PDA

View Full Version : Primer Hardness?



antelopedundee
07-19-2019, 11:16 AM
Is there a generally agreed upon order of primer hardness among CCI, Remington, Federal and Winchester? I was led to believe that Remington is the hardest and Federal the softest? So maybe Rem, Win, CCI, Fed?

glp
07-19-2019, 12:19 PM
https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/

some info along the lines of what you are asking.

retired
07-19-2019, 02:50 PM
i would take exception to their small rifle limitations.
cci400 and win sr work well in modern rifles..no 44000psi limit.


https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/

some info along the lines of what you are asking.

FBecigneul
07-19-2019, 04:13 PM
Iím still trying to figure what the pressure is with regard to an .062 flash hole. PSI be damned.

Wilbur
07-19-2019, 05:01 PM
If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi.

mwezell
07-19-2019, 05:05 PM
If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi.

Interesting! How did you calculate that Wilbur?

RJM
07-20-2019, 08:06 AM
I did a small test to see if different primers would reduce cratering in my 30BR on a 700 action.

In particular, I was interested if the primers that are advertised as milspec to reduce the chance of a slam-fire in ARís would show less cratering. I tried CCI #41 and Fed 205M-AR, with Fed 205M, 205, Winchester small rifle, CCI small rifle, CCI BR-4, and Rem 7 1/2 as standards.

The only one that visibly had smaller craters was the CCI #41. The 205M-AR did not appear any different than the 205 or 205M.

No, itís not scientific. I didnít measure thickness, velocity, or anything else. All I did was load them the same, fire, and look at the craters. ďYour mileage may vary!Ē

Regards, Ron

antelopedundee
07-20-2019, 10:46 AM
Does primer cup hardness have much to do with consistency; i.e. one brand gives more consistent velocities shot to shot than another brand does? All other factors being equal.

FBecigneul
07-20-2019, 12:17 PM
You know, you can do a search on all these factors and come up with lengthy tests and conclusions instead of speculation.
https://precisionrifleblog.com/2012/07/02/most-accurate-rifle-primers-for-precision-reloading/

antelopedundee
07-20-2019, 07:25 PM
You know, you can do a search on all these factors and come up with lengthy tests and conclusions instead of speculation.
https://precisionrifleblog.com/2012/07/02/most-accurate-rifle-primers-for-precision-reloading/

I can but I'd just as soon go direct to those likely to know. Someone on another message board was asking about primer variation and that reference was posted elsewhere also. The obvious answer to whether or not primers make a difference is to take your best load and simply try different brands keeping in mind that a different lot of the same brand may not give the exact same results.

Wilbur
07-20-2019, 07:50 PM
Don't know if that's right or not but suspect it's not. I just calculated the area of a .062 inch round hole and applied that to 50,000 psi. I realized after I posted that the total pressure on the primer would be the result of the diameter of the space inside the primer...but who cares. If the primer gives up the ghost you have two choices...get a tougher primer or reduce the powder charge.

retired
07-20-2019, 08:45 PM
in the br game. It DOES NOT MATTER.
what matters is what happens on the TARGET.
SO WORK UP A LOAD with each PRIMER and then go shoot the best.

or do what most do , shoot a primer KNOWN to give uniform great results
that tends to be federal small rifle or small rifle match.
specific loads some time work better with a different primer.
an example is the cc450 in 6mm dasher and rl15.

antelopedundee
07-20-2019, 10:41 PM
If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi.

If the pressure inside of a case the instant before the bullet departs is 50,000 psi or pounds then it's equal in all directions, no?

Kevin Gullette
07-21-2019, 12:33 AM
......Wilbur meant to type "83 pounds" ??

I recall Jerry Stiller writing a very concise Precision Shooting article, concerning primer cratering/blanking and reducing the boltface firing pin hole diameter.
Anyone else remember?

Kevin

John Kielly
07-21-2019, 04:28 AM
If the pressure inside of a case the instant before the bullet departs is 50,000 psi then it's equal in all directions, no?
At a rate of 50,000 pounds of force per square inch of area, or 25,000 pounds of force per half of a square inch etc etc.

Richard
07-21-2019, 09:24 AM
The best way on any of the benchrest stuff is to do the hard work and test it yourself.
Retired has it right, the target tells the story.

Richard

Wilbur
07-21-2019, 11:07 AM
If the pressure inside of a case the instant before the bullet departs is 50,00 psi then it's equal in all directions, no?

