How much difference

[Pete Wass]

I am wondering how much difference, if any, extra priming compound makes in the ignition and velocity of a Rimfire .22 cartridge? Some time ago, I weighed a bunch of Black Box and took a few ( I think 6) , half of the heaviest and half of the lightest. I weighed the bullets, the powder and then the cases. I found that all the difference in weight was in the cases, all of which had differing levels of priming compound. So, does the extra or less amount of primer matter? Can't tell once one pulls the bullets; not easily anyway.

Pete

 

[Wilbur]

It would seem the easy way would be to assume the differences in weight were purely primer stuff....and then shoot them. The problem there is...that's what you do anyway....without any tinkering or any assumption.

 

[RegisG]

Interesting. But, I would shoot them, thoroughly clean them inside and out. Weigh again to see if the difference was primer or brass/

Regis

I am wondering how much difference, if any, extra priming compound makes in the ignition and velocity of a Rimfire .22 cartridge? Some time ago, I weighed a bunch of Black Box and took a few ( I think 6) , half of the heaviest and half of the lightest. I weighed the bullets, the powder and then the cases. I found that all the difference in weight was in the cases, all of which had differing levels of priming compound. So, does the extra or less amount of primer matter? Can't tell once one pulls the bullets; not easily anyway.

Pete

 

[Pete Wass]

The level of primer compound

Interesting. But, I would shoot them, thoroughly clean them inside and out. Weigh again to see if the difference was primer or brass/

Regis

is clearly visible. Assuming it has uniform weight, I don't see the point, me. There were some pictures of primed cases that had been milled in half awhile ago that were interesting. Cases using the red compound seem to be more uniform with regard to the level of compound. Perhaps this primer thing is a nn-issue but I thought it worth thinking about and discussing. Mebby it isn't.

Pete

 

[Jerry H]

Since a primed case without powder when fired with a no crimp bullet only, will push the bullet 10 inches down the barrel, the priming is likely a significant factor the variation of the pressure curve form shot to shot and therefore a possible cause of poor accuracy of a given lot. Most all lots exhibit poor uniformity in the area under the curve, uniform rise times, and uneven pressure drops as the bullet travels down the barrel which is critical for consistent bullet exit times. The uneven pressure drops are likely due to very small variations bore diameter. The easiest practice is to simply test different lots to see which shoots best. If one evaluates a barrel blank by slugging, some interesting results are likely to show up in 9 out of 10 blanks. As a .0001 can be easily felt with practice, the judgement criteria should be substantially smaller. Not an easy thing to do when measuring lead. A re-lap prior to cutting the chamber may prove out to be beneficial.

 

[tim]

As for huge priming varience, somebody kindly refer friend Wass to the 2011 Shooting Times article. The priming methodology complete with tolerances is comprehensively reviewed. The standard is plus/minus 1.0 millogram.
What some are probably misreading is the varience of color away from the rim, no doubt from the adding of water to activate the compound which is a computer controled pellet added, pressed, and then activated with a computer controled droplet of water.
I suspect that if it boils down to their computers or Pete's measurement........well you probably guess where this is headed.

 

[404tbang]

Not really, just provided a simple reference to a well documented article, simple read. Don't even need to be a shooter to comprehend, so, well....you know.
Any who, talk to Bill, get permission, read it for yourself.
On the other hand, it seems you have kind of a thing for Pete??? I mean, not that there's anything wrong with that.

Have not read that one, as far as I can recall. Did read something about the Eley Prime System a few years ago. If I recall, I posted it on RA. It was fairly detailed, and quite interesting. Probably had the same info. If I recall correctly, Geoff Kolbe had some interesting comments about priming compound after I posted the link. Seems he may have explained in even further detail about variations of priming compound vs. variations in powder.

Long story short, variations in priming compound cause greater variations in velocity than variations in powder. Priming compound is substantially more potent than powder.

Perhaps you've never noticed that you're usually on Pete like a Beagle on a rabbit. With the majority of things he posts. More so than on other folks, it seems. Y'all have gone back and forth enough to merit popcorn on a slow Saturday night.

 

[Wilbur]

Pete - was 6 bullets all you had of this lot? If you have more, a couple or three groups would give you the answer. Would be interesting as to how they shoot with that difference in priming compound.

 

[glp]

Taking the Eley info at face value

1 milligram primer variance works out to .015432 of a grain. I have no idea if that amount of primer mixture would make a significant variation in velocity. It seems quite small and not significant, but I don't know. And I don't know if Eley meets this high degree of uniformity at all times, with all ammo colors. Pete, I think the suggestion of firing the bulletless case/primer, then cleaning the case, then re-weighing it would be interesting. It would give you a fast answer as to where the weight variation is and a window into primer mix weight uniformity.

But for shooting at paper plate sized NRA targets, I think I'll leave that to you fly speck shooters. Nice winter up here so far, not much snow and temps are finally cold enough to freeze the lakes but not bitter cold. Just right for this time of year.