How critical is cleaning out the primer pocket?

[Viperdoc]

Again, thanks for the data. It should be the only thing that makes us change what we do, not old wives tails, rumors, or stories from guys with more gray hair than we have. I took some graduate level courses in statistics, and now it is all done by computer, so easy to calculate (but I worked all night most of the weekend, and was too fried to try). Basically, the questions are: is the data normally distributed, and is there a statistically significant difference between the groups.

The next experiment should be to see if the SD increases with multiple loadings, or, as the primer pocket gets dirtier, does the consistency decrease? You said you did not clean the pockets, but did you use the ultrasonic cleaning technique (clean and shiny), or were the cases simply resized and prepped as they came out of the gun? If the former, the US technique by itself does a fair amount of cleaning compared to uncleaned brass, or brass just run through a vibratory media.

I have been struggling to get max accuracy out of my 223 AR, including primer pocket uniforming, neck turning, chamfering, controlling neck tension, etc. However, it seems that the AR platform is so rough on brass that none of these things will do much good, and that largely bullet choice followed by powder choice and load are the only real factors.

However, the only way to make logical changes is through the analysis of data, and this is what you provided, so thanks.

 

[chevytruck_83]

I just like to get it out there that im not exactly hathcock at the moment. I'm doing my best to get rounds down range and soak up as much info from anyone willing to share. I'm wasnt trying to bash the rifle by any means, its great. I see some of them on here and i was trying be clear that thats not the level im at. Not yet.

 

[necchi]

Good for you Chevy, we where ALL beginners at one time,
,,some just seem to forget that

 

[archerross]

There is one very good and resonable reason why I didn't post the SD for these testing results. I don't have a clue on how to figure SD. That is a shame really I have been shooting almost all of my life, competiting for over 45 years in one disipline or another and I still don't know how to do this. So someone please hear my plee--- 6BRonwheels maybe --- as it is evident you know how--- but someone show me how to do this.....

Roland,
Here is how to calculate standard deviation (SD):

1) Calculate the mean or average value. From your "Clean primer Pockets: ES 13 FPS" data:
(2928+2931+2934+2928+2935+2930+2940+2941+2928+2930)/10 = 2932.5 fps

2) Subtract the mean from each shot and square that value (multiply it by itself):
(2928-2932.5) = (-4.5)2 = 20.25
The remaining squared differences are:
2.25
2.25
20.25
6.5
56.25
72.25
20.25
6.25

3) Add the squared differences and divide by the total number of shots minus 1:
(20.25+2.25+2.25+20.25+6.5+56.25+72.25+20.25+6.25)/(10-1) = 23.61

4) Take the square root of the result in #3 = 4.86 fps or approx. 5 fps.

PM or email me if you have questions about the calculation or what it means.

Ross

 

[chevytruck_83]

No reason to stress over it. All im getting is good info from knowledgable people trying to help. I'm pretty sure that comment was more aimed to my feeling like i need to be clear im no elite. On some forums and even on here perhaps I've asked some dumb questions to most other standards so i guess i've gotten some expected smart answers over the course for more info. So please nobody take any offense to anything and thanks again for the help. p.s. thats awesome you have had the privelage to learn along side such talented individuals. I'm jealous.

 

[necchi]

Sorry Roland, didn't mean to direct the comment too anyone, it was just general, you'll see this across the board with alot of guys and should be takin with a grain of salt. But sometimes new guys get jumped on pretty bad with what seems like common knowledge questions.
Again, I meant you no disrespect. (eating Crow here, :-[ )

For those looking to calculate various math sequences and calculations, I use this one for SD, it's easy and free;
http://easycalculation.com/statistics/standard-deviation.php

 

[archerross]

For all of you spreadsheet (Excel) users out there who want to calculate average and SD, all you need to do is enter your velocities in a column (example: data are in cells A1, A2, A3, A4, A5). Then select a cell location for your average and type =AVERAGE(A1:A5) and hit enter. For SD, select a different cell location and type =STDEV(A1:A5) and hit enter. Sorry to digress from the primer pocket question.

 

[Rustystud]

I'll ask how hard is it to breath when you have a chunk of steak stuck in your throat?

It does not take but one piece of fouling or tumbling media to stop up one primer hole and you have a mis fire.

The whole idea in loading and reloading ammunition is to create consistancy. All clean pockets and primer holes mean the primer flash is un obstructed. Primers all seated to the bottom of the primer pocket receive the same firing pin strike.

Why add an unessary varriable.
enough said.
Nat Lambeth

 

[Viperdoc]

I've been shooting between 200-300 shots a week. This is a lot of brass to process, and I uniform each pocket every firing.

The data suggest it might not matter, and if so, why do it?

Will try the same experiment shortly.