New 338 Lapua Brass Problem... Out of spec?

SMH

Sergeant
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Apr 11, 2007
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Until recently, I hadn't purchased 338 Lapua brass for 10+ years.
They varied in weight between lots by several grains but were otherwise very uniform with shoulders set back around .0025.

I added another 338 to my collection and purchased 2 boxes of new brass in the hope that they would have matching lot codes. (they did, unfortunately)
Here is the problem...
The majority of the new brass will not function in my new rifle. It chambers easily, but the extractor is not engaging.
The new brass varies greatly in shoulder set back as measured with my RCBS precision mic.
It varies from -.003 to -.008. (Fired rounds are around +.002 from this rifle)

The rifle is flawless with up to .0045 set back but has a 1/3 failure rate at .005, 2/3 failure at .0055 and 100% failure rate for .006 and greater.
57% of my $600+ of new brass falls in the "failure zone".

What is the "expected" measurement?
My 308 Lapua and old 338 Lapua brass lots were never this varied, never set back this far, nor did they ever fail to function.

Has anyone else run into this issue? If so, how did you remedy it?
I'm planning to contact Lapua and see if they will swap out the brass but wanted to see if this was an unusual occurrence.
 

SMH

Sergeant
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Apr 11, 2007
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How far under would you expect to still be able to function reliably?
How far under would you expect the new brass to be? (.003-.008 under seemed excessive to me)
 

Doom

Balding Eagle
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Mar 24, 2013
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Sounds like your measurements are relative to a new chamber you have little/no experience with. How does this brass do in the older rifle? Do you have a case gage to check the brass?
 

SMH

Sergeant
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Apr 11, 2007
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The "case gauge" I'm using is the RCBS device that consists of 2 open end cylinders. You drop the case into one and screw down another and read the scale around the outside. The "0" setting should (presumably) be SAAMI.

The unfired "old" Lapua brass was usually .002-.003 under and after firing they were around .002 over.

The new brass will extract in the old rifle.
I'm not sure how the fired brass measures out of the old rifle (forgot to check before resizing it) although it is too tight to chamber in the new one.
 

nn8734

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    How far under would you expect to still be able to function reliably?
    How far under would you expect the new brass to be? (.003-.008 under seemed excessive to me)
    If all of your new brass extracts in the old rifle, you have a rifle problem not a brass problem.

    .005” variance is nothing. I run all new brass through a sizer anyway so initial unit variance doesn’t matter to me.

    Also, do you know your new rifle chamber’s length?

    Lastly, “SAAMI” is a range of values for cartridge headspace not just one measurement value. For example, 308 headspace length ranges from 1.630-1.640 (more accurately, .308 is considered to be anything 1.630-1.634 while 7.62 nato is considered 1.635-1.640). Anything in that range is considered SAAMI. Hence why some fired brass will fit in some chambers but not others despite the cartridge being the same. Hence why every rifle is unique from a reloader‘a point of view.
     

    Doom

    Balding Eagle
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    Mar 24, 2013
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    This is 30-06. Not sure if that tool references minimum chamber or maximum cartridge if it simply is a shoulder setback tool. The SAAMI allowance on head space is - 0.010" and on cartridge shoulder is -.007".

    From your description I think you have slightly longer headspace on the new rifle and maybe a stronger spring on the extractor. You might want to clean the bolt completely.
     

    SMH

    Sergeant
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    Apr 11, 2007
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    The headspace has been checked and double checked and allegedly passed the go/no go gauge.

    I will see if I can figure out how to measure the chamber length. Not sure how long it is and I realize it isn't totally relevant but a 225 Barnes TTSX hits the rifling at 3.642 OAL in the new rifle and 3.712 in the old rifle (new rifle has ~55 rds and old rifle has ~550rds through it)
    (It shoots amazing groups with any N560 charge under 250 Scenars or 225 TTSXs)

    The RCBS tool measures from base to datum point on shoulder.

