How close to max powder do you typically find good loads?

[SGK]

Ok so there is likely no simple answer to this one but...

I'm doing my first incremental powder test having done some seating depth tests at a somewhat conservative powder charge of 4% below max. (Charges of 6%, 5% and now 4% below max show no obvious pressure signs.)

Varget, 308 Win, Hornady ELD Match 168 grain

This is for my Blaser rifle. At 4% below max (Hornady list 44 grains as max), 42.24 grains, velocities are still below my existing purchased target ammo (from HPS in the UK - this is Sierra Match King bullets and I do not know the powder load they used) and groups worse.** So I'm planning on doing a little more seating depth testing and an incremental powder charge test, with a fixed seating depth, of 5 rounds at each of:

98.5% 43.34 grains
98.0% 43.12
97.5% 42.90
97.0% 42.68
96.5% 42.46

I confess to being a little nervous as I now start to head closer to that max listed load figure and want to make absolutely sure what I should be on the look out for etc. Sound advice appreciated.




** Seating depth results have been interesting thus far. I tested 4 CBTO lengths equating to an estimated 90, 50, 30 and 10 jump. 50 off was the clear winner. The HPS ammo I have has CBTO consistent with a jump of closer to 40 thou and so I have loaded another 5 rounds at 50 thou jump and 5 at 40 thou jump to compare and then extended the powder test at 40 thou jump for now.

 

[Bart B.]

I've found loads with Varget and imr4064 from max down to 90% that showed near zero changes in accuracy though 300 yards with 168's.

Longer ranges with heavier bullets as well as 155's usually need at least 96% or more of maximum.

US military teams shooting rebulleted 7.62 M80 ammo at about proof load pressures (67,500 cup, 81,000 psi) in M14/M1A and M1 match rifles got excellent accuracy and no harm to rifles.

 

[Fotheringill]

I don't go near the "max". I look at at least three sources and general toss out the heaviest and lightest and work from there. If I hear the crunch of the bottom of the bullet hitting the powder near the neck, I back off.

I have had 80 off the lands best in a rifle until I changed barrels and now it is 2 off the lands. Each set up is different.

 

[Papa Charlie]

I shoot .308 Winchester and find that 42.9gr of Varget performs exceptionally well in my system. When I went above this, the groups opened up very quickly.

Parameters:
.308 Win
Lapua .308 Win Brass
Berger 185gr Juggernauts
Varget 42.9gr
Chamber SAAMI Match
Barrel is Benchmark, 1:10 Twist, 5R, 30"
Muzzle Velocity 2745 fps

 

[Bart B.]

Chamber SAAMI Match

What is a SAAMI match chamber?

I ask because I've never heard of one and they're not spec'd in their standards.

 

[ms6852]

I am not a velocity chaser, so when I load I load for what gives me the smallest shot group. In my case all my firearms I load for end up liking loads in the midrange.

 

[Papa Charlie]

What is a SAAMI match chamber?

I ask because I've never heard of one and they're not spec'd in their standards.

This is what Benchmark called it. I am no expert about reamers and the many variations of them. The reamer that they used should have produced 0.110" Freebore from what they told me. After break in and a thousands rounds the freebore has opened up another 0.016" comparing measurements from new to now.

 

[rammac]

...US military teams shooting rebulleted 7.62 M80 ammo at about proof load pressures (67,500 cup, 81,000 psi) in M14/M1A and M1 match rifles got excellent accuracy and no harm to rifles.

I wont call you a liar but I'd need to see proof of this before I'd believe it.

 

[Bart B.]

I wont call you a liar but I'd need to see proof of this before I'd believe it.

I and other military team members have pulled bullets from M80 ammo with 41 grains of IMR4475 powder then seated Sierra 168's or arsenal 173 grain match bullets in them. I was issued a thousand or more from the USN Match Conditioning Unit in San Diego. LC65 lot 12638 was a favorite for use in our Garands;


Numerous on line sources have listed the same case (stannic stained light blue), primer and powder charge with the 173 grain FMJBT bullet for M60 7,62 NATO proof loads. It was often called Mexican match ammo.

PS: IMR4475 was replaced with W846 when Winchester took over ops at Lake City arsenal. Don't think it was ever rebulleted for match use.

 

[Depart123]

Ok so there is likely no simple answer to this one but...

I'm doing my first incremental powder test having done some seating depth tests at a somewhat conservative powder charge of 4% below max. (Charges of 6%, 5% and now 4% below max show no obvious pressure signs.)

Varget, 308 Win, Hornady ELD Match 168 grain

This is for my Blaser rifle. At 4% below max (Hornady list 44 grains as max), 42.24 grains, velocities are still below my existing purchased target ammo (from HPS in the UK - this is Sierra Match King bullets and I do not know the powder load they used) and groups worse.** So I'm planning on doing a little more seating depth testing and an incremental powder charge test, with a fixed seating depth, of 5 rounds at each of:

98.5% 43.34 grains
98.0% 43.12
97.5% 42.90
97.0% 42.68
96.5% 42.46

I confess to being a little nervous as I now start to head closer to that max listed load figure and want to make absolutely sure what I should be on the look out for etc. Sound advice appreciated.




** Seating depth results have been interesting thus far. I tested 4 CBTO lengths equating to an estimated 90, 50, 30 and 10 jump. 50 off was the clear winner. The HPS ammo I have has CBTO consistent with a jump of closer to 40 thou and so I have loaded another 5 rounds at 50 thou jump and 5 at 40 thou jump to compare and then extended the powder test at 40 thou jump for now.

