Primers!

[Dougfirtree]

What's the biggest difference you've ever seen from switching primers? I've recently been playing with a load that I had originally done with CCI 200's, but did it with Winchester Large Rifles this time. According to my chrono, it's moving 100 fps faster than it used to. Everything else is the same. Unusual? What's been your experience?

 

[JLS]

I've seen significant reduction in group sizes.

 

[cahunter805]

That’s a lot of velocity gain. Usually I don’t see much change in velocity but like JLS group size changes.
Are you using the same lot of powder from your previous load?

 

[VikingsGuy]

The famous Houston Warehouse studies generated a ton of data that concluded no accuracy difference between primers. But I have read others anecdotal experiences suggested otherwise, YMMV.

 

[Dougfirtree]

That’s a lot of velocity gain. Usