Pressure Differences 6.5 Creedmoor Lapua Brass (Small Vs Lg Primer)?

[Kel]

I did a search and as best I can tell this topic hasn't been fully covered?

I purchased a RPR in 6.5 Creedmoor and picked up a bunch of the Lapua that has the small primer pocket. I have done tons of reloading and competition benchrest shooting going back a few years now.

As such, I am aware that changing to a small rifle primer from a large one is going to alter pressures. I searched the web pretty extensively and can't find any Creedmoor specific pressure comparison of load data between the large and small rifle primers. As best I can tell folks are just using the large primer load data and applying that to the Lapua brass?

Anyway, please advise on what you are doing and have discovered with respect to load data, pressures and velocity in the 6.5 Creedmoor between lg and sml rifle primer.
Thks

 

[jamesh]

The difference in case capacity between Hornady and Lapua brass will have a far larger effect on pressures than the difference between large and small rifle primers. You are comparing apples and oranges.

 

[spclark]

As such, I am aware that changing to a small rifle primer from a large one is going to alter pressures.

When the small-primer Lapua Palma brass first appeared I'd been shooting their large-rifle 308 brass for two or three years for Palma. I'd been disappointed by the (relatively) short case life span; six loads was the exception, more typical was three or four before case heads failed to hold primers.

So I was glad to find with the Palma brass the case heads apparently benefitted from the extra material surrounding primer pockets. Case life improved to the point I'm still shooting some of that very first batch of cases I started with back in 2010.

I tested identical loads - save for primers used of course - in both large- and small-primered cases. There was virtually no significant performance variation between them discernible on paper, at distance. With load spreads over .3 - .7 grains I found negligible changes in velocities while SD numbers were greater by a small amount for the large primers.

Perhaps the smaller case volume of the 6.5 Creedmoor will not behave similarly? I'll be curious to read what others might post. As Jamesh suggests, changing brand of brass will have greater effect than changing from large to small primer brass.

(I believe Peterson Cartridge Company to be the only source for both right now.)

 

[Kel]

Ok thanks, some good feedback so far.

I will have to check but I wasn't aware the case volumes varied much between Lapua and the other manufacturers. I will have to do some more searching online.

 

[MSS]

H2O capacity.
Hornady = 53.27
Lapua = 52.23
This was after firing and an average of 10 cases each. Rifle was Tikka T3x Tac a1.

 

[riflewoman]

The 6.5 Creedmoor has other issues with small primers. The slower powders used in this cartridge can hangfire or even misfire with Small primers. It is somewhat temperature and powder type related but it is repeatable and some primers work better than others.

This guy published a series of videos on the subject.

https://m.youtube.com/playlist?list=PLTTrjvDib94npQZ29LL_pcUcxtFlx4lqm

 

[ZenArchery]

I tested identical loads - save for primers used of course - in both large- and small-primered cases. There was virtually no significant performance variation between them discernible on paper, at distance. With load spreads over .3 - .7 grains I found negligible changes in velocities while SD numbers were greater by a small amount for the large primers.

(I believe Peterson Cartridge Company to be the only source for both right now.)

I've suspected this but thanks for the field report!!!

 

[Shane Roya]

The 6.5 Creedmoor has other issues with small primers. The slower powders used in this cartridge can hangfire or even misfire with Small primers. It is somewhat temperature and powder type related but it is repeatable and some primers work better than others.

This guy published a series of videos on the subject.

https://m.youtube.com/playlist?list=PLTTrjvDib94npQZ29LL_pcUcxtFlx4lqm

Interesting.

 

[Milo 2.0]

I may be off base, but a cartridge gets a saami designation for allowable pressures. Yes, small primer brass pockets last longer, but what are acceptable pressures. I think brass companies should set their own limits(I know), most I know use Quckload and manipulate the crap out of numbers to match loads to guns.

 

[hikfromstik]

I don't know the formula ,but I've always dropped 2-3 tenths of a grain when switching to lapua brass from Hornady . Every powder is different , so I doubt there is a formula.

 

[ReconDo17]

I have recently built a Bartlein barrel 26" 7mm Creedmoor on a remington 700 SS action, I am also wondering what the pressures are. The only bases I could find was the Hornady brass @ 63091 CIP so I used that starting at 41gr of reloader 17 and a max so far of 45.5gr with no pressure signs getting 2900+ from a 168 Sierra MK. I would be very interested to see what the real pressures are from these cases.

 

[mugadutz]

The 6.5 Creedmoor has other issues with small primers. The slower powders used in this cartridge can hangfire or even misfire with Small primers. It is somewhat temperature and powder type related but it is repeatable and some primers work better than others.

This guy published a series of videos on the subject.

https://m.youtube.com/playlist?list=PLTTrjvDib94npQZ29LL_pcUcxtFlx4lqm

Are the flash holes the same diameter
If not maybe the smaller could be made larger and remedy the problem.

 

[riflewoman]

Are the flash holes the same diameter
If not maybe the smaller could be made larger and remedy the problem.

No clue. I don’t shoot a 6.5 Creed. Probably never will. But the issue is not always flash holes. This phenomenon has been noted in a lot of other larger cases like 308 with small primers.

 

[dreever]

I did a search and as best I can tell this topic hasn't been fully covered?

I purchased a RPR in 6.5 Creedmoor and picked up a bunch of the Lapua that has the small primer pocket. I have done tons of reloading and competition benchrest shooting going back a few years now.

As such, I am aware that changing to a small rifle primer from a large one is going to alter pressures. I searched the web pretty extensively and can't find any Creedmoor specific pressure comparison of load data between the large and small rifle primers. As best I can tell folks are just using the large primer load data and applying that to the Lapua brass?

Anyway, please advise on what you are doing and have discovered with respect to load data, pressures and velocity in the 6.5 Creedmoor between lg and sml rifle primer.
Thks

I use Alpha Munitions brass. They did a report on LRP verses SRP.

http://alphamunitions.com/kaubers-corner-large-vs-small-rifle-primers/