Component tolerances

[std7mag]

What about some of the older, dare i say obsolete cartridges with different bullet weights and newer powders?

I just built a 284 Win and would like to see what the new IMR powders do.

[hdwhit]

std7mag wrote:
10+gr bullet weight has no effect...

I couldn't disagree more.

In the 9mm/38/357 caliber the OP was loading, 10 grains puts him into an entirely different category in the manuals with 148 grain bullets having different loads from 158 grain.

[std7mag]

Ummm, HD...

I did NOT write that. You quoted someone else and tagged my name to it. Please correct..

[hdwhit]

std7mag wrote:
What about some of the older, dare i say obsolete cartridges with different bullet weights and newer powders?

If there is no published data for them, then they would treated as wildcat cartridges. Get out your chronograph, your stain gauges, your epoxy and your pressure device.

But orphan or obsolete cartridges are not what the OP is posting about. He's posting about bullets that are varying by as much as 10 grains - a variance that puts him into the category of different loadings per the manual he is following.

[hdwhit]

std7mag wrote:
I did NOT write that. You quoted someone else and tagged my name to it. Please correct..

Post #24, third line.

If what you were meaning was that a 1/10 grain difference was immaterial in bullets weighing more than 10 grains, we would have no dispute, but what I read was you saying that a 10 grain fluctuation was not material.

The quote is yours. If I misread or misinterpreted it, I apologize.

[hdwhit]

hdwhit wrote:
He's posting about bullets that are varying by as much as 10 grains...

I see now that the OP is saying that the difference was not 10 grains, but 1/10 of a grain.

1/10 grain variance between bullets, particularly in the 120 grain class is less than 0.1% and indicates very good consistent quality control on the part of the maker. I often encounter variations on bullets in the 50-60 grain class of as much as 0.3 grain and still consider them to be well made.

[Gary Wells]

1/10 of a grain variation would most likely be immaterial, but a 10.0 grain variation would most likely be the difference between winning & losing. Quite a few of the bullseye shooters on the 50 yd line for matches generally weigh out their bullets & categorize them in similar groups.

[Don Fischer]

Originally Posted by hdwhit

I've been handloading for 40+ years and I don't depart the consensus of the manuals at all - except in the case of wildcat cartridges which have no load data (or for which the published load data was subsequently disavowed by the published).

When Vernon Speer still owned the company, they put out a manual with wildcatt loads in it. I had it and lost it somewhere along the way. I wrote Speer after Vernon was gone and asked about it. I was told it's no longer available! Crushed me. Was a really interesting manual. I think it was originally printed in 1954, something like that. I think it was called, Speer Wildcatt manual.

[kmw1954]

Actually the total variance from low to high was just over 1.2 grains with this 100 grain bullet.

Of 300 weighed bullets one was 99.5 grain and the heaviest was 100.7 grain

Actual numbers;
099.9 = 39
100.0 = 60
100.1 = 61
100.2 = 50
100.3 = 51
100.4 = 25

Then there were about 40 total that were lighter or heavier than this main group.

One thought I had was the few that were way on the far edge like the 99.5gr or the 100.7grain even though they are very few could they help explain some of the odd fliers that are seen on targets? I mean to me those were so few and far from everything thing else they would be outliers.

Another question as to variance. After loading and marking your loads how would you mark a powder charge that has a .1 grain variance? For instance this; the target weight is 4.0gr of whatever powder but you know that the powder charge varies from 3.9 to 4.05 because of the powder measure drop. Would you still list it as 4.0gr?

[Unclenick]

The old rule of thumb used by folks casting .38 and .45 bullets for match shooting was to reject bullets with more than about 3 grains spread (this was for bull's eye matches, so 50 yard slow fire targets with 3.36" 10 ring and 1.695" X-ring). But here's the kicker: that wasn't for accuracy, that was because a bigger spread than 3% suggested there was something wrong with the casting job you did on the bullet. Too heavy meant the mold hadn't been fully closed so the bullet wasn't round and probably wouldn't go through a sizing die or a bore with good mass symmetry at the end, so it will pick up some tangential drift when it exits the muzzle due to that imbalance. If it was too light, a dross inclusion might be in there, again unbalancing the bullet.

