I have brass with both SRP and LRP for my 6mm creedmoor so I loaded up some identical loads with 40.5gr IMR4350 and 105gr Barnes match burners, for the small primers I used CCI 450 SRMP and for the large primers I used Fed 210 then headed off to the range to test them. The SR brass was Lapua and the LR brass was Hornady.
The rifle is an insite arms build the scope is a bushnell elite tactical XRS - 4.5 - 30 x 50mm FFP Mil the gun complete weighs in at 19.2 lbs.
I shot 2 groups of 5 shots each with both, it's a small sample size I know but figured if there is a big difference it would show up.
CCI 450 - average velocity 3011 ES 34.7 SD 12.6 average of both groups .512"
FED 210 - average velocity 3011 ES 26.5 SD 10.15 average of both groups .521"
Strangely enough both were identical average velocity, the LRP had a better ES and SD but the groups were just a tad larger by .009" which could be the shooter
The best group was with the FED 210 @ .387 but also the worst group @ .655"
There is clearly no winner as both shot really well and stay around that magical .500" that I am looking for.
I have more loaded but really didn't have time to shoot any more groups as I was also doing some load development for my 6.5 PRC with 143gr ELDX and my 7 PRC with 175gr ELDX so I had a lot of shooting to do.
Anyway it's fun to play and I love burning gun powder.