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Large vs. Small primer

  • roy cobb
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10 Jan 2018 17:35 - 10 Jan 2018 17:37 #1 by roy cobb
roy cobb created the topic: Large vs. Small primer
Ok here is something different my 6.5 creedmoor Lapau brass have small primer pocket and Fusion (Federal) brass I just cleaned up after shooting on the weekend has large primer pocket has any one come across this befor and if so how much of a difference does this make in shooting loads

This isn't rocket science guys ... it's more complicated than that, and it has aspects of the Dark Arts, And this smokeless stuff will not last
Last Edit: 10 Jan 2018 17:37 by roy cobb.

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10 Jan 2018 18:06 #2 by sigsako
sigsako replied the topic: Large vs. Small primer
Hi Roy.
I only just became aware of that the night before last, whilst researching calibers, Bullet coefficients, trajectories and all that head churning stuff.
I was shocked and thought how bizarre, but is not unusual apparently.

Can't offer any thing else but this may help,

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10 Jan 2018 21:06 #3 by Send-it
Send-it replied the topic: Large vs. Small primer
Cases with small primer pockets are believed to handle higher pressures due to having more brass remaining around the case base.
Hence why many long range 308 target shooters use the 308 'palmer' brass as it has a small primer, and it can be loaded higher to help keep those 308 pills supersonic for longer.

I suspect certain manufacturers are doing the same for the creedmoor.
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11 Jan 2018 08:38 #4 by Westy
Westy replied the topic: Large vs. Small primer
I take it you used Magnum Primers in the Small primer Brass???
Like we use in the 6BR cases right?
:huh: :blink: :huh:

Everyone has a plan till they get punched in the mouth.
-Mike Tyson-

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11 Jan 2018 09:44 #5 by magoo
magoo replied the topic: Large vs. Small primer
Heard talk of people having probs with small primers.
When I asked my smith he said they would be using the wrong primers. Can only assume magnums would be the go but not sure.
Also said it was like the case, more about even consistent burn.
ie : smaller ignition and it burns even from base to neck rather than just explode or what not.

Makes sense to me but not really studied up on the matter.

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11 Jan 2018 17:35 - 11 Jan 2018 17:45 #6 by Top Gun
Top Gun replied the topic: Large vs. Small primer
Its not so much about the case handling more pressure its more a matter of the smaller primer pocket & smaller flash hole being designed to reduce ES & SD through a deeper jet type ignition.

Does this reduce pressure or just give a more even ignition?

Both probably & probably reduces spiking which equates to better ES & SD which combined will reduce verticle dispersion, especially at longer ranges & this is why the Palmer case was developed & introduced for comp shooting.
Last Edit: 11 Jan 2018 17:45 by Top Gun.

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15 Jan 2018 08:18 #7 by Straightshooter
Straightshooter replied the topic: Large vs. Small primer

Top Gun wrote: Its not so much about the case handling more pressure its more a matter of the smaller primer pocket & smaller flash hole being designed to reduce ES & SD through a deeper jet type ignition.

Does this reduce pressure or just give a more even ignition?

Both probably & probably reduces spiking which equates to better ES & SD which combined will reduce verticle dispersion, especially at longer ranges & this is why the Palmer case was developed & introduced for comp shooting.


Not so.
What you are repeating is part of the verbal mythology surrounding small rifle primer cases. Not surprisingly these myths are unprovable and 'true believers' thus cling to them tenaciously as equally they they can't be disproven.

Send-it has pretty well got it right.

If you can get a few more firings out of your prepped cases before the primer pockets get too loose then it is all worthwhile. Just ask any match rifle shooter.

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15 Jan 2018 08:48 - 15 Jan 2018 09:16 #8 by Top Gun
Top Gun replied the topic: Large vs. Small primer

Straightshooter wrote:

Top Gun wrote: Its not so much about the case handling more pressure its more a matter of the smaller primer pocket & smaller flash hole being designed to reduce ES & SD through a deeper jet type ignition.

Does this reduce pressure or just give a more even ignition?

Both probably & probably reduces spiking which equates to better ES & SD which combined will reduce verticle dispersion, especially at longer ranges & this is why the Palmer case was developed & introduced for comp shooting.



Not so.
What you are repeating is part of the verbal mythology surrounding small rifle primer cases.



Really :blink:

Well SS you had better let Lapua know that they are spreading verbal mythology, read the top page ;)

www.lapua.com/upload/news/lapua308winpalmacase2010.pdf

While some of what I said was some of my own input, the basis of what I was saying is that the smaller primer delivers a more consistent ignition and reduced variations.
Last Edit: 15 Jan 2018 09:16 by Top Gun.

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15 Jan 2018 10:35 #9 by roy cobb
roy cobb replied the topic: Large vs. Small primer
Is there any one shooting 6.5 Creedmoor with Lapua brass if so what primer are you using
Thanks Roy

This isn't rocket science guys ... it's more complicated than that, and it has aspects of the Dark Arts, And this smokeless stuff will not last

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15 Jan 2018 14:33 #10 by Aushunter
Aushunter replied the topic: Large vs. Small primer
Id be looking at any match/benchrest small rifle primer Roy

The CCI BR2's work very consistantly in my .260 for LR work so the BR4's would be my fisrt choice.
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16 Jan 2018 18:31 #11 by Straightshooter
Straightshooter replied the topic: Large vs. Small primer

Top Gun wrote: Really :blink:

Well SS you had better let Lapua know that they are spreading verbal mythology, read the top page ;)

www.lapua.com/upload/news/lapua308winpalmacase2010.pdf

While some of what I said was some of my own input, the basis of what I was saying is that the smaller primer delivers a more consistent ignition and reduced variations.


OMG Who'd of thought it?
A manufacturer of premium priced stuff offering reasons why their product is a desirable purchase by reinforcing a potential purchaser's beliefs.

Now you assert "that the smaller primer delivers a more consistent ignition and reduced variations".
Why should that be so? Why should a small primer in of itself be any more consistent than a large primer particularly if both are held to similar production tolerances?

If you really want to further your understanding, I suggest you do some research on how and why the PPC cartridge was developed and how it's success led to the Rem BR case and also why it's success displaced the 222 case.

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16 Jan 2018 18:47 #12 by roy cobb
roy cobb replied the topic: Large vs. Small primer
Well I will see how I go.
I have made up some different powder loads both with small and large primers and will put them through the chronograph this weekend if I can get too the range

This isn't rocket science guys ... it's more complicated than that, and it has aspects of the Dark Arts, And this smokeless stuff will not last
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