OAL length discovery and how you all deal with it

[BoydAllen]

I have played with a friend's Forster press quite a bit and although I like some of the features there are a couple of things that I did not care for. One was that the height of the die relative to the part of the press that pushes and pulls the case, varies a little depending on how tight the lock ring is. This can make setting shoulder bump to .001 a little tedious. The other thing that I quickly learned not to use that press for, was using an expander die to expand .220 Russian cases to 6mm....ugly runout compared to my Harrell Combo press(the best...very tight die fit, and excellent alignment). My Rockchucker was somewhere in the middle. For loading at home I have really come to like my Rockchucker since I changed it over to Lock-N-Load.

 

[6BRinNZ]

Boyd, this is exactly what the Bob Green BGC does. It uses the same datums as a Kevin Cram meplat trimmer + an indicator mounted Wilson seater plug.
And with it you can go through a bunch of bullets quickly.
If you go from CRs to SMKs,,,, night & day difference.

But his SEATING variance is caused by something other than ogive radius. I'm pretty sure of this because the same ogive that causes his measuring datum to move down the nose, will cause his seater plug to push the bullet further into a neck(countering).
That's not to say ogive variance isn't a contributor to his seating variance, just that it isn't the root cause.
My prediction is high & varying seating forces combined with a threaded die & press. His seater plug might also ride too high on noses(causing wedging).

I'm with MikeCR...reference to my earlier post in this thread

Quote from: Tuckerp229 on 10:50 PM, 09/02/12

Low seating forces intrigues me I thought one needed 2-3 th of undersize pressure for good neck tension. Do you multi load or always insert one cartridge into your rifle at a time?

IMO - high neck tension is a large contributor to seating variances, along with neck thickness variations and poor seating technique. By using .001 - .0015" neck tension and controlling the other two I expect to be +- .001" seating depth before sorting bullets (A-maxes). I measure every single round I fire. Bullet sorting IMO brings into alignment the last .001 - .002 of variation.

I have also found annealing to be conducive to consistent seating depths, however IMO the effectiveness of this is dependant on chamber specs, so YMMV.

To support one of my statements have a read of the thread listed below.

http://forum.accurateshooter.com/index.php?topic=3783184.0

 

[300 RUM]

I use the Redding F/L sizer with neck bushing and sizer ball. The sizer ball is .306 in dia and the neck bushing is well I have two different one for Lapua and W-W brass, but I get a perfect .002" neck tension and near perfect seating depth every time. I had the same problem you have had and it was all due to neck tension.

Below is a photo of some Sierra 175's check out many different length's measuring the ogive to base they have.. .028" from end to end!

 

[MVW]

I ran across a friend that has a comparator made by Bob Green and he let me borrow it to sort some bullets. It measures the distance between the seater and the ogive. What I found was that most of the 500 bullets clumped into three groups with a handful of misc lengths. This doesn't directly solve the variable Ogive diameter issue, but my suspicion is that this sorts bullets by the mold that they came from and hence leaves you will several hunderd bullets with similar dimensions.

For what it is worth, I have a micrometer seater, but when I sort bullets this way the OAL measured with a separate tool on my calipers is always within .001 without making any adjustments to the micrometer. Given consistent bullets, one can then make minor tweaks to the OAL from there.

Mike

 

[BoydAllen]

With longer bullets, it may be that having more neck tension is not as critical as it can be with shorter bullets, because of their greater inertia. Also, longer bullets may have more shank in the case neck, and develop greater bullet pull by more frictional area. Another issue is neck thickness. Thicker necks have more pull at a given difference of loaded and sized neck diameter. For my 6PPCs, with necks that are between .0077 and .0086, I like around .003 neck tension with 133, because it seems to produce better results at the target. If I were looking at another situation I would test to determine what worked best. As always, accuracy trumps all other considerations.

 

[mikecr]

Internal ballistics with a 6PPC completely fails to compare with larger capacity cartridges.
If you were to crank back a 6PPC load, and use heavy for cal boat tail bullets, to force an apples-apples comparison with something like a 7WSM, the 6PPC wouldn't shoot like your used to.

Larger cartridges w/heavier bullets(unlike small underbore cartridges/light bullets), can't run extreme pressure peaks to work around all beneath it.
They run more of slow powder, with far lower/flatter pressure peaks. They can't handle extreme pressures given their chamber area, and faster powders only leave bad load density. They produce higher muzzle pressures against boat tail bases(uglier bullet release) even with longer barrels(no standard ~22" here). They recoil and torque a helluvalot more.
So they do not benefit from jamming, fast powders, short barrels, and high neck tension, like a 6PPC or 30BR. Nor will they EVER shoot like a 6PPC or 30BR.

Best seating with something like a 7WSM(just using this for example) could be anywhere it ends up being. It could shoot best with any one of a dozen powders and several primers. And neck tension consistency just doesn't buy as much with it. Hell, the bullet are ~4" from the neck at pressure peak.

Accuracy from a 6PPC won't 'trump' truths across a broader spectrum.
It's just one cartridge with one purpose.

 

[Bart B.]

I've got sub 1/2 MOA accuracy through 600 yards and sub 5/8ths MOA accuracy at 1000 yards from several 30 caliber match barrels in .308 Win. and 30 caliber magnums with bullets soft-seated a bit long so they set back a few thousandths in the leade when chambered. I've never had any concerns about bullet's dimensions from one point on them to another. Even with the non-perfect and inconsistant bullet seating (and their new cases) dimensions in commercial match ammo, it would shoot sub 2/3 MOA at 600 yards in semiauto M1 and M14 match grade service rifles with all their inconsistancies at play.

