Lapua 338 magnum pressure

ping · Sep 24, 2016

So i get out my sierra reload book and look up data. Decided on 4350 pwder as it was indicated most accurate. Loading 300 gr sierra hpbt. The powder range is
72.9 to 78.2.
I started at 74.4 than incremented .5 all the way to 78. At 76 the bolt was difficult to open. All the wat to 78 grains. I had to use a rod on every round from the muzzle to get the cartridge out.
So looks looks like pressure. I am following everything in the book. Same primers even same rifle.
Wonder why the load data is giving me high pressure. I know its a guide but i have never had the problem.
And the best groups were with 77 and 78 grains. I mean major accurate. Less than half inche at 200 yards.
I see 4350 as faster than h1000 and retumbo. So if i load the 4350 at low end i dont get good groups. If i use one of the others i wonder. Also - do a slower burning powder produce higher pressures than a fast burning
Ugggh so aggravating.

LoonWulf · Sep 25, 2016

Please, next time, stop at the hard bolt lift and check everything out....thqts a sure indicator you have a problem, could be as simple as a dirty chamber, or it could be one of the middling signs of impending doom....dun dun dun....

Anyway, pressure, is pressure, is pressure. fast powder reaches peek pressure sooner, but 60k psi is still 60k psi.

Broad coverage of your issues. Reloads are out of spec (equipment issue, usere error etc), your chamber is out of spec or the specs are much diffrent than what sierras pressure barrel use, or you have other gun related issues....what model of rifle might i ask?

Also which 4350 were you using?

I just cruised hodgdons website, fastest powder they list for the 300grn smk are the 4831s...im not familiar with the .338 but it SEEMS way to fast for that 300grn bullet.

ping · Sep 25, 2016

Brand new rifle. I figred they eere hot bot looking at cartridge no real sign of fatigue and primers were fine. I am going to contact sierra and question. And yeh i should have stopped when bolt was tough. I understand. Only has a few cartridges and all loked ok except extraction. I drpped the load down to 73 and afew to 75. Looks like i probably need h1000. Oh using imr 4350. Faster than the h1000

Reloadron · Sep 25, 2016

Several things can cause a hard or difficult bolt lift including the chamber headspace. I am not aware of the SAAMI drawing specifications but there is also how your brass was sized? Anyway while high pressure can cause a hard or difficult bolt lift there are other things possible.

Ron

MEHavey · Sep 25, 2016

Primers notwithstanding, if your brass has a bright spot on the head/hard extraction,
you are waaaay over pressure -- regardless of what "the book" says.

Any idea what the velocity was?
BTW: QuickLoad tells me that's a 70,000psi load (on a 60,000 psi cartridge).

LoonWulf · Sep 25, 2016

You sure you didnt get the data for the 250 and the 300 mixed?
MEHaveys idea of quickloads got me thinking. 78grns of h4350 is a max load with a 250smk, atleast according to quickloads lol.

Casefull · Sep 25, 2016

If it was me I would make sure my brass is trimmed to spec length and that the bullets are sufficiently free to the lands. I caused my self "pressure problems in a 300wm because of this...it acted just as you describe. Good luck. Also check your velocity as someone else suggested.

ArchAngelCD · Sep 26, 2016

Like said above, Hodgdon does not list either 4350 with a 300gr bullet in the 338 Lapua. It is too fast a powder according to the company who distributes the powder and supplies data.

H1000 seems to be a very popular power for loading the 338 Lapua. I have also heard loaders using Retumbo and one guy is using RL33. You might want to try the new IMR7977 too if you want something new. I would not be using 4350 on that cartridge with a 300gr bullet. I'm guessing you got that data from Sierra from what you said. Please let us know what the say when you hear from them.

Nature Boy · Sep 27, 2016

I'd be curious to see what the brass looks like. Post some pictures if you can. I'm always looking at my brass and I'd love to see yours for reference.

I've encountered pressure signs like you described 2 full grains below published max in .308

Bart B. · Sep 27, 2016

Sierra's data's velocity is typically on the slower end of all published data from other sources. Sierra's known for lower pressure loads. 2650 fps for 300's with 78.2 grains of IMR4350.

Your barrel may well be on the tight size for bore and groove diameters compared to their others of the same type and chambering.

BigBore45 · Sep 27, 2016

MEHavey said:
Primers notwithstanding, if your brass has a bright spot on the head/hard extraction,
you are waaaay over pressure -- regardless of what "the book" says.

