Correct initial settings for 338 lapua?

[JimGnitecki]

I have all my required supplies and tools coming, to be able to load 338 Lapua, using the following components:

.338 caliber 300g Sierra Matchking bullet

Federal "Match" Magnum Large Rifle primers

Norma once-fired 338 Lapua cases (fired in a Macmillan rifle)

Retumbo powder

Sako TRG 42 in 338 Lapua

Standard TRG magazine (I want to be able to ALWAYS feed from a magazine)

Redding Competition die set with sizing bushing and also micrometer adjsutments on both neck sizing die and seating die


I have not yet been able to measure the COAL that results in the bullet ogive just touching the lands. I have the Hornady gage and pre-tapped/prepared generic 338 case, but the Sierra bullets are in transit and not yet here. Once I get the bullets in hand, I will measure a bunch to find a good "typical" one, mark it with a marker, and use it to find the COAL that just touches the lands. Then I'll set a target COAL based on getting somehwat into the lands, while still enabling magazine feed, so I can do a proper, safe ladder test.

I'm not sure how to determine, or how to measure, some of the key controls though, and need to ask:

- In my standard Hornady set of 5 headspace gages, which one do I use for 338 lapua? The .420 gage, or?

- What is a "typical" headspace value for a Sako TRG 42 in 338 Lapua?

- I have a Sinclair bullet ogive gage coming. What is a "typical" case-base-to-bullet-ogive value, given the 330g Sierra Matchking bulelt is being used?

- The Hodgon loading guide suggests, for Retumbo,a range of 85 grains (start) to 94 grains (maximu, and compressed). I plan to start at 85 and work upwards carefully. But, what end values have owners of other TRG 42 rifles found to be the optimal "nodes" for ACCURACY versus power? (I will be shooting at a MAXIMUM of 1000 yards since that is the longest range available to me, so no point in powering up for more, plus I want to limit my barrel wear since I don't NEED the higher velocities)

- Based on information I have assembled from others on the forum, I am expecting that my Norma cases will likely be .014" neck wall thickness, and I have a .365" bushing coming for the sizing die, so I should end up with .365" minus .338" minus (.014 x 2) = -.001" clearance (i.e. interference fit) between bullet and neck walls. Will this be enough to prevent bullet setback in the magazine during firing of previous rounds, given the stout recoil of a 338 Lapua?

Jim G

 

[ChrisGarrett]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">I have all my required supplies and tools coming, to be able to load 338 Lapua, using the following components:

.338 caliber 300g Sierra Matchking bullet

Federal "Match" Magnum Large Rifle primers

Norma once-fired 338 Lapua cases (fired in a Macmillan rifle)

Retumbo powder

Sako TRG 42 in 338 Lapua

Standard TRG magazine (I want to be able to ALWAYS feed from a magazine)

<span style="color: #6633FF"> You're going to just load the 300s to mag length, whatever that length is. My TRG-42 mags I can go 3.677", IIRC. The 300s take up a lot of case capacity, so this is the reason for just loading them long. Don't worry about touching the lands, you won't be able to from the box mags.</span>

Redding Competition die set with sizing bushing and also micrometer adjsutments on both neck sizing die and seating die


I have not yet been able to measure the COAL that results in the bullet ogive just touching the lands. I have the Hornady gage and pre-tapped/prepared generic 338 case, but the Sierra bullets are in transit and not yet here. Once I get the bullets in hand, I will measure a bunch to find a good "typical" one, mark it with a marker, and use it to find the COAL that just touches the lands. Then I'll set a target COAL based on getting somehwat into the lands, while still enabling magazine feed, so I can do a proper, safe ladder test.

<span style="color: #6633FF"> COAL will be determined by your mag box length. You won't be near the lands, so don't worry about finding the lands unless you'll be single feeding them, which can yield accuracy improvements, at times.</span>

I'm not sure how to determine, or how to measure, some of the key controls though, and need to ask:

- In my standard Hornady set of 5 headspace gages, which one do I use for 338 lapua? The .420 gage, or?

