338 Lapua Improved searching for pressure signs

[trental]

Looking for opinions on finding max pressure in my 338 Lapua "Rogue" which is an improved cartridge with taper reduced, shoulder moved forward, and 37 degree shoulder. This rifle is a custom with a Nesika action that has no ejector which means that I can't watch for pressure via brass flow into the ejector hole. I also don't have a pressure trace so that leaves me with primer interpretation, bolt lift, and Case Head Expansion (CHE).

I am loading 285gr Hornady ELD-M on top of VV N570. I started at the conservative max load listed by VV for the standard 338 Lapua Mag (~94 grains) and worked my way up to 103gr. My primers showed no signs of pressure and bolt lift is buttery smooth at all charge weights. I start seeing 0.0005" CHE at 99.5gr and at 103gr I am at or just under 0.001" CHE. I really need to get a micrometer since my caliper can only display half thousandths.

My question is, should I ignore the fact that I am not getting any primer flattening (see photo) and bolt lift is smooth (custom action) and keep going up in charge weight, or should I take the case head expansion alone as a sign of max pressure. None of these indications on their own are generally super accurate measures of pressure but normally by combining them it makes it a little easier. At 103gr I am at 3100fps which is plenty fast out of a 27.5" barrel. I found velocity nodes at 3075 and also 3040 fps and will investigate those for accuracy but would like to know how you all would watch for pressure in this situation. Drill a hole in the bolt face so brass can flow into it? (Just kidding, I'm not doing that)

 

[LA50SHOOTER]

Looking for opinions on finding max pressure in my 338 Lapua "Rogue" which is an improved cartridge with taper reduced, shoulder moved forward, and 37 degree shoulder. This rifle is a custom with a Nesika action that has no ejector which means that I can't watch for pressure via brass flow into the ejector hole. I also don't have a pressure trace so that leaves me with primer interpretation, bolt lift, and Case Head Expansion (CHE).

I am loading 285gr Hornady ELD-M on top of VV N570. I started at the conservative max load listed by VV for the standard 338 Lapua Mag (~94 grains) and worked my way up to 103gr. My primers showed no signs of pressure and bolt lift is buttery smooth at all charge weights. I start seeing 0.0005" CHE at 99.5gr and at 103gr I am at or just under 0.001" CHE. I really need to get a micrometer since my caliper can only display half thousandths.

My question is, should I ignore the fact that I am not getting any primer flattening (see photo) and bolt lift is smooth (custom action) and keep going up in charge weight, or should I take the case head expansion alone as a sign of max pressure. None of these indications on their own are generally super accurate measures of pressure but normally by combining them it makes it a little easier. At 103gr I am at 3100fps which is plenty fast out of a 27.5" barrel. I found velocity nodes at 3075 and also 3040 fps and will investigate those for accuracy but would like to know how you all would watch for pressure in this situation. Drill a hole in the bolt face so brass can flow into it? (Just kidding, I'm not doing that)

I shoot the 40 degree Ackley Improved version and I fully understand what you are saying. - I've run Alliant RL-33 up to 106.2 gr. with the same type of results you are speaking of. - Bottom line, IF your going to "push it" then your brass life will suffer, even if your shooting Lapua, Peterson or ADG brass. - 3 stout 106 grain loads and primer pockets have loosened up a whole bunch which indicates that pressure has reached 1.25 times the CIP rating (so +75 Kpsi). - Micrometer readings of the case head will revile signs of pressure probably better than about any other method IMO. - What I did was settle on an "accuracy node" that is compatible with decent case life for each of the 3 rifles that I'm shooting in this caliber. - In your case, I'd determine if 3040 or 3075 fps produces the best accuracy and go with it unless you want to burn through brass. - You can take a few pieces and run a "stress-test" and see how the life expectancy is.
- I see in the photo your using the BBS 15 (Lapua) - Have you tried with any other manufacturer ?

- Ron -

 

[moondog]

Listen to Ron! He is a wealth of info on the 338 Imp. He definitely help steer me in the right direction with mine.

