Primer cup query

A

Andy Cross

Guest
Recently took the .17 rem to the range to tune up for 30gn projectiles. Needed a longer projectile to chase the lands as they get burned away and still have enough in the case. The best groups came from a fairly stout load. I found the rem 7 1/2 primers didn't show any cratering or flattening when compared with the fed 205M when the same load was being used. The bolt handle remained easy to lift irrespective of which primer was used. Can there be this much difference in the hardness of primer cup material ?
Andy
 
David Halblom said:
the thickest, strongest primer cup out there is the CCI-BR-4.
Click to expand...

Actually I believe the CCI #34 & #41 are the toughest primers available. They are designed specificly to prevent slam fires in semi auto rifle with floating fireing pins.

The Rem 7 1/2 was also designed to replace the 6 1/2 in the old 222 mag and 5.56 cartridges during early military development IIRC, when they found they (the 6 1/2) were too thin to withstand the pressures of these cartridges and pierced. Today Remington only recommends the old 6 1/2 small rifle be used in the 22 Hornet and similar low pressure cartridges.
CCI std and mag primers as well as WSR and WLR have very similar cup strength. I don`t know it for sure but there was an artical in the Rifleman magazine a few years back claiming all regular primers, std and mag, used by the major brands had the same base cup thickness and material. The difference in how easily they ignited or pressure they produced was due to the compounds used in them, with Federal being the most sensitive. Plating has no effect on the strength over bare brass.
 
Joe S said:
Actually I believe the CCI #34 & #41 are the toughest primers available. They are designed specificly to prevent slam fires in semi auto rifle with floating fireing pins.

The Rem 7 1/2 was also designed to replace the 6 1/2 in the old 222 mag and 5.56 cartridges during early military development IIRC, when they found they (the 6 1/2) were too thin to withstand the pressures of these cartridges and pierced. Today Remington only recommends the old 6 1/2 small rifle be used in the 22 Hornet and similar low pressure cartridges.
CCI std and mag primers as well as WSR and WLR have very similar cup strength. I don`t know it for sure but there was an artical in the Rifleman magazine a few years back claiming all regular primers, std and mag, used by the major brands had the same base cup thickness and material. The difference in how easily they ignited or pressure they produced was due to the compounds used in them, with Federal being the most sensitive. Plating has no effect on the strength over bare brass.
Click to expand...

Too bad both the CCI #34 and #41 are missing from this article.
http://www.jamescalhoon.com/primers_and_pressure.php
 
What about flash strength

David Halblom said:
the thickest, strongest primer cup out there is the CCI-BR-4.
Click to expand...

I have heard that primers that are constructed with strong cups often produce the largest flash or a flash of longer duration. Is there any truth in that statement. Also if a primer cup can withstand higher pressures the only other symptom of a near maximum load would be a harder to lift bolt handle. Does anyone have any thoughts on this.
Andy.
 
I have heard that primers that are constructed with strong cups often produce the largest flash or a flash of longer duration. Is there any truth in that statement.


In some cases that's true... The one exception........ Wolf / Tula primers.......... Very mild priming mix.. VERY tough cup on the SRM small rifle magnum but the priming compound is VERY mild... Works well enough for single based powders... But ball powder, even in the heat.. Click bang... Click.......Bang...

Seen this in a 6BR / 22BR / 22-250.... Replace with 7 1/2 / 205 / 205M / Win WSR / CCI 400.........Bang every time.

Andy, the 7 1/2 Rem primers these days are DAMN good...! I have several agg and yard wins with them... I have FULL faith in there consistency and sensitivity.
They ARE Benchrest primers to be trusted as such. Ought to be wonderful in your 17..

cale
 
Maybe it's just me, but I've had problems with 7 1/2's being too hard or something. I gave up on them maybe 15 or 20 years ago after experiencing blowouts on the edge of the cups in loads that didn't seem too hot at all. Recently I bought some more to try in an AR after using Winchester WSR's. The WSR's flatten like they'd been hit with a BIG hammer, but I've never had a problem with them blanking. Using the same load and getting about the same velocity with the 7 1/2's as the WSR's, I got about 20% blanked primers in firing 40-50 rounds with them. The 7 1/2's didn't show any flattening at all with the load that squashed the WSR's which is ~0.8 gr less than a manual max with the 75 gr Hornady HPBT at 2700 fps which is what Hornady shows as the top velocity from an AR with that bullet.

