need some help with trimming

Discussion in 'The Ammo & Reloading Forum' started by rgm19, Sep 11, 2008.

  1. rgm19

    rgm19 New Member

    Aug 22, 2008
    I'm just getting started, I need some help. Im loading .308 I have two books
    Lyman (came with my reloading kit) and a Nosler. I want to reload the Silver balistic tip for hunting this year. The Lyman gives a trim to length, but the Nosler doesnt just a maximum. They both give suggested starting loads, both are different. My first question is do you trim all new brass? And what if the manual you want to use doesnt list A trim to length? I want to use the nosler book because its their bullet. The Lyman book gives OAL for each bullet design, but the nossler book only gives one OAL. My second question is: For both Powder charge and OAL what are the acceptable variances to Specifications? Sorry if I'm rambling guess Im just getting overwhelmed with all the data. Thanks in advance for any help
  2. .308 shooter

    .308 shooter Member

    May 3, 2008
    Welcome to the world of reloading. I am also new to reloading. I just bought my kit about 1-1/2 months ago. I've reloaded two batches and results were remarkeable. You're gonna love it!!!!

    I will start of telling you what everyone told me. Read the manuals and completey understand everything before you start.
    Regarding the trimming of the case. The length listed in the manuals in 2.015" and that's the maximum overall length and that's what it means. I had the same question you did. The suggested trim to length is 2.005". If your cases are varying from that, then you should measure each case and trim them all to the trim to dimension. The brass will "grow" overtime as it expands through the firing process and eventually you'll have to trim again.

    With regards the the variances of powder charges, you should start at the beginning load and work your way up, never exceeding the maximum. As you move up in charge, inspect your brass for signs of high pressure. I started at the minimum load and increase in increments of 1-1/2 to 2 grains with each load.

    The COL listed in the manuals is the length that most factory guns will chamber without any problems. As you get more familiar with reloading you may want to customize you COL to where the bullet is just off the lands. Once you do that, you'll need to readjust all your loads starting at the minimum load once again and inspecting for signs of high pressure as you increase the charges. That's where I'm at now. I haven't had the opportunity to test my loads with that yet.

    GOOD LUCK!!!!
    Last edited: Sep 11, 2008

  3. Bindernut

    Bindernut Well-Known Member

    Oct 24, 2007
    ND, USA
    Welcome rgm! Both to reloading and to TFF. Lots of good folks around here to help ya get started. Don't forget to dig around in the old posts here too...lots of good info.
    .308 Shooter gave you a pretty good rundown on what to watch for on the trimming issue...not bad considering he's another new guy! :D Just kidding ya .308...old-timers need to ask for help too!

    In my opinion, you can't have too many reloading manuals. Most of them have a very good section on how things work inside that rifle chamber when you pull the trigger. The Lyman manual is pretty good, but the Hornady manual probably does it best. That one would be a good investment for reading material. Reading those sections will give you most of the basics and you can build from there.

    The trim-to length will be the same for a cartridge regardless of what manual the info comes from. Not sure why Nosler left that out of their manual...probably going by the general rule of thumb that it's recommended to trim cases 0.010" shorter than the max case length listed.

    Use the load data for the specific bullet you're using. Even if a bullet from one maker is the same weight/profile/etc, it may behave differently than the same weight/profile bullet from another maker. Differences in material used, nose profile, flat-base or boat-tail, etc...all of these can throw variables into the mix that might get you into a dangerous spot with your particular rifle and loads. Since you're interested in the Nosler bullet, stick with the data from that manual when loading it. Also, different brand brass or primers can change the recipe too...stick with the specific brand primer listed for the loads in the manual you're using.

    You can usually substitute brass of another brand, but since you mentioned that you're also reloading the .308 then I'll also add a warning about using NATO 7.62x51 brass for your loads. The military brass is usually built thicker, which means it'll have a smaller internal volume than a commercial .308 Winchester case does. This can cause a dangerous high pressure condition, and your powder charge will need to be lightened up accordingly. As a new guy, just stick with commercial .308 brass for your loads until you have a little more experience/knowledge under your belt.

    If you're using brand-new brass, it is recommended to full-length resize them and then check the length before the first loading. You probably won't have to trim them but it's better to be safe.

    Like the powder charge data, stick with the brand bullet you're using for it's recommended cartridge OAL. Once you're a little more familiar with how things work you might want to try fine-tuning this a bit, but for starters it's best to stick with what's listed in the manual.

    Acceptable variances...
    There aren't really any standard tolerance levels for either charge weight or OAL.
    Most every manufacturer of reloading components will develop loads around their products and while some of it will co-relate to data from other makers, some will also be higher or lower. This can be due to differences in the firearm used to develop the data or even variations in different manufacturing lots of the same item over time.
    OAL variances...
    Different rifles can have different length "throat" dimensions...meaning that the rifiling starts either closer or further away from the mouth of the cartridge. If you go shorter than the recommended dimension, you can run into high-pressure conditions due to the bullet taking up more space inside the case. If you go longer, again you can run into high-pressure conditions due to the bullet touching the rifling. Both can be dangerous, so another warning to stick with what the manuals say until you've got a bit more experience.
  4. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    Both the above posts contain very good advice but let me add a little.

    case trim length:

    The maximum listed is the "stop using and trim" point. The minumum trim length is just that, the length you should trim to and no less. It is usually 0.010 inches shorter than the Maximum case length. Any case that AFTER SIZING falls between those min and max numbers need not be trimmed.

    But..... (there is always a but) for cases that you wish to crimp, the finished products look better if all the cases are exactly the same length as the crimp will look the same on all cases and will hold the bullets with exactly the same neck tension, enhancing accuracy. For bolt action rifle cases you normally don't crimp them.

    Over All Length (OAL):

    Most manuals list two numbers. The recommended number for the cartridge/bullet combination and a maximum OAL. Using the recommended OAL is the one to start with. It guarantees that the bullet will perform close to what is listed in the manual and be safe in most all guns. The maximum OAL is the industry standard for any loaded cartridge that probably will fit most gun's magazine and not jam into the rifling.

    But..... (here we go again) an advanced reloading technique is to make the OAL such that the bullet is just NOT touching the rifling lands in the barrel for a specific gun (and only that gun, and no others). Some like to vary the OAL from that point and shorter to give the bullet some jump to the lands. Accuracy nuts like to put the bullet as close to the rifling lands as possible without touching them. Experts now claim it is a waste of time to adjust the OAL in small incremental variations of OAL as testing has shown it affects the accuracy very little and other things are a lot more instrumental in maximun accuracy (like concentricity of the bullet in the cartridge and the concentricity of the case itself).

  5. artabr

    artabr New Member

    Mar 3, 2008
    New Iberia, Louisiana
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