 

[trental]

I shoot the 40 degree Ackley Improved version and I fully understand what you are saying. - I've run Alliant RL-33 up to 106.2 gr. with the same type of results you are speaking of. - Bottom line, IF your going to "push it" then your brass life will suffer, even if your shooting Lapua, Peterson or ADG brass. - 3 stout 106 grain loads and primer pockets have loosened up a whole bunch which indicates that pressure has reached 1.25 times the CIP rating (so +75 Kpsi). - Micrometer readings of the case head will revile signs of pressure probably better than about any other method IMO. - What I did was settle on an "accuracy node" that is compatible with decent case life for each of the 3 rifles that I'm shooting in this caliber. - In your case, I'd determine if 3040 or 3075 fps produces the best accuracy and go with it unless you want to burn through brass. - You can take a few pieces and run a "stress-test" and see how the life expectancy is.
- I see in the photo your using the BBS 15 (Lapua) - Have you tried with any other manufacturer ?

- Ron -

Thanks Ron. That's valuable information and personal experience. I do have some normal Lapua brass I could try. I think your point about running a stress test on some pieces of brass is a great one. It'd be easy to take a press and hand priming tool to the range and see at what # of firings the pockets loosen up. I'll be happy at the more conservative nodes but I'd like to know what the max pressure & velocity is just for the sake of answering that question. Thanks again Ron.

 

[LA50SHOOTER]

Thanks Ron. That's valuable information and personal experience. I do have some normal Lapua brass I could try. I think your point about running a stress test on some pieces of brass is a great one. It'd be easy to take a press and hand priming tool to the range and see at what # of firings the pockets loosen up. I'll be happy at the more conservative nodes but I'd like to know what the max pressure & velocity is just for the sake of answering that question. Thanks again Ron.

Based on my experience in my guns, a 29" Bartlein 5R with 106.2 gr. of RL-33 produced 3025 fps and cases have loose primer pockets in 3 firings. - I found that 104.8 gr. at 2930 fps produced decent accuracy @ 2000 yards & good case life. - I'm running a 0.265 throat for the 300 gr. Berger Hybrids on this chamber.

Never at any time did I experience any bolt lift signs and primers appeared rounded at the corner radius area, the most that I saw was ejector swipe at 105.4 gr. and above.

On a 34" Benchmark in a second rifle which I've extended the throat an additional 0.060, I've run 105.2 gr. of RL-33 and producing velocity of 3060 fps and good case life. - This rifle currently hold the E2k (2000 yard) Unlimited Score record.

On a 30" Krieger 5R barrel in the 3rd rifle 104.8 gr. of RL-33 is producing 2975 fps.
I have not yet tried v/v N-570 as Alliant RL-33 produced very good results.

- You may want to give RL-33 a try if you are so inclined, it's burn rate is very close to v/v N-570 and both are optimal for improved 338 Lapua cartridges.

- All The Best !!

- Ron -

 

[trental]

Based on my experience in my guns, a 29" Bartlein 5R with 106.2 gr. of RL-33 produced 3025 fps and cases have loose primer pockets in 3 firings. - I found that 104.8 gr. at 2930 fps produced decent accuracy @ 2000 yards & good case life. - I'm running a 0.265 throat for the 300 gr. Berger Hybrids on this chamber.

Never at any time did I experience any bolt lift signs and primers appeared rounded at the corner radius area, the most that I saw was ejector swipe at 105.4 gr. and above.

On a 34" Benchmark in a second rifle which I've extended the throat an additional 0.060, I've run 105.2 gr. of RL-33 and producing velocity of 3060 fps and good case life. - This rifle currently hold the E2k (2000 yard) Unlimited Score record.

On a 30" Krieger 5R barrel in the 3rd rifle 104.8 gr. of RL-33 is producing 2975 fps.
I have not yet tried v/v N-570 as Alliant RL-33 produced very good results.

- You may want to give RL-33 a try if you are so inclined, it's burn rate is very close to v/v N-570 and both are optimal for improved 338 Lapua cartridges.

- All The Best !!