I'm going to cross my fingers and try the 7 1/2's again as soon as I can find some time, but if they blank on me again I'm unloading those puppies.
 
those 7 1/2's

The reason I hadn't used the 7 1/2's in the .17 rem previously is that the rem primers were off the market here in Oz for a while
and I had no choice but to use something else. When I came to tune the .17 up after not shooting it for some time
I just used the federals as I had been for the BR rifle and the 222. That's when I run into primer cup issues.
The rem certainly seem to have solved that issue.
Andy.
 
"experiencing blowouts on the edge of the cups in loads that didn't seem too hot at all."


Hum... Primarily with the AR platform..? Can't help here, Bolt gun guy...

In my findings, I have found the Fed 205 / 205M , Winchester WSR and CCI 400 to be tops in sensitivity...
The 400's though do not like lots of pressure... Not as bad as the Rem 6 1/2's, they pierce way easy.!.. Remington states that the 6 1/2 are NOT for high pressure cartridges, heed this...

Guess every gun has a unique primer "interface"... Larry, don't give-up on the 7 1/2's, "IF" just the AR platform then try 450 CCI's or those "mil spec" CCI primers.... Try the 7 1/2 in "other" guns.... THEY ARE as good as the 205/205M as far as Benchrest terms go, just a "touch" less sensitive than 205 / 205M's...

Andy and all....
Far as I know Midway, Brunos and Powder Valley have 7 1/2's on hand... Every now and again, Midway has them for 125.00 per case and too they give dicounts for previous customers that'll pay for Haz and a portion of the shipping fee... Just checked >>>... Powder Valley has them on hand for 130.00 a case...

Ohhh duuuuhhh.... Sorry Andy, forgot your in OZ.............. Well crud..! Some shop around Aussi land must have current produced Rem 71/2's... Hopefully...

cale
 
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The cup blowouts were in bolt guns though.

What I can't understand with the 7 1/2's blanking in the AR is that spec AR's have very small firing pin holes and consequently very small firing pins. I've tried WSR's, CCI 400's and 450's, and 7 1/2's in the AR, and all of them in bolt rifles along with F205/205M's. The only primer that's given problems with blanking is the 7 1/2. I've never had a bit of problems with Rem 9 1/2's though.

As with many things in this life I'm baffled by this one.
 
I found the rem 7 1/2 primers didn't show any cratering or flattening when compared with the fed 205M when the same load was being used. The bolt handle remained easy to lift irrespective of which primer was used. Can there be this much difference in the hardness of primer cup material ?
Click to expand...
Yes is my guess. CCI 400 was flowing back into the firing pin hole. Changing to Rem 7 1/2 showed no flow or pressure. Rem must be harder or thicker.
I've had problems with 7 1/2's being too hard or something. I gave up on them maybe 15 or 20 years ago after experiencing blowouts on the edge of the cups in loads that didn't seem too hot at all.
Click to expand...
This would be a defective primer. Seems to happen in all brands.
DefectivePrimer.jpg
94b28580.jpg
 
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caroby said:
Ohhh duuuuhhh.... Sorry Andy, forgot your in OZ.............. Well crud..! Some shop around Aussi land must have current produced Rem 71/2's... Hopefully...

cale
Click to expand...
Oh you can get them again now. That's how I was able to compare them to the Federals and noticed the difference in the
cups after firing them. I wonder if I can run a hotter load in the 6ppc without running into cup issues ?
Andy.
 
I also had a series of blownout Remington Large Rifle primers 15 or so years ago. Sent them back to Rem. with the box showing the lot#. They denied there was anything wrong. Then sent them another 4 or 5, also with the box they came in ( different lot#) & they then admitted there was a problem, saying that the brass was too hard. They sent 2000 LR primers as a peace offering. Sold them to someone who had to have them & have never used them again. Mine also ruptured at the top corner, nowhere near the firing pin. For the past 4 or 5 years have used 7 1/2's and never had a problem.
 
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