Bullet weight SD and when is it an issue?

[Sealesniper]

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 **** 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?

Please give you two cents if you have had expereince with these type spreads in bullet weights from the same box and lot and what you feel is acceptable Standard Deviations from the manufacturers.

Thank you,

Roger

Note, the reason I have been looking for an alternative bullet than the Berger, is it does not seem to offer dead right there performance, and blood trails are sometimes non existent. If I had confidence in the Berger knock down and blood trail capabilities, this would not be a discussion... Right Jett????

 

[Canhunter35]

How many rounds do you have down your barrel?
Do the bergers produce the irregular groups or do they shoot the same as before?

 

[Sealesniper]

About 230 down the tube. Bergers are very tight. I clean between different manufactures Bullets. The first group of Accubonds grouped better but not as tight as the bergers. Bergers consistently make clover leaf or snowmen.

 

[Canhunter35]

Well, all other things being equal it must be the bullets, but I don't have any experience with that. Perhaps you're on the edge of seating depth those bullets like and the differences are causing the erratic groups, but I think that's unlikely.
Sorry I couldn't be of more help. I wondered if your barrel was going? But not at 230rds
Hopefully someone else can help, there's some pretty knowledgeable ppl on the forum

 

[jrock]

I have also found that most main stream bullets and manufacturers do not have the same level of tolerance that Berger bullets do. The LRAB that I've worked with are no exception. I could not get them to shoot well enough in my guns to warrant continued efforts. I think there are some recent forum conversations about how the Hornady Eld-x's vary as well.

One can't compare the consistent weight of one shaped bullet to the 0.16 SD of a different shaped bullet in terms of accuracy. Apples and oranges. To find out, you would need to sort your bullets. Take the 20% that are good and test with a combined batch of highs and lows. You may see a difference you may not. Benchrest folk sort bullets. Youtube has a couple videos of people testing this.

 

[Sealesniper]

Thank you for the responses, but the question remains, is there an acceptable tolerance variation for weight deviations, or are we all hurting ourselves by continuing to buy from manufactures that list a weight on the box, but only fill the box with 20% of bullets matching those descriptions?

 

[JTB]

I love hunting with the LR Accubonds but admit it can be challenging to dial them in to that 1/3-1/2 MOA range. I finally began sorting them and have much less trouble. I generally order 300 or so from the same batch. For example I just received 300 6.5 142gr and 95% were split evenly into 3 weights (141.9, 142.0 and 142.1). There were about 10 outliers some as light as 138.5 to as heavy as 143.0. I load the outliers to work up to maximum load/velocity. I find the outliers will group together based on similar bullet weight with groups being as much a 2" apart at 100 yards. I have not taken the time to compare how much a wt. variance will spread groups but can say a 143gr has grouped as far as 2 MOA away from a 138.5gr. By wt matching the bullets it is much easier to dial them in. It is that unexpected flier from that 138.5gr outlier that will make you doubt their accuracy potential. Frustrating I know

 

[Trnelson]

I haven't spent much time with the LRAB admittedly. I can report though that I saw very similar things when I first started working with the 143 ELDX. I first noticed unexplained velocity variations and fliers that I couldn't honestly attribute to my marksmanship. I'm mortal, not a YouTube expert or TV star, and readily accept and admit that once in a while I pull a shot or flinch or just have a crappy trigger squeeze. It happens.
I do everything I can do to give myself the best chance at success with the lowest SD I can get from my equipment. I do all my load workup and testing with a magnetospeed in place. It doesn't consider any of my mortal faults, or make me a better shooter, it just records exactly what the velocity was and what the ES and SD are. If a shot falls inside the SD but the impact isn't what I thought it should be it was likely me. If it's outside the normal SD it's maybe something else, and maybe still me. It's all history at that point, either you learn something from it or you don't. It slightly changes the POI but not the precision of the groups in my rifles. I don't hunt with it on, yet.
Once I sorted the bullets by weight and bearing surface the vast majority of those unexplained impacts went away and the SD settled in right where I expected it to be and has held steady. If I slip in one of the bullets that isn't within the lot I'm currently shooting it changes the velocity, sometimes a little and it doesn't really matter and sometimes enough that it shows up on the target.