The bullet weight itself, if symmetry of its distribution around the bullet is good, has surprisingly small effect. When the shape of the bullets is identical, the BC will change in proportion to the weight, so that's the biggest effect. I used QuickLOAD to load a 200 grain .452" lead wadcutter over 3.8 grains of Bullseye (an old slow load I used in my Goldcup for a time long ago), but changed the bullet weight between 190 and 210 grains (±10%) along with the BC. I used QuickLOAD because I wanted the weight change to change velocity from a 5" tube, just to dot the i's and cross the t's, but that change was small. It went from 669 fps with the heavy bullet to 681 fps with the light one. Not unexpected. Lighter bullets go faster if the pressures profiles are identical, but when you lighten the bullet, expansion happens faster so pressure goes down a little from that, tending to compensate. The other change was G1 ballistic coefficient went from 0.0665 to 0.0735 between light and heavy, respectively. I used the QuickTARGET exterior ballistic program that comes with QuickLOAD to look at the difference in total drop of the bullet in flight to 50 yards (the difference you will see on the target if the sights have the same setting). I did this by copying the QuickTARGET outputs to Excel to get the maximum number of decimal places and to eliminate QuickTARGET's tendency to have single digit rounding errors in the standard output. I found that the difference in total drop was about a third of an inch. So, ballistically, at pistol ranges, that 10% spread in bullet weight made little difference.

Incidentally, Brian Litz notes that he's measured BC's varying 3% even among match bullets from the same box. This is likely due to bullets off different tooling being combined and therefore having slight mismatches in ogive contour. So the next time you choose a bullet because of a BC difference that small, keep in mind you aren't really getting much if you pay more for it just for that number. It is much more important to see which one your gun groups best with.

Load manuals are records of what happens when a particular combination of components are fired in a particular gun. That should serve as an approximation for other combinations, and usually does so within 10%, meaning, the starting load for one combination is rarely unsafe for others. Note that rarely doesn't mean "never". Manual publishers can have typo's, too. That said, I do not recommend sticking to just the bullet manufacturer's data. If he used different cases and primers and if he had a slow lot of powder for his development work, it could still be off in another combination. I like the rule to always check three sources. This gives you the lowest and safest starting load and perhaps more important, it lets you see that one of the sources doesn't stand out as being significantly higher than the others and therefore to be taken with a grain of salt.

If you can stand to do it, I recommend reading through either the rifle or pistol SAAMI standard to try to understand the statistical underpinnings of how they test pressures and calibrate instruments for measuring them. I think you will be surprised at how much variation they actually have to allow for to be sure of producing universally compatible ammunition in a chambering. Producing ammunition has a lot of variables even for the professionals.

[Don P]

Well then if staying within published data should I then use the 95gr load data or the 100gr load data? After all the bullet is not 100gr. Same for those that are 105gr or 106gr.?

Is this over thinking it? or is it following the manual?

That's why I posted again#7

[kmw1954]

Which is why I clarified again in post #34. Decimal points do make a difference.

Still curious as to why it is so important to know the brand especially when the claim has been found to be untrue.

[Don P]

Still curious as to why it is so important to know the brand especially when the claim has been found to be untrue

Curiosity, and if it were true its a product I would not want to buy for the obvious reason

[BBarn]

Three hundred 100 grain bullets that weighed 100.1 gr. +/- 0.6 grain (+/- 0.6%). Nearly 75% of them weighed between 100.0 and 100.3 grains. Not match quality perhaps, but not bad.

[F. Guffey]

tolerances

What brand? Next time purchase 1,000 bullets in a box and then separate by weight. Load the 95 grain bullets like they were 95 grain bullets, load the 100 grain bullets like they were 100 grain bullets etc. etc. If you are not happy with the weight of the bullets and the manufacturer did not include the warning about the 100 grain +/-5 grains ask for your money back or separate the bullets by weight.

F. Guffey

[Unclenick]

The OP has requested I close this thread, as he is concerned his initial decimal place error has caused failure to follow as many are not reading the thread far enough to find his correction, which proved well within acceptable limits.