300WM Load Development Methods | Berger Bullets

D

dmossu

Private
Minuteman
Mar 18, 2021
52
11
Pennsylvania
#1
Hi everyone! I am fairly new to reloading and was hoping to get some advice from some of you that have been doing it for awhile! I am getting ready to start load development for my 300WM with Berger 205’s, CCI250 primers, H1000, and Norma Brass and was hoping to get some tips on where to start. For load development, I can only shoot out to 150 yards – but I do have access to a range out to 500 yards, but it is a hike from my house and prefer to get the majority of it done at 100 yards and fine tune at the longer distances.

With that being said, how does everyone start load development? I was thinking of starting about 2-3gr lower than Berger’s max load data and performing a pressure test in .5gr increments at .010 off all while looking for similar vertical points of impact. If I get a few consecutive similar points, to select the middle of them and perform seating depth testing at 10, 20, 30, and 40 off. Once I find the seating depth node, go back and fine tune the powder charge. My question with this being, how reliable are the vertical impacts on the pressure test if my rifle hates to shoot this bullet at 10 off (don’t know if it does, just wondering)? What does everyone usually do here? What do you do if during the pressure test none of the vertical points of impact are really that close?

Has anyone ever tried the Berger recommended load development method of starting with the minimum charge listed in the manual and seat the bullets at 10, 50, 90, and 130 off? I feel like the minimum charge is way too low and the jumps of seating depth are way too large. I know for the 205's for example the minimum load is 70.9 and the maximum load is 77.9 - so if I do seating depth at 70.9 and say it likes .050, and I bump the powder charge up to 76 gr, would that not dramatically change the pressure and likely change that seating depth node? So, it all seems counterintuitive lol.

I appreciate any feedback/advice!
 
#2
Always start by consulting published load data for you powder/bullet combo!

Since you're new, your plan to run a pressure test is a good idea. Just pay close attention to pressure signs (sticky bolt, flattened primers, ejector marks). You might track velocity when you do that, but understand that it'll just be a ballpark value. You'll need to shoot multiple of the same load to get accurate velocity.

Now that you have an idea of what your pressure window is you can start loading some 3-shot strings in a range to see how they shoot (OCW method is popular for this). A lot of folks try to find a consistent powder charge first, then do seating depth testing to see what the barrel likes. You can do that first, but since you're new I would suggest just loading some small distance off the lands and do seating depth testing later.

Just some thoughts - others can chime-in in detail.

PS Norma brass kind of sucks
 
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#4
Dogtown said:
Always start by consulting published load data for you powder/bullet combo!

Since you're new, your plan to run a pressure test is a good idea. Just pay close attention to pressure signs (sticky bolt, flattened primers, ejector marks). You might track velocity when you do that, but understand that it'll just be a ballpark value. You'll need to shoot multiple of the same load to get accurate velocity.

Now that you have an idea of what your pressure window is you can start loading some 3-shot strings in a range to see how they shoot (OCW method is popular for this). A lot of folks try to find a consistent powder charge first, then do seating depth testing to see what the barrel likes. You can do that first, but since you're new I would suggest just loading some small distance off the lands and do seating depth testing later.

Just some thoughts - others can chime-in in detail.

PS Norma brass kind of sucks
Click to expand...
So what jump do you recommend loading the OCW test at? Will those results be reliable if the gun does not like the seating depth?
 
#7
dmossu said:
So what jump do you recommend loading the OCW test at? Will those results be reliable if the gun does not like the seating depth?
Click to expand...

A lot of folks just pick a consistent COAL and test from there. For some that may be mag length; for others it might be 0.02" off the lands; and for me I usually just start with the bullet kissing the lands. It's up to you - none is better than any other.

With the OCW test you're not looking for groups; you're looking for point of impact shifts over different charges. There are plenty of webpages and YouTube videos explaining the process. You can also go the old school route and just measure the velocity of 3-shot strings and pick one that you like, then test different seating depths to see which combo shoots best.

The general rule of thumb:
  • find a powder charge that is consistent
  • find a COAL that shoots small groups
Something to keep in mind: you'll likely want to develop a tolerant load. One that can handle a bit of variation in all of the parameters and still shoot really well. That takes some time and practice, but is a good long term goal. Sometimes the smallest groups are incredibly picky and shoot not so great if you're off a tiny bit with powder/COAL/temperature. Also, the faster loads aren't always the most accurate.
 
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#11
dmossu said:
So what jump do you recommend loading the OCW test at? Will those results be reliable if the gun does not like the seating depth?
Click to expand...
Read your manual.
Read your other manual.
Consult Online Manuals.

Then....

I have a very similar rifle Bergara Premier 300 WM.
When I start, I use Book COAL. (cartridge overall length). Some of the best advice I got as a new reloader (and I am still new) is "Duplicate Factory" first.
Basically use the OCW at book COAL to find a good load. I will generally go 10% below max and work up in 0.5 grain increments for this round.

If you want to save wear and tear, just load 1 instead of 3 for the lower portion of the test (first 4-5 charges). I also load singles above max value for 3 increments to see if I have any margin. QUIT AT THE FIRST SIGN OF PRESSURE. ALWAYS.

so I'd have 1@70, [email protected], 1@71, [email protected], 1@72, [email protected], 3@73, etc...3@78, [email protected], 1@79, 1@79,5

Using a chrono helps as well as you can start to see where your load gives a consistent veloctity over a range of powder charges.

Ejector Swipe, Flattened Primers, Heavy Bolt Lift are signs of pressure. Compare to a factory round. Do a ton of google searches on each of those to educate yourself.

