Gents and Madams,
Maybe this subject can/will generate some interest?
The never ending search for that "cure all" primer flame with results that are measureable at the target is still ongoing.
Some lament that the Federal 415 primer is the single only primer to use for everything. Others swear by or at the Winchester WLR.
Another faction insist on using Large Pistol primers instead of Large Rifle Primers. Remington's seem to get the nod. All are .210 in diameter.
The difference between large rifle and large pistol primers is in their respective cup heights/lengths and also their metal thickness. The cup height of Large Rifle primers is .115/.123, whereas the cup height for large Pistol primers is .110/.115. Priming compounds and anvil protrusion add to the total depth/thickness. Another consideration is the material thickness of the respective primer cups. Metal strips from which primer cups are punched vary between .0265/.0270 thickness for Large Rifle Primers. Large Pistol primer cups are punched from metal strips varying in thickness from .0205/.0210. Resultant possibilities of Large Pistol Primers being seated lower into the primer pocket are well documented. Few if any speak of the thinner (weaker) cup material.
Recommended primer seating calls for, from .001 to .004 beneath flush. Assuming that everyone uniforms primer pocket depths. Obviously utilizing Large Pistol primers will then cause about a .005 +/- beneath flush condition. As we all know the primer, upon ignition, will then take a run at the breech block and cause damage, sooner or later. Punctured primers aren't heard of too much in Black Powder loads, but the use of thinner material Large Pistol primer cups can surely set up the possibilty.
Another avenue in the "Quest for Fire" and a lesser amount of primer compound to ignite the powder column is readily available! The use of Small Rifle Primers instead of Large Rifle/Pistol Primers.
Small Rifle Primer Cup metal thickness falls into two categories; Commercial and Military. Commercial is .0205/.0210 thick and Military is .0240/.0245 thick. Primer Cup height for Small Rifle is .100/.115 versus .115/.123 for Large Rifle. The "seating too deep" bugaboo again raises it's head, but the smaller amount of priming compound should help to alleviate the rearward thrust of the cup against the breech block.
How does one use Small Rifle Primers in a cartridge case designed to utilize Large Rifle Primers? Adapters/bushings, of course. My supply of steel adapters measure .212 OD, .173 ID and .128 deep/thick. They were obtained from: Tincup Sports, P.O. Box 110, 5160 S.H. 34, Freedom, Wyoming 83120. Cost was $17.00 per hundred. The concept was first utilized in .454 Casull Handgun cartridge cases.
My future project is to test fire ten, new, R-P .45-70 cases so equipped with Small Rifle Primers. Loads utilized will be those already existing and identical with the exception of Primer Size. The Primer of choice will be Remington 7 1/2. Which is a tough/thicker yet primer cup designed for the .17 Remington. Hopefully my chronograph will reveal some new information and group sizes will diminish?
If anyone else has experimented with this exercise, your comments will be greatly appreciated.
Lastly, much of the primer information was appropriated (stolen) from"Ammunition Making", by George E. Frost, A publication fo the NRA. Copyright 1990, ISBN 0-935998-57-8. This book has more meat in it then most anything else in my meager library of "gun stuff".
