Brass question

[243LPR]

I've been using Remington brass in my 6mm AI since new and was wondering about switching. I thought about 7x57 or 257 Roberts. Now I found some 257 Roberts +P in stock was curious how it would fire form. Is this brass harder or thicker enough to cause a problem? I know I'll probably have to neck turn but have a K&M for that. Any thoughts?

[bigedp51]

The hardness of the brass and how thick the flash hole web is in the base of the cases determines how much pressure the case can take. Meaning before you have brass flow or radial expansion in the base of the case.

Below Federal cases have the softest brass and the thinnest flash hole web. I have factory loaded Federal .223 cases with over sized primer pockets after the first firing.

http://i122.photobucket.com/albums/o254/bigedp51/federal_zpsbp4r0zok.jpg

CatShooter posted the information below in a posting when I was in a heated argument about how hard Lake City brass was and it was turned into a permanent article. The "heated discussion" was with someone who thought his Lupua brass was the best and hardest brass you can get. It got ugly when I told him I could buy 500 once fired 5.56 case at a small fraction for what he paid for 100 new Lapua cases.

How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/2014/05/how-hard-is-your-brass-5-56-and-223-rem-base-hardness-tests/

TEST RESULTS
Using Rockwell hardness standards (.062″x100kg, Rockwell “B”), the brass measured as follows:

LC 2008 = 96

Lapua 223 Match = 86

Winchester 223 = 69

Remington “R-P” = 49

Summary of Test Results
Catshooter writes: “For all you guys that have believed that Winchester cases were tougher than Remington — you are vindicated, they are a lot tougher! However, Lake City and Lapua are ‘the pick of the litter'”. Catshooter notes that both Lake City and Lapua are significantly harder than either Winchester and Remington .223 brass. That’s something that we’ve observed empirically (Lapua and LC stand up better to stout loads), but now we have some hard numbers to back that up. Hats off to Catshooter for settling the hardness debate with his Ames Hardness Gauge.



Bottom line if you want tougher brass then switch to Winchester or other harder brands of brass.

[FW Conch]

But, back a few years ago, Handloader Magazine fired over 2,000 reloads, using every brand of case they could get their hands on. They shot each brand of reload brass until the case failed. Remington won with 19 reloads. They were all 308's.

I think Rem brass, as others was of better quality then. This test would tend to indicate that brass hardness does not make a game changer?

[bigedp51]

All the test proved was how well the cases withstood full length resizing with the die making hard contact with the shell holder. Meaning resizing without using minimum shoulder bump and no reference to the rifles actual headspace and how much head clearance or "air space" between the rear of the case and the bolt face.


http://i122.photobucket.com/albums/o254/bigedp51/308fail-1_zps30d387ab.jpg

http://i122.photobucket.com/albums/o254/bigedp51/308fail2-1_zps3ca31f6b.jpg

Your head clearance deals with how far the case must stretch to meet the bolt face when fired and why minimum shoulder bump is used when resizing your cases. With a bolt action rifle and .002 shoulder bump/head clearance you are not exceeding the yield strength of the brass and its ability to spring back. And this is why a properly resized case dies from over sized primer pockets or split necks.

http://i122.photobucket.com/albums/o254/bigedp51/HEADCLEARANCE-a_zps1a9a1011.jpg

Brass hardness deals with the strength of the base of the case and resisting radial expansion when fired. Meaning what good is a case with a oversized primer pocket that will not hold a primer even if the case has not had a case head separation.

http://i122.photobucket.com/albums/o254/bigedp51/base%20expanshion_zpss3c0gjcm.png

You can over resize a Lake City case and still have a case head separation and still not have radial expansion just above the extractor groove. Meaning still having tight primer pockets.

The harder the brass the higher the chamber pressure will be before the brass flows into the ejector or the brass expands in the base radially. At AccurateShooter.com many long range shooters will increase the load until they get brass flow into the ejector and then back off 1 or 2 grains of powder. This tells them the maximum strength of the brass before its yield strength is reached, meaning brass flow.

http://i122.photobucket.com/albums/o254/bigedp51/marks_zps63d0459a.jpg

Summary of Test Results
Catshooter writes: “For all you guys that have believed that Winchester cases were tougher than Remington — you are vindicated, they are a lot tougher! However, Lake City and Lapua are ‘the pick of the litter'”. Catshooter notes that both Lake City and Lapua are significantly harder than either Winchester and Remington .223 brass. That’s something that we’ve observed empirically (Lapua and LC stand up better to stout loads), but now we have some hard numbers to back that up. Hats off to Catshooter for settling the hardness debate with his Ames Hardness Gauge.

[bigedp51]

X-Ray Spectrometry of Cartridge Brass
X-Ray Spectrometers Reveal Metal Content of Major Cartridge Brass Brands
http://www.accurateshooter.com/technical-articles/x-ray-spectrometry-of-cartridge-brass/

[Robinhood]

Holy cow!! Look at the graphics. Very impressive.

[243LPR]

So the +P brass just has a thicker base/web?

[bigedp51]

So the +P brass just has a thicker base/web?

What I'm telling you is Federal and then Remington make the softest brass. Lake City 5.56 has the hardest and thickest brass in their base and still has the most case capacity.

You can buy the +P cases and Winchester cases and see which cases last the longest. But its up to you on how long your cases last by how hot you load and what you want to spend.

Below is from AccurateShooter "243 Win Cartridge Guide" http://www.accurateshooter.com/cartridge-guides/243win/

.243 Win For Tactical Comps
We asked GA Precision’s George Gardner why he chose .243 Winchester for his Tactical Comp Gun. He replied, “Why would I run anything else? Think about it. I’m sending a .585 BC 115 at 3150 fps–that’ll shoot inside the 6XC and .260 Rem with ease. I’m pretty sure I have found the Holy Grail of Comp Rifles. There are no brass issues like you can get forming .260 brass. I don’t have to worry about doughnuts, reaming necks–none of that. And the choice in brass is great too–run Lapua if you want max reloads and great accuracy. Run Winchester if you’re on a budget, and so you won’t cry if you lose some cases in a match. I can get 10-round mags, and feeding is 100% reliable, since the case is identical to a .308 except for the neck. Accuracy-wise, I don’t think I’m giving up anything to the .260 Rem or the 6XC.” We then asked George if he’d considered using a .243 AI instead: “Yeah, the cases look cool with that 40° shoulder, but I think the standard .243 feeds a little better. And I don’t think I really need the extra performance of an improved case. Run the ballistics for my load–115 moly DTAC at 3150 fps. You’ve got less windage than a 2950 fps 6.5-284, with cheaper brass, cheaper dies, cheaper bullets, and less recoil.”

The point being above is this competitive shooters second choice in brass is Winchester for hardness and cost savings.

Bottom line, I use a 2 inch steel rod to measure the web thickness of Federal .223 cases and I don't even bother reloading these cases with thin webs for my AR15 rifles.

Below you can measure web thickness without cutting and sectioning a case with a metal rod.

http://i122.photobucket.com/albums/o254/bigedp51/primerpocket-a_zps50f5bf3c.jpg

The end inserted into the case has been counter bored to fit over any sprue from punched flash holes and prevent false readings.

http://i122.photobucket.com/albums/o254/bigedp51/IMG_2028_zpsb357ed59.jpg

http://i122.photobucket.com/albums/o254/bigedp51/IMG_2030_zps54dd0d9e.jpg

So you are the only one who can answer your question with a few new tools.