155 Tipped Matchking lesson learned

Discussion in 'Reloading Forum (All Calibers)' started by 370bc, Feb 10, 2019.

  1. 370bc

    370bc Silver $$ Contributor

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    Being in a hurry, I thought the next magic bullet/load would be the 155 TMK in my 300 WSM. I just went with the suggested bullet seating depth per the Sierra manual, and it would be good enough. No way! Loading 3 at a time for an OCW test @ 200, some of the bullets weren't even hitting the butcher paper! I called the Sierra techs, and they said try changing the depth setting.
    The berger method of up the the lands and then further away had worked for me in the past, so I tried it again for the TMK. Wow! It went form not even hitting paper to going 3/8'' vertical for one load and 1/2'' for another! I wish they would of said load this like any other VLD bullet. It would of saved me $$ and them having to take a call from me. Anyone else have this problem? Their suggested manual depth setting was 2 miles from the lands from this Model 70 super shadow. Im going to test how they behave on a coyote or 2 if I can get out in time.
     
    Last edited: Feb 11, 2019
  2. grovey

    grovey Silver $$ Contributor

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    I don't have the particulars in front of me, but the 155's shot like crap out of a factory 700 in .308 for me. If memory serves the best it shot them was about moa. The same rifle would stack the 150gr berger fb match bullets on top of each other, as well as the extremely blunt 130gr Hornady fb sp for some reason. I was definetely jumping both.
     
    Last edited: Feb 10, 2019
  3. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    Extremely long throats are not unheard of in factory production rifles. Bullet and/or powder manufacturer's suggested reloading data are typically given in terms of magazine length COAL, which really doesn't address seating depth in a useful way. Their primary concerns are allowing loaded rounds to fit into and feed properly from a magazine, and not exceeding SAAMI pressure specs for rounds loaded to mag-length COAL. They really have no way of knowing how long the throat of your rifle is. The good news is that it sounds like you've figured out where your loads need to be.
     
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  4. Sniper338

    Sniper338

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    I havent heard much any good things about the TMK bullets.
     
  5. Laurie

    Laurie

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    Some of the TMKs are tolerant largely tangent ogive designs, not exactly as per old fashioned SMKs with 7 or 8-radius ogive nose sections and on or near 1.0 Rt/R junction ratio values, but as per more recent long-range tangent designs like Berger's LRBT models. I shoot the 7mm 160 gn TMK a lot and it's a very tolerant easy to tune model.

    However, other TMKs are much more like VLDs or maybe Hybrids and only seem to shoot well with large jumps. As far as I can see all 30-cal TMKs are VLDs or 'VLD-ish'. Exactly the same applies to many of the new pointed models. The problem is that there is no across the range consistency and unless you invest in

    https://store.appliedballisticsllc.com/Ballistic_Performance_of_Rifle_Bullets_3rd_Edition_p/0010.htm

    you simply don't know unless you can get information on this forum or other such source, from somebody you know who has tried them, or by contacting Sierra's tech helpline.

    Many of the new-model pointed bullets are what I'd call uber-VLDs with very long secant nose sections at around 28-calibre radius and Rt/R values well below the 0.50 mark that signifies an original type VLD 'form' as designed by Bill Davis for US military 300M ISSF team use back in the in the 80s and made by Walt Berger. The new 110gn 6mm and 183gn 7mm SMKs which are of identical design, but 'scaled' to calibre fall into this category. I assume the new 200 and 230gn SMKs

    http://bulletin.accurateshooter.com...ierra-matchkings-in-223-264-and-308-calibers/

    fall into this category too looking at the pictures and also based on some data about the 200gn model on another thread in this forum. I wouldn't be surprised to learn that the 230 is the same 'form' as the 110 six and 183 seven simply scaled up to 308 diameter.

    Some other existing older SMKs now being produced in 'pointed' form are identical to their predecessors, the smaller meplat aside ..... but compare drawings and dimensions in Bryan's book and you find some others have had modest but still significant changes made to their nose lengths and shapes. So simply loading a new-version pointed SMK as per its traditional predecessor as you have for years may or may not work. This wopn't be helped either by both original and modified forms being on shop shelves or classified ads too for years to come. (This distinction applies of course to the original pointed model, the second generation 0.308 155gn Palma MK #2156 which is a very different shape from its still in production older brother the 2155 and saw a considerable learning curve needed among fullbore and Palma shooters to make it work optimally.)

    I certainly don't want to sound like I'm knocking Sierra, a company whose products I've used for around 40 years and always liked. In fact, I'm really pleased that Sierra has uprated its MK range and introduced so many good new models. Its quality control has improved enormously too as far as I can tell through checking weights and BTO consistency. I only wish that it would group its bullets into differently named categories as Berger does with VLD, BT, BTLR, and Hybrid, or at the least provide more information on its literature. As far as I'm concerned, the antediluvian 168gn 7mm MK and new 183gn MK are such dissimilar designs they should be differentiated in their branding and the latter also provided with advice (as Berger does on tuning COALs for VLDs and Hybrids). The former is completely jump tolerant; the latter needs IME a very large jump indeed to make it group.

    I suspect this also applies to the 6mm 110, and 308 200/230 models. It does the customer no favours at all, or Sierra's sales either in the long run if an inexperienced buyer trades up to one of these uber-VLD 28 cal nose radius models and then can't get it to shoot or wastes most of the first box and a slice of expensive barrel life in experimentation. There is more to necessary technical advice than recommended twist rates - which Sierra is very good at giving even if half of AS Forum members then argue about them and tell others to ignore the advice (!!) - to making many modern bullets perform well.
     
