338 Lapua Magnum - insufficient FPS

[gnomus]

I have just started reloading for 338 Lapua Magnum.

Details:

Sako TRG 42 338 Lapua Magnum Rifle
Brand New Lapua Cases (full length resized)
250 gr Lapua Scenar Heads
Federal 215 Large Rifle Magnum Primers
Vihtavouri N165 Powder

I appear to be having some problems with this combination. I worked up some loads using the Vihtavuori loading guide. The max powder load given is 83.2 gr. The problem I had was that I was getting gas leakage even at this load - a heavy sooting up of cases, all round the neck and down the case until it was caked into the rim of the cartridge.

The sooting up disappeared when I went up to 84 gr (and beyond) powder-wise. That, of course, is above the max load - something I was not all that keen on doing.

The Vihtavourhi guide states that I should be getting 2775 fps with the max load. I have gradually worked my way up now to 89 gr of powder (5.8 gr above max) and I am still only getting 2630 fps. I am advised that I should be aiming for around 3000 fps. However, I am not at all sure that I should continue onwards.

Has anyone any idea why I should be so far off from the "book" data with my own loads?

Thanks

[thekyrifleman]

I'd say "STOP IMMEDIATELY" before you blow up your self and the rifle!! Never loaded for the Lapua but to be that far above stated max and be so far from your objective tells me that something is drastically out of whack. Check some other manuals to see if your current reference is close. To be aiming, no pun intended for 3000fps, now at 2630 and that far over max is disater waiting to happen. Period!!

[Unclenick]

The manual will probably have employed a test barrel. A test barrel will be a 700 mm barrel (27.559") and will have a minimum tolerance chamber. Your barrel may be shorter and your commercial chamber will almost certainly be a bit larger, which lowers pressure. Both those factors would reduce velocity.

I have a 1995 edition of the VihtaVuori Oy manual, and it's data is quite different. It lists Lapua cases and a 250 grain Lapua bullet (it does not say it is a Scenar, and that may matter, depending on the length) but uses 85.5 gr (5.54 gm) of N165 as the starting load and 94.6 gr (6.13 gm) as maximum. Velocities given were 2665 fps (812 m/s) and 2992 fps (891 m/s), respectively. The peak pressure is rated lower than is current, so I suspect the old manual pressure is for a copper crusher and is therefore less reliable. They used a Remington 9 1/2 primer, which may also make a difference.

On velocity measurements. With the large magnum cartridge in particular, you need to keep the chronograph a good 15 feet or about 5 m out in front of the gun or powder particles and shock wave from the muzzle blast can cause false readings either high or low.

At any rate, you might want to email VV with their old and new data and ask why the difference? From your description, it sounds like the old manual's minimum load was more appropriate in your gun. If your barrel is 650 mm, I would expect you to lose 50 fps and if it is 600 mm I would expect you to lose 100 fps compared to their 700 mm test barrel.

[mrawesome22]

Just an observation, but N570 looks like a much better powder for that cartridge.

[Unclenick]

My old manual was published before the high energy line had got above N560. I don't know what the current manual has?

[rwilson452]

looking at their web site it lists 88.5 gr as max.
http://www.lapua.com/fileadmin/user_...deEdition8.pdf

[gnomus]

Thanks everyone for their responses so far. Wilson: The data you give is for the 250 gr Lock Base head not the Scenar.

Here are some official max loads for other 250 gr heads with N165:

(NB: Max Load for the Scenar with N165 is 83.2 gr)

Lapua Lock Base 250gr.................Max Load: 88.5 gr - 2906 fps (Lock Base is 1.477"; Scenar is 1.552")
Hornady #s 3335 & 3330 (250gr)..Max Load: 93.7 gr - 2800 fps
Sierra #s 2600 & 2650 (250 gr).....Max Load: 92.4 gr - 2900 fps

The other odd thing about the Vihtavouri data is that for N170 powder it recommends 93.9 gr for the Scenar (2854 fps) but only 91.0 gr (2816 fps) for the Lock Base.

So for a Scenar bullet using N165, it recommends I use ~5 gr less powder than for the Lock Base. If I change to N170, it recommends I use ~3 gr more.

