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Old February 2, 2013, 09:38 AM   #1
vito
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What's the difference between "match" primers and regular primers?

Just getting started in reloading and could not find small pistol primers anywhere. Then in a local gunshop I found they had Federal small pistol match primers. Although they were expensive, I bought the two boxes of 1,000 each anyway, just so that I had something for when I actually get to start reloading. I was just wondering what if any difference there is between match and non-match and does this affect the powder load that I should be using?
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Old February 2, 2013, 09:53 AM   #2
Bart B.
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Primers labeled "match" are done so for two reasons.

One is the priming mixture is made by the best folks at the plant who mix the putty like slurry compound the most uniform and tests with those primers indicate they have the most uniform fire and heat ouitput.

The other is marketing hype that may well not end up being as good in actual performance as standard primers.

There are primers out there that are not labeled "match" but outperform those that are labeled as such.
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Old February 2, 2013, 10:39 AM   #3
tank1949
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Bart and Vito:

I have been trying to issolate inconsistancy concerning a bull barreled AR 223. Groups were shifting and formula for tighter groups seemed to change per each range visit. I replace older leuplod with NF to rule out scope being problem. The NF came off my bolt gun and I KNOW IT IS OK. So far I have determined that fouling the barrel seems to initiate a better baseline for comparing the following powder workups. While I was testing loads, I made sure to compare CCI BR primers/powder formula to std CCI SR using same powder/bullet. I discovered that BR primers used over the array of different powder weights, seemed to produce slightly larger groups at 100yds, but both std and BR primer groups stayed in one spot. This results was a bit confusing to me too! I was graduating in 1/2 grain increments from digitial RCBS scale that I had also carefully calibrated.The results, so far, indicates that BR primers used with my bull barrel AR don't preform as well as STD primers. I am still scratching my head over this.

I keep all of my primers in an air tight 50 cal ammo box. So mosture shouldn't be a problem. In can is the decatant stuff. I also have primers dated and use them by older dated ones first.
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Old February 2, 2013, 10:52 AM   #4
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In the mid-2012 issue of Rifle's Varmint Rifles and Cartridges, there was a very interesting article on primers. The rifle in question was a 223, and with most primers available in the US (not including Wolf and Tula), they did accuracy and velocity consistency tests. I was relieved to see that the CCI BR4 primers that I use tested out extremely well, but others did also. Well worth the read, if you can find it on the internet (I have not tried, since I have the magazine).
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Old February 2, 2013, 01:55 PM   #5
Bart B.
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tank1949, how many shots are you putting in each test group?

If you shoot several groups with the same load and they're not all the same size within a 10% spread, you're not putting enough bullets into each one for them to be at least 90% valid.
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Old February 2, 2013, 09:45 PM   #6
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Quote:
Primers labeled "match" are done so for two reasons.

One is the priming mixture is made by the best folks at the plant who mix the putty like slurry compound the most uniform and tests with those primers indicate they have the most uniform fire and heat ouitput.
I met a gentleman at the range whose job is in ammunition gaging. He verified that this is true and that the workers who make the most consistent primer mix get cash awards. He also stated that the instrumented equipment used today measures an ungodly amount of parameters. I remember pressure wave, material ejected, and I am certain there are lots more.

Quote:
The other is marketing hype that may well not end up being as good in actual performance as standard primers.

There are primers out there that are not labeled "match" but outperform those that are labeled as such.
Very true, and I am sorry I only bought 15,000 of those of those "non-match" fantastic primers as I only recently found out how good they were and did not anticipate the current primer panic.
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Old February 3, 2013, 01:41 PM   #7
tank1949
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Bart and others, I usually shoot a 10 shot spread between 1/2 grain powder increments. I take time using rest. But, what is more disturbing is the whole center of group may shift between range visits. And, our range tempature has only differed by 15 pr so degrees. I try my very best when wouking up loads wit this rifle to make sure wind is in face or back. So far I have narrowed it to maybe older leupold. I will post.