    Last edited: Feb 10, 2019
  6. 370bc

    370bc Silver $$ Contributor

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    That's a lot of great info there Laurie. Thx!
     
  7. r bose

    r bose

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    I'd like to believe based on my very limited experience, these longer, sleeker, VLDish secant shaped, ultra high BC bullets require faster twist barrels than a tangent shaped projectile of equal weight, no matter what caliber you're using.
     
  8. 370bc

    370bc Silver $$ Contributor

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    I did a berger stability test & it said my 1-10 was dead on! I couldn't believe it either.
     
  9. r bose

    r bose

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    Yes sir, that was my point. 15 years ago if someone was to build a rifle to shoot 155g #2155 sierra bullets they would have been told a 13 twist would work just fine like those found in most palma rifles.
     
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  10. Laurie

    Laurie

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    When Bryan Litz started his publishing work some years back, he was (sling) shooting the 185 Berger Juggernaut in a 1:13 barrel Palma rifle ..... and winning a lot of L-R Palma USA Rules matches with it too. I've a feeling he won a regional Palma championship that year with this combination. At the time, he said that 13 was a little too slow and that he was going to rebarrel with a 1:12 which was then believed optimal.

    Run them through the Berger calculator and assuming 2,800 fps MV which may well be on the high side, and 80*F temperatures and you get:

    1:13 ............ 1.28 Sg / 7% BC loss
    1:12 ............ 1.47 Sg / 1% BC loss

    So, 1:12 isn't too far from optimal providing it's warm, and better still if the range is a thousand ft or two ASL which would give you >1.5.

    Back then when the Juggernaut first appeared, I tried them in a 1:13.5 Bartlein in the chilly north of England. 100-yards groups in a bit warmer (~55*F) weather were exceptionally good, a one and only F-Class match outing with this bullet-barrel combination in the first cold day of November at just over freezing at 800 yards saw terrible elevations and scattergun grouping. Sg values in this twist on a range 1,000 ft up were 1.17 for the warmer day and 1.13 for the cold morning.

    There is evidence that Sg values around 1.26-1.3 are a tipping point. Get above that and they'll group at all distances even if you lose BC. Nevertheless, it shows just how good a wind reader and Sling shooter Bryan Litz is, as well as how far thinking has changed in around 10 years. These days, 13.5 twists be hanged, I shoot 1:10 in one of my thirties and am moving to 1:9.5 in t'other. Some people though in the UK used 1:14s with surprisingly good results with 155s in the early days of F/TR.
     
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  11. 370bc

    370bc Silver $$ Contributor

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    I guess the 3250 fps I'm getting in the 300 WSM and the RL16 makes it compatible with the 1-10''.
     
  12. 284winner

    284winner Gold $$ Contributor

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    I have a 10 twist Rem 700 in 308. It loves the 168 TMKs. Shot the 168 SMKs very well and now shoots the TMKs better. Pushing them around 2880 from a 26" barrel, they shoot like no other bullet I have shot in that rifle. I use them for hunting out to maybe 400 yards are they shoot phenomenally well out to 600. Haven't gone beyond that range yet with them. Going to give the 155s a go this summer.
     
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  13. Sniper338

    Sniper338

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    Good to hear. Glad they work for someone. I personally have been scared away from trying them. Hell they could shoot in my gun.. just never heard good things.
     
  14. AckleymanII

    AckleymanII Gold $$ Contributor

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    My neighbor has a 10t Krieger, 30", custom action, F class stock, 308 win with .070 FB. Those 168g TMK shoot very tiny groups! I watched him work up a load at the rifle range, he tweeked the seating depth, found bug hole loads with both IMR 4064 and C2.
     
  15. 284winner

    284winner Gold $$ Contributor

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    Heard the same. In fact I bought these from Eric because they didn't shoot for him either. Never know what a barrel will like.
     
  16. Laurie

    Laurie

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    That's the issue I believe with many new designs. They're much more position-sensitive in relation to the lands than older models. Put simply, BC has been gained at the expense of flexibility / ease of 'tune'. Apparently hopeless cases can often be made to perform well, but after a lot of work on COALs. Traditional SMKs on the other hand were not only very jump tolerant, but also seemed to shoot at least half decently in any barrel in good condition.
     
  17. 370bc

    370bc Silver $$ Contributor

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    Is the A.B.'s .464 confirmed more than Sierra's .519 out to distance? My higher velocity of 3250 fps from the 300 wsm is different from the A.P.'s of the .308. I haven't been able to take mine out past 200 yards yet. Which number would be more applicable for my set up? Thx!
     
  18. eric32

    eric32 Shooting when I can Gold $$ Contributor

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    I would start with the litz numbers of .522 G1-.267 G7. But i think your going to have to up your for your particular system. Since your muzzle velocity is super high.

    Just also want to confirm you are indeed using the 155 TMK
     
  19. 370bc

    370bc Silver $$ Contributor

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    Yes. I am using the .308 155 TMK. I thought Litz's was .464 G1?
    Is The .522 G1 - .267 G7 for the 175's?
     
  20. eric32

    eric32 Shooting when I can Gold $$ Contributor

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    Your right i looked at the wrong numbers. My apologizes, only one cup of coffee so far. I would use .464 and tweak BC based on drop value. But it my guesstimate that your going to have raise it by 15% to correlate with your dope
     
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