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Thread: 110BA .338 Lapua Mag. Headspace

  1. #1

    110BA .338 Lapua Mag. Headspace

    Like many, I've had trouble with hard bolt lift, retraction, etc. I can work around the problem by loading down my ammo but that's getting to be a pain.
    Today, just for giggles, I tried to close the bolt on a "no-go" gauge from PTG and the bolt closed just like it would on a "go" gauge This can't be good can it? Any thoughts would be appreciated.

  2. #2

    Re: 110BA .338 Lapua Mag. Headspace

    That's why the call it a no-go gauge, I suspect. If a no-good gauge goes that's a bad thing. When you get yours done can you send me those gauges? Would like to see where mine's at. FWIW, switching from hornady to lapua brass did fix my bolt lift problem but I'd like to know that my headspace is right...

  3. #3

    Re: 110BA .338 Lapua Mag. Headspace

    I spoke with a tech at PTG today after another fruitless conversation with Savage Customer Service. Apparently Savage runs fast and loose with headspace dimensions and the tech was very familiar with the 110BA problems. He suggested setting the barrel back to "go" gauge and then rethroating forward .060". I ordered a reamer and we'll see what happens. At this point I've got nothing to lose since I'm about to buy a Shilen barrel for the rifle. I'll keep you posted. If the reamer works I've saved $450.00.
    I also switched to Lapua brass (both commercial and military), and it helped, but I can't get over 2650fps without bolt extraction problelms.
    That round should be capable of 2950fps with a 250gr projectile since that's what the Lapua military ammo does.
    I'll be happy to loan out the headspace gauges once I get my rifle squared away.

  4. #4

    Re: 110BA .338 Lapua Mag. Headspace

    When did the US military start publishing their ballistic data?

  5. #5

    Re: 110BA .338 Lapua Mag. Headspace

    Who said anything about " U.S." Military ballistic data. As far as I know the U.S. Military hasn't done much more than play around with the .338 Lapua Magnum. It is used extensively by Canadain, British, Australian, Swedish and German forces though, and ballistic data is readily available. Wikipedia is probably the easiest to access.
    The standard military ball round as loaded by Lapua is their 250 grain lock-base bullet at 2950-3000fps. That's what I've been trying to duplicate. While I've gotten some excellent accuracy the velocity still falls short before the rifle starts getting balky.

  6. #6

    Re: 110BA .338 Lapua Mag. Headspace

    Thanks!

  7. #7
    bigjet
    Guest

    Re: 110BA .338 Lapua Mag. Headspace

    My 110BA has no problem with bolt lift, or any other pressure signs, shooting 300gr SMK's with 91.5 gr of N570, getting a muzzle velocity of about 2675 fps. Grouping at 100 well under 1/2 MOA.

    New Lapua brass. Excellent concentricity right off the bat, with a case capacity of about 111-112 grs H2O.

  8. #8

    Re: 110BA .338 Lapua Mag. Headspace

    What brass?

  9. #9

    Re: 110BA .338 Lapua Mag. Headspace

    That N570 Load was one of the first ones I tried, though with 300 gr. Berger Hybrids instead of SMK's. Still haven't gotten my reamer but hopefully today. Really looking forward to trying the rifle with correct headspace and sufficient throat area.

  10. #10

    Re: 110BA .338 Lapua Mag. Headspace

    Success! I changed so much on the rifle that I went back to start loads and worked up to where I wanted to be. 2900fps with 250 gr lock-base or scenar Lapuas and 2700fps with Berger or Sierra 300s.
    I only extended the throat .040" but the reamer from PTG has a much shallower angle than the factory throat. Set the headspace to a "loose" go gauge. Now the rifle does what it's supposed to. It seems to be just a tad more accurate too, although it was no slouch before.

    PS- You guys using the Lapua Military brass (headstamp Lapua 86) - I've had two case separations so I'm going to retire it and stick to commercial Lapua brass.

  11. #11
    bigjet
    Guest

    Re: 110BA .338 Lapua Mag. Headspace

    What was your headspace problem? Just a stiff bolt? From what vie been reading, the bolt problems may have been eliminated when switching over to new Lapua brass.

    QuickLoad shows impressive pressure increases with small differences in case capacity. I measured the fired cases at ~112 gr of water. Using the stock case values in QL of 108 gr, boosted the chamber pressure a few thousand psi with the same loads.

    Could the cases have been your problem?

    Using the Sinclair shoulder gauge I&#39;m seeing fired Lapua (not military) brass measuring ~2.196", and the unfired cases just a bit tighter at 2.193". There hasn&#39;t been the least signs of pressure with 91.5 gr of N570, with the 300 SMKs seated with the ogive at 2.8545", (OAL ~ 3.720") which is giving about a .018" jump to the lands. Muzzle is close to 2700 fps, and the groups are very tight - < 1/2MOA.

