Reloading Issue: Why do measurements vary?

[orkan]

If you want exact CBTO, here is what you can do. Back your seating die off by .003". Seat the bullet, measure CBTO, adjust your die however much you need, reseat and remeasure. Then back it back off and repeat. Much easier with a micrometer seater, but can be done with a standard seater too. I usually strive for CBTO within .0005" of target. Meaning no more than .001" variation.

Virgin brass seems to show far more variation, even with an expanding mandrel process. Properly sized fired brass is usually much better.

I'll disagree with this slightly. While it may be that some can have success with this which will show up on target, its very likely to actually cause worse results.

The reason is the velocity of the seating op has a bearing on the bullets ability to overcome the friction differential between the bullet and neck. Once it comes to a stop, it will take considerably more force to get it moving again. This will result in non-uniform ogive deformation in most instances with standard bullets. This will be difficult to "measure" as comparators do not genuinely generally hit exactly where the seating stem does, and its the alteration of the shape that has the lasting effect, rather than only the distance to datum. It will also result in non-uniform surface interaction at the bullet/neck interface.

This same thing is true of seating primers, but the deformation is significantly more severe on primers and has a much larger impact on target.

However, if you change your recommendation from 3 thousandths, to say, 30 thousandths. Its much more likely to yield positive results. There is enough movement to break the static lock, and get the bullet to achieve some momentum again. If the first seating op was super uniform, then the second one can be more uniform as well if it's moving some reasonable distance.

Though it is noteworthy that doing something twice, will almost universally introduce more variance than doing something once. The only time this would possibly be minimized is if bullet seating is done with automation, such as an AMP press.

It's not just the seating depth uniformity that is important here, but the seating force uniformity as well as component deformation uniformity.


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[31pointer]

There are too many variables to the question. Are you annealing the brass? Are you cleaning before sizing? Are you measuring to the tip of the bullet, or ogive? Wet tumbling or dry?
Tumbling or vibratory cleaners will cause the necks of the brass to collide with each other. If you've already sized the brass, the dimensions amongst all of them, have changed. Now it will require more or less pressure to seat the bullet. Possibly deformming the bullet or possibly the brass.

 

[RidgeTop]

You can feel the extra pressure when you seat the bullets after wet tumbling. It work hardens the necks. You probably don't shoot in competitions either.

I do O.K.

 

[31pointer]

My son gave me a Frankford Arsenal Universal Bullet Seater. So far I am extremely impressed with it. I started running all the brass through the neck sizer and cleaning the inside of the necks with rubbing alcohol. Loading for 3 different fire arms, there wasn't more than .002" difference measuring each one.

 

[hawk-i]

The dimensional consistence of my loaded ammo went up greatly when I started annealing with my AMP every reload.

 

[skipglo]

Always had the same thoughts...but gave up looking for the answer...and shoot what I load! As long as I get a decent result...no point in questioning the Universe! Because the inconsistencies persist to be there!

 

[Koda_]

your comment was pertaining to Hammer bullets......
if they are more consistent in dimensions..... would,nt you see them used for that quality.... in competitions...???

Consistent bullet dimensions are only one element... Hunting bullets have a totally different design intent than competition bullets which typically results in lower ballistic coefficients than competition bullets.

 

[Lenny Foffa]

Excellent Question Judge, I have the same issue all the time. My cases are the same length, within a few Thousands. My cases are the same weight within 1/2 Grn or less of each other. My Bullets are within 1/10th of a grain of each other, and from one finished case to the next, there is always a few thousands difference. I use a Summit in line press for seating only, with Forester Micrometer seating dies, and there still always some difference. The Biggest difference for me, is the COAL, which can vary as much as 7/1000Th TO 10/1000 th. The OGIVE measurement can be 3/1000 to 4/1000 difference form case to case. What I have noticed is that the tips of the Nosler Ballistic tip bullets are almost never perfect. and therefore, the COAL will be off by that amount. A slightly crushed tip will result in a shorter COAL. My Hornady tool for measuring the OGIVE has Aluminum Bushings , not steel, so I can see a difference in the OGIVE Length from base of Bullet to Ogive. My Bench rest friends all use custom made bullets and Measure each bullet from base of Bullet to OGIVE of Bullet. Its done with Gauges that come from sources , other than Sinclair, I am not even aware of. I have come to think I am simply working within the limits of my Modest Middle of the Road Reloading Equpment, using Off the shelf Bullets. My bench rest friends have Equpment and Tools that exhibit a much higher level of quality and precision, than I do. As Hunting rifles are concerned, 3/1000 or 4/1000 difference in OGIVE does not mean I will not shoot very good groups at 100 to 300 yards. I continue to shoot excellent groups, with my Weatherby Hunting rifles, which allows me to hunt with confidence. As Bench Rest matches are concerned, I am simply not in their category. I have no .1000 5 shot groups to display and. brag about. I do have several .2500 which is respectable, but not competitive. I just cannot make ammo as perfect as they do. I think when that becomes important to me, I will need to invest in High end, or even Custom Equpment to get even more uniform and precise Reloads and reduce the differences from Finished Load to Finished Load.

