What am I missing on a 100fps SD?

Triggerhappy

Triggerhappy

General Nuscience
Full Member
Minuteman
    • Feb 15, 2009
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    Calif., MO
    #1
    I have built a Savage rifle in 260 Rem. with a 28" L-W barrel using a similar load to another rifle I have that has a SD of 10fps, yet this one is 100fps. I have anywhere from 2825-2989fps with the same load new prepped brass and weighed everything brass +/- .5gr and trickled powder load to perfect. But the kicker is that I am shooting sub 1.5" groups @ 400yds with it. What am I missing????????
    confused.gif
     
    #3
    Re: What am I missing on a 100fps SD?

    As far as consistent seating depth? Because that should not be an issue they are Lapua 139gr bullet loaded on a Dillon 550b that is set to .015 off the lands.
     
    #4
    Re: What am I missing on a 100fps SD?

    Case's need trimming maybe? If they are too long they could get pinched at the end of the chamber when fired since the case mouth can't expand to release the bullet. It might be your chronograph too. If the light is not even across both screens the readings can be off.
     
    #7
    Re: What am I missing on a 100fps SD?

    I have found that loads just touching the lands will always give better SD's. Even better if the gun likes it is to load touching the lands. This does not allow (or very little) gas to escape around the bullet and exit the barrel. Thus getting the maximum bang for your powder charge!

    I try to keep all my loads touching the lands if the gun will shoot there!

    Terry
     
    #8
    Re: What am I missing on a 100fps SD?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">Case's need trimming maybe? If they are too long they could get pinched at the end of the chamber when fired since the case mouth can't expand to release the bullet. It might be your chronograph too. If the light is not even across both screens the readings can be off. </div></div>

    The brass is new and trimmed and the chrono is a beta master from Shooting Chrony. I thought of that too but my 223 I checked right after that was really good.
     
    #9
    Re: What am I missing on a 100fps SD?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I would start by checking the velocity on another chronograph.
    </div></div>

    +1 for Lindy.
     
    #11
    Re: What am I missing on a 100fps SD?

    +1 should have thought about that first.
    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I would start by checking the velocity on another chronograph.
    </div></div>

    +1 for Lindy.</div></div>
     
    #12
    Re: What am I missing on a 100fps SD?

    Thanks for the ideas. I think you maybe on to something with the chrony. I may have had it too close to the rifle and with the long barrel the muzzle blast may have messed up the reading. The 223 has a little short barrel with little muzzle blast that would not effect the reading as much. I may try again this weekend and position it a little farther away this time.
     
    #13
    Re: What am I missing on a 100fps SD?

    100 fps is over 2" of vertical at 400, so I don't think there's that much swing. I've never had a load with those kind of high ES numbers and shoot that well. So, I think your chrony numers are no bueno per caca! Replace the battery, shield it from direct sunlight, and set the chrony atleast 15' away from the muzzle. You can set it closer if you have a muzzle brake or can.
     
    #15
    Re: What am I missing on a 100fps SD?

    I knew that I should be 15' away but space did not allow (there was a big mud puddle in front of the bench) and I was more like 5-6' away at the most. That was probably the problem because my vertical spread was almost 0 the groups were almost perfectly horizontal, that's why I was so confused.
     
    #17
    Re: What am I missing on a 100fps SD?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triggerhappy</div><div class="ubbcode-body">I knew that I should be 15' away but space did not allow (there was a big mud puddle in front of the bench) and I was more like 5-6' away at the most. That was probably the problem because my vertical spread was almost 0 the groups were almost perfectly horizontal, that's why I was so confused. </div></div>

    Yelp, that's why your spreads were so high. You were getting muzzle flash in the chrono. 12-15' is minimum without a can or brake, and maybe 10-12' with brake or can.
     
    #19
    Re: What am I missing on a 100fps SD?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triggerhappy</div><div class="ubbcode-body">I knew that I should be 15' away but space did not allow (there was a big mud puddle in front of the bench) <span style="font-weight: bold">and I was more like 5-6' away at the most. </span> That was probably the problem because my vertical spread was almost 0 the groups were almost perfectly horizontal, that's why I was so confused. </div></div>

    Bingo!

    If I were shooting a CONSISTANT 1.5" at 400yds I couldn't give a rip less what the Chrono says!

    Keith
     
    #20
    Re: What am I missing on a 100fps SD?

    +10, the target tells the real story.

    STP and I have an identical pair of 28" 1:8" L-W barrels. We load 142SMK's and 140AMax touching lands with 43.89/43.9gr H4350 for around 2850fps.

    Greg
     
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