Any thoughts?

[gnomus]

Unclenick: Thanks for your detailed post. The barrel on my Sako is 690 mm in length. The chronometer readings were taken 10 feet out. You think I need to move it further away?

[mrawesome22]

The chronometer readings were taken 10 feet out

Double that distance.

[rwilson452]

I stand corrected.

[jaybirdjtski]

Just looked in Ammoguide.com. I subscribe to this online reloading guide.
Using N165 and a 250 grn bullet, it shows loads from 74.9 grns. (producing 2558 fps) to 88.5 grns. (producing 2906 fps) out of a 27.5" bbl.

In stepping the bullet weight down to 225 grns, a few loads clock at just over 3000 fps. 92.5/N-165 gets an even 3000 with the 225 grn Hornady.

Point of reference, the 338 RUM squeaks just over 3000 fps with the 250 grn bullet (only one load), 338 Win mag gets 2803 fps on it's top load and the 340Weatherby shows one chrono'd @ +3100.

Hope this helps!

Adding this: Bullet used (88.5 grn Lapua load) was a Lapua Lock Base
OAL was 3.602"

[Unclenick]

Gnomus,

Yes to moving the chronometer out. 10 ft is usually a dead minimum safe distance with standard rifles. You don't want muzzle blast from your big bruiser triggering the first screen early and giving you a false slow reading. I usually use fifteen feet because that's what the magazines and manufacturers seem to use, and I want to duplicate their test conditions. You can try using more, as Mr. Awesome suggested, to check for anomalous triggering.

I looked again at my old Lapua manual and see now that it does indicate that data I gave was for the Lock Base. I am still surprised by how much larger the charges are in the old manual than in the current on-line manual. The only difference in the new verses the old load data is use of the Lapua rather than the Remington primer. That could account for it. You do see differences of up to 4% or 5% powder charge equivalent based on primer selection, though that usually is going from standard to magnum primers, and not just between magnum primers of different brands. But that doesn't mean it can't happen. Your smokey case still says, at least with the Federal 215's, that you have low pressure at the listed maximum load for the Scenar.

Difference in the maximum loads for different bullets don't always rank identically with different powders. Powders change burning rate with pressure, and not with the same timing. The point in the pressure rise at which the bullet makes it into the throat and from there, into the bore will alter it too.

Nonetheless, every gun is a law unto itself to some degree. Check the case water capacity thing. QuickLOAD's default case capacity is 108 grains of water, but the velocities and loads in the old manual suggest something nearly 10 grains greater. I'd be interested to know what capacity your fired cases come up with?

[kraigwy]

I dont load the 338 Lup, but I'l throw this out for S!TS & Giggles.

When I first got my Ruger #1 in 204, I chose the Seirra's Accuracy Load for the 32 grn bullet. I was using hornady bullets instead of Seirra's.

I started the load with Fed SR Match primers and got a hair over 3700 FPS and more pressure signs then I was comfortable with.

I went to the CCI SR Standard primer and WOW, changing nothing else, my velocity went to 4300 and change, with ZERO pressure signs.

It shoots pretty good.

Moral of the story, dont get hooked on one component, either powder, primer, bullet, brass, etc.

[Zak Smith]

Proven loads for the TRG-42 and AI-AWSM .338LM rifles:

Lapua brass, Lapua 250gr Scenar seat at factory length 3.60"
Fed 215M primer

H4831SC, start 87gr, max somewhere around 90-91gr

Retumbo, start 92gr, max somewhere around 96gr

These will both yield over 2900 fps in an AI or TRG and should shoot half MOA or less to 1300 yards if you are capable of it.

[gnomus]

I checked the water case capacity. The case took 115.3 grs of water.

What do you think?

[Unclenick]

Gnomus,

I forgot to ask what COL you are using? 93.5 mm? Can you verify for me that the Scenar bullets are 40 mm long?

[gnomus]

Unclenick: COL is 3.681 inches. The length of the bullet is 39.36 mm (or 1.55 inches).

[gnomus]

I have taken a couple of pictures of my fired cases and primers. This is a picture of a fired case.

