I can only regurgitate what I read Steve Garbe said about them, especially in smaller calibers like 32-40 and 38-55. He indicated they were more accurate than using Large Rifle primers.

One drawback is the head spacing. The LP primers will sink in further in the primer pocket and cause indention in the breech if it's soft enough. I don't know how hard it would have to be to eliminate that and perhaps most American manufacturers harden it enough so there's little chance of damage. Another possibility is to put maybe a small 3/8x3/8 inch piece of card stock like 90# under the shell holder and as you seat the primer it cuts through the card in effect being more flush with the top of the rim and eliminating a problem.

What is different? What match would that be?

tenx wrote on Sep 14^th, 2013 at 6:45pm:

Nice shooting. 
What cartridge and bullet?

As I understand it, standard pistol primers are a mite shorter, appear to carry a little less priming compound, and are made with either a softer or thinner metal cup than rifle primers. (I'm not exactly sure what makes the diff between a standard and a mag. primer)
  In theory in a low pressure rifle cartridge they will give a less explosive ignition that may ignite the main charge more reliably.
However there are a whole bunch of variables that may or may not make it work to your advantage.

Some powders simply seem to require a hotter or more powerful "spark" to get a consistent shot to shot burn/pressure rate. The relative case shape and volume and the charge volume may also make a difference.
   Some rifles may have mechanical issues that prevent pistol primers from working well---the firing pin strike may cause problems due to the shorter primer being deep or erratically seated in a deeper pocket.  In addition a older rifle may have a larger diameter firing pin either due to wear or perhaps for older black powder cartridge primers.  This can allow the "softer" pistol primers to flow back into the breechface firing pin hole, even with very moderate pressures. 
An old German/swiss martini built for a BN / BP cartridge equivalent of the 38-55 I am trying to resuscitate is currently at Johnson's so SteveD can re-do the blockface/firing pin.  Even with low BP pressure loads, primers would flow back enough to almost lock up the action.  I tried both rifle and pistol with the same load and pistol primers were significantly worse.
     Deep seated short pistol primers [i]may[/i] have room to "back out" and slam into the breech face and create wear and damage  (especially in older rifles with worn or unhardened block faces) --- IF pressure is high, and/or primer pockets are worn and enlarged by repeated use and scraping out.

If I am in error or am missing other relevant points I'd be happy to be corrected.

To answer the OP's question regarding 4227. I've used a lot of 4227 and I use pistol primers with it. both F150 and Wolf. I would shoot one of those against Rem 2 1/2 before I would commit to the 2 1/2's for matches, as I haven't tried them. 

That said, I've shot with many guys that use rifle primers with 4227 and they also did well. From what I've seen, 4227 seems to like most any primer.

Also, keep in mind that 4227 holds the ASSRA 100 yard group record shot with a 32/40.

Frank

  Other than size and height, it'd be interesting to know exactly what the diff is between pistol and rifle primers and their mag versions.,  cup hardness??  primer compound??  amount of compound??

Maybe I'm imagining things but I seem to recall an article or a post that showed pics of the flash from different kinds of primers against a graph board background.

Pretty sure i've seen the comparison of primmer Brisnance I think they call it on the Shiloh Forum.

Terry