- Ron -

Judging by your velocities from longer barrels, albeit with RL-33 (similar burn rate), I am thinking I am at or near max pressure (probably over). I'm pretty sure my throat is a PTG "Bore Rider" but I need to confirm it with a chamber cast. Rifle was built by a gentleman that fell ill and I am unable to get some of the detail (it's a beautiful new build though). I'll update with a stress test on a couple pieces of the BBR-15 brass and maybe a couple of the normal Lapua brass.

I have a pound of RL-33 I can test at some point, but I have 8lbs of N570 so planning on making that my powder for the next 500'ish rounds.

Again, I thank you for all your details with loads and velocities. Also that you experienced the same lack of primer deformation and easy bolt lift. I am glad I stopped where I did and can get more info on where I am at. I'll let you know how the primer pockets hold up.

 

[LA50SHOOTER]

Judging by your velocities from longer barrels, albeit with RL-33 (similar burn rate), I am thinking I am at or near max pressure (probably over). I'm pretty sure my throat is a PTG "Bore Rider" but I need to confirm it with a chamber cast. Rifle was built by a gentleman that fell ill and I am unable to get some of the detail (it's a beautiful new build though). I'll update with a stress test on a couple pieces of the BBR-15 brass and maybe a couple of the normal Lapua brass.

I have a pound of RL-33 I can test at some point, but I have 8lbs of N570 so planning on making that my powder for the next 500'ish rounds.

Again, I thank you for all your details with loads and velocities. Also that you experienced the same lack of primer deformation and easy bolt lift. I am glad I stopped where I did and can get more info on where I am at. I'll let you know how the primer pockets hold up.

Thank You @trental,
I'm sure you will do very well with your "Rogue" Improved. - It is an excellent improved version of the parent cartridge.
- I recently was lucky enough to get hands onto an 8 Lb. Jug of v/v N-570 which I was planning on using in a 300 Norma Mag. Imp., but you've motivated me to give it a try in the 338 as well. (Now if I can just get more of 570 then I'll be set).
I look forward to hearing how your test go, so please share that with us, as there are a few on here that are shooting 338 Lapua & derivatives there-of for long range accuracy work beyond 1000 yds.

- Ron -

 

[germanlongbow]

I shoot a 338AI with 40 degree shoulder. I started with rl 33 and 300 bergers pushed to 107 grains with similar results. I sent back to my smith and had throated to the 277 gr cutting edge bullets. I switched from rl 33 to Retumbo backed the powder charge to 95.0 and 96.5 (both nodes shoot 1/4 moa at 100 yards) but distance testing at 700 yards showed less vertical with the 95 grain node. Velocity is 3020 with 95 and 3080 with 96.5 grains of powder. I shoot a 32 in Krieger 5r barrel 1.450 diameter barrel. Both buddies shoot rl 33 out of their 338 LM and 338 edges with great results and obvious lower velocities. Personally I favor the V/V powders in several other cartridges, wouldn't mind trying the N570 to see how it compares. good luck Scott

 

[carlsbad]

Part of your ability to deal with such high pressures depends on how your reamer fits your brass and your resizing die fits your chamber. --Jerrry

 

[trental]

Part of your ability to deal with such high pressures depends on how your reamer fits your brass and your resizing die fits your chamber. --Jerrry

My FL die sizes the body at the shoulder/body junction only 0.0005" and my normal method is a 0.001" bump on the shoulder. About as minimal sizing as possible.

That won't help the primer pockets survive any longer though correct?

 

[carlsbad]

Trental,
I'm speaking of the diameter of the base of the chamber reamer to base of the brass.

Then your sizing die should be the same profile as your chamber reamer and have a nice tight base. To get your .001" sizing, your die is probably .004" less.

Not speaking of shoulder bump here but sounds like you're doing it right.

You do need inside and outside micrometers, 0-1". i find the best everyday ones are the moderately expensive mechanically digital ones.

--Jerry

 

[charlieyankeesierra]

The max load I ran when I used to have a 338 Rogue Bore Rider gave me 3149 fps using RL33 out of a 30 inch barrel with 300 gr Berger OTM's. The load I settled on was 108.5 gr RL33 lot#404231, 3008 fps. I personally found a great deal of lot to lot variability with RL33. I used Peterson brass and never had any trouble with primer pockets loosening.

