300 PRC 225 ELD, 220 LRHt Retumbo

[Max_The_Phoenix]

HiGuys
I had 2 range trips and did some tests to confirm the results,
100 rounds through the barrel before tests, barrel was cleaned and all the copper and carbon removed, borescoped to make sure there is no copper in there.
Brass has been annealed and full length sized and shoulder bump is 0.0015-0.002
-Bartlein 1:9 28” HV
-Defiance Ruckus
-300 Prc Aw2 chamber
-1x fired Lapua brass
-225 ELD-M
- 220 LRHT
- CCI 250
- Hodgdon Retumbo
-10thou off the lands
Temp ~ 75F

225 ELD-M
Powder charge test was from 74.5 to 80.2

Test 1
76.0-76.3 @ 2755-2761fps
78.4-78.7 @ 2849-2851fps

Test 2
76.0-76.3 @ 2755-2775fps
78.4-78.7 @ 2858-2850
79.0-79.3 @ 2888-2878


Berger 220 LRHT
Test 1
77.1-77.4 @2806-2812fps
78.3-78.6 @ 2856-2853fps

Test 2
77.1-77.4 @ 2789-2800fps
78.3-78.6 @ 2855-2856fps
78.9-79.2 @ 2862-2864fps

As You see berger gave me a really consistent node around 78.3-78.6

I removed a few coils from ejector spring since it was putting marks on the virgin or once fired dummy rounds, it looked better.

-why I am getting ejector mark at the lightest load all the way up to the highest load but the thing is it looks like the higher I go the signs are getting smaller.
- there is zero primer cratering
Bolt got a tiny bit sticky on 76 grs @ 2755fps but the feeling was going loose and tight towards the higher powder charges.

I am not sure the marks are from high pressure or from the bad ejector.
Quickload shows I am around 55k psi with 78.7grs of Retumbo.

- does the bolt lift goes away after seating the bullet deeper?

- I see some other folks are getting 2850-2900 fps only with 76.5grs of Retumbo. Why are they getting higher velocity with lower powder charges (+100 fps)?

 

[918v]

Maybe your power is too wet. What is the humidity where you load?

 

[Max_The_Phoenix]

Maybe your power is too wet. What is the humidity where you load?

I am in Bay Area and the humidity id always above %50
I always keep the powder in its container. What’s the acceptable humidity?

 

[culater]

I am in Bay Area and the humidity id always above %50
I always keep the powder in its container. What’s the acceptable humidity?

Get de humidifier for you loading room. Just a suggestion

 

[Max_The_Phoenix]

Get de humidifier for you loading room. Just a suggestion

Thanks, I do reloading in the garage but that’s somyI have to look into.

 

[Dogtown]

It’s not humid in the Bay Area the way it’s humid in other parts of the country.

I would lean towards heavy bolt lift being your most reliable sign of pressure that you listed. Magnums can also be kind of weird in that regard, so don’t get too focused on flattened primers and ejector marks unless they come with heavy bolt lift.

Another point, some barrels can just be kind of slow for less than obvious reasons. I had .338LM barrel that never really sped-up and shot the same load slower than my other barrels. I’ve also had barrels that took longer than expected to stabilize. There’s really no rhyme or reason to it.

Heavy bolt lift won’t go away with seating - it’s a symptom of approaching max pressure. Of course closing the bolt is a different story.

 

[Max_The_Phoenix]

It’s not humid in the Bay Area the way it’s humid in other parts of the country.

I would lean towards heavy bolt lift being your most reliable sign of pressure that you listed. Magnums can also be kind of weird in that regard, so don’t get too focused on flattened primers and ejector marks unless they come with heavy bolt lift.

Another point, some barrels can just be kind of slow for less than obvious reasons. I had .338LM barrel that never really sped-up and shot the same load slower than my other barrels. I’ve also had barrels that took longer than expected to stabilize. There’s really no rhyme or reason to it.

Heavy bolt lift won’t go away with seating - it’s a symptom of approaching max pressure. Of course closing the bolt is a different story.

