I have done primer tests before, and found very little difference in either velocity or accuracy between them.

A few days ago I got a Steyer CL II VARMINT in 22-250 Remington.

I put a LEUPOLF VX6 5-14X scope on it.

I had primed brass with RWS 5333 primers, and a few primed cases with Federal 210M

I thought I will shoot them with the same loads and see what happens.

I started off with VVN 130 and VVN 135.

Bullets are BRAWAND 52 gr match.

So far I have fired 10, 5 shot groups.

Out of these ten, 8 groups were better with the RWS 5333 primers.

This got me thinking if there is anything to to it, so I will continue and see what the results are.

I will post my results.

Shot a few more groups.

Out of fifteen, RWS was better in 12.

Average of 15 groups: RWS 0.6383, Federal 0.8802.

Smallest group, RWS 0.418, Federal 0.447

Largest group, RWS 0.992, Federal 1.630

Interesting trial, thankyou Saeed.
Thankfully the Federals seem quite acceptable still and I won't have to ditch mine
Might have to try some RWS though if I find some one day.

Several years ago I decided to test the magnum primer for ball powder mantra with some Winchester 760 and a 7X57. I was suprised to see that the same load with a magnum primer was considerably slower over the chrony than with a standard primer. If memory serves I believe it was about an 80 fs variation. Accuracy was good with both. I wondered if using the magnum primer had a similar effect as using a slightly faster powder.

I found some CCI BR2, and I will add these to my test.

A primer with less brisance will be more accurate in some loads over a much stronger primer.
This is because with a really strong primer the powder charge will be blown forward against the base of the bullet possibly dislodging the bullet from is seating and causing movement of the bullet before the powder has burned properly. This movement will increase the case volume by a slight amount effecting not only the volume of the case but the so called bullet jump into the origin of the rifling as the bullet is moving slightly forward by the force of the primer. Of course SD will be affected but it may be showing a "low" number however accuracy is also effected.
We studied this in interior ballistics and how it effected exterior ballistics when the bullet reached 200 yards.
There is much more going on but you are on the right course.
I learned of this abnormal movement back in the 70's while on active duty and how we had to remove this factor from our long range loads.
It will be interesting to read what you find on paper after your further test.

I have shot many hundreds of rounds with my .300 Win Mag from bench and for Elk and Deer and Bear. I found out early on the Fed-210M primer gave me three shots touching at 100 yards. When I loaded the Fed 215M primer reccomended by the books my groups went from the ragged hole three shot groups to 2 inchs. Just my experience with many years shooting. The above posts I read with great interest. Good Shooting.

Working up a true max load with std fed 210s primers, then went to a 215 and things got real hot, bolt stiff, cratered primer and edxtracter indention? Happened several times with different calibers..Not scientific but food for thought. loaded up one more load with 215 and another grain, nope I didnt shoot it,saw no reason too, pulled the bullet and powder and got a cup of coffee!!

Primers seem to exert a greater influence on the performance in smaller rounds than in larger rounds. For example, the .22 Hornet is infamous for reacting significantly to changes in primers, with small pistol primers often providing better consistency and accuracy than small rifle primers.

Many years ago I "inherited" a large quantity of RWS "Sinoxid" large rifle primers. Since I had so many I used them in everything from .22-250 to .264 magnum to .338 Magnum. Although not listed as "magnum" primers they provided consistent ignition with even the slowest ball powders in anything I used them in; and excellent accuracy in the smaller rounds. This batch was marked made in 1968 and while I have since run out of them I still have loaded ammunition primed with them which still shoots as well as it did on day one. Wish I had some more of them (especially at the zero price I paid for them.)

Saeed, Interesting. A month ago, shooting my 700 .223, I shot 2 strings with exactly the same load (52 Berger N133(Neil Jones 40.0)). The only difference being primers; new 205M and very old 7 1/2 SBR. The old benchrest primer loads shot approximately 4" low and 4" left of the previously shot 205Ms. Age? Go figure. Your thoughts?