<span style="color: #6633FF"> Yes, the .420 bushing will work. This is used to measure 'fired' brass and to set your sizing die up to just bump the shoulders back .002", or so. I can go 2-3 cycles only neck sizing before I need to do a shoulder bump.</span>

- What is a "typical" headspace value for a Sako TRG 42 in 338 Lapua?

<span style="color: #6633FF"> Your particular chamber will tell, we won't. Take fired cases in YOUR chamber and bump them back .002", or just neck size for a bit, until the cases yield resistant bolt closure. It's a 'relative' gage, not an absolute one.</span>

- I have a Sinclair bullet ogive gage coming. What is a "typical" case-base-to-bullet-ogive value, given the 330g Sierra Matchking bulelt is being used?

<span style="color: #6633FF"> Again, this is determined by your chamber/throat and bore. You measure the ogive to compare bullets to one another for uniformity, or in conjunction with their modified case gage for finding the lands with a particular bullet.</span>

- The Hodgon loading guide suggests, for Retumbo,a range of 85 grains (start) to 94 grains (maximu, and compressed). I plan to start at 85 and work upwards carefully. But, what end values have owners of other TRG 42 rifles found to be the optimal "nodes" for ACCURACY versus power? (I will be shooting at a MAXIMUM of 1000 yards since that is the longest range available to me, so no point in powering up for more, plus I want to limit my barrel wear since I don't NEED the higher velocities)

- Based on information I have assembled from others on the forum, I am expecting that my Norma cases will likely be .014" neck wall thickness, and I have a .365" bushing coming for the sizing die, so I should end up with .365" minus .338" minus (.014 x 2) = -.001" clearance (i.e. interference fit) between bullet and neck walls. Will this be enough to prevent bullet setback in the magazine during firing of previous rounds, given the stout recoil of a 338 Lapua?

Jim G </div></div>

 

[JimGnitecki]

Re: Correct initial settings for 338 lapua?

Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G

 

[mrbig]

Re: Correct initial settings for 338 lapua?

my Savage magazine is marked 338 Lapua Magnum 3.850" ,,hopefully I will be able to load the 300`s touching and fit the mag,,I have to wait for a funds recovery before I can try it out..

 

[LineofDeparture]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G</div></div>

I too wasn't aware that i would not be able to get near the lands.. However does simplify tons of things. I was just about to take my gun to get the OAL measured. Should i save my time and money?

 

[dstewart51]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrbig</div><div class="ubbcode-body">my Savage magazine is marked 338 Lapua Magnum 3.850" ,,hopefully I will be able to load the 300`s touching and fit the mag,,I have to wait for a funds recovery before I can try it out..</div></div>

Thats the outside dimension. You will be able to fit ~3.740" in the mag. With my Savage, I found COAL with 300gr SMK's at the lands to be 3.714" IIRC (not in front of my data). But I am able to to seat the bullet at the lands and still have room to fit in the DBM.

 

[Hoverp]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrbig</div><div class="ubbcode-body">my Savage magazine is marked 338 Lapua Magnum 3.850" ,,hopefully I will be able to load the 300`s touching and fit the mag,,I have to wait for a funds recovery before I can try it out.. </div></div>
Don't we all wish, but no that measurement is the outside dimensions of the box mag not the inside, and loading to mag length you won't be able to touch the lands.

Sorry.

 

[dstewart51]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G</div></div>

You may want to give the Scenars a try. They seem to be quite insensitive to seating depth and they seem to perform best with some jump.

 

[mrbig]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hoverp</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrbig</div><div class="ubbcode-body">my Savage magazine is marked 338 Lapua Magnum 3.850" ,,hopefully I will be able to load the 300`s touching and fit the mag,,I have to wait for a funds recovery before I can try it out.. </div></div>
Don't we all wish, but no that measurement is the outside dimensions of the box mag not the inside, and loading to mag length you won't be able to touch the lands.

