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Trimming to max or close to?

Discussion in 'The Powder Keg' started by jgang, Mar 29, 2002.

  1. jgang

    jgang G&G Newbie

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    How critical is it to trim each .308 Win cartridge to col or close. I'm getting ready to test half grain increments find the load that works best in mine. I am using col of 2.012-2.015. Anything less is kicked out and all are trimmed to within this. Is this enuf or not enuf accuracy? I can get my oal within a .001. I wonder if my accuracy would matter more if I found which load works best and if I was trying to find my load within a .1 of a grain. Any ideas? jgang
     
  2. Jack O

    Jack O G&G Newbie

    The way I see it the more you can make the cases alike the more they will tend to shoot to the same place. ( Isn't that accauracy) Some differences would have to be in your loads but anything you could make the same ie. neck tention, case length, brand of cases, flash hole size, volume of case, all of these things effect acurracy one way or another. Just my OP.
     

  3. I use a LEE ZIP TRIM to size my .308 brass. It's cheap, quick and it does an excellent job. You didn't say what kind of shooting, you want to do. If you want to do some match shooting, then like JACKO said, you'll want all your cases to be ,as identical, as you can get them. If your just working up a load for plinking or hunting, you won't have to be that critical.
    Have a good one, ****.
     
  4. jgang

    jgang G&G Newbie

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    My shooting will be aimed at getting a 3" group at 500 yds. I have heard that neck sizing is the way to go with once fired rounds. Can you guys help me with the ins and outs of neck sizing?
     
  5. Jack O

    Jack O G&G Newbie

    That's alot farther than I have shot but I guess you would have to shoot 1/2" at 100 yards to be in your 3'' bracket that's a tall order. As to answer your question the ins and outs of neck sizing. Brass should last longer by neck sizing only you work the case less so there isn't as much mechanical strecthing of the case. The case would be formed to the chamber so it should give more consistent groups. Most importantly is what ever your rifle wants to shoot. Hope this helps need anything else just ask.
     
  6. kenny

    kenny G&G Newbie

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    I use Lee collet dies and have very good luck with them. Case length and brand are very important (federal and rem. may shoot a little differant at that range).
     
  7. squirrelsniper

    squirrelsniper G&G Newbie

    For 500yd shooting.....

    I would buy a Lee Collet die and neck size only. The only downside to neck sizing is that you may not be able to chamber your ammo in another rifle, it will only work in the rifle that the brass was fired in. For the kind of accuracy you want, I would use only cases of the same brand and preferably of the same lot number (BTW,I like Lapua 308 brass) and I would trim the cases as close as possible to the same length. You will probably also want to deburr the flash holes, chamfer the inside and outside of the neck, uniform the primer pockets, throw away any cases that have an off center flash hole, and weigh the cases and seperate them into groups based on weight. Be sure that you don't weigh the brass until AFTER you have performed all trimming, deburring, and uniforming operations, because any brass that you remove in those operations will change the weight of the case. If you use Lapua brass, you can probably get by without having to deburr the flash holes and seperate them by weight. If you aren't experienced at deburring flash holes, you can actually make Lapua brass worse, so practice on something else first. Your goal of 3" groups at 500yds shouldn't be too hard to obtain if you use an accurate rifle with carefully prepared ammo. If you have a rifle that will consistently hold 100yd groups in the .5" range, then the only thing left is your ability to read the conditions and know when to pull the trigger. The bad part is that it is much harder to learn how to read the conditions than it is to learn how to build a rifle and load good ammo. Hope this helps, and good luck.:)
     
  8. jgang

    jgang G&G Newbie

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    Wow, lots o info Mr. Squirrelsniper. Thanx. Would neck turning keep the concentric lineup the same throughout the cases? I am still a youngin when it comes to all of this. I have yet to find the best powder, bullet, and etc setup for my .308. What would be my best range to find the setup? She is dead on at 200yds. Practically, without measuring, better than 100yds. Should I find a load at 100 or 200yds or reach out and learn how to compensate for the drop and windage? Thanx again for all the help. jgang.
     