PAY ATTENTION TO YOU GUN!! How it sounds, how the bolt feels, how the round feels as it goes off, what the brass looks like. Go out into the sun and look at the brass. (Rifle has to cool off anyway).
 
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#12
dmossu said:
What are some of the tell tale signs of pressure? I feel like even with lighter loads I see the ejector circle on the brass. Very slight, but can see it on almost every load I fire. Is that normal? What do you usually see first?
Click to expand...
Flattening of primers is often the first sign, but understand that it's sometimes a false positive. Just keep an eye on them.

Ejector marks on the case head often start showing up after you see primers flatten. There can be really slight marks and then there can be really pronounced ones. If you're getting slight ejector marks on light loads, you could have soft brass (Norma is notorious for that) and/or you could be seating too long and be getting a pressure spike from the bullet being jammed into the lands.

Heavy bolt lift tends to be the last sign that you're heading into the danger zone. Definitely stop when you get this.
 
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#13
DocRDS said:
Read your manual.
Read your other manual.
Consult Online Manuals.

Then....

I have a very similar rifle Bergara Premier 300 WM.
When I start, I use Book COAL. (cartridge overall length). Some of the best advice I got as a new reloader (and I am still new) is "Duplicate Factory" first.
Basically use the OCW at book COAL to find a good load. I will generally go 10% below max and work up in 0.5 grain increments for this round.

If you want to save wear and tear, just load 1 instead of 3 for the lower portion of the test (first 4-5 charges). I also load singles above max value for 3 increments to see if I have any margin. QUIT AT THE FIRST SIGN OF PRESSURE. ALWAYS.

so I'd have 1@70, [email protected], 1@71, [email protected], 1@72, [email protected], 3@73, etc...3@78, [email protected], 1@79, 1@79,5

Using a chrono helps as well as you can start to see where your load gives a consistent veloctity over a range of powder charges.

Ejector Swipe, Flattened Primers, Heavy Bolt Lift are signs of pressure. Compare to a factory round. Do a ton of google searches on each of those to educate yourself.

PAY ATTENTION TO YOU GUN!! How it sounds, how the bolt feels, how the round feels as it goes off, what the brass looks like. Go out into the sun and look at the brass. (Rifle has to cool off anyway).
Click to expand...
Good idea on just loading 1 at the lower and upper ends to conserve some components.
 
#16
Dogtown said:
A lot of folks just pick a consistent COAL and test from there. For some that may be mag length; for others it might be 0.02" off the lands; and for me I usually just start with the bullet kissing the lands. It's up to you - none is better than any other.

With the OCW test you're not looking for groups; you're looking for point of impact shifts over different charges. There are plenty of webpages and YouTube videos explaining the process. You can also go the old school route and just measure the velocity of 3-shot strings and pick one that you like, then test different seating depths to see which combo shoots best.

The general rule of thumb:
  • find a powder charge that is consistent
  • find a COAL that shoots small groups
Something to keep in mind: you'll likely want to develop a tolerant load. One that can handle a bit of variation in all of the parameters and still shoot really well. That takes some time and practice, but is a good long term goal. Sometimes the smallest groups are incredibly picky and shoot not so great if you're off a tiny bit with powder/COAL/temperature. Also, the faster loads aren't always the most accurate.
Click to expand...
I am considering starting at .010 off for the OCW test because this will yield the highest pressure, right? I will make sure that the .010 will feed in my magazine before I do anything though and maybe that will answer my question. I think it will
 
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#22
918v said:
That’s not coal. That’s jump length. Coal tells us how much case volume you have available. 3.400” at .025” jump has less than 3.600” for example.
Click to expand...
The COAL is hovering between 3.590 - 3.600 - is this .010 variation normal? I honestly never even look at COAL because I always measure from the CBTO. Could that variation just be due to a slight difference between the Berger tips?
 
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#23
dmossu said:
The COAL is hovering between 3.590 - 3.600 - is this .010 variation normal? I honestly never even look at COAL because I always measure from the CBTO. Could that variation just be due to a slight difference between the Berger tips?
Click to expand...

Yeah. That’s the case with almost all bullets.

So how much did your fired cases expand?
 
#27
And at the bottom north of the belt to .514” or so?

It looks like you have a big chamber. I think 77grs will be too light. I would up the ladder to 80. Doesn’t mean you have to shoot that high if you see pressure sooner but I’m guessing you’ll be slow at 77grs.
 
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#28
918v said:
And at the bottom north of the belt to .514” or so?

It looks like you have a big chamber. I think 77grs will be too light. I would up the ladder to 80. Doesn’t mean you have to shoot that high if you see pressure sooner but I’m guessing you’ll be slow at 77grs.
Click to expand...
Yes I am thinking that the chamber on this rifle is huge. I have up to three fired brass and I still can't bump the shoulders because it chambers fine, so I am pretty much just sizing the necks.
 
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#29
So this is the result of my OCW test, what would you all do now?

The one 75 that is far off was 100% my fault
 

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#31
No pressure and I did not bring my chrono because it is just a cheap Caldwell and I am fairly positive it does not read accurately lol. I am going to hook it up during seating depth testing though.

I am thinking of running it at 75.5?
 
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#33
I have 30 years reloading the 300 WM
IMR 4350 with IMR 4831 most excellent with 165/168 bullets especially the Nosler Accubond and Ballistic Tip.
IMR 4831 with 180 Accubond and BT
Reloader 22 with Sierra 190gr MK
H4831 with 200 to 220
H1000 with 230

I mainly shoot the 180’s with IMR 4831 and WLR primers in WW cases for most my hunting @ 74.0
 
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