Throat errosion concerning the large case 6.5's

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Brent, May 19, 2003.

  1. Brent

    Brent Well-Known Member

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    Throat errosion concerning the large case 6.5\'s

    I am interested as to what is the barrel life expectancy of the "larger" case 6.5 caliber cartridges is (6.5/300WBY and larger cases).

    As well as a "normal" top end MV for those cartridges shooting the 140gr bullets and what case capacity might be.

    Any case "designs" that are claimed to help throat life would be interesting as well.

    Thanks in advance. [​IMG]
     
  2. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Brent

    Over the years I have had the pleasure of owning and shooting the 6.5/06, 6.5 Gibbs, 264 Mag, 6.5/300 Weatherby and now have 3 6.5/284 guns for 1000 yard match shooting.

    The velocity from the 6.5/300 Weatherby can be as high as 3450 using the 139 to 142 gr bullets. When running that speed barrel wear is a factor.
    I know of several 6.5/300 Weatherbys that have 2000 rounds through them and are still shooting well.

    The 6.5/06 is a great cartridge as are the 6.5 Gibbs and 6.5/284 cartirdges.

    At 2950 to 3000 Fps in the 6.5/06 or the 6.5/284 the barrels will ALWAYS last to at least 2000 rounds without fail. This of course if you don't overheat them.

    The 6.5 Gibbs will duplicate the 264 Mag ballistics in 30" barrels. This one is another good 6.5.

    One of the best shooters at Williamsport uses the 6.5/284 case and changes his barrels when they reach 2000 rounds fired even if they are still shooting well.

    For length of barrel rear, and accurate shooting ability, I will say the 6.5/06 or the 6.5/284 is a great pair of cartridges to consider.

    If a person wants extreme power from the 6.5 Bullet, then the well documented 6.5/300 Weatherby would be one to consider. It was and still is one of the finest LR hunting cartridges used in this area of PA.for deer.

    Later
    DC
     
  3. Brent

    Brent Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Thanks alot Darryl. [​IMG]

    I'm thinking of necking down and improving the 338 Lapua case to 6.5, using a long neck in the area of .450" - .500" long to help protect the throat.

    You think an honest 3500 fps with a 140 at reasonably lower pressures might be doable with a 30" bbl?

    Setting one up to work with the 155gr bullet might not be a bad idea too.

    Just testing the water a bit, seeing what others think of the idea and the comparable large case designs that might lend a better understanding of what I might expect.

    Ideally, 3500 with a 140 but, being able to acheive 3600 or a bit more would let a guy play around at 3400 or more at much lower pressures, possibly in the 55-60k range... this is what I'm hoping for anyway. We'll see how it's likely to fit that mold though. [​IMG] Sounds good though. [​IMG]

    Appreciate any more input from the large case and/or 6.5 gurus. [​IMG]
     
  4. ar15dcm

    ar15dcm New Member

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    Re: Throat errosion concerning the large case 6.5\'s

    One of the guys I shot a 1000 yard match with shot his 6.5/284 Kreiger barrel out in 1000 rounds. Throat was toast..


    Dean
     
  5. Steve Shelp

    Steve Shelp Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Brent,
    I've got both 6.5-300 Weatherby and a 6.5-300 Win Mag. The Weatherby (WWH) has had many rounds through it. I don't know how many because I didn't keep good records to be honest. But a couple simple calculations say it's over 1500rds easily. Right now the throat is so far gone from the original "140gr" throat in it that I can take a 155gr SMK and put it on the case mouth upside down, the chamber that round and pull it back out and the 155 will still be sitting loosly on top of the case. That throat is gone to say the least. BUT, I had this rifle out at our club last year or the year before firing on a Friday evening before a match jsut for fun and I never hit one of the clay pigions on the dirt bank at 1000yds but I threw dirt on many of them. I would say of the 15 or so rounds I fired that once I got it sighted in, all rounds would've killed a deer sized animal. But it's not shooting BR competition accuracy by any means.

    My 6.5-300 Win Mag is throated for the 155s and has less than 400rds through it. The throat is still fresh and evenly worn. I bought this rifle off from my old shooting partner who retired from any serious shooting after eye surgery so I can't tell you how much the throat has burnt out in those 400+- rds because I don't know where it was brand new. But in any event it is not excessive.