Velocity is your most reliable indicator of your pressure level.

I use the max overall length I am willing to live with, and run my charges up to the book max velocity for my bullet, adjusted for barrel length of course. I then back off 2% and start running depth tests.

 

[dcali]

I don’t bother with loads that aren’t near max other than to check for pressure signs along the way (they’re almost never seen before they are expected). What’s the point of downloading (or overloading) a cartridge? I have always been able to get a stout load to shoot.

 

[Bart B.]

What’s the point of downloading (or overloading) a cartridge?

Ask the folks running the US Army AMU who first had the overloading idea back in the day it all started. They also replaced M118 173's with Sierra 180 HPMK's. Their International unit downloaded Sierra 168's to 2100 fps for use in 300 metre free rifles with 308 Win. ammo

 

[Homerange]

Contrary to others advice I research the loading books to find max listed loads as compressed and start a little below to check there's no pressure surprises and try to finish development with close to 100% case fill.

In general it's my understanding that a high % case fill offers the most consistent ES.
Please enlighten me if I have that wrong.

 

[dmoran]

@Bart B.
What will all the nostalgia info and component swapping info do for anyone today?
Betting most the Army people that might have any clue to what your talking about, likely are retired or even died by now.
Are the components and ammo readily available still?
I mean is any of this stuff your talking about even close to post year 2000?
Wasn't it like 40-years ago (1985 or so) that Winchester/Olin took over Lake City arsenal?

 

[NorCalMikie]

ES or SD don't mean SQUAT if you can't hit what you're aiming at!!
Load on the "high side" and you don't leave yourself any "wiggle room". Got no where to turn when your accuracy goes south.
Load at a lower node and you can go up or down to fine tune.
You load at 65*/70*, you head out the door to go shooting and it's 90*+.
You've loaded on the high side and can't figure out why you're having to beat the bolt open of you bolt won't operate on your gas gun. You didn't leave yourself any "wiggle room". And the next thing you know, your expensive brass that you paid BIG $$ for is junk. Fast FPS? You bet, but no where dependable. Mid range lower pressure loads will get the job done with less to worry about.

 

[Bart B.]

What will all the nostalgia info and component swapping info do for anyone today?

I'll let other readers decide.
[Quote]Betting most the Army people that might have any clue to what your talking about, likely are retired or even died by now.[/quote]Could be. Other services knew about it, too
[Quote]Are the components readily available still?[/quote]
I don't know.
[Quote]I mean is any of this stuff your talking about even close to post year 2000?[/quote]I'll let other readers decide.
[Quote]Wasn't it like 40-years ago (1985 or so) that Winchester/Olin took over Lake City arsenal?[/QUOTE]Probably.

 

[SGK]

Sounds like I plod along doing what I'm doing. Obviously I want to find a node closer to max/best velocity. I was wondering if that typically fell in the last couple of percent or lower down. People talk about 'high side' or 'near max' or 'midrange' etc but I don't yet have a benchmark for what these adjectives mean. 96.5% as a number already seems rather high. If I shake my 43.34 grain 98.5% of max loaded rounds I can still here the Varget moving around so they're far from compressed.

 

[Homerange]

Sounds like I plod along doing what I'm doing. Obviously I want to find a node closer to max/best velocity. I was wondering if that typically fell in the last couple of percent or lower down. People talk about 'high side' or 'near max' or 'midrange' etc but I don't yet have a benchmark for what these adjectives mean. 96.5% as a number already seems rather high. If I shake my 43.34 grain 98.5% of max loaded rounds I can still here the Varget moving around so they're far from compressed.

Sure, as far as a load in print from a manual that in the vast majority of cases will be well on the safe side.
Just know some push into what's never in print and they are still comparatively safe in the modern or robust actions. The brass will advise you when you're heading into dangerous territory.
Getting near to compressed is desirable IMO just to increase the chances of lower ES but it doesn't always come out that way. The more manuals you have to compare against each other along with the latest loading data from the powder makers websites can steer you to loads that generally perform well.

Still, whatever guidance or pointers you come up with, you still have to do the work.

 

[JFrank]

Sounds like I plod along doing what I'm doing. Obviously I want to find a node closer to max/best velocity. I was wondering if that typically fell in the last couple of percent or lower down. People talk about 'high side' or 'near max' or 'midrange' etc but I don't yet have a benchmark for what these adjectives mean. 96.5% as a number already seems rather high. If I shake my 43.34 grain 98.5% of max loaded rounds I can still here the Varget moving around so they're far from compressed.

I use a ladder test and read the paper.

 

[corsair4360]

My 700 clone 6xc is right at the ragged edge of maximum and accurate (less than 0.5" at 100 yards) just under 3100fps 105 grain berger. The other Savage 6xc (same reamer) with a different barrel has to be 1 grain less powder, otherwise the primers crater badly about the same size groups. My 270 WSM has a new barrel, have not shot it yet, my 30-06 likes hot loads, over maximum in the book, but no signs of pressure at all. My 338 Win Mag does not like maximum loads, but is .75" groups at 100 yards, which is fine for an elk rifle. I let the rifle tell me what it likes, both bullets and powder (within reason), about 1K rounds in a 6.5x284 and inconsistent groups., new barrel fixed it.