More reading = 3 more questions... for now.

Discussion in 'The Ammo & Reloading Forum' started by .308 shooter, Aug 17, 2008.

  1. .308 shooter

    .308 shooter New Member

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    Okay... here we go again... more questions.

    First question:
    Reading the Hornady manual.... they suggest neck sizing the brass over full length sizing. I have to reread this section, but my first take is neck sizing reduces the amount of wear on the case. Thus eliminating the need for trimming as frequently and improving the life length of the brass. True? Are their neck dies versus full length dies and can you neck size only with a full length die. I know I need to read more, but I like to compare answers from here with the manuals.

    2nd question:
    I'm initially going with the bullet manufacture manuals, versus the powder manufacture manuals. I have both Hodgdon Varget and BLC2 powders. I'm using Hornaday 168gr. AMax boat tail bullets. The Hornady manual does not have a listing for the BLC2 powder. Does anyone have the full Hodgdon manual? If so, what are the min. / max. listings. I actually have the maximum as it's in the .pdf that I downloaded and in the small catalog type manual I got with the powder. And..... I know the Maximum is too much for my gun as that was my first experience with supervised reloading that actually caused me to send my gun back to Savage. It screwed up my ejector.... way too hot.

    I'm assuming the powder wouldn't affect the COL?

    3rd question:
    My Savage 10FP (.308) has a 1 in 10 twist rate. The Hornady A-Max bullets are rated at 1 in 12. Is this a problem?
  2. jinn

    jinn New Member

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    (compressed to save space). 1. Still talking .308? You did not say. My understanding of the mechanics of sizing is this: If your fired brass was used in arms with wallowed-out, or high-end of tolerance diameter-wise, and your end-use gun is chambered low-end, that is smaller diameter, failing to full-length size will result in reloaded rounds not chambering fully. One of my manuals states that if your brass is ALWAYS used in the same firearm, full-length sizing is not needed. Be aware that given a caliber, chambers are not ALL IDENTICAL in diameter, by just a little bit; it's called "tolerance".

    You cannot neck-size only with a full-length die, as the neck is the LAST part of the case to receive treatment.

    2. I will consult my Hodgdon manuals, and get back to you on this, if info. pertinent.

    3. 1 in 10 will use up more of the energy available, in spinning the bullet, than 1 in 12. All other things equal, higher spin will increase pressure slightly, but if you load within reason, I see no problem with 1 in 10.
  3. BigJakeJ1s

    BigJakeJ1s New Member

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    Hodgdon online reloading data center has blc2 load data for Sierra 168gr HPBT.

    Andy
  4. .308 shooter

    .308 shooter New Member

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    Thanks.... Okay - forget about the twist rate question. I got mixed up and was thinking 1 in 12 was faster than 1 in 10. I completly got that backwards, so I know my bullets are okay. They say 1 in 12 or faster. I'm good. Thanks again.
  5. artabr

    artabr New Member

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    .308,
    Hodgdon date for a Sierra 168 gr. Match King HPBT using BL-C(2) is:
    44.0 grs. at 39,400 CUP TO 47.0 grs. at 50,200 CUP (MAX LOAD)

    Note: This is why you want more than 1 manual
    Do not use the Hodgdon data. Their max load is 2 grains higher than the 3 manuals I will list below.

    Speer manual #12
    168 grain Speer Match HP-BT
    BL-C(2)
    Min. : 41.0 grains = 2336 Feet Per Second
    Max. : 45.0 grains = 2625 FPS


    Lyman manual #47
    168 grain HP-BT ( no manufacturer specified )
    BL-C(2)
    Min. : 41.0 grains = 2444 FPS at 37,700 CUP
    Max. : 45.0 grains = 2695 FPS at 48,800 CUP


    Sierra manual #5
    168 grain Match King HP-BT
    BL-C(2)
    Min. : 42.7 grains = 2500 FPS
    Max. : 44.5 grains = 2600 FPS

    Note: Sierra list the Min. load for the 165 grain bullet using BL-C(2) as 40.5 grains. I think the min. for the 168 grain bullet should probably be about 41.0 grains of BL-C(2).
    If you have questions about this you can call Sierra's Tech-Line at 1-800-223-8799. They will be more than happy to help.

