help with pressure signs, loads below book minimum

[climb-101]

I'm loading for my 338 lapua mag. I am getting a ejector mark and every now and then a smear from the bolt. I am trying to figure out why i'm getting pressure even below the book minimum of if 82.7g of H1000. I loaded them up at 80g of H1000. the velocity is also consistent with what the book showed as 5g more power (85g). I tried different seating depths and they don't seem to have any affect on the pressure signs. Any ideas as to where the pressure is coming from, do i need to go to a slower burning powder? it seems consistent at 80g but the pressure is my concern. my specs are below.

stiller tac 338 action
rock creek 29" barrel 9.4 twist
lapua brass
300 Smk
80g H1000
federal 215 primers
3.015 base to ogive load length, gives me .020 jump
3 over the crono were 11ft/sec different. 2581, 2585, 2579
standard deviation with those rounds was just over 3

any ideas, drop down lower on the powdercharge till the ejector mark goes away and shoot it at a lower velocity. I'm getting tired of fighting pressure.

thanks for the help. i will try to add some pics of the back of the shells. I tried a few ata 80.5g H1000 and it was worse, very flat primers but still easy bolt lift.

 

[climb-101]

pic of the back end. hard to get a good pic on my phone for some reason. i can't get ejector marks to show on the pics.

 

[dok7mm]

All rifles vary on max pressure and velocity. Looks like a definite ejector mark on far right case. Couldn't make out charge weight. Also you didn't specify which charge was running around 2580 fps. That is max speed in Hogdon's data. Max speed usually means you're already into the max pressure range for your setup, regardless of charge weight. You can measure dimension changes on case diameter on loads that didn't show pressure against those that did, to confirm this. My best guess is to back off and try to find a lower node. If this is a full custom, it's not unusual to have them show pressure below book max charge weight. Good Luck

 

[243winxb]

As said above, seems to cover it well.

Make sure chamber is dry.

Remove all signs of lube from the brass.

I would be tempted to increase the powder charge, looking for hard bolt lift. A true sign of pressure.

Watch for primer flow into the firing pin channel.

Right shows first sign of press. Working up. The one on the left has expanded the primer pocket and primer fell out.

Note that factory loaded ammo may produce the ejector hole mark, like on the right case head.

 

[918v]

Excessive headspace causes the case head to violently impact the bolt face causing a false pressure sign via ejector mark.

 

[Engineering101]

Pretty clear that the burn rate of your powder is faster than nominal. Powder is made to be near its nominal burn rate with around 1% moisture content and that equates to RH in the range 40 to 50% which is controlled by the powder manufacturer. If your powder is stored in an environment with humidity less than that it will dry out and burn faster. I have this issue with every powder I have since my loading room humidity tends to be around 30% in winter when the furnace is running.

 

[243winxb]

AR2217 Is H1000

AR2217 Is H1000 http://www.adi-powders.com.au/handloaders/rifle.asp?Calibre=338+Lapua+Magnum


Note the difference in barrel length data 24", your 29" inch. 35 fps per inch x 5 inch = 175 fps

 

[climb-101]

All rifles vary on max pressure and velocity. Looks like a definite ejector mark on far right case. Couldn't make out charge weight. Also you didn't specify which charge was running around 2580 fps. That is max speed in Hogdon's data. Max speed usually means you're already into the max pressure range for your setup, regardless of charge weight. You can measure dimension changes on case diameter on loads that didn't show pressure against those that did, to confirm this. My best guess is to back off and try to find a lower node. If this is a full custom, it's not unusual to have them show pressure below book max charge weight. Good Luck

the 2580 ft/sec velocity was the 80 g h1000. i know all rifles act different, i just figured something was off that i was missing it and couldn't figure out. that interesting that they show 2500-2600 as max velocity because in the sierra book it's about the middle velocity ( i know all books are different also) don't remember what the max was and the book is at home.

what area of the cases should i measure?

As said above, seems to cover it well.

Make sure chamber is dry.

Remove all signs of lube from the brass.

I would be tempted to increase the powder charge, looking for hard bolt lift. A true sign of pressure.

Watch for primer flow into the firing pin channel.

Right shows first sign of press. Working up. The one on the left has expanded the primer pocket and primer fell out.

Note that factory loaded ammo may produce the ejector hole mark, like on the right case head.

the chamber is dry, all lube was removed by tumbling then wiping down with lacquer thinner on the cases. that was my first thought, so i made sure that it was clean and lube free. the 80.5g charge i think showed the start of the primer starting to flow around the pin but just barely. still an easy bolt lift and the primers are tight.

AR2217 Is H1000 http://www.adi-powders.com.au/handloaders/rifle.asp?Calibre=338+Lapua+Magnum


Note the difference in barrel length data 24", your 29" inch. 35 fps per inch x 5 inch = 175 fps

interesting, never thought of this as to why the velocity would be higher but makes sense.

i will see if i can check the headspace and back the charge down, maybe go down to 78g of H1000 and see if the ejector mark goes away. thanks for the help guys

 

[LaHunter]

I use Federal 215GM match primers. I'm not sure, but I have often wandered if Federal primers are 'softer' than other primers and more prone to flattening. Reason is, before I started hand loading, I shot Federal Premium factory ammo in my 7 mm mag. Every single spent brass would have a 'flattened' primer. Not spread out of the pocket, but flattened. This was consistent for 3 different M700 7mm rem mag rifles. Looking at your photos, your primers look fairly similar to most spent Federal primers I have seen, my hand loads and factory ammo that I have fired.

During load development for my rifle, I experienced a sticky bolt before I ever started seeing ejector marks. This is where I considered 'over pressure' and I backed off a little from there.

The above post about head space is interesting. How are you resizing your brass?

Good Luck

 

[climb-101]

the first time with new brass it was a full length resize, after that it was just sizing the neck. i'm using forester and redding dies.

the primers could be soft, the 80g load they are flat but still a slight radius on the corner, the 80.5 load there is no radius and they filled the primer pocket. i will punch them out tonight and see what they look like

 

[TonyQ]

I am dealing with the same issue myself on my 338 Terminator. I am pretty sure I figured out what the problem was. I was using a hornady comparator and it was measuring the ogive at .325 and the lands marks I saw on the bullet were at .338. The guns smith sent the test target and the measurement was 2.998 -.10 off the lands. My measurement with the hornady comparator was at 3.073 -.10 off the lands. That's a huge difference I am getting a new comparator and I will let you know if this solves my problem. I am pretty sure it will just want to test it out to make sure.

 

[fmuguira]

I couldn't tell from picture what brass you re using. I had pressure signs and stuck cases in my 338 Lapua when I first got it and those loads were 4-5 grains below some published Max's. Switched to Lapua brass ( it's spendy) and problem solved.

May or may not be part of your problem.

 

[climb-101]

I couldn't tell from picture what brass you re using. I had pressure signs and stuck cases in my 338 Lapua when I first got it and those loads were 4-5 grains below some published Max's. Switched to Lapua brass ( it's spendy) and problem solved.

May or may not be part of your problem.

im using lapua brass

 

[fmuguira]

One potential problem eliminated. Good luck!