What is acceptable Standard Deviation in Bullet grain in same lot?

Discussion in 'Extreme Long Range Hunting & Shooting (ELR)' started by Sealesniper, Mar 2, 2018.

  1. Sealesniper

    Sealesniper Well-Known Member

    Messages:
    1,135
    Joined:
    Oct 14, 2009
    I have a custom 6.5x284 and it has been a laser with 140 LVD Berger bullets. Over the last 12 months I have been working with Nosler Accubonds Long Range 142 grain Spitzers with great terminal effects on deer and bear at extended ranges. This past Sunday I went to the range with a new batch of LR Accubonds as I had worked through the first box. WTH???? I sight in at 250 and I would have the first two touching, then the next two would be 1/2" high and a spread of 3/4" to 5/8". I normally get snowmen or clover leaf patterns (if I do my part). I backed off, took a breath, let the barrel cool and over the next hour and a half, continued to get the same unusual groups. I did not shoot all the rounds I had loaded as I wanted to verify them when I got home.

    Once home I verified Ogive, OAL, pulled the bullets and verified the charge, verified the necks as best I could with just pulled brass and nothing was off. I then decided since I had the scale zeroed and calibrated to check a few bullet weights. I took 50 rounds out of the Nosler box and WOW, not at all uniform. I had variences from 141.6 grains up to 142.3 grains. Out of the 50 I tested only 10 (20% were exactly 142 grains). I came up with a Standard Deviation of 0.164639 grains, a Mean of 141.894 grains and a variance of 0.027106 grains. Just for kicks, I took the box of 140 grain Berger VLD's down and weighed 50 of them. 49 were exactly 140 grains and one was 139.9. I did not run any calculations on them as that is about as perfect as one could ask.

    So here is my question. How much difference does that SD make at 1000 yards? I did not have my chronograph with me Sunday to get velocity (wish I had) but using my standard balistics program it does not show any apparent vaiance in POI even out to 1000 yards which I dont believe. As shooters, how willing are we as a group to support what I feel is piss poor quality control? For over the past 12 months I have been singing praises of the Long Range Accubond. Should I be? Then, will this small variance really make any difference on any ethicaly shot I take at deer? Should we as shooters and customers continue to purchase bullets from manufactures that claim 142 grain bullets and only 20% of the bullets in that lot actually are that weight? Berger has the quality control, why does not Nosler?

    Roger
     
    alcesgigas likes this.
  2. RandyinVa

    RandyinVa Well-Known Member

    Messages:
    189
    Joined:
    Mar 31, 2007
    I will guess. Most all Bergers used for target shooting, Not so much Noslers.
     
  3. Sealesniper

    Sealesniper Well-Known Member

    Messages:
    1,135
    Joined:
    Oct 14, 2009
    Berger makes Match and Hunting bullets. I was using the hunting bullets and their tolerances are excellent.
     
  4. Plinker147

    Plinker147 Well-Known Member

    Messages:
    324
    Joined:
    Feb 7, 2015
    My feeling is your not going to see much difference since it’s such a small variance. Only way to know for sure is to sort them them load some rounds with with the different weight bullets and shoot them as a group at distance, at least 600 yards. I don’t think the difference will show enough at 250 yds for you to be sure. If you do please post results, it would be good to see a real world results.

    I’ve been shooting the LRABs in my 6.5-06. In that particular gun they have been a little more accurate than Berger’s at 600 yds. 1/2 compared to 3/4 moa
     
  5. rscottb

    rscottb Active Member

    Messages:
    32
    Joined:
    Jun 16, 2017
    I would appreciate any information if and when you sort and shoot the different weights bullets. I understand the theory about bullet weight consistency along with consistent everything when we shoot. This would be a great learning experience for me about real world differences in bullets weights and how much this affects accuracy.
     
  6. raz175

    raz175 Member

    Messages:
    10
    Joined:
    Apr 15, 2015
    What I've found in Nosler bullets is that the base to ogive (bearing surface)measurements can vary greatly between lots. This variance has shown more impact on group size than just weight alone. If you have one lot that has a larger base to ogive and is seated at the same CBTO, it will have greater bearing surface and will be seated further into the case. I have seen this affect my groups quite a bit, and had me chasing my tail for quite a while.
     
    alcesgigas and jasent like this.
  7. jasent

    jasent Well-Known Member

    Messages:
    394
    Joined:
    Nov 16, 2010
    I agree. I've had the same results. Bearing surface can have a large affect on accuracy. I have had bergers that where terrible for consistancey and they threw my sd&es from single digits to over 50fps. Most bergers are great and it's not common to have much variation but I have seen a few boxes. Nosler, Sierra, Hornady not so much. All bergers on the shelf now.