  9. squirrelsniper

    squirrelsniper G&G Newbie

    I'm not sure that neck turning would help much if the ammo will be used in a factory rifle with a standard chamber. Neck turning can make a large improvement in tight necked custom chambers, but in factory chambers that are usually pretty loose in the neck area, it makes the neck have to expand that much farther until it reaches the walls of the chamber's neck area. For this reason I don't like to turn the necks 100% on cases for standard chambers, but a small bit of turning to help "clean-up" the neck might make a small improvement. By "clean-up" I mean just take off the really high spots till about 50-65% of the neck shows shiny brass where material was removed. Anywhere that a high spot was, there should now be shiny brass.
    As for what distance to find your rifle's preferred load, the ideal situation would be to test everything at the distance you plan to do your shooting. However, testing loads (or any other setup for that matter) is much more difficult at that long of a range because of the effects of the conditions on the bullet flight, and you probably aren't going to be able to see where your bullets hit at 500yds and going 500yds to put up a target gets annoying after a while. For these reasons, I prefer to work up my loads at 100 or sometimes 200yds. I can easily assess what is going on and if I call a condition wrong the shot may be off a bit, but at least it will hit the target somewhere. At 500yds, if you don't have a fairly large target and you miss a condition, you may miss the entire target so you have no idea where the bullet impacted. I would suggest that you work up a load at either 100 or 200 yards, depending on which you personally prefer, and when you get out to 500yds you can just do some tweaking to get the load tailored to that distance. You might even get lucky and won't have to change anything about the load, but most likely you will have to vary the powder charge by a few tenths and you could possibly (but not likely) need to vary bullet seating depth a couple thousandths to get the load tailored for that distance. Also, just to get used to shooting for groups at that distance and to help get your scope zeroed for it, you could move the target back in 50-100yd intervals. This way you can bring the scope up as you go and shoot a few groups on your way out to the 500yd mark. The real trick is just learning how the different conditions affect the bullet flight and how to compensate. Just be aware that your first few groups at 500yds probably aren't going to be that good, but with enough practice distance becomes just a state of mind.:D
     
    Last edited: Apr 2, 2002
  10. jgang

    jgang G&G Newbie

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    So neck turning does square the case to bullet? I am sorry if I am asking too many ?, but you have alot of good answers. How do you feel about different bullet combo's after you find the best powder load? I guess what I want to know is how many 168hpbt do I try, even if I am satisfied with what I got? Do Savages like other bullets that Remmy's, or Brownie's? I think that practice will dictate the answers to my questions, but have you tried the Swift Scirrocco's or other combo's that would limit my search? jgang
    s
     
  11. squirrelsniper

    squirrelsniper G&G Newbie

    There's no such thing as too many questions, a shooter can learn something new every day if he is willing to ask enough questions.
    As far as what neck turning helps, it doesn't really help make the bullet and case square with one-another. The amount of squareness, or in scientific terms "concentricity", of the bullet to case is determined mostly by the bullet seating die. If the bullet seating die isn't perfectly square, or concentric, with the case and shell holder, then the bullet will be pointing slightly in one direction. There are devices made to check the amount that the bullet is pointing by spinning the entire loaded round on bearings and measuring how much the bullet moves up and down. The amount of movement is called "runout", similar to how axles and crankshafts in a vehicle are measured only on a vehicle it is usually called endplay. Cases can also be made with the neck not quite centered and it will cause this, but since most factory rifles have the entire chamber cut slightly off-center from the bore I wouldn't worry too much about it. Just use a quality press and die set and bullet runout should be pretty low.
    What outside neck turning helps (most people don't do inside neck turning) is the tension on and release of the bullet. If the case neck is slightly thicker on one side than on the other, the bullet is held with different amounts of pressure on each side. Then when the gun fires and the neck expands to release the bullet, the sides of the neck expand until they hit the sides of the chamber in the neck area. On factory rifles there is usually room for the bullet to be completely released from the neck before the case neck is stopped by the neck portion of the chamber walls. On tight neck custom chambers, the neck of the case hits the sides of the chamber before the bullet is completely released. Therefore, if one side of the neck is thicker than the other, the bullet is pushed to one side as it comes out of the case and now there is a slightly off center bullet heading down the barrel. Although it may sound like the factory chamber would be more accurate, when everything is equal the tight neck match chamber will hold the bullet perfectly until it enters the rifling.
    As for changing bullets, every time you change a bullet you will have to tailor you powder charge to that bullet. Even though two bullets may be 168gr BTHP's, if they are different brands then they will perform differently and the powder charge must be tailored to that individual bullet. The bullets may look almost identical, but the thickness and metal composition of the bullet jacket and core will be different. Basically, if you change one thing, no matter how small, such as primers or brand of cases, it will require a complete start over from the beginning.
    As for what bullet your rifle likes, that can only be found from testing. Even if you take two rifles off the assembly line that were made back-to-back, they will both be a bit different and will have their own preferred load. I can give you an idea of what bullets seem to do well in the majority of rifles though. In 308 I've had good luck with Sierra 168gr HPBT MatchKing's and Hornady 168gr HPBT Match. Some rifles also like the Sierra 175gr HPBT MatchKing and I haven't used them but I have heard many good reports on the Sierra 155gr HPBT MatchKing. For good accuracy, the only hunting bullets that I've gotten good groups from is the Nosler Ballistic Tips. Also, I've had good luck with Hodgdon Varget powder in the 308. Basically, when you start going for pin-point accuracy, it is just one long test; trying different powders, primers, cases, bullets, seating depths, powder charges, and on and on and on, but it sure is fun in the process. The main thing about finding new loads is to just be safe and follow published loading data; the best group in the world isn't worth getting hurt in the process of finding it.
     
  12. kenny

    kenny G&G Newbie

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    That's good info squirrelsniper. The best I can say as a novice reloader is to start small and take little steps. Everything counts in the end but keep it simple to start. Every gun shoots different even if it's the same brand and cal. Keep trying and be sure to make it safe first and fun after that. That way you can pass it on to the kid the right way.