Primer consistancy

[Sludge]

A couple of questions about primer consistancy...

1 - Has anyone studied variability of groups of primers as they affect the MV, ES and SD of chronograph results? If so, what primers indicated the greatest variability? Do the chronograph results also have a correlation to weight changes measured prior to firing of the primers?

2 - Has anyone ever studied the affect of different primers on the MV of identical loads shot from the same rifle? (to include different manufacturer and different lot number from the same manufacturer) In other words which primers were hot (fast) or cold?

I know im probably getting caught up in minutia, but im curious about this none the less.

 

[royinidaho]

Go here for a start: http://www.longrangehunting.com/forums/f28/do-primers-effect-accuracy-27511/

 

[Sludge]

lookin for numbers... Overbore mentions a table with ES's but he didnt link to it or anything.

 

[Sludge]

NM, I found it. His reference partially answers my questions. Tks Roy for pointing me and tks Overbore for finding that reference material.

Primer Testing Reference

 

[overbore]

Primers

Sludge, my pleasure to help--now having said that, there are new variables in our hobby: supply. From my inquiries, Wolf primers are in supply as are CCI BUT the rest are not to be had in quantity. Wolf ranks as the most consistent but has some seating issues whereas I have used CCI ( both BR and Large Rifle ) for over 25 years with no failures at all temperatures. ZERO. Cordially, Overbore

 

[Sludge]

Yea the primers are in short supply it seems. I have plenty of the CCI bench rest and winchester. Federal GM primers are really hard to get. I have almost no Small Rifle left in that, and im real low in GM215s. However, I got lucky the other day and a shop near me got in a shipment. I got 3k of those to add to the 500 or so I had left. w00t!! I got lucky He said that the suppliers were telling him that he wouldnt get any more GM Feds this year.

The wolf primers you mentioned, I have never used those...

 

[Natty Bumpo]

In Handloader No. 236 (Aug-Sept 2005) John Barsness authored an article titled Velocity and Pressure. In it he provides a table giving average muzzle velocity and average pressure for a 7mm Rem Mag using a 160 gr Sierra Boat tail, 66.0 grains of H4831 and Winchester brass. They tried different primers for the above load. Results were:

Winchester WLRM 3,045ft/sec 67,600PSI
Winchester WLR 3,024 64,400
Federal 215 3,036 61,400
CCI 250 3,039 61,500
Remington 9.5M 3,041 59,300
CCI 200 3,011 54,800

There's not much change in velocity, but changing from a CCI200 primer to a WLRM resulted in a 23% jump in pressure. I'm no engineer or internal ballistics expert, but since velocity didn't change appreciably, I can only figure these must have been peak pressure values. I suppose velocity must be more strongly correlated with the total pressure curve rather than peak pressure (I'm speculating on matters I have absolutely no education or training in).

 

[Sludge]

Mr. Barsness didnt happen to pass along any SD info on the muzzle velocities between the different primers did he? Or what, if any, the corrilation between primer weights and the SD were?

So far as speculation goes... Im right there with ya Natty. However, thats how we get educated I guess. We formulate a hypothesis then we (or someone else if we can con them into it) test the hypothesis.

 

[Natty Bumpo]

Mr. Barsness didnt happen to pass along any SD info on the muzzle velocities between the different primers did he? Or what, if any, the corrilation between primer weights and the SD were?

No, he didn't provide any standard deviations. The table in the article I took the values from was described as a condensed version of the A-square primer experiment. Maybe the folks at A-square could provide more details.

 

[overbore]

Sludge and Natty

If you will look up my primer post, you should have the SD numbers. Overbore