.308 bullet sorting

[wboggs]

Did some base to ogive measurements and found max. to min. variations of 0.0055 for Sierra 175s, 0.007 for Lapua 155s, and 0.004 for Sierra 155s(2155). What tolerances are acceptable for LR target loading? Best way to measure and sort?
Thanks

 

[Johnboy]

ok I am no pro by no means.but here goes.I wouldn't think it would matter if there is a tolerance or not to a length.but would think of just how many you can find of the same length that matters the most.and useing a good bullet ogive measureing tool will do.the Sinclaire nut works for me with the choice of bullet size in it.

 

[whiskey08]

I dont think the bullet lengths are as critical, as how consistent you are seating from the ogive to the lands. I personnaly think that .003 makes a big difference and is to much for my accuracy tastes.

 

[GermanS1]

This is the only dimension that matters in sorting bullets - unfortunately, it can't be measured with any degree of precision.

The complete article on this topic is here: http://riflemansjournal.blogspot.com/2010/09/reloading-measuring-bullets.html

 

[dtucker]

Salazar, I just read your articul on bullet seating and it was great. Makes alot of sense to me.

 

[Bob3700]

German,

Thought I would weigh in on this topic as I have done my share of bullet sorting. I took the time to review the article you have written and as always I like your logical approach to the subject.

You measured bullets in several ways and I will not dispute that the two marks you indicated on the bullet are certainly one dimension that is worth measuring. As you indicated, I don't know how to measure that dimension either. To avoid any issues with variations in that dimension, if you soft seat your bullets to a significant jam, you eliminate the effects of that variation. An extra added attraction to this method is that you don't have to chase the throat of the bbl as it wears. That removes one variable while you are shooting that bbl.

One dimension that you didn't mention was the bullets bearing surface length. That is what I consider to be one of the valuable measurements. The BSL constitutes the friction that the bullet generates in the bore. It is one of the reasons that you can obtain more velocity from a bullet of the same wt with a shorter BSL, Say a 105B vs a 107 SMK. Depending on the color of the box your bullets come out of, the BSL can vary a considerable amount. Being able to sort bullets by BSL and coupling that with soft seating/jamming, definitely reduces ES and SD as well as group sizes with any of my 6MM cartridges.

Some will say to just shoot better bullets that don't have these variation in dimensions. Each box of bullets, no matter what the color, has variation in different dimensions that will affect external, on target performance. It just depends on what your balance is between time spent sorting vs costs of product. Everybody makes their own choice on that one.

Thanks for the good discussion.

Bob

 

[jonbearman]

So basically allow for a little extra jam or jump and that is it.Do you measure the completed cartridges and take an average using the sinclair nut. And set the seating depth to take into account for the shortest cartridge? Am I learning disabled? I read your article and I have a small learning deficieny since forever.Reading doesnt always make sense to me.Can you help?

 

[7x57]

what are measuring the base to ogive distance with? I mean are you using a $35 set of generic dial calipers or some Starretts? I think when you are measuring at the limits of a measuring device, down to the thousanths of an inch for a 6" dial caliper, the inherent quality of a top shelf caliper is what you pay the extra money for. I wouldn't be so sure a 5/1000 inch variance is bullet variance or the inherent range of the average caliper or a combination of both. Having said that, I have found the Sierra MK not to really mind jumping so it doesn't show on paper for me. I also have found Bergers to be alot more consistent in length, bullet to bullet in the same box, as well as in different lots of the same bullet.

 

[GermanS1]

Bob, thanks for the comments. I agree with you that bearing surface can be an important element in load variance and it can be measured. When I wrote the piece, I was focusing on seating depth and didn't think about bearing surface, thanks for pointing it out.

Jon, if you either jump or jam at least 0.015" the variance in the bullets that leads to inconsistent cartridge base to ogive length is largely rendered moot. The worst place to try to seat bullets is "just touching" because some will actually be jammed and others will be jumping. As Bob mentioned, soft seating and thus allowing the lands to "final seat" the bullet is another approach.

 

[dtucker]

When you are talking about BSL is that from the base to where the ogive ends. Also, can someone explain the term soft seating for me. I find this interesting and i am trying to sort this out in my mind some. If BSL is from base to ogive can you give me an example of how you are measuring this.

 

[Laurie]

Jon, if you either jump or jam at least 0.015" the variance in the bullets that leads to inconsistent cartridge base to ogive length is largely rendered moot. The worst place to try to seat bullets is "just touching" because some will actually be jammed and others will be jumping. As Bob mentioned, soft seating and thus allowing the lands to "final seat" the bullet is another approach

German,
I believe this is excellent advice and 'just touching' (or maybe not with some rounds) is a significant cause of 'fliers'. It's one that people who are loading into the lands need to be very aware of too thanks to erosion, especially with hot numbers that can see a round loaded several thou' 'in' move to the inconsistent state relatively quickly. I know that our top 7mm short magnum F-Class competitors in the UK update their COALs between league rounds, or a couple of league rounds at most for this reason. (They involve a minimum of 75 rounds, and a maximum of maybe 150 depending on the course of fire.)

I've taken to setting my (Forster Ultra) seater die for my long-range .223 Rem / 90gn VLD ammo marginally 'on the long side' and checking each round with callipers + comparator as it comes off the press, reseating the bullet marginally deeper if needed. With a micrometer top die, this is an easy and quick job. It means that I know every round has identical dimensions from the case-head to that point where the bullet ogive should hit the lands within a thou' variation. Bullets have been previously checked and batched by BSL using callipers and two comparators - not strictly speaking true BSL as the comparator inserts 'stop' just short of the bearing surface ends, but one hopes close enough. So far as my lot of Berger 90gn 0.224" VLDs go, out of the box variances are very small anyway - not something I can say about some other makes and models I've looked at!

With them all seated well into the lands, light neck tension, and careful / slow bolt closure I'm getting into soft-seating territory anyway, so this is probably adding belt to braces as we say here (braces = suspenders to speakers of US English), but when you're tying to hit a five inch-diameter circle at 1,000 yards I reckon the extra effort is worth it.

(For the record, the Savage .223 Rem held its elevation really well at 1,000 - better than many of the .308W F/TR shooters were managing with their ammo - in the F-Class European Championship matches at Bisley at the beginning of this month. And .... while I ended up 17th F/TR out of 60 odd, I did manage to hit that five-inch circle, the 'V' or 'X' as you'd call it, 23 times out of 85 attempts, 2nd equal in F/TR behind reigning European and World F/TR champion Russell Simmonds on 27. Now if only I can read the wind 5% better and turn the marginal threes into fours, and the marginal fours into fives ...... !!)

Laurie,
York, England

 

[RonAKA]

The other issue that I have not seen mentioned yet is bullet diameter. Seems to me that a large diameter bullet will increase the friction force compared to a smaller diameter bullet.