    Velocity:
    WWH: I've been over 3500fps with 140s in a 30" barrel. BUT I'll admit, I was standing on them to see what it would do. As Darryl said you can get 3400+ and when I've shot the Weatherby in competition it was normally backed off to 3350 approx and barrel life was pretty good. My shooting partner I mentioned earlier, shot his 6.5-300 WWH for several years when he started competition shooting with decent success and not really unusual throat wear with the lower velocity.

    6.5-300 Win Mag w/ 155gr bullets and 8" twist: If I remember correctly this would go up to 3250. The last time I chrono'd the accuracy load in that it was 3050.

    So you might be on to something with going to the big case and backing down on the pressure/velocity to maintain a decent barrel life.

    Case designs to reduce wear: I'm familiar with the long neck theory and several guys I shoot with are proponents of it. I simply don't know one way or the other. There are some working on the elliptical shoulder case to gain more effiecency but have seen any hard data to support that theory either... only opinions.

    I could get the water volume of both of my cases for you. Gotta load my HG rounds tonight for the VA match this weekend. I can do it then.

    Steve
     
  6. Steve Shelp

    Steve Shelp Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Brent,
    I'm very familiar with the TP angle theory and article that was published. As a matter of fact in the original article when printed had an error in the equation that PA gunsmiths, Jim Borden and Kenny Kleinendorst (and I'm sure others spoke to the author about and a correction was made a couple of issues later.) Kenny did all of my gun work at the time.
    The only thing I don't care for about the whole idea behind it is it's based on the the assumption that the PPC case is the end-all-solve-all to accuracy and I really don't sign up to that theory. There are a lot of things that make that cartridge accurate and the case itself is one of them but not everything. My opinion only. One of my biggest arguements agaisnt the PPC being the "ultimate" case design is look at the powder buring rate chart and see how many powders are available right around what the PPC needs..... you can tune and re-tune that case to do anything you want in any weather condition or bullet weight. But if you size that case up dimensionally to be a 1 to 1 ratio for a 30 caliber case.... if the "ultimate" case design theory is true then you just designed the most accurate 30 caliber case ever. BUT.... is the right burning rate powder available for the increased volume of that case? maybe.... maybe not.
    So take that for however you will that's my opinion only and I'm sure others and maybe yourself will disagree. I've watched guys day in and day out shoot 300 Weatherby Improved cases in competition with that long slender powder column and some of the groups that have been produced are almost incomprehensable. So does the short fat theory really work??? OR have so many people shot the Fed210, 52+- clicks of 322, 68 bullet in the PPC for so many years that you can't win if you try something different because it would take a man 40yrs to gather the info that is available for a PPC when you pick it up from the gunsmiths without ever firing a shot. So it will continue to be the most accurate cartridge for a long time. And myself nor anyone else can argue against it's success whether you like the case or not. It is accurate, question is why? And I beleive that question is answered in book form and not one sentence.

    I do beleive there is something to the fact that a longer neck simply provides more physical protection to the throat area. But then the successful 300 Win Mag shooters have a pretty good arguement against that theory it also.

    FYI: the 155 with NOT shoot out of a 9 twist barrel. I've tried out of my 6.5-300 WWH barrel that had a 9 twist (actually measured at 9 1/8"). It shot about 5" groups at 100yds with oblong holes in the paper, so I don't think the WSM case is going to work with the lower velocity.
    I haven't bought any 155 SMK is sevral years, but I had bought at least 1 box of 500 out of each of the previous lots that they made up until '98 or '99.. The very first run were dead-nuts for out-of round but the ogive variation wasn't that good but could easily be sorted into groups. But since then every box that I bought over the year have progressivly gotten worse for out-of round and the ogive variations are some of the worst I've seen in any bullets. I've seen between .020 and .030 of variation for ogive.
    The quality of the 142 is still top notch at present and the BC is only a couple of point shy of the 155 grain bullet and you don't need the tight 8" twist to stabilize it either. That's why you don't see the 155s used or talked about that much.

    I'll measure those cases up tonight. Going to pick my bolt up at the smiths from having the ejector fixed from the primer rupture a couple of weeks ago. Had to drill and tap the old ejector out. It would not budge. It bent it and locked itself in place.

    Steve
     
  7. Steve Shelp

    Steve Shelp Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Brent,
    Just water volumed those cases:

    6.5-300 WWH: it gave me 96.6gr of H2O right even to the top of the neck with an inverted primer cup. This is WW Super 300 H&H brass necked down and blown out and not sized after firing. Weatherby brand brass would have a little more internal volume than the Winchester stuff but I don't have any more that had been fired in my chambers to compare them 1 for 1. I got tired of loose primer pockets and with the Weatherby brass so I used the WW brass and just cruised along at 3350+-. I didn't need the extra volume to shoot that speed.