  12. #12

    Re: 110BA .338 Lapua Mag. Headspace

    bigjet - what does your shoulder gauge measure? The numbers you give don&#39;t correspond to any .338 case dimensions I can find: Base to bottom of shoulder 2.161", base to datum line 2.4425", base to top of shoulder 2.724".
    My fired cases measured 2.4515 base to datum line. While I don&#39;t believe that would be a problem except for stretched brass, I prefer headspace to be closer to minimum SAAMI specs. At $2.50 each I want the brass to last as long as possible. Savage gets away with sloppy headspace because of the "floating head" bolt, but it&#39;s not an ideal situation and is easily corrected.
    Most of my problem was caused by the short sharp leade (freebore)... I suspect that your chamber was cut with a fresh reamer while mine was cut with a tired one.

  13. #13
    bigjet
    Guest

    Re: 110BA .338 Lapua Mag. Headspace

    I&#39;m using the Sinclair Bump Gauge, #20B. It simply picks its own reference point...I don&#39;t think it&#39;s a SAAMI datum, which I have not been able to find anywhere for the .338 LM. A fire-formed case should be close to the dimensions of the chamber, itself, minus a linkage spring back after forming to the chamber walls. The gauge, at closer inspection, gives me about 2.1985", which is a bit larger number than I originally gave you. A arbitrary datum seems okay to me, as long as the shoulder is set to slightly less than that value.

    As to the leade in my rifle, I measured the chamber to 2.7495" using a Sinclair Chamber Length Gauge insert, and measured the 300gr SMKs at 2.8545" to the lands. Seating the projectiles to 2.8525 ogive, or so, seems to work pretty well for me.

    I think the serial number on my 110BA shows it to be about number 240, or so, off the line. Don&#39;t know how well the reamer was holding up for the cut, but the rifle is very impressive in terms of accuracy. Shoots a bit better than my 22-250, but I&#39;ll still leave the ground hogs to the 22.

    I haven&#39;t zeroed with a batch of Scenars I&#39;ve loaded, nor with the Berger Hybrids, which I&#39;m still waiting for. I sent the original batch they sent me back after finding out about the slump issue. Probably didn&#39;t need to do that with only ~2700 fps MVs, but they&#39;re changing the boattail angle also, so why shoot the older design?

    When you decided to ream the rifle, did you give any thought to bringing it up to a .338 LM AI?




  14. #14

    Re: 110BA .338 Lapua Mag. Headspace

    Accurate indeed! I put four Berger 300 Hybrids (moly) literally into one hole this morning and it was windy. Only 100 yards but I was impressed. It was windy enough that I seriously considered turning around and going home without shooting. I pulled the fifth shot about .250" to the right. The Bergers shoot just a little better and have a better BC than SMKs and since they cost about the same that&#39;s probably what I&#39;ll stick with. As soon as the new ones become available I&#39;ll stock up. I&#39;ve only got about 75 of the old design left

    I didn&#39;t ream the whole chamber, just pushed the throat forward and changed the leade angle of the lands. I see no need for more powder so haven&#39;t thought about the AI idea.

    I use a Redding Competition Neck Die with a .365" bushing and a Redding Body Die which sets the shoulder to SAAMI specs. Now that my headspace is the same I shouldn&#39;t have any more problems

  15. #15
    bigjet
    Guest

    Re: 110BA .338 Lapua Mag. Headspace

    Yes, overlapping holes at 100 seems not too difficult with this rifle. I kind of wish I hadn&#39;t sent the Bergers back. I&#39;m awaiting 350 of them when the new ones are released. I think they&#39;ll be my standard round once I shoot the 50 SMKs, and the 50 Scenars I have loaded. Also changing to Federal 215M primers, which I had a whole bunch of trouble finding. Used Winchester LRM primers up until now.

    Just recently got a Redding Competition seating die, which I haven&#39;t used yet, and have an order in for the Redding neck and body dies, too. I ordered three bushings, .365, .366, and .367. With the results you&#39;re getting, looks like I may only need the one.

    I have access to a couple of 1000 yard ranges here in WV, and hope to stretch out the rifle before the weather gets too brisk. I&#39;m using a Premier Reticles 5-25 mildot scope, which is really a great tactical scope, but I&#39;m a little uncertain as to how well it will serve on 1000 yard targets. The FFP reticle will get kind of large at 25 power.

    By the way, I worked for an outfit that Captain Eddie started. Good old EAL.

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