For some time, I've heard different opinions regarding which primer is the most accurate to use with 45-70 BP loads.  So, I decided to "double-blind test" two primers, with the same load in each.  I say "double-blind," because I had no idea which primer was used in the rounds I fired until after I fired them.  The loads consisted of 62 gr. GOEX FFg, compressed 1/8 inch, in a Winchester case, without cannelure.  The bullet was a 512 gr. Lyman 457125 bullet at a 30:1 ratio, sized to .459", and made by Chey Cast bullets.  The primers were CCI Large Pistol, and Winchester WLRM-Winchester Large Rifle Magnum.  I fired test rounds through 3 different rifles, and swabbed the bore with a damp patch between each shot.  Each shot alternated between rounds containing one primer, and then rounds containing the other primer.  The three rifles were:  1)  Model 1888 Springfield Trapdoor; 2)  Peabody 45-70 (Connecticut), and a Rolling Block receiver attached to a new 8-groove barrel.  Results:  For each rifle, the results were the same:  the Winchester Large Rifle Magnum primers delivered tight groups, as opposed to the CCI Large Pistol primers, where the shots were all over the target.  Upon cleaning the cases, I noticed that there was a lot of burnt/un-burnt powder left in the Large Pistol primed cases, as opposed to the Magnum primed cases, that had little or no residue.  However, I also noticed that the WLRM cases had cratered primers, and that the Large Pistol primed cases' primers were un-cratered.  So, there it is.  I am convinced that Large Rifle Magnum primers are the way to go if accuracy is the end result.  Comments?

Hi Lead,

i also had tested some sorts of Primers with and without over "Flashole Wad" and my conclusion is that Pistol primers are good as Rifle primers.
The residue in the Brass depends on Brand of Black i use  for or the kind of compressing the powdercharge.
Finaly i remain on Pistol Magnum Primers or Pistol Primers and 63 grs of FFFG Sporting Powder 

My Rifle Pedersoli Rolling Block 45-70
Lyman 457125 Bullet
Emmerts Lube

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i`ve been able to shoot 40 shoots without cleaning 
but blowtubing after each shoot and have no lack of accuracy

regards
Klaus

Lead, would seem that you have found a good primer for your Goex powder. Next i would try different primers with Swiss 1 1/2 or 3f and no or very little compression. Hammer strike makes a big difference just ask a sharps owner.