Sorry. </div></div>

I pinched the neck on a case and chambered it with the 300 Scenar to push the bullet back in the case with the rifelings,,that round would fit in the mag,,but my calipers are at my brothers,

the Scenar has a much shorter nose than the Berger,,and it shoots better in daddys TRG42,

 

[JimGnitecki]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dstewart51</div><div class="ubbcode-body"> <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G</div></div>

You may want to give the Scenars a try. They seem to be quite insensitive to seating depth and they seem to perform best with some jump. </div></div>

Yes, but the Scenars are not only WAY more expensive, but they have a worse ballistic coefficient than the Sierra 300g (.736 versus .768).

Jim G

 

[Blackbrush]

Re: Correct initial settings for 338 lapua?

420 on the headspace gauge
you need to make your own "modified" case for the oal tool as the one from Hornady doesn't account for the headspace of your specific chamber - use one of your own fired cases
you must measure the Norma brass to be precise about its neck wall thickness - my 2 lots of Lapua are slightly different
get a body die to keep your shoulders/headspace in check - I use a type s fl die

Good luck - you're off to a good start with a fun rig!

 

[mavrick10_2000]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dstewart51</div><div class="ubbcode-body"> <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G</div></div>

You may want to give the Scenars a try. They seem to be quite insensitive to seating depth and they seem to perform best with some jump. </div></div>

Yes, but the Scenars are not only WAY more expensive, but they have a worse ballistic coefficient than the Sierra 300g (.736 versus .768).

Jim G </div></div>

And this is one of the cases where the B.C. numbers do not give you the entire picture.

The SMK's are good, but when pushing out to the limits of the round the Scenars transition very well through the transonic range.

 

[mrbig]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mavrick10_2000</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dstewart51</div><div class="ubbcode-body"> <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JimGnitecki</div><div class="ubbcode-body">Well the fact that I probably won't be able to get near the lands simplifies things! Thanks!

Jim G</div></div>

You may want to give the Scenars a try. They seem to be quite insensitive to seating depth and they seem to perform best with some jump. </div></div>

Yes, but the Scenars are not only WAY more expensive, but they have a worse ballistic coefficient than the Sierra 300g (.736 versus .768).

Jim G </div></div>

And this is one of the cases where the B.C. numbers do not give you the entire picture.

The SMK's are good, but when pushing out to the limits of the round the Scenars transition very well through the transonic range. </div></div>

I too believe in the Scenar,,we quit taking into consideration the BC and just tested for accuracy,,the Lapua smoked the Berger and Sierra in the one rifle we had at the time..10 twist TRG42,,

you are gonna have to dial in wind and elevation anyway,,it doesnt help much to be 10 inches better in the wind if the groups are bigger than the target.

 

[JimGnitecki]

Re: Correct initial settings for 338 lapua?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gabbott</div><div class="ubbcode-body">420 on the headspace gauge
you need to make your own "modified" case for the oal tool as the one from Hornady doesn't account for the headspace of your specific chamber - use one of your own fired cases
you must measure the Norma brass to be precise about its neck wall thickness - my 2 lots of Lapua are slightly different
get a body die to keep your shoulders/headspace in check - I use a type s fl die

Good luck - you're off to a good start with a fun rig!
</div></div>

All good advice.

Yes, the only fired cases I have right now from MY specific rifle are from factory Hornady rounds, so not representative of the Norma cases I will be using. I will need to use the Hornady "generic" gage for the first batch of rounds I load, but then can correct the dimesniosn after using one of my own fired cases to re-measure using the Hornady gage.

I do have a FULL set of Redding Compeition dies arriving today: micrometer-equipped neck sizing die, body die, and micrometer-equipped seating die. I will need to do a FULL LENGHT sizing initially, as the Norma cases I am going to use have previosuly been fired in a MacMillan rifle, so I need to ensure they are "corrected" down to "generic" dimensions before laoding and firing them (in case the MacMillan chamber was bigger than my TRG chamber).I suppsoe it will be obvious after subsequent firings in my rifle when I need to full length size again after that, via harder chmabering and extraction of the cases? (This is my first precision BOLT rifle).

Jim G

 

[JimGnitecki]

Re: Correct initial settings for 338 lapua?

I will have to give the Scenar's a try later too.

Jim G

 

[Aimsmall55]

Re: Correct initial settings for 338 lapua?

Anybody tried the hornadys 250 bt hp