Judging by your velocities from longer barrels, albeit with RL-33 (similar burn rate), I am thinking I am at or near max pressure (probably over). I'm pretty sure my throat is a PTG "Bore Rider" but I need to confirm it with a chamber cast. Rifle was built by a gentleman that fell ill and I am unable to get some of the detail (it's a beautiful new build though). I'll update with a stress test on a couple pieces of the BBR-15 brass and maybe a couple of the normal Lapua brass.

I have a pound of RL-33 I can test at some point, but I have 8lbs of N570 so planning on making that my powder for the next 500'ish rounds.

Again, I thank you for all your details with loads and velocities. Also that you experienced the same lack of primer deformation and easy bolt lift. I am glad I stopped where I did and can get more info on where I am at. I'll let you know how the primer pockets hold up.

 

[Alex Wheeler]

I am at 104.5 grains of rl33 in my 338 improved (40 degree) to get 3030 fps in a 32" Krieger. Most of the guys on my reamer end up right around that 3000 fps mark with a 300 hybrid in 30-32" barrels. We have not experienced any loose primers in Lapua cases at this speed. I run into the earliest pressure signs about 3050, but a couple of guys have went over 3100 before seeing signs. Theres a lot of factors that go into when you will hit pressure. Bore geometry, reamer design, chamber quality, component lots, ext.

 

[IdahoCTD]

Powder Valley and Natchez had N570 this week. I'm not sure if it's all gone or not though. I had 2lb and bought 12 more the last time it was available.

 

[trental]

Took a break from finding max pressure and decided to explore a node that showed up in my velocity ladder around 3045fps between 100.6 and 100.9 grains of N570. Had an issue with my Nesika scope rail coming loose from the action during my first group. I thought it was me flinching but noticed the loose rail and was able to fix it (now have blue thread lock on it). Had planned on doing 5-shot groups but switched to 3 after correcting the rail in the middle of the second group. I think the rail was loose during the entire first group so that one is junk.

I think there is definitely a node here but will need to validate at distance. The group at 100.8gr is fantastic and hopefully repeatable.

 

[trental]

I resized the 50 pieces of brass I had been working on and primed them. I feel like I could perceive a very slight difference between the cases fired with 103gr and the cases loaded with 101gr or less. These cases have been fire formed with 25gr of Unique and Cream of Wheat, and then one firing. Definitely seeing 0.001" of head expansion on the 101+ grain loads.

 

[LA50SHOOTER]

IMO "accuracy lives" at 2940 to 3050 fps in the improved versions of this cartridge depending on barrel length, and pushing it harder (which can be done) will only wear the brass out quicker. - My goal is to get the rifle to shoot small groups. - The necessary "come-up" required can all be handled with the elevation adjustment knob on the scope when we are shooting at ELR distances. "Flyers" will surely show up at 2000 yards and beyond and there's enough challenges to deal with regarding conditions (wind, mirage, light, etc.) that the extra 30-80 fps just isn't worth it.

 

[DIBBS]

I have a 338 Lapua Ackley Improved with~ 150 2x fired freshly annealed cases. My case lengths vary from 2.70 - 2.71, with the majority being 2.705-2.707. Should I trim/chamfer so that all lengths match the shortest case or do so after the next firing or ? Thanks for your recommendations.

 

[LA50SHOOTER]

I have a 338 Lapua Ackley Improved with~ 150 2x fired freshly annealed cases. My case lengths vary from 2.70 - 2.71, with the majority being 2.705-2.707. Should I trim/chamfer so that all lengths match the shortest case or do so after the next firing or ? Thanks for your recommendations.

If you have fired them twice, then I would trim them to match the shortest case and chamfer them. It will probably be the only & last time you’ll need to do it.

- Ron -

 

[Desert Fox]

My 338 Lapua Ackley with 40 degrees shoulder, will push the 300 grain Berger or SMK at around 2920 fps. A velocity of around 2900 to 2950 is ideal if you want your brass to last longer. My brass had been reloaded over 20 times and it's still going strong. Barrel is 30 inch Broughton 5C 9.3" twist. My powder of choice is Retumbo and haven't tried anything else. I anneal my brass every 2-3 firings.