If ones rifle doesn't shoot very accurate as they hold it with ammo that's reasonably uniform, reducing all the variables one can find or dream up to zero on their reloaded rounds will never show up on target. And one needs to shoot at least 30 shots per test group and determine the mean radius of all shots to group center to have 95% confidence that's what all the ammo will do in that rifle by that shooter. 5-shot groups so measured only give a 60% confidence level.

Sierra Bullets' best 30 caliber match bullets from .308 Win. and .300 Win. Mag. test cases in rail guns shoot under 1/4 MOA at 200 yards. That's the same accuracy as what the PPC cartridges get at 200 yards. I've seen test targets at their California plant with 30 caliber match bullets with 10-shot groups at 100 yards in the ones; group after group after group. Cases much bigger than the PPC ones can be pin drivers (tacks are much bigger than pins).

 

[mikecr]

Did Sierra shoot any 6PPCs from railguns at 200?
Do you have any 308Win/300WinMags that can shoot with 6PPCs at 200?

 

[BoydAllen]

Mike,
When we were putting in full days at the range, tuning up my friends well built 7 WSM and .338 Lapua, shooting 175 SMKs and H1000, in the 7, and .250 gr. iforgets, and Rtumbo in the .338, we ran pressure tests, with bullets into the rifling, (not at full jam) just to find out where the bolt would get tight, and I believe we found accuracy a little farther back on the pressure, and in one case with the bullet jumping (if I remember because of magazine length issues). The sweet spots were in area of 2,950 -3,000 fps. and getting the best results off of the bench proved to be quite an undertaking because of the recoil and torque. In both cases we were able to come up with three shot groups (100 yd.) that touched (that few because of barrel heat issues) but is was far from easy. MY friend grew to like my PAST magnum recoil shield, and we both learned quite a bit about how to rest and hold these types of hunting rifles. I did the loading. He did the shooting. The one "tirck" thing that came out of this was getting an annealing machine to make the shoulder bump come out more consistent on both calibers. We were able to do that, and still have good neck tension. IMO throwing around neck tension numbers without specifying caliber or the amount of shank in necks can lead to misunderstanding. For long thick necks and long bullets, seated well into them, I would think that .0015 would be enough, although this experience was not with coated bullets. Different games have different rules. BTW he did all of his African non dangerous shooting with the 7. all one shot kills. He can shoot.

 

[DennisH]

..the more I think about it...hell maybe I ought to just seat 'em to my target length and be done with it all!

Good point above!

I have read all the post. I have found all of them interesting and informative.

What I don't understand is how some people just pull the bullets out of the box, load them up, and dayum near shoot a perfect score. No brass prep, annealing or anything. They will shoot a 2 1/2 group at 600yds. There is others on this site to verify this.

But I do know shooters who wash the bullets straight out of the box and spend 3 days getting them loaded.

Unfortunetly most working people don't have time to do the above, which is the area I fall into. Plus the cost of the equipment might not be in the budget for some.

JMO, I will continue to follow this thread. It's interesting.

 

[Bart B.]

Did Sierra shoot any 6PPCs from railguns at 200?

I think so, but you should contact them and find out if they do these days. They've tested a lot of 22 caliber bullets with .222 Rem. cases.

Do you have any 308Win/300WinMags that can shoot with 6PPCs at 200?

Probably, but I don't have a machine rest to clamp the rifles in so they shoot free recoil. Some of the 30 caliber match bullets I've got tested in the ones at that range when fired in Sierra's rail guns from both .308 Win. (168's and 180's) and .300 Win. Mag. cases (190's and 200's). Sierra packaged these separately in plain brown boxes of 1000 each and were sold only at high power matches by two folks that bought them in a special order process. These bullets shot about 40% more accurate than what Sierra polished shiny bright and put 100 each in green boxes for retail sales. Good enough to shoot under 1/4 MOA at 200 which is what the PPC's do. And just like the PPC cases, a few of those groups were well under 1/10th MOA.

 

[Bart B.]

What I don't understand is how some people just pull the bullets out of the box, load them up, and dayum near shoot a perfect score. No brass prep, annealing or anything. They will shoot a 2 1/2 group at 600yds. There is others on this site to verify this.

I'm convinced that some folks focus on using the smallest test group they get with a given load or process or tool. They often ignore the size of the biggest group. I've learned over the years that many benchresters seldom remember what the largest group they get is nor is it published outside of the scoreboard at their competitions. In asking some of the record holders what their largest groups were, they don't remember; they only keep track of the smallest ones. It's my opinion that the load that produces the lowest mean radius for a 30+ shot group is the most accurate. You gotta include all those widest ones to make the result meaningful.

If one looks at the benchrest records for many-group aggregates, they'll see they're much bigger than the single, few-shot ones. And the largest group fired in an aggregate is typically 30 to 60 percent bigger than the average group size that's used for comparison with others. At the longer ranges, the best of them for the most groups holding the records have their largest single group in the 6/10ths to almost 1 MOA range. Few, if any, aggregate record holding groups are fired by the same person holding the few-shot single group records. Go figure.

'Twas proved in the early 1970's that if good match bullets could be checked for balance spinning them at 30,000 rpm and shooting only the perfect ones, full length sized unprepped fired cases in SAAMI spec chambers, they would shoot .7 to 1.5 inch 10-shot groups at 600 yards. . . .from a Hart barreled classic pre-'64 Win. 70 action conventionally epoxy bedded in a wood stock. More or less proves that if you only do the important stuff reloading ammo and building rifles, that'll produce excellent accuracy with good bullets. The more detail one pursures, the harder it is to see the improvements they make.