Thx
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Old February 3, 2013, 05:06 PM   #8
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Tank, I had a scope go bad on me. New scope and new rifle, so I thought the problem was the rifle or the loads I was testing. I'd get a few good groups and then some bad ones and as you said, the center of the group would sorta relocate. And one day's good group with a powder and bullet would not be good the next day. I really really burned up some powder and bullets before I read an article about a guy and a bad scope. I tried a used and trusted scope and it became obvious that the new scope was a bad one. The rifle shoots great now, and loves the 65 gr Sierra GK over AA2230 powder (near max load) and CCI BR4 primers and just about anybody's brass cases.
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Old February 3, 2013, 06:12 PM   #9
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603Country,

If you see Tank's post #3, you will see he already changed scopes out.


Tank1949,

Switching between primers in .223 causes different pressures and muzzle velocities. Charles Petty did a comparison in a 2006 Handloader issue with one fixed powder charge and bullet and got up to almost 5% velocity difference from different primers under the same charge, indicating the warmest primer he used was making higher pressure. Obviously the barrel time is shorter when the pressure and velocity are higher. This can move a round off a sweet spot, so you may need to adjust the powder charge for each primer to find the best accuracy load with it.

Changing the powder charge half a grain in that small case can cause you to sail right past the middle of a sweet spot range. That's roughly a 2% change, which is fine for searching for pressure signs, but is too coarse for finding the ends of a sweet spot range with some powders. 0.7% to 1.0% is better for that, so try 0.2 or 0.3 grain steps. Take a look at Dan Newberry's round robin procedure as one way to help identify the middle of an accuracy sweet spot with those small increments.

You didn't say what powder you are using, what bullet you are using, or what your barrel twist rate is. These affect best choices of bullet and powder. It's perfectly possible to have a marginally stable bullet or an excessively stabilized bullet that is happy under one set of atmospheric conditions, but not another.

To have each group the same size within 10% of one another with 95% confidence (meaning it will be true for 19 groups out of 20) takes about 25 shots per group to achieve. With 10 shot groups, 19 out of 20 will vary about 22% randomly, so if you have a difference that small, it doesn't mean your load has lost its touch. If the difference is much larger, and consistently so, then something else has changed.

Seating your primers properly can have a big influence on ignition consistency. That not only affects muzzle velocity, but it can introduce ignition delays that are too small for the shooter to notice, but that are as long as the rifle lock time in some instances. That allows small mechanical firing disturbances to get to the muzzle ahead of the bullet and open groups up. To avoid this, you want to set the bridge on primers properly. This generally means seating fairly hard. You want the primer to go in at least two additional thousandths (small rifle; three thousandths for large rifle) and as much as six more thousandths after the anvil feet find the bottom of the primer pocket.

Forster solved the above fairly neatly on the Co-ax press by creating a priming mechanism that forces the primer 0.005" below flush with the case head. You can also set up the Sinclair hand priming tool to do this. The K&M Primer Gage tool will let you measure exactly how far you seat below anvil contact on an individual case and primer basis, but it is slow going and intended for brenchrest shooters with lots of time to dote on every detail of every round. Though not practical for AR shooting volume, it can help diagnose an ammo issue by process of elimination.

With any priming tool, you can see if it has pushed deeply enough by taking some 20 lb bond printer paper and cutting a thin strip about a quarter to a third the width of the primer. Then bridge the primer pocket with the flat blade of a screwdriver and see that the strip of paper slips between it and the primer. If it gets trapped, you need to push in a little harder.

I can think of other factors, but further diagnosis will get you into more tools. If your chamber is sensitive to bullet tilt, as some are, you may need a runout gage to check how straight the ammo is. If your chamber is sensitive to bullet seating depth, you need to get that dialed in. If you have a velocity consistency issue do to other factors, you'll need a chronograph for diagnosis. Of particular interest would be whether or not the average velocity was different on days when a load shot well or didn't shoot well. If not, you need to figure out why not?

After all that's sorted out, you'll be able to tell if match primers help or hurt your cause.
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