 

[Rocketeer77]

Reloading any cartridge, when you finish seating the bullet and measure successive fully-loaded cartridges, the measurements should be identical. That is, the distance between the shell holder and the bullet seating die are a constant. So regardless of variations in cartridge case length and carrying bullet lengths, the overall length, Cartridge Base to Orgive should be constant. This assumes no "stretch" or play in the loading machinery. I notice this in all different calibers. What am I missing"

You should be within +/- .004" even with dodgy gear. I push the projectile in about 0.100" then lift off slightly and slowly and firmly seat the projectile gives very consistent COL

 

[BillLarson]

I must have misunderstood when you said "they will vary in length therefore vary in weight".

Hammers vary in neither. And yet they are not used much (if at all?) in match scenarios.

But, look at the ELR shoots like KOT2M. They all use lathe turned tipped monos.

From what you say..... I,m surprised more people aren't using them in LR matches.....

 

[Doug Herold]

Thanks all of you who contributed to the confusion. Yes, I recognize all the variations talked about. BUT, the distance between the shell holder and the seating die SHOULD be consistent. If that distance is consistent then cartridge base to bullet orgive should be consistent. UNLESS something happens to shrink or expand that distance AFTER the bullet has been seated. Powder de-compressing, brass somehow pinching bullet outward...might have something to do with it. That exhausts my imagination on the subject.

The bullet ogive will vary by 0.001 M/L during the manufacturing process on those "cull" pieces of ammunition.

 

[orkan]

From what you say..... I,m surprised more people aren't using them in LR matches.....

There are other considerations.

ELR is typically a .375cal or bigger affair. Those larger bullets are difficult to do correctly in a standard jacketed configuration. The solids perform better, and are certainly easier to make, especially with the high BC designs.

The cost of solids is typically much higher than standard projectiles, which keeps the "good enough" crowd from adopting them. That crowd parrots what they read and see, and so nothing will ever be popular until a couple of personalities most of them parrot tell them they should use solids.

Then, with the exception of a rare few, most solids are quite a lot more demanding on the handloader. Some can be very finicky, and the same aforementioned crowd doesn't shoot enough to get that worked out. Where as standard bullets tend to be forgiving enough where they can just dump "what the internet says" in the case and it will shoot "good enough."

My recent experiences with Hammer bullets have demonstrated there are certainly some designs that lend themselves to being fairly easy for most people to get along with. Cutting edge 352gr 375cal bullets certainly were easy to run back when I was using the big guns.


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[hunter0528]

Assuming no powder compression, base to ogive length and bullet oal differences by the thousands of an inch, etc. will cause slight variations. Ultimately accuracy with satisfactory velocity is what matters. The rest is a hair pulling exercise. I know this because I've got few left and getting worse everyday. Either that or my hat is pinching the blood off to my hairs.

Another possibility is the elasticity of the brass. variations in wall thickness along the length of the brass may contribute to this also.

 

[BillLarson]

There are other considerations.

ELR is typically a .375cal or bigger affair. Those larger bullets are difficult to do correctly in a standard jacketed configuration. The solids perform better, and are certainly easier to make, especially with the high BC designs.

The cost of solids is typically much higher than standard projectiles, which keeps the "good enough" crowd from adopting them. That crowd parrots what they read and see, and so nothing will ever be popular until a couple of personalities most of them parrot tell them they should use solids.

Then, with the exception of a rare few, most solids are quite a lot more demanding on the handloader. Some can be very finicky, and the same aforementioned crowd doesn't shoot enough to get that worked out. Where as standard bullets tend to be forgiving enough where they can just dump "what the internet says" in the case and it will shoot "good enough."

My recent experiences with Hammer bullets have demonstrated there are certainly some designs that lend themselves to being fairly easy for most people to get along with. Cutting edge 352gr 375cal bullets certainly were easy to run back when I was using the big

there are lots of 600,800,900,1000,1200 yd.matches run regularly throughout the country.
All who pay money to compete use the best materials to do it with....

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