Any idea what the velocity was?
BTW: QuickLoad tells me that's a 70,000psi load (on a 60,000 psi cartridge).

Yeah I checked on Quickload. Your over pressure by 8k-10k psi. Stop now and recheck all your data and books. I also suggest investing in a chronograph. That's why we work up loads. You should of stopped at first hard bolt lift. If its not getting good groups try a different powder. Preferably one more suited to the cartridge. Be safe out there. As Always YMMV.

MEHavey · Sep 27, 2016

In order of velocity, with highest case-fill/burn-completion as predicates:

Vihtavuori N570
Alliant Reloder 33
Hodgdon Retumbo
Ramshot Magnum (Big Boy)
Accurate MAGPRO
Vihtavuori N560

ping · Sep 27, 2016

Sure appreciate the info guys. I was sure reckless on this one. The load data is from the 5th edition sirrea reload manual. Very clear. And it was for 300 gr sierra hpbt. Again dumb on my part. I shot 10 and no joke at 200 they were almost same hole. I have stopped belive me. I did call sierra and ask him to turn to that page. He acted like a jerk as i explained. I finally just hung up. Oh well. I will try some h1000. The brass by the wat looks great. No signs of stress. Primers were cratered very slightly compared to my lower loads. Sure hope i did not damage my rifle.

ArchAngelCD · Sep 27, 2016

If not pressure was yourself tight when closing and not only after you shot the ammo?

ants · Sep 28, 2016

Case capacity, jump to the lands, and bore diameter are among many factors that affect pressure. When Sierrs's lab tested that load eons ago on their universal receiver, it was within SAAMI Max Average Pressure. With your brass in your rifle it was excessive. Lesson learned. Start low and work up methodically. You found excellent accuracy at the top end, it is often possible to find excellent accuracy at lower loads. Might as well try starting load.

Thank you Harvey for some good powder choices.

ping · Sep 30, 2016

Yes the loads all closed fine with the bolt. Just fist time my book has been so wrong on a load. Going to try h1000 but not easy to find till next gun show. Ugggh. And start low

MEHavey · Sep 30, 2016

I would offer that any of the powders above H1000 would as good -- if not better.
They are listed in descending order of "predicted goodness"

Vihtavuori N570
Alliant Reloder 33
Hodgdon Retumbo
Ramshot Magnum (Big Boy)
Accurate MAGPRO
Vihtavuori N560
IMR 7828
IMR 7828 SSC
Vihtavuori 24N41
Hodgdon H1000
Alliant Reloder-25
Winchester WXR
Alliant Reloder-22

Weflyfast · Oct 18, 2016

I use R25.... retumbo...and US869 with 250,285 and 300 gr bullets with great results in the Lapua. I think 4350 is too fast....big heavy bullets like 26in barrels and SLOW powder.......DONT PUSH THE PRESSURES....you don't need to in this powerhouse.

nofishbob · Oct 19, 2016

The OP stated that he has a new rifle.

A few years back, I was reloading for a new Savage 110 in 338 Lapua, and had similar hard bolt lift even with starting loads. For me, it was one shot, force bolt open, then head home to pull loads apart and verify everything. After two more times back and forth to the range with one shot each, I was sure it was not my load, so at the suggestion of internet experts, I bought Lapua brand brass ($$$) to replace the Norma brass I was using. it was a little better, but still not right.

I sent the rifle back to Savage, and they fixed it under warranty.

My loads extracted as expected after the repair. I wasted a lot of time driving back and forth to the range, and pulling what turned out to be safe loads.

If you are still having problems, consider looking at the rifle itself.

Hope this helps!
Bob

Fusion602 · Mar 30, 2017

I am using IMR 4350 but only for light bullets such as the Nosler accubond 200g and the Swift scirocco 2 210g and have had excellent results. I can't stress enough the importance of bullet jump with this fast burning powder. I like it so much, it's all I use for the light stuff. Good luck sir.

Savage 111
Caliber 338 lapua
Bullet 210g swift scirocco2
83g Imr 4350 .025 to lands
Win case trimed to 2.714
Cci 250 magnum

I have had extreme pressure spikes when the bullet is seated against the lands. This happens with all powders in my experience and is more dramatic with faster burn rates.

Lapua 338 magnum pressure

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