    I have had great results if I keep the 168 grain bullets at about 2550 to 2625 FPS. My small group at 100 yds. with my Rem. 40X .308 is 5 shots that miked out at .062" center to center. My small group at 200 yds. is 3 shots miked out at .192" with a Ruger 77 MkII VT in .308 Win.

    Art
  6. steve4102

    steve4102 Former Guest

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    1.) When neck sizing all brass must be loaded for one specific rifle. Fired and neck sized brass from rifle A will most likely not chamber in rifle B. Every time a round is fired it grows. At some point your "neck" sized brass will be difficult to chamber and must be FL sized. Neck sizing is not an option in a semi-auto. Each rifle is different, yours may shoot better with neck sized brass or it may like FL or PFL sized brass. Only testing and range time will answer that one.
    There are many that say you can neck size with an FL die. I say No, you cannot truly neck size with an FL die. At some point the die body will come in contact with the case body. At this point you have altered the body and you are no longer neck sizing. You can however, partial neck size with an FL die. That is to back the die way out of the press so there is no contact with the body. This however will only size the top part of the neck leaving several thousands of the neck untouched.

    2.) http://data.hodgdon.com/main_menu.asp
  7. LDBennett

    LDBennett Well-Known Member

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    308 shooter:

    To start out full length resize, including NEW brass. That way the ammo can be used in any gun, not just the one it was first fired in. Also there is nothing more frustrating than to reload a bunch of ammo to find it will not fit your gun and you have to unload it and reload it again. Full length resizing is the easiest one to do if you follow the directions given with the dies and you stand a much better chance of your ammo coming out correct.

    The brass case is a gasket to keep the in excess of 45,000 psi gases inside the chamber of the gun. The brass case stretches to fill all the voids of the chamber and when the pressure is relieved it springs back, close to but not exactly, to its original shape. It, of course, will fit into the chamber it came out of but probably not in anyone elses 308. No two gun chambers are exactly the same.

    When we neck size only the neck of the case is reduced to accept a bullet. The rest of the case is left unaltered by the die. When we full length size we push the brass into a shape that will fit any gun of the same caliber. It is generally best to full length resize but if you are chasing accuracy in only one gun neck sizing only is OK but eventually you may have to full length resize the cases to get them to fit even your gun. Neck sizing is suppose to be easier on the case but the common failure of most brass is neck splits from working the throat (neck) of the case. Whether you neck size only or full length size, neck splits will occur at the same rate, in my opinion.

    There is a more advanced technique that I think the best for accurate reloading. That is to resize the case but only enough so as to not push the case shoulder back, but so that the shoulder position exactly matches you gun. This ammo can only be used in this gun. It is not a technique you should start out with because it takes detailed knowledge of reloading and special case gages to implement. I use this on all my "accurate" guns unless they are auto loaders, levers, or pumps. Save this technique for a couple of years down the line. This is the technique NOW touted as the "accurate" way to reload but is not covered in most reloading manuals.

    LDBennett
  8. .308 shooter

    .308 shooter New Member

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    Thanks ARTABR and Steve4102. I know I can't use the max load in my gun, tried that already.... very unpleasant results. All the data I was given was for the Sierra HP-BT. I'm shooting the Hornady A-MAX. The difference may not be much, but I don't want to repeat the same mistake as last time. I'm hesitant to use the BLC2 without actual data from the Manufacture for that specific bullet. At least just starting off that is.

    Thanks for the information.
  9. artabr

    artabr New Member

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    .308 Shooter,
    I'm pretty anal when it comes to reloading. I turn necks, weigh my cases, weigh and measure ogive lenght of each bullet. IMO, for what its worth, I would not worry that much about the data being for Hornady A-Max or Sierra Match King bullets of the same weight and profile. The Ballistic Coefficient difference is a minimal .0013.

    Ballisitic Coefficient of 168 grain bullets.

    Hornady A-MAX - .0475
    Sierra Match King - .0462
    Hornady BT-HP Match - .0450

    EDIT: I don't shoot max loads so I am able to switch bullets without problems. It is a wise move to dial your load back if you make a bullet switch and then work your way back up.

    Call Hornady and ask what their data is for BL-C(2).
    Their number is I-800-338-3220

    Art
    Last edited: Aug 18, 2008
  10. jinn

    jinn New Member

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    Your understanding of the mechanics of cartridge chambering suggests considerable technical savvy beyond that simply gained by reloading experience.

