Optimum velocity for .338-LM

[rustyinbend]

Hopefully this isn't a stupid question. If it is, I'm sure I'll find out really quickly as I get virtually pummeled.
Starting load development on the .338-LM barrel on my Barrett MRAD (24" 1:9.4). I've got the Start and Max numbers from Berger for the 300gr Hybrid OTM Tactical bullets I'm going to use with testing on both Accurate MagPro and Hodgdon Retumbo. My question is this ... Do any of you reloading guru's have a favorite velocity for a 338-LM 300gr bullet that you've found works well for shooting accurately to and through a one mile target? Just curious to know as I start this journey with a new caliber.

 

[nn8734]

300 Berger OTM as fast as you can launch it safely. I always felt the 300+ bullets were a tad heavy for the std 338LM and more suited to the improved versions of that (and 338 NM) cartridges.

2700+ should get you to a mile, 2750+ is ideal.

Good luck with it.

 

[rustyinbend]

300 Berger OTM as fast as you can launch it safely. I always felt the 300+ bullets were a tad heavy for the std 338LM and more suited to the improved versions of that (and 338 NM) cartridges.

2700+ should get you to a mile, 2750+ is ideal.

Good luck with it.

Thanks ... very helpful. Picked the 300gr bullets because (a) I have a bunch of them, and (b) they have a crazy good BC (421 G7). I've got a lesser number of Berger 250's and Hornady 285's that I'll try if I don't get great results from the 300's.

It'll be interesting to see if I can approach 2700 f/s without pressure signs. The published max is 89.2gr at 2737 f/s. That said, in other calibers, my results varied significantly from the published numbers. We shall see ...

 

[Dogtown]

Generally with that cartridge you’ll be aiming for numbers like this with a standard 26” barrel:

• 250s @ 2900fps
• 285s @ 2800fps
• 300s @ 2700fps

You can go a bit hotter and add another 100fps, but often not safely. I tend to agree that the 300s are better suited to an Improved version. For example, I shoot 300s at 3050fps out of a long .338LM Improved 40. But I also shoot a vanilla .338LM with an 18” and it slings 300s at 2500fps, which is still good to a mile (barely).

So if you’ve got 300s already, then try to get them in the 2650-2750fps zone, but just be aware that running them hot can kill your brass quicker and doesn’t always equate to better accuracy.

 

[Steel head]

2650-2750 is a common range.
Especially with a 24”
Even at mid 2500’s they get to a mile comfortably.

 

[nn8734]

Thanks ... very helpful. Picked the 300gr bullets because (a) I have a bunch of them, and (b) they have a crazy good BC (421 G7). I've got a lesser number of Berger 250's and Hornady 285's that I'll try if I don't get great results from the 300's.

It'll be interesting to see if I can approach 2700 f/s without pressure signs. The published max is 89.2gr at 2737 f/s. That said, in other calibers, my results varied significantly from the published numbers. We shall see ...

Yea “book max” is a misnomer, it really means the point in which that test rifle used to generate the data they published for that bullet reached its max at that charge weight. As you know every rifle is different…

Do you know how to measure cases for the presence of overpressure? If not, ill lay it out.

 

[babyguppy]

Hopefully this isn't a stupid question. If it is, I'm sure I'll find out really quickly as I get virtually pummeled.
Starting load development on the .338-LM barrel on my Barrett MRAD (24" 1:9.4). I've got the Start and Max numbers from Berger for the 300gr Hybrid OTM Tactical bullets I'm going to use with testing on both Accurate MagPro and Hodgdon Retumbo. My question is this ... Do any of you reloading guru's have a favorite velocity for a 338-LM 300gr bullet that you've found works well for shooting accurately to and through a one mile target? Just curious to know as I start this journey with a new caliber.

The following thread on Snipers Hide lists lots of powder loads, optimum FPS with their loads, lots of great info
338 Lapua Magnum

 

[Huskydriver]

2700-2750 is about as safe as you can push a 300 with retumbo as others have stated.

With Lapua brass I top out at 88 grains of retumbo with a 300

 

[Steel head]

2700-2750 is about as safe as you can push a 300 with retumbo as others have stated.

