard muzzle brake Remington action jewell trigger McMillan game hunter stock. I haven't been able to shoot it yet but thanks to Rum Man I've got brass and bullets to play with. Anyone have a favorite 338 Rum 300gr Berger recipe?

Just send that baby over here ...I can get it all set up fo you !

Rum Man

 

[Rum Man]

Your going to be 90 to 92 gr. Of H-1000 @ 2850 to 2885 ft.per.sec tested in a 30" carbon. I'm 15 thou . Off the lands .

If you try the 250 gr bergers, rl-26 92 to 94 gr will get you 3000 ft.per.sec in a 24" Carbon !! My new favorite Rum !
PLEASE WORK UP !

I'm going to try some Ramshot LRT shortly .
Rl'33 works but I haven't tryed it yet .
Nv570 will also give you some good sd , es and accuracy !

Rum Man

 

[Timnterra]

The powders I've got that would probably work best are, h1000, lbs Retumbo, and Ramshot LRT

 

[codyadams]

H1000 will probably give you best overall consistency but lowest velocity, Retumbo will give good temp stability with better velocity, but maybe a little more picky on velocity nodes and accuracy, and LRT will likely give best velocity, good case fill, good accuracy and excellent metering, however is pretty temperature sensitive in my testing. I tested all of those in a couple .338 Norma Mags, and ended up going with Retumbo. A 28" carbon six barrel was running 2850 with 88.5 grains Retumbo and an HBN coated 300 Berger, and was a little below max. A RUM has a little more capacity.

 

[skipglo]

I'm filling a big hole in my cartridge line up with a big boomer. I've been set on the 338 edge, but shopping around for dies and brass has been a little frustrating. This has got me thinking about opening up my options. I'm now debating between the 338 Rum, 338 Edge, 338 lapua and the 338 Norma. I will not be doing an improved chamber of any kind because I don't have time or a desire to fire form. Lapua brass and dies seem to be everywhere and no more expensive than any other. I was going to use a 300 Rum donor action so the bolt change for the lapua and NM factor in a little. What would you build?

Lapua...Available everything

 

[sp6x6]

I have a couple normas and like them.300 OTM,retumbo,lapua brass,fed 215.11 years now,one light for hunting.Id do it again.

 

[Timnterra]

H1000 will probably give you best overall consistency but lowest velocity, Retumbo will give good temp stability with better velocity, but maybe a little more picky on velocity nodes and accuracy, and LRT will likely give best velocity, good case fill, good accuracy and excellent metering, however is pretty temperature sensitive in my testing. I tested all of those in a couple .338 Norma Mags, and ended up going with Retumbo. A 28" carbon six barrel was running 2850 with 88.5 grains Retumbo and an HBN coated 300 Berger, and was a little below max. A RUM has a little more capacity.

Did you get a number on how much the lrt varies per degree of temp?

 

[codyadams]

Did you get a number on how much the lrt varies per degree of temp?

Not a solid number at specific temperatures, but I shot a 6 shot string from a 28 nosler, 2 different 3 shot groups, with the same load, shot all 6 in about 3ish minutes. The velocity rose consistently, and a little over 90 fps total. If I waited 3-5 minutes between shots, the same load had an e.s. in the teens for 10 shots. Both Retumbo and H1000 in the .338 Norma's, .264 win mag, 7 mags, .270 Sherman, and a couple others I have tested are much more consistent. I will still see a rise, but it's usually much less, under 30fps if I had to summarize.

I stuck with it on that 28 nosler load, because it had a massive velocity node where it shot really well. I developed the load in 75-80° Temps and kept a fair margin from top pressure, so it will be a safe load in any conditions it should encounter. As long as the gun still shoots well and the velocity change is consistent, I don't mind some temp sensitivity in my powders, but it is another factor that I will test and account for if I choose to use them, so an added step

 

[Timnterra]

Not a solid number at specific temperatures, but I shot a 6 shot string from a 28 nosler, 2 different 3 shot groups, with the same load, shot all 6 in about 3ish minutes. The velocity rose consistently, and a little over 90 fps total. If I waited 3-5 minutes between shots, the same load had an e.s. in the teens for 10 shots. Both Retumbo and H1000 in the .338 Norma's, .264 win mag, 7 mags, .270 Sherman, and a couple others I have tested are much more consistent. I will still see a rise, but it's usually much less, under 30fps if I had to summarize.

I stuck with it on that 28 nosler load, because it had a massive velocity node where it shot really well. I developed the load in 75-80° Temps and kept a fair margin from top pressure, so it will be a safe load in any conditions it should encounter. As long as the gun still shoots well and the velocity change is consistent, I don't mind some temp sensitivity in my powders, but it is another factor that I will test and account for if I choose to use them, so an added step

I had never heard of LRT until I saw it on the shelf at the local Scheels. I picked it up and read the back that it was developed for the 338 Lapua. I bought 6lbs Not knowing anything about it. Looks like it will fill a case for sure. The 339 Lapua data shows a full case and 103gr max for a 300gr Berger. I figured the 338 rum should be close to the same. I'm thinking I'll do load development at or close to predicted hunting weather to avoid temp sensitivity if it ends up shooting good.

 

[codyadams]

I had never heard of LRT until I saw it on the shelf at the local Scheels. I picked it up and read the back that it was developed for the 338 Lapua. I bought 6lbs Not knowing anything about it. Looks like it will fill a case for sure. The 339 Lapua data shows a full case and 103gr max for a 300gr Berger. I figured the 338 rum should be close to the same. I'm thinking I'll do load development at or close to predicted hunting weather to avoid temp sensitivity if it ends up shooting good.

It had really good performance for me and great accuracy too, would be a good option if you don't have major temp swings where you hunt. In Wyoming, pronghorn season may be 80ish, but you can wait until it cools down too. Deer and elk are usually 20-60°, so really not a huge difference.