Firedprimers4.jpg

When I popped out the primer, however, I noticed a flanging.

Firedprimers.jpg

The primer on the left is from a fired .308 case. What is this flanging? Is it normal or an indication that something is wrong?

[Zak Smith]

Those primers are fine. When there is no radius on the corner of the primer or the primer is blanked flat with the case head, or you can see an imprint of the ejector slot on the case head, those are all indications of high pressure.

If you don't want to use the proven good data I posted in the earlier post and use VV powder instead, the same load recipe but with N170 can also work. My starting load was 96.0gr for 2815 fps, final load 98.0gr at 2900 fps in the AI rifle.

Other loads I've tried with acceptable results: For N560, 89gr was 2896 fps. For RL25, I started at 92gr and worked up to 94gr for 2977 fps.

The two "money" loads I posted before.



article | Military .338 Lapua Magnum Rifles: the Sako TRG-42 and the AI-AWSM

Two separate sub half MOA groups at 940 yards





Fairly typical fire case condition for max loads

[gnomus]

Zak: Thanks again. It's not that I'm particularly wedded to the N165. However, I do have 2kg of the stuff - and that cost me £140 (~$210).

What is your opinion of the flaring/flanging of the primers as shown in the second photo? What could be causing that?

My concern is that I have: a) gas leakage at supposedly max loads; failure to get anywhere near the fps shown in the manuals; and c) this odd sign on the primer. Could I have a headspace issue?

PS: What is that scope you have on your Sako?

[Zak Smith]

The flanging is nothing to worry about. I just looked at some of my old primers and some of them are like that and some of them are straight (not all of these were from .338, but they were all good/safe loads). What is happening is that the primer is conforming to the inside shape of the primer pocket. Those cases' pockets probably flare out a little bit near the top.

In the following photo, you can see part of the spectrum of primer corner roundness. The one on the far left is most "flat", that is, the radius of the corner is the sharpest, but it's not "smeared" or "blanked" across the case head.



In this photo, you can see a smear on the "AG" letters from where the brass was raised slightly into the ejector and then smeared as the bolt was opened. This is from one of my match-grade reloads, and is indicative of the pressure getting up there; however, there are plenty of factory loads that do the same thing.



(The firing pin indent "cupping" is due to pressure pushing the primer material into the firing pin hole in the bolt face. The AI bolt dimensions and dynamics seem to make this more common than other bolt designs.)

If you have sooting down the body of the case, it's de facto evidence of underpressure. A case running a proper pressure will have case walls that expand to grip the chamber surface and provide a gas seal.

Looking at the Lapua reloading data, I would not choose N165 to start with. If their data is correct, then N170 and N570 and N560 would all be better choices. Unless the load is at 100% density, the published data that shows N165 having a lower max speed indicates that it has a faster than optimum burn rate for the cartridge and bullet. (If it were at 100%+ load density, it would indicate that it is too bulky for the given case size.) Generally you'll get more and safer performance using a powder that it towards the slow-burning range of what will work for a particular cartridge and bullet.

In .338LM (and other cartridges), I have found that some powders simply do not perform close to the published data or don't seem to behave in a linear or predictable fashion. When this happens, I try to find another powder that is more predictable vs. published data and linear near a would-be final load point. Although others had some luck with N560, I didn't like how it worked in my rifle. But the others I listed gave very similar and consistent performance. The other powder that we didn't have luck with was H1000: in both rifles it would shoot good at 100 yards but completely fall apart at 1000-- that was a mystery.

On the scope-- the TRG is my buddy's rifle, mine is the AI. But he has a US Optics SN-3 3.8-22x44mm on his TRG-42.

If you can't get H4831SC, there is an ADI equivalent: ADI AR2213SC. My load using the ADI version is about 1.7gr less than my 4831SC load but otherwise performs the same.

-z

[gnomus]

Zak: Thanks for the prompt response. I will see if I can track down some H4831SC and try it out.

