My primer and neck tension testing, interesting results…

[ZA206]

Decided to test one of my best loads with neck tension and primers as the variables instead of powder charge or seating depth.

Cases were all the same year of LC, annealed, trimmed, flash hole deburred, resized, then neck tension set with my Sinclair expander & turning mandrels mandrels. The turning mandrel is .001” smaller in OD than the expander mandrel, so it gives more neck tension.

The primers are what I had on hand…. Wolf SRP (original load development done with this one), CCI 400, CCI 41 and my favorite REM 7.5.

Accuracy was definitely better with the turning mandrel, mainly eliminating flyers. I’ve also noticed the same with other load developments with other powders and bullets over time. Slightly higher velocities were also pretty consistent with the higher neck tension. As for the primers, other than CCI 41’s being hotter than the rest, not sure if there is a real pattern…

I may run this test again sometime with one of my good loads that use a stick powder vs. primers and do 10 rounds each and see if there is any difference.

 

[BuildingConceptsllc]

Decided to test one of my best loads with neck tension and primers as the variables instead of powder charge or seating depth.

Cases were all the same year of LC, annealed, trimmed, flash hole deburred, resized, then neck tension set with my Sinclair expander & turning mandrels mandrels. The turning mandrel is .001” smaller in OD than the expander mandrel, so it gives more neck tension.

The primers are what I had on hand…. Wolf SRP (original load development done with this one), CCI 400, CCI 41 and my favorite REM 7.5.

Accuracy was definitely better with the turning mandrel, mainly eliminating flyers. I’ve also noticed the same with other load developments with other powders and bullets over time. Slightly higher velocities were also pretty consistent with the higher neck tension. As for the primers, other than CCI 41’s being hotter than the rest, not sure if there is a real pattern…

I may run this test again sometime with one of my good loads that use a stick powder vs. primers and do 10 rounds each and see if there is any difference.

View attachment 8235125

I did one with 223 and win primer vs cci 400 and got absolutely zero difference in group or speed. Never tested wolf or rem against it but I did the same test with lrp in 6.5cm and got the same results. That ended my testing. That said, I only use cci primers and the same version for whatever the load was feveloped with. I would definitely switch if I ran out though

 

[secondofangle2]

what we've been learning the past few years is that tests like this show just random variation because sample size is too small.

I don't think you should draw any strong conclusions.

 

[supercorndogs]

Did you adjust your sights or was the POI lower for the mandrel group? AR-15?

 

[ZA206]

Yes, AR15.

I didn’t adjust anything. All were shot at the same POA

 

[ZA206]

I will say the bottom row were shot with some mirage, as I was short on time and needed to get off the range.

 

[Tokay444]

I’ve eliminated mandrels all together and never looked back. I have incremental bushing sizes, and that’s all I mess with now.
Checking runout with a Sinclair indicator has shown that my runout gauge was a waste of money.

 

[iceng]

I think this post was good. Keeping himself honest, while learning.

Ill add that 5 groups of 5 shots, would be MUCH stronger, statistically. Still, well done for wanting to learn.

 

[Hickswr]

A-for effort….but zero conclusions can be drawn from it.

Shoot five 5-shot groups with the exact same loads and post up the results.

 

[ZA206]

This simple test confirmed what I already knew about neck tension in my AR rifles, more is better.
I agree with the “not enough data points“ on the primer testing though, but this sort of testing is very low priority to me.

 

[Doom]

Interesting results. It would be more interesting to see what the mean radius would work out to on 5-5shot groups.