With Lapua brass I top out at 88 grains of retumbo with a 300

What is your case fill at that point?

 

[Huskydriver]

What is your case fill at that point?

#reallyfull

 

[Lowlight]

If you are not pushing the 300s over 2800fps, you are wasting your time

They want 2850fps, a 338LM Is better with lighter bullets, I have proved it over and over, guys always default to heavies and they are wrong, don't listen above I can stomp their under 2800fps results in a heartbeat with 250s out of the box

The 300 in a 338LM is a joke, you are were HAD

 

[Huskydriver]

If you are not pushing the 300s over 2800fps, you are wasting your time

They want 2850fps, a 338LM Is better with lighter bullets, I have proved it over and over, guys always default to heavies and they are wrong, don't listen above I can stomp their under 2800fps results in a heartbeat with 250s out of the box

The 300 in a 338LM is a joke, you are were HAD

I agree but if the OP only has 300s gotta run what you got.

 

[Lowlight]

Cause he believed the bullshit, everyone has 300s, except the people that know ...

300s are stupid under 2850

 

[Huskydriver]

Cause he believed the bullshit, everyone has 300s, except the people that know ...

300s are stupid under 2850

Experience is the best teacher

 

[Dogtown]

"Three hunerts are bad, mmkay"

 

[nn8734]

If you are not pushing the 300s over 2800fps, you are wasting your time

They want 2850fps, a 338LM Is better with lighter bullets, I have proved it over and over, guys always default to heavies and they are wrong, don't listen above I can stomp their under 2800fps results in a heartbeat with 250s out of the box

The 300 in a 338LM is a joke, you are were HAD

Yep, 250s in the LM work very nicely to a mile and beyond. I have had good success with the 250 lapua scenars. They shot well in my Timberwolf and AXMC.

 

[Lowlight]

easily proven by every standard we have

both drop and drift ...

 

[babyguppy]

I run my 300's at 2865 - 2885 fps.. bad days I get a 2900 ish (damn scale)..
Now, I have a 250gr load that pushes them at 3200 fps.... I do love this load, but I worry that I'll burn my barrel out, since this is a MAX load; and a 338LM not a 220 swift.. barrels aren't cheap; and take forever to get here from Finland.

 

[rustyinbend]

Yea “book max” is a misnomer, it really means the point in which that test rifle used to generate the data they published for that bullet reached its max at that charge weight. As you know every rifle is different…

Do you know how to measure cases for the presence of overpressure? If not, ill lay it out.

Thanks ... yup ... I know the full range of pressure signs. From heavy bolt, to ejector print, through cratered primers, all the way to stuck cases. Seen ‘em all.

 

[nn8734]

Thanks ... yup ... I know the full range of pressure signs. From heavy bolt, to ejector print, through cratered primers, all the way to stuck cases. Seen ‘em all.

Im talking about using 1” micrometer to measure the case just above the extractor groove before and after firing for each charge weight, comparing the values and flagging anything with an expansion greater than .0005”.

you already do that?

Once you see the physical signs on the case head or sticky bolt, hard lift etc you are usually way over pressure.

 

[rustyinbend]

Im talking about using 1” micrometer to measure the case just above the extractor groove before and after firing for each charge weight, comparing the values and flagging anything with an expansion greater than .0005”.

you already do that?

Yikes ... not sure I even understand that sequence. And measuring something in the 5/10,000's range seems impossibly hard ... at least with the tools I have. Is there somewhere I can read about that process in more detail (and with pictures)?

 

[nn8734]

Lol, get better tools. take a 1” micrometer to the base of the case before and after firing then compare the two measurements.

 

[rustyinbend]

Lol, get better tools. take a 1” micrometer to the base of the case before and after firing then compare the two measurements.

That helps ... I have that micrometer (use it for neck-wall measurements). But I don't understand. Won't the fired case "always" be larger than the unfired measurement? And won't sizing the case in a FL sizing die bring it back to standard size? I guess I'll have to try it and find out ... eh?