[Unclenick]

Gnomus,

I forgot to ask the length of the case you weighed the water in, which will adjust this a little, but I can tell you that if your lot of N165 matched the lot that is modeled in QuickLOAD's database, with the case, bullet and seating depth you are using, then the starting load would be about 83.5 grains and the absolute maximum would be 91.6 grains. If I had that particular powder, then 90 grains would be the upper limit I would use on the premise that any time you exceed about 58,000 psi throat wear starts growing faster. That depends on the powder temperature and the steel, of course, but its a rule of thumb that Scottish Ballistician Geoffry Kolbe came up with and that, empirically, seems to me to be in the ballpark.

QuickLOAD thinks the VihtaVuori manual maximum of 83.2 grains you would get about 2615 fps. At 89 grains you are reporting 2630 fps. QuickLOAD thinks you should be about 140 fps faster at that point. What was the velocity you got from 83.2 grains? Have you set the chronograph back yet? If you have set it back and are still getting low velocities, then you may be able to go take the load still higher.

When a cartridge fires, first the primer backs out like a little piston because the flash hole doesn't vent its gas fast enough to prevent that. What stops the backup is the primer running into the breech face. As pressure builds from the burning powder, it stretches the case at the pressure ring, pushing the head back over the primer to reseat it. If the pressure is high enough, or if the primer sticks out far enough it may partly inflate before the reseating is completed. That creates the primer mushrooming you saw in your primers.

You seem to be getting mushrooming, but without high pressure because, as Zak points out, you don't have sharp corners on the primer. That suggests the primer is pushing back pretty far to inflate, but is doing it without extreme pressure. So, you may indeed have a headspace issue. That will contribute to needing more powder to reach a given velocity. It is easy to test. Just make some loads by neck sizing so the case still fills the chamber and has no excess headspace. You can do this by running the cases into the sizing die far enough to just resize about 2/3 of the neck. Use your same powder charge weight and see if the primer mushrooming stops? If so, then getting the barrel shoulder set back 5 mm and rechambered with shorter headspace may be something you want to consider?

Get back with the velocity information and fired with the chronograph set further back. Also, be sure the chronograph is registering accurately in you lighting condition? .22 rim fire match ammunition is usually within 50 fps of the velocity it is rated for because they stop accelerating after about 19" of barrel. They give you a rough calibration check.

[gnomus]

Unclenick

Firstly, thanks for your ongoing interest and assistance.

Here's some of the data you requested:

1) The length of the case in which I weighed the water was 2.715 inches.

2) I didn't measure velocity at 83.2 grains. I did measure at 84 grains. I got an average velocity of 2425 fps.

Here is all my data:

84 grs - 2425 fps
85 grs - 2430 fps
86 grs - 2503 fps
87 grs - 2549 fps
88 grs - 2607 fps
89 grs - 2630 fps

I don't know if this is relevant or not, but it has generally been around 8-10 degrees centigrade (45-50 Fahrenheit) when I have been doing these tests.

3) I did check some .22 ammunition. I was using SK Jagd Standard Plus 40 grs. (http://www.the-armory.com/shopsite_s...oduct1321.html). This gave an average velocity of 1057 fps using my Chrony. Does this seem about right? [Edit: I just checked the side of the .22 box. It's all in German but seems to report a velocity of 320 m/s. This is 1050 fps so the Chrony seems to be about right)

I have ordered a headspace gauge and so will find out in a few days whether or not I have a headspace issue. As has probably become clear, I am a novice in these matters. Are you suggesting that if I had excessive headspace, then this could be repaired? I thought the gun was knackered if it had a headspace issue. I've only had the weapon a few weeks. (I purchased it used).

Until I check the headspace with the gauge, I am somewhat reluctant to fire the gun since I am concerned that it may not be "safe" to do so.

Thanks again to everyone for their (ongoing) help.

[Zak Smith]

I don't think there is any reason to think your headspace is off. From SAKO, the headspace would have been right. It could only be screwed up if someone has replaced the barrel or mucked with it. If the headspace is excessive, it can be repaired by moving the barrel shoulder back.

The cheap way to check for excessive headspace is to see if two layers of masking tape on the case head will prevent the bolt from closing.

Alternatively, you can take a case shoulder comparator and measure the fired cases "headspace" to see where it's at.

But I see no evidence of anything bad going on, other than you're not getting expected data from N165. Try one of the proven loads and see what you get.