Yes, that's correct, but it's psi rather than pressure at ANY given point. John Kielly stated this a bit more eloquently earlier but I'm just being Wilbur and sayin' it differently

Wilbur
07-21-2019, 11:12 AM
......Wilbur meant to type "83 pounds" ??
Kevin

I think you're right...but I'm pretty easy these days.

antelopedundee
07-21-2019, 12:22 PM
in the br game. It DOES NOT MATTER.
what matters is what happens on the TARGET.
SO WORK UP A LOAD with each PRIMER and then go shoot the best.

or do what most do , shoot a primer KNOWN to give uniform great results
that tends to be federal small rifle or small rifle match.
specific loads some time work better with a different primer.
an example is the cc450 in 6mm dasher and rl15.

I've never handled a small rifle primer so would the generalization about Federal being the best most uniform carry over to large rifle primers?

antelopedundee
07-21-2019, 07:04 PM
If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi.

How does 83 pounds blow out a primer?

retired
07-21-2019, 07:17 PM
if you have never handled a small rifle primer, you are pretty much wasting your time on most of these forums. IMHO



I've never handled a small rifle primer so would the generalization about Federal being the best most uniform carry over to large rifle primers?

R.G. Robinett
07-21-2019, 09:03 PM
How does 83 psi blow out a primer?

I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds.:eek: I'm notorious for confusing radius and diameter.:p RG

mwezell
07-21-2019, 09:06 PM
I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds.:eek: I'm notorious for confusing radius and diameter.:p RG

After asking my previous question, I stopped and thought about it for a second and came up with the same as you...152. something. I didn't follow up as I didn't get an answer to my question to begin with...so. No biggie.

antelopedundee
07-21-2019, 11:35 PM
I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds.:eek: I'm notorious for confusing radius and diameter.:p RG

Cept nobody mentioned firing pin until your post, it was firing pin hole which was said to have a diameter of .062 inches and a calculated area of .00302 square inches. In the example cited of 50,000 psi the pressure available at the flash hole would be 50,000 psi and not 152. Going back to post 3 where a pressure limit of 41,000 psi was mentioned one would expect that 50,000 psi would blow that primer in some way. Otherwise with your 152 psi thing you're saying that when I check the air pressure in my truck tires that the pressure at the valve stem is NOT equal to the pressure elsewhere in the tire. The pressure inside of a round of ammo when the bullet is ready to start moving is the same everywhere inside the case be it primer, case wall or bullet base.

If I took my truck wheel and put in a second valve stem of a different size then according to your explanation I should get a different reading at each one. I don't think that would be the case at all. How would a primer even flatten with only 152 psi pushing on it?

Wilbur
07-22-2019, 12:02 AM
If you had two tire guages and they gave you a different pressure on the same tire (quite common) ...what would cause that?

antelopedundee
07-22-2019, 12:53 AM
If you had two tire guages and they gave you a different pressure on the same tire (quite common) ...what would cause that?

I didn't say gauges. The reading [with properly working gauges] should be the same at both valve stems is my point, otherwise your pressure measurement system is no good.

By your logic a .30 cal flat base bullet with an area of .07447 sq in at 50,000 psi working pressure would have 3723 psi against it. I don't see that getting a bullet of a barrel at 2800+ fps.

R.G. Robinett
07-22-2019, 08:57 AM
I didn't say gauges. The reading [with properly working gauges] should be the same at both valve stems is my point, otherwise your pressure measurement system is no good.

By your logic a .30 cal flat base bullet with an area of .07447 sq in at 50,000 psi working pressure would have 3723 psi against it. I don't see that getting a bullet of a barrel at 2800+ fps.

The two key issues are square inches (area) and calibration (the tire gauge): 50,000 PSI is just that - 50K pounds of force applied to each square inch: your muzzle pressure is pretty spot on.;) You are overlooking the rate of expansion = speed! :eek:RG

Wilbur
07-22-2019, 11:22 AM
I may have it wrong....thought it meant "pounds per square inch" rather than just "pounds". My earlier point concerning the tire gauge was that they are calibrated to report a pressure in PSI rather than what is experienced at the valve stem. Further, the tire pressure gauge sees the pressure at the gauge rather than the stem pressure...which may or may not be different....just like the primer sees a bit more pressure than the flash hole.