 

[Steel head]

That helps ... I have that micrometer (use it for neck-wall measurements). But I don't understand. Won't the fired case "always" be larger than the unfired measurement? And won't sizing the case in a FL sizing die bring it back to standard size? I guess I'll have to try it and find out ... eh?

That’s the stoutest part of the case and should grow very little.
A sizing die doesn’t have a chance of changing the dimension there.
Ideally you take the measurement right at the forward edge of extractor grove.

 

[nn8734]

That helps ... I have that micrometer (use it for neck-wall measurements). But I don't understand. Won't the fired case "always" be larger than the unfired measurement? And won't sizing the case in a FL sizing die bring it back to standard size? I guess I'll have to try it and find out ... eh?

I’m not sure why you are over analyzing this as it’s a very simple concept. And no the fired measurement will not be larger until over pressure is present.

 

[rustyinbend]

I get it ... will give it a try on my next range visit. Thanks.

 

[rustyinbend]

I’m not sure why you are over analyzing this as it’s a very simple concept. And no the fired measurement will not be larger until over pressure is present.

Always thought it was simple ... heavy bolt, primer craters, ejector marks, etc. ... but if this measurement is more "predictive", then it's worth at least a try. I'm always looking for a better way.

 

[nn8734]

Always thought it was simple ... heavy bolt, primer craters, ejector marks, etc. ... but if this measurement is more "predictive", then it's worth at least a try. I'm always looking for a better way.

Yes, it’s a leading indicator vs lagging. With large bore cartridges and 90+ grains of powder going off inches from your face a little extra caution and diligence can pay off. I didn’t think you knew what I was talking about when initially asked as many don’t so wanted to make you aware of it.

 

[rustyinbend]

Yes, it’s a leading indicator vs lagging. With large bore cartridges and 90+ grains of powder going off inches from your face a little extra caution and diligence can pay off. I didn’t think you knew what I was talking about when initially asked as many don’t so wanted to make you aware of it.

Totally unaware of that indicator, but now I know and can adjust. Thanks!

 

[spife7980]

Always thought it was simple ... heavy bolt, primer craters, ejector marks, etc. ... but if this measurement is more "predictive", then it's worth at least a try. I'm always looking for a better way.

It only sorta works on a virgin case and you have to build your own relative comparison because each different brand of brass will behave differently in each different chamber etc. And get this, that measurement getting larger and wedging itself in the chamber is also what give you the heavy bolt lift symptom.

The reason you havent read it before is because it doesnt really work and people are only using to to try and guess at a relative range of pressure. It was much more popular back in the day.

https://www.shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdf

 

[rustyinbend]

It only sorta works on a virgin case and you have to build your own relative comparison because each different brand of brass will behave differently in each different chamber etc. And get this, that measurement getting larger and wedging itself in the chamber is also what give you the heavy bolt lift symptom.

The reason you havent read it before is because it doesnt really work and people are only using to to try and guess at a relative range of pressure. It was much more popular back in the day.

Interesting ... makes sense that case expansion in this area, and a heavy bolt, would go hand-in-hand. Are you suggesting to skip the measurement and just stick with the early physical symptoms (like heavy bolt)?

 

[spife7980]

Interesting ... makes sense that case expansion in this area, and a heavy bolt, would go hand-in-hand. Are you suggesting to skip the measurement and just stick with the early physical symptoms (like heavy bolt)?

yes

Understanding Pressure :: Primal Rights, Inc

Reading pressure is a required skill that all shooters must have. Whether you are shooting factory ammunition or your own handloads, you absolutely must be able to detect and interpret pressure signs on your fired brass.

www.primalrights.com

 

[nn8734]

And get this, that measurement getting larger and wedging itself in the chamber is also what give you the heavy bolt lift symptom.

That’s why you measure. Once you’re at heavy bolt lift, you’re already way over.

Measuring detects the presence of increased pressure before the case wedges itself up against the chamber causing hard extraction, etc. And it works on any case, regardless of how many firings assuming you f/l size the case before each firing.

Yea, a little record keeping is involved and sure, every case brand is going to react a little differently. I only worry about the brass I’m working with.

But to say it doesn’t work isn’t accurate.