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Flat primers, can I avoid it?

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15 April 2004, 12:14
EXPRESS
Flat primers, can I avoid it?
I am getting flattened primers in my .308 starting at reletaively light loads.
42.2gn VV N140 is clear, 42.5gn and I get flattened primers.
The Vihta Vuori manual gives 43.2 as max which is coincedently the most accurate load with a mean MV of 2686fps.

Could I try some other powders/primers and still get the same velocity with less pressure?
15 April 2004, 13:44
Curly
Different primers might do the trick for you. I had slightly flattened primers in my .300WM when I was trying RL22 and CCI 250 primers. Then I tried Winchester standard rifle (WLR) primers and I had better velocity spread, better groups, and no flattening of the primers. So, you just might want to try a different combination.
15 April 2004, 14:02
DigitalDan
This is a common puzzle in the reloading world and this my take on it. You may need to change primer brand or powder. The range of charge weight between your "not flat" and "flat" is very small, and would not make an large difference in pressure or velocity. What are you calling "flat" anyway? Most primers will flatten noticably at very low load density and at very high as well but it does not necessarily mean high pressure. Some primers are notoriously soft as well but "flattening" says little about pressure. Flowing is another story entirely, are the sides of your primers still parallel after you decap them?


In your case I don't read your load density as being particulary high so maybe a slower powder would be in order. Hornady's data suggests this as they do not indicate VV140 for bullet weights above 155 grains. Their Max load recommendation at that level is 45.8 gr BTW.

Another thought is this: If it ain't broke at 42.2 grains, why fix it?
15 April 2004, 14:10
bartsche
Flattened primers unto themselves don't necessarily indicate that your pressure is too high. IT MIGHT BE! Are you having any other pressure indications such as hard bolt handle lift , loose primers after firing or sticky extraction? roger
15 April 2004, 14:11
Atkinson
When primers are flat, that is a indicator of high pressure, so do not ignore it, cut back a grain or two..A lot can contribute to flat primers but thats not for you to decide...Changing brass, primers is one route but I would still cut back 3 grains and work up....
15 April 2004, 18:06
muck
I can solve your flattened primer problem! It will never happen again if you are brave enough to follow my instructions to the letter!











NEVER NEVER PUT A LIVE CARTRIDGE INTO A FIREARM AGAIN EVER! PERIOD.
16 April 2004, 00:02
Nordic
My rifle indicates that max load with vv n140, norma brass , hornady sp 165gr seated to cannilure, Winchester primer is 44gr in my rifle. The primers are much flatter than they normaly are in a 3006 or 6,5*55, but not as flat that it is hard to se the edge.

Kimmo
16 April 2004, 01:03
kk
I imagine this is self-evident, but how close is the bullet seated to the lands?

kk
16 April 2004, 01:42
<eldeguello>
Quote:

When primers are flat, that is a indicator of high pressure, so do not ignore it, cut back a grain or two..A lot can contribute to flat primers but thats not for you to decide...Changing brass, primers is one route but I would still cut back 3 grains and work up....



Well, I have to chime in here also. Flat primers amy or may not mean too-high presures! Some guns make flattened primers no matter what the pressure level is. I have one that does. As suggested above, changing primer brands might stop this. Some makes may fit the brass with less tension in the pocket, and back out when fired! This causes them to flatten out. There are other factors as well, BUT REMEMBER THAT ALL RIFLES ARE INDIVIDUALS, AND WHAT MAY BE MAXIMUM IN MINE MIGHT BE WAY OVER MAX OR WAY UNDER IN YOURS!
16 April 2004, 04:15
308Sako
There really are many causes of Flat primers, one of which is high pressure. Another is the firing pin protrusion and it's dimensions. Then there is the flash hole in the brass, and the neck diameter versus loaded round diameter. My .340 diameter neck Sako .308 was also sensitive to loads with VV140, but shoots best with VV540 and 165/168 grain bullets. Visual signs are but an indication that something MAY BE WRONG, so act accordingly. Use your experience not some printed reference which should act as a guide only. Each and every rifle is an individual unto itself.
16 April 2004, 06:52
Stonecreek
A "flat" primer is more often the result of greater-than-necessary headspace than it is of excessive pressure. With long headspace, the cartridge is shoved forward in the chamber upon the strike of the firing pin. The expanding brass case grabs the walls of the chamber and is held forward while the pressure inside the case forces the primer slightly out of the pocket until it bears against the bolt face. When the case stretches rearward to bear against the bolt face it "reseats" the slightly expanded primer, making it appear to be spread to the extremes of the primer pocket radius and thus appear similar to a primer subjected to excessive pressure.

If your "flattened" primers are not accompanied by extrusion of the primer metal into the firing pin hole, sticky bolt lift, bright spots in the cartridge head where the extractor groove or cut is, or other such indications of high pressure, then the "flatness" is irrelevant (except that you need to correct the headspace in your ammunition).
16 April 2004, 11:51
bartsche
Well said Stone Creek Nay sayers may look to safe withdrawl but an astute approach to gain understanding yeilds greater safety in the future for those who achieve that usefull tool. roger
16 April 2004, 13:23
bigbull
Are you new to reloading?
You say that you are within .7 grains of maximum and are getting flattened primers! This is normal, what's the problem! Are you trying to get maximum loads without flattened primers?
If you are new then be aware that there are alot of variables that effect pressure and trying to answer without specific information is next to impossible. Some guns show pressure while others show none with the exact same load!
Of coarse you can try other combinations.
16 April 2004, 18:30
SST
If your loads really are light, you probably have excessive headspace. If you eliminate headspace and still get flat primers, pressure is more than likely too high.