You know it’s not heavy, it’s a tiny bit heavy and the weird part is that the feeling of the bolt is kind of like a sinus wave from 77.5 to 80. At some charges there was no heavy bolt lift feeling at all that really confuses me

 

[Dogtown]

The math of sinus waves is brutal: y(t) = Asin(cough + theta) / runny-nose

You shouldn't be getting a wave of heavy bolt lift; it should be predictably linear, all things being consistent. But suppose you seat one round too long and it's jammed in the lands; when you shoot it you'll get more pressure, velocity, and potentially a heavy bolt lift, while the next round may be totally fine.

So maybe it's all in your head?

 

[Max_The_Phoenix]

The math of sinus waves is brutal: y(t) = Asin(cough + theta) / runny-nose

You shouldn't be getting a wave of heavy bolt lift; it should be predictably linear, all things being consistent. But suppose you seat one round too long and it's jammed in the lands; when you shoot it you'll get more pressure, velocity, and potentially a heavy bolt lift, while the next round may be totally fine.

So maybe it's all in your head?

Thanks for the reply brother,
All the bullets were seated within 0.0005 range, you are right, it might be in my head, I only remember even at 80.2 lift was very light but different than normal.
So how much of the bolt lift considered safe and quickload showing 55kpsi at 78.7grs ?

 

[Dogtown]

Generally you don’t start seeing heavy bolt lift until you’re within a grain or so of max (depending on the cartridge).

Don’t get too focused on QL numbers too - it’s a predictive guide, not ground truth. Your case’s H20 capacity may not match, and some powder burn rates and resulting pressure curves need to be trued to your own data.

According to Hodgdon, book max for that Retumbo combo is 76.4. Your COAL may be different, but the difference is probably insignificant. I’m all for going above book max sometimes, but think of that as a potential clue.

 

[Max_The_Phoenix]

Generally you don’t start seeing heavy bolt lift until you’re within a grain or so of max (depending on the cartridge).

Don’t get too focused on QL numbers too - it’s a predictive guide, not ground truth. Your case’s H20 capacity may not match, and some powder burn rates and resulting pressure curves need to be trued to your own data.

According to Hodgdon, book max for that Retumbo combo is 76.4. Your COAL may be different, but the difference is probably insignificant. I’m all for going above book max sometimes, but think of that as a potential clue.

I trued the h2o capacity to the average 95.42 in the app and played with the burn rate to match the velocity
Hornady book states the 78.9grs as the max charge, hodgdon is much lower then,
I guess I have to go and shoot those charges in 5 shots group to see what it shows. My COL is 3.722

 

[Max_The_Phoenix]

my barrel has about 250 rounds in it now,
I see some velocity changes.
I had a node @771.-77.4 from 2800-2809fps
another one 78.3-78.9 2855-2864fps when the barrel had 160 rounds on it

now looks like at 77.1-77.4 I have 2839,2845,2848,2856fps(0.1grs increaments) and 77.4 gives me the ES:4, SD:2.3

it shoots under .3 MOA but the problem is that I don't have that .3grs window anymore.

should I do another ladder test?

 

[Rocketmandb]

should I do another ladder test?

Your sample size is still small. Load like 25 at somewhere in that range and go shoot and see what you end up with. If you can get an SD in the mid-upper single digits, then you're good to play with seating depth.

And use the Bergers - better to shoot copper than plastic

Also, I also live in the Bay Area and humidity this time of year is not an issue. I have a dehumidifying photographic equipment cabinet that I keep my open containers in. I keep it at just under 50%, which helps during winter (which is when I do my long range shooting).

 

[Max_The_Phoenix]

Your sample size is still small. Load like 25 at somewhere in that range and go shoot and see what you end up with. If you can get an SD in the mid-upper single digits, then you're good to play with seating depth.

And use the Bergers - better to shoot copper than plastic

Also, I also live in the Bay Area and humidity this time of year is not an issue. I have a dehumidifying photographic equipment cabinet that I keep my open containers in. I keep it at just under 50%, which helps during winter (which is when I do my long range shooting).

You mean in the middle of 77.1-77.4?
I agree with you, I had the best consistency in seating pressure with Bergers, Hornady ELDMs require a lot more pressure to seat the bullets.
- so you just put the dehumidifiers next to them and leave it?

 

[Rocketmandb]

You mean in the middle of 77.1-77.4

Yes - maybe 77.3

so you just put the dehumidifiers next to them and leave it?

The photographic equipment case actually is the dehumidifier.