    6.5-300 Win Mag: 91.6gr of H2O even with the top of the neck and the inverted primer cup. This is WW brass also and is simply a 300 Win Mag necked down to 6.5 with no changes. You talk about a short neck!! [​IMG]

    Off to work.... gotta run [​IMG]

    Steve
     
  8. Brent

    Brent Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Thanks a lot Steve. [​IMG] If you get a chance, the capacities would be handy in evaluating them for sure.

    I wonder if that long neck theory has been seriously tested on very many barrels or just enough to convince the right people that it spread real far and fast.
    http://www.angelfire.com/ma/ZERMEL/twist2.html

    Here's a link I found last night that might explain where it started or maybe it's just another wright up on it too. I'm still wondering how this smith up here figured out a .405" neck length in my 30/338 Lapua Imp would be optimal, it differs from the formula that was explaned to me by another smith that was telling me how the other smith figured it. The other smith, he's a little tight lipped about how he figures it exactly, but did figure mine out for me though. He may be using the formula presented in that link, I've not checked to see what that one suggests for the 30/338 yet.

    I'm getting a good idea on the possible throat errosion and MV with all the good info comming in. [​IMG]

    Funny you mention the 155gr SMK, my dad and I were talking about it last night, basically wondering why if his 9 twist 6.5 WSM would shoot them at all, it is pushin the 140's a little faster than some of the smaller, more popular 6.5's but, nobody ever talks about the 155 though, been wondering why. They would probably be moving along at 3100-3200 or so if he tried them.

    Dad gave me money to order him a 28" Pacnor .338" bbl last night for a 338WSM he's building. He wants it for shooting the 300gr SMK in another Rem 700 LALH he picked up. I don't know what MV he's likely to get, maybe 2500 or so. He wants a 10 twist, and I told him about the 3 groove bbl I think Pacnor has but, I'm wondering if he might need more twist if he's pushing them 300's that much slower.... I know, why the 300 SMK in a little WSM case at only 2500? He just wants it for 500-600 yds, and loves the 300 SMK, did I also mention his love affair with the WSM case. [​IMG] [​IMG] I can't convince him to get a neck and throater reamer to use with this 30/338 Lapua Imp reamer I'm getting, I know he'd be much happier with the external ballistics of it... but at the rate he's building all these damn guns he'll have one of them by this fall too! [​IMG]
     
  9. Brent

    Brent Well-Known Member

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    Re: Throat errosion concerning the large case 6.5\'s

    Steve,

    I'm so glad you responded to this post. I swear, I learn more from you in one or two posts than I learn all year on some things! [​IMG] I appreciate your time sharing all this with me. Glad you didn't leave one sentance out either. [​IMG]

    I'll let dad know about the 155's, that's interesting stuff.

    I agree with you on the PPC case design word for word. There are definately diminishing returns the longer the case is, that's about the only difference I can see. When my dad was busting out 180gr bullets in his 300wsm at over 3275 fps and my 300 Ultra was only 20-30 fps faster, I was simply amazed! His bbl was only 1.5 inches longer too. Dad really thinks he's hot $hit now, with all those super accurate WSM's he's building! [​IMG] I'm workin hard on building something to knock that big chip off his shoulder. [​IMG]

    I used to whoop his a$$ at the range routinely, now he almost routinely just cleans my clock! He's gotta be stopped! [​IMG]

    That throat errosion formula stuff is pretty deep "theory", I think. Like you, the best thing about the longer necks, I thought, was to offer better protection by funneling the abrasive burning powder better down the center of the bore. Less direct "abrasive" blasting of the throat as it comes off the shoulder by bouncing back off the neck again. That's just theory too though. [​IMG]

    Some guys shooting 300WM's in Highpower Comp (shooting Fast) say they don't get much over 1000 rounds before they rebarrel, but the round works!

    Thanks for the capacities on those two, I'm saving all this good info ya know. [​IMG] Thanks for using fireformed pieces too! You da man. [​IMG] I appreciate ALL the insight here!

    Now, tell me when you run accross someone shooting a 6.5/338 Lapua, I'm diein to know how their doing with one. Thanks again Steve.