That said, it doesn't matter which of us is right or which of us is wrong....won't change things in the slightest. If your primer doesn't look good you need to try another primer or reduce the powder charge.

antelopedundee
07-22-2019, 03:51 PM
I may have it wrong....thought it meant "pounds per square inch" rather than just "pounds". My earlier point concerning the tire gauge was that they are calibrated to report a pressure in PSI rather than what is experienced at the valve stem. Further, the tire pressure gauge sees the pressure at the gauge rather than the stem pressure...which may or may not be different....just like the primer sees a bit more pressure than the flash hole.

That said, it doesn't matter which of us is right or which of us is wrong....won't change things in the slightest. If your primer doesn't look good you need to try another primer or reduce the powder charge.

I gathered/interpreted from your comment that you would say that 2 valve stems of differing diameter would give 2 different pressure readings for the pressure inside the tire.

As for this comment..............

"If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi."

While the corrected value was 152 since it is acting on a small area then the pressure available at the flash hole and then to the primer on the other side is in effect 50,000 psi when normalized to 1 sq in. A better answer IMO to the question preceding it would have been the equivalent of 50,000 psi as it is everywhere inside the case.

So in your opinion is primer hardness a useful indicator of whether or not a primer will give more consistent shot to shot velocity variation? It seems that ones that are GRAB Generally Recognized As Best are the ones that RG told me long ago are the softest.

Wilbur
07-23-2019, 08:48 AM
No, that's not what I'm saying at all...when the air exits the valve stem it enters the tire gauge which is a consistent area and calibrated to read psi....it's not seeing the actual psi but is calibrated to show us something really close.

Kevin Gullette
07-24-2019, 10:38 PM
.....I wrote on the small caliber board, a few years ago.

A little Jerry Stiller math.....

A 0.082" firing pin probably has an 0.084" boltface hole. The hole is 0.005412 square inches. At 50,000psi, this results in a total shearing force of 277.1 pounds.

Now use a 0.060" firing pin, with a 0.062" boltface hole. The hole is 0.003019 square inches. At 50,000psi, this gives a total shearing force of 151.0 pounds.

So.....for a 0.022" reduction in the boltface hole diameter, there is a 45.5 percent reduction in the shearing force.

As a reference, and a good read, refer to Precision Shooting magazine, May 2001, page 31, "The Real Reason Primers Pierce" by Jerry Stiller.

As would be expected, a stronger firing pin spring has little effect.........been there, tried that.

Why these things only seem to happen with small rifle primers AND small calibers????.....I do not know, or can prove........but I strongly suspect that as the sectional density is lowered, a more "focused" pressure spike through the flash hole is created.....and the firing pin is pushed rearward. BUT.......that's just me.

BTW.....my old 20BR had about the same situation as above. Quite an eye-opening experience. Greg Tannel reduced the firing pin diameter, and bushed the boltface to a smaller firing pin hole size. The result.........with 40gr bullets blanking at 3400fps.........to NO cratering whatsoever at 4150fps.

Hope this helps.

Kevin

antelopedundee
07-25-2019, 11:25 AM
.....I wrote on the small caliber board, a few years ago.

A little Jerry Stiller math.....

A 0.082" firing pin probably has an 0.084" boltface hole. The hole is 0.005412 square inches. At 50,000psi, this results in a total shearing force of 277.1 pounds.

Now use a 0.060" firing pin, with a 0.062" boltface hole. The hole is 0.003019 square inches. At 50,000psi, this gives a total shearing force of 151.0 pounds.

So.....for a 0.022" reduction in the boltface hole diameter, there is a 45.5 percent reduction in the shearing force.

As a reference, and a good read, refer to Precision Shooting magazine, May 2001, page 31, "The Real Reason Primers Pierce" by Jerry Stiller.

As would be expected, a stronger firing pin spring has little effect.........been there, tried that.

Why these things only seem to happen with small rifle primers AND small calibers????.....I do not know, or can prove........but I strongly suspect that as the sectional density is lowered, a more "focused" pressure spike through the flash hole is created.....and the firing pin is pushed rearward. BUT.......that's just me.

BTW.....my old 20BR had about the same situation as above. Quite an eye-opening experience. Greg Tannel reduced the firing pin diameter, and bushed the boltface to a smaller firing pin hole size. The result.........with 40gr bullets blanking at 3400fps.........to NO cratering whatsoever at 4150fps.

Hope this helps.

Kevin

I thought the advantage of a stronger firing pin spring was in reduced lock time resulting in the FP hitting the primer sooner as opposed to harder which means that the bullet should hit the target a scosch quicker. Wasn't fast lock time one of the extolled virtues of the Rem 788 action?