    If I may ask, perhaps you can put numbers to some of the things I have often wondered about. For example, what is a reasonable clearance amount for loaded ammunition to have to possess adequate sealing characteristics, but still allow easy and flawless insertion into the chamber? 0.003"? 0.005?
    0.010? I often see obvious signs of gas leakage on spent casings, especially semi-auto handgun casings, which would seem to indicate considerable leakage occurring during the "sealing" phase of case expansion, or perhaps too-early release of lock-up? I have no clue just how much gas loss this represents, probably little, but could it be sufficient to allow reasonable loss of velocity?

    Furthermore, just how important is "lock-up" of breech in small arms (handgun caliber) ammunition? I cite as an example, the H&K VP70Z pistol (9mm) which has a solidly fixed barrel, and no mechanical lock-up whatsoever, and spent cases do not appear any the worse for wear. Or arms such as MAC-10, fixed barrel, open-bolt firing.

    Thank you in advance!

    Edit: (Some things "searched" yield little or nothing)
    Last edited: Aug 18, 2008
  11. LDBennett

    LDBennett Well-Known Member

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    While my "experience" is really no more than the usual lots of reading, it is tempered with an engineering degree. I don't have hard numbers for your questions because I have not seen it in my readings or ran across it in my experience.

    In locked breech or delayed blow back guns the bullet has left the gun barrel before the barrel is unlocked enough to leak much gas. Straight blowback guns use inertia and springs to slow the opening of the slide and the slide actually starts moving when the bullet does but, due to the inertia and the high pressure holding the brass case walls against the chamber internally, more slowly. If timed right the bullet is gone before any significant amount of gas is released.

    I have seen slow motion pictures of a semi-autos firing and the bullet appears long gone before the breech is open enough to see the breech end of the barrel.

    If the timing is wrong and the case is pulled out of the barrel before the bullet has left and the gas pressure released then usually bulging of the case occurs because the case becomes unsupport at its base area when the gas pressure is still high. Rim fires, for example, will bulge the base and even blow out at the base area. Centerfire brass will usually just bulge at the head of the case, on the case wall.

    If the timing is wrong the rim of the case head may show marks where the extractor worked hard to pull the case from the barrel as the internal pressure attempted to hold it tight against the chamber walls. I have an gas operated rifle with a operating gas adjustment. If I get it wrong (too much gas with early opening of the bolt) it does terrible damage to the rim of the case making the brass un-reloadable and can pull chunks out of the rim.

    Smudging on the case walls at the mouth of the pistol cases means that the brass did not stretch enough in that area to seal the chamber sufficiently, perhaps because the pressure was not sufficient for the size of the chamber or the hardness of the brass. Too mild of a load will do that but some cartridges like the 45LC seem to always smudge the cases regardless the load level (??).

    There is a class of guns (mostly European) that use the gas to hold the bolt closed long enough untill the bullet leaves the barrel and the gas pressure subsides. I don't know what operating principals the VP70Z uses, but maybe it is in this class of gun?

    How important is "lockup"? It is the timing of the opening of the bolt that is important, not the way the timing is achieved (Delayed blow back, locked breech, Inertia delayed, roller locked, gas operated, gas delayed). The case should not be attempted to be removed until the gas pressure subsides by the bullet leaving the barrel and the gas pressure falling.

    It turns out that gun design is not as easy as falling off a log, as some think, but requires real knowledge and experience to do it right. The worst example of what can happen when home tinkers screw up is the current rage of converting Ruger 10/22's to 17HM2. The 10/22 is a crude gun but sufficiently designed for the pressures of the 22LR cartridge. When the fast rise time 17HM2 cartridge is used in an after market barrel fitted wrong (easy to do because the 10/22 is crude) with the wrong head space, wrong recoil spring, insufficient bolt mass, and an ill fitting extractor that holds the bolt open slightly, then blown cases and bulging cases can be the norm. Gun design is best left to real gun engineers and designers.

    LDBennett
    Last edited: Aug 19, 2008
  12. Shellback

    Shellback New Member

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    Wow this is great reading LD, very informative replys!!!
    Tim
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