Went to the Tuesday morning open shoot at the NOSC club this morning. I had some testing to do to compare Rem 1 1/2 small pistol primer vs Rem 7 1/2 small rifle primer. The Rem 7 1/2 SR primer is an AR15/223/5.56 primer because of its' thicker metal cup. Since I have no firearm that would use the Rem 7 1/2 primer, that put me at a surplus on hand of about 5K of them. Tested 38sp in a M586 4" and a M36-1 3".I had 38sp target loads (many previously made/on hand) of 1 1/2 primer, 4.5grs-SR7625, and Speer 158gr lead semi-wadcutter. So I made up some identical loads except using the Rem 7 1/2 SR primer instead of the Rem 1 1/2 primer.
Targets were at 50ft/16-17yrds. Tested first the M586, One of the std followed by one with the 7 1/2 primer. There was no felt perceived difference and placement on target was same so no difference in velocity. Fired 5 more of the test rounds for an overall, no change in recoil or placement. Tested second was the M36, same results as with the M586. Recoil and placement equal to the standard load.
Also of concern was firing pin pressure to ignite the thicker cup, all were OK.
I can't speak for other brands so who knows if there would be a change.
But for me, a repetitive question on this forum in the reloading area is 'can SR primers be substituted for SP primers.
Next testing will be in 9mm, maybe next Tuesday.