    I'm not opposed to FL sizing the new brass to uniform it, but in my experience it is easy to move the shoulder back but not forward. (using Redding bushing die) I just tried with one of the .007 under and it didn't change the set back, nor would it engage the extractor after sizing

    I haven't cleaned the bolt in detail but the extractor is strong and there are (2) plunger ejectors on the bolt face so it does take more force than normal to snap onto the cartridge.

    I guess one option is to fire the new brass in the old rifle and then resize it for the new rifle. The chamber in the old rifle isn't as tight so I will be working the brass considerably but I seldom use it more than 2-3X anyway before retiring it.

    My previous "old" lot of brass was flawless in the new rifle but I don't know what to expect if I source more brass.

    I appreciate the comments and expertise being shared!
     

    nn8734

    nn8734
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    allegedly passed the go/no go gauge.
    Allegedly?
    LI realize it isn't totally relevant but a 225 Barnes TTSX hits the rifling at 3.642 OAL in the new rifle and 3.712 in the old rifle
    Totally Irrelevant
    I guess one option is to fire the new brass in the old rifle and then resize it for the new rifle.
    I’d compare a few fired cases between the two rifles and note the casehead-shoulder length difference. Otherwise, I don’t recommend fireformimg in one rifle the using in another. Also clean the bolt thoroughly as others have mentioned. Also get a chamber drawing for your rifle so you know what the chamber dimensions should be (i get them for all of my bolt guns whenever possible).

    ETA: get a go, no-go and field gauge for your rifle as well.
     
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    SMH

    Sergeant
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    I fired identical rounds that had .0045 set back in both rifles. I wasn't able to measure a clear difference in the case head to shoulder junction after firing. The fired brass in the "old" rifle was 2.711 OAL and -.0010 vs 2.726 and +.0025 in the new one. (The new one showed slight primer flattening)
    (I would estimate that the new rifle will run about 2 grains less N560 for equal pressure)

    I did succeed in finding another lot of new Lapua brass that was more consistent in measurements than the current batch but averaged about the same set back. Apparently my batch of -.002ish was not necessarily the typical expectation.

    Comparing the bolts, the new rifle takes exponentially more pressure to push a cartridge into the face. (two heavy plungers)
    The extractor also appears to have very minimal gap although it is enough to reliably capture the rim.
    I suspect this could be a contributor to the issue?

    The "0" on the RCBS gauge is supposed to be an ANSI minimum headspace so the .0025 expansion doesn't seem out of line.
    I will look for a field gauge although I know at least 2 different people checked the go/no go and they said all was good. (I didn't see it)

    It appears that the issue is more with the rifle than the brass so I probably won't gain anything by returning the brass for a different lot. (Unless I could find a batch that was only .002-.003 under)

    The brass that will engage the extractor isn't a problem. I can fire it and resize to +.0005 and have my .002 under.
    The brass that won't engage leaves me the option of shooting it in the other rifle first, or manually engaging the extractor in the new rifle.
    I wouldn't try to fire it (nor do I think it would fire) if I wasn't sure that it was engaged.
    Thoughts on the pros or cons of this idea?
     

    Mark23

    From Italy
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    Apr 6, 2022
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    Questa è la dimensione di un nuovo ottone Lapua.
    I miei nuovi vanno da -0.004" a -0.002"
    Impossibile che non venga agganciato dall'estrattore
     

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    b6graham

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    Questa è la dimensione di un nuovo ottone Lapua.
    I miei nuovi vanno da -0.004" a -0.002"
    Impossibile che non venga agganciato dall'estrattore

    '
    This is the size of a new Lapua brass.
    My new ones range from -0.004 "to -0.002"
    Impossible not to be hooked by the extractor'
     

    SMH

    Sergeant
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    Apr 11, 2007
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    Thank you Mark23 & b6graham.
    Brass that is -.002 through -.004 would work in either of the rifles. (TRG42, Defiance Deviant/Bartlein)
    Unfortunately, my new lot of brass is -.003 through -.008. It works in the TRG42 but only 1/2 of it works in the Custom rifle.
    Fortunately, this still gives me plenty of brass for working up new hunting loads.