284 brass

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agro
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Location: Regional Vic.

284 brass

#1 Postby agro » Tue Sep 26, 2017 4:18 pm

I can remember reading sometime back that someone raised a suggestion of having 284 brass made with small primer pockets.
Did that idea ever get off the ground??

thx

Gyro
Posts: 764
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: 284 brass

#2 Postby Gyro » Tue Sep 26, 2017 5:02 pm

I have no bloody idea but i remember an experienced guy from West Oz made a comment a while back about running the 260AI made with the small primer brass and felt there were issues with the small primers not giving good consistent ignition with the slower powders ........ so if true then this same problem may apply to your question ???

johnk
Posts: 2211
Joined: Sun Sep 07, 2008 7:55 pm
Location: Brisbane

Re: 284 brass

#3 Postby johnk » Tue Sep 26, 2017 6:58 pm

I've concluded that there is an issue - case volume/powder required - which determines when a small rifle primer runs out of grunt.

AlanF
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Joined: Wed Jun 15, 2005 8:22 pm
Location: Maffra, Vic

Re: 284 brass

#4 Postby AlanF » Tue Sep 26, 2017 9:14 pm

agro wrote:I can remember reading sometime back that someone raised a suggestion of having 284 brass made with small primer pockets.
Did that idea ever get off the ground??

No it didn't. The best option if you want to run a 284 over 2900 fps with 180gn projectiles is to get a SAUM.

GSells
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Joined: Sun Aug 13, 2017 11:04 pm
Location: Qld

Re: 284 brass

#5 Postby GSells » Tue Sep 26, 2017 9:18 pm

AlanF wrote:
agro wrote:I can remember reading sometime back that someone raised a suggestion of having 284 brass made with small primer pockets.
Did that idea ever get off the ground??

No it didn't. The best option if you want to run a 284 over 2900 fps with 180gn projectiles is to get a SAUM.

Or a 280 ackley :lol:

KHGS
Posts: 934
Joined: Thu Oct 20, 2005 12:46 am
Location: Cowra NSW

Re: 284 brass

#6 Postby KHGS » Wed Sep 27, 2017 7:55 am

You cant beat cubic inches if performance (velocity) is your primary goal!! High pressures kill barrels fast & high pressure is not usually where best accuracy lives & accuracy is king.
Keith H.

RDavies
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Joined: Sun Feb 12, 2006 7:23 pm
Location: Singleton NSW

Re: 284 brass

#7 Postby RDavies » Thu Sep 28, 2017 9:37 am

KHGS wrote:You cant beat cubic inches if performance (velocity) is your primary goal!! High pressures kill barrels fast & high pressure is not usually where best accuracy lives & accuracy is king.
Keith H.

I wonder if the shortcomings of the 284 case design work out to be one of its strong points? Not being able to run very high pressures in this case without losing primers means more people are running their 284s at pressures which work out to be more CONSISTANTLY accurate over the long term, don't burn out barrels or cause velocity spikes, bullet deformation, sharp recoil etc.
As for small primers in a case this big, I don't think it would be too popular. In a 6PPC, 6BR, 6 Dasher, with its short powder column and relatively fast burning, easy to ignite powders, the small primers work great. When you step up to a 6x47 some people are getting great accuracy, some not, and my suspicions (amateur, non expert guess) is that moving to a longer powder column of the 6x47 case with a slower, slightly harder to ignite powder like 2209, or even worse with 2213sc is pushing the small primers ignition to the limits. The 308s with their faster burning, easier to ignite powders might be the limits.

williada
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Joined: Wed Jul 22, 2009 12:37 am

Re: 284 brass

#8 Postby williada » Thu Sep 28, 2017 3:15 pm

On the money Rod with the powder column.

As such, marrying the primer to the powder is very important assuming there is nothing wrong with the ignition system of your gear i.e. pin protrusion, spring pressure etc. As we know every setup has its own personality.

Remember Ecomeat was reluctant to go down the 2209 path for the 284 until a few suggested experiments opened his eyes 3 years ago in selecting a node with the right amount of barrel lift generated by the 2209 and complete powder burn.

Results in cases with longer powder columns also depend on powder density. Also depends on the jam or unjammed projectile which plays with peak pressures and consequently nodes, ES and SD. As you know groups can be misleading if they are not repeatable as Dave Mc says. So it takes a little sorting out around suggested loads of others to be sure, with horizontal ladders to judge each variable own its merits. But the generalization can find a starting point.

A paper by Culver, US Naval Post Graduate School in 1972, was an interesting examination of velocity and pressure effects on projectiles due to variation of ignition parameters. They experimented with inner tubes which let the spark out along different points in the powder column. They also experimented with duplex and triplex loads. They could lower their peak pressure and yet still increase muzzle velocity with the same powder volume and same primer with ignition taking place further up the powder column. The implication is the primer must be able to efficiently light the powder column in the right spot at a suitable powder density. Small magnum primers are used in Palma cases by many and obviously light the powder a long way up the column. However they are not usually bench rest grade. The best way to sort or batch them is the weigh them on very accurate scales. To get the last nuance out of the primer ignition pattern some taper the ignition hole in the case so the spread of flash is directed to the junction of the body and neck of the case. Its not done to remove burrs as some think although unifying holes is a good thing.

Just as a generalization for the .308 guys, 2206h from a few experiments lit better in a test configuration using 155's with small primers in cool weather and the powder density was not as critical. This aligns with Rod's thinking. Similarly, in 308W, full bottle loads with a little powder compression with 2209 for heavier pills steadied the ship a tad. There was less carbon in the barrels with a compressed load to ensure the slower powder of 2209 burned thoroughly and did not lead to fouling issues. Things are at the margins here in 308W - it depends on how your pipe smokes, leed angle etc. as well. The concepts are transferable to the 284. People may observe at 25 yard testing, while running in a barrel, dark rings around the bullet holes on the paper if your powder is too slow or ignition is poor if you are using naked bullets after a number of shots.

RAVEN
Posts: 1978
Joined: Sun Jun 19, 2005 9:37 pm
Location: Adelaide South Australia (CTV)

Re: 284 brass

#9 Postby RAVEN » Mon Oct 09, 2017 10:17 pm

Hi Willanda
Jack Neary short range bench rester talks about small bullet holes and load tuning in a youtube clip
I have also found this to be true when I'm on a node.

Keith I agree completely accuracy is King EVERY TIME.

RB

Brad Y
Posts: 2181
Joined: Fri Jun 26, 2009 8:21 pm

Re: 284 brass

#10 Postby Brad Y » Mon Oct 09, 2017 10:36 pm

RDavies wrote:
KHGS wrote:You cant beat cubic inches if performance (velocity) is your primary goal!! High pressures kill barrels fast & high pressure is not usually where best accuracy lives & accuracy is king.
Keith H.

I wonder if the shortcomings of the 284 case design work out to be one of its strong points? Not being able to run very high pressures in this case without losing primers means more people are running their 284s at pressures which work out to be more CONSISTANTLY accurate over the long term, don't burn out barrels or cause velocity spikes, bullet deformation, sharp recoil etc.
As for small primers in a case this big, I don't think it would be too popular. In a 6PPC, 6BR, 6 Dasher, with its short powder column and relatively fast burning, easy to ignite powders, the small primers work great. When you step up to a 6x47 some people are getting great accuracy, some not, and my suspicions (amateur, non expert guess) is that moving to a longer powder column of the 6x47 case with a slower, slightly harder to ignite powder like 2209, or even worse with 2213sc is pushing the small primers ignition to the limits. The 308s with their faster burning, easier to ignite powders might be the limits.


In other words Rod likes em short and fat :D


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