 

[HARPERC]

It sounds like they're working well on game so far, I'm uncertain as to what "extended ranges" means to you, or what group size you're actually getting at 250 yards.

My guess is, the difference's won't change your first shot hit probability in the field in a meaningful way.

How much variation in product do we accept? What is the variation +/- of the scale we are using, and what other variables are involved in actually measuring, that may need to be considered?

I haven't played with the LRAB, but the standard Accubonds have had about that much variation in them for me. Which at the time was an improvement over most of the other bullets I had weight sorted at the time, and that was/is acceptable for my limits shooting at big game.

The 2 that I have played with, within the technical limits of my ability to measure such things, that provide the consistency you're desiring, are the Bergers, and the
Hammers.

I "believe" meaning based on others experience, the Berger is a very capable big game bullet, but the folks I see that are getting the most consistent results on game with them are doing more prep with them, than I have inclination for. Squaring meplats, verifying hollow point integrity, single loading, etc.

I'm still hoping to put Hammer's to use on game, but they shoot great in a variety of rifles for me, load and shoot.

For me, all of the bullet manufacturers are more consistent than what they were when I started playing this game.

 

[Sealesniper]

UPDATE:

I just called and spoke with Nosler technical support. Their tolerances are +/- .3 of a grain. Out of the 50 bullets I checked only three were out of those specs. I had 2 at 141.6 grains and 1 at 141.5. The gentelman offered to send me three bullets which I declined but it still does raise the question, if they have a maximum allowable variance of .3 of a grain, WHY did I get three out of 50, which means 6%, out of their maximum specifications for variance? I plan to go back to the range this weekend if the winds lay down and attempt to shoot groups with simialr weighted rounds so see if the inaccuracy was me, or the variance in bullet mass. I will aslo bring my cleaning supplies and loaded rounds with Amax and Bergers for this test.

 

[dok7mm]

I don't know the answer to your question, but I sort by weight to .2 gr. lots, then BTO by .001". I don't get the fliers now, unless it's my fault. Gives me something to do in the winter.

Bergers have the fewest outliers by weight or BTO measurements, but I'll find 5-10 culls in a box of 500. Very consistent, but bad luck at a trophy long-range shot if you're chambering a bad outlier. JMO

It would be interesting to find out what effect .1 gr bullet weight would have at 1000 yds, if any. Too many variables involved to get accurate answer, I bet.

 

[MagnumManiac]

I have found that base to ogive length differences affect accuracy far more than weight differences by +/- .3gr.
When I sort bullets for 1000mtr F-Class Open, I sort by BTO and don't even weigh them. Whatever has variance is placed aside for 300-600mtr short range F-Class.
I use Berger for comp and hunting, I use Nosler ABLR for hunting and short range comp.
Other than BTO difference between batches, I don't find many fliers at all.
Maybe I should weigh them too.

Cheers.

 

[Mikecr]

I doubt your bullet weight variance matters from a 6.5x284. A standard external ballistics program doesn't care about bullet weight(as it isn't needed). An internal ballistic program (like QuickLoad) would tell you affects to MV. Nothing can predict tune.
For me, I would pick a bullet with best accuracy, as there is no other attribute more powerful than accuracy.

 

[DUSTY NOGGIN]

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.

i have not experienced that level of perfection with bergers, usually i find very similar tolerances as most other projectile brands ,i get tolerances almost exactly to what JTB wrote above:

as far as the bergers go , i bought 700 and only 300 of them were the same 180.1 , about 150 were 180.0 , about 100 were 179.9 , 75 were 180.2 and all the others less or below went into the random pile ( roughly 75 )

i would ask, did you purchase the LRAB's as seconds from shooterspro or did you buy these as an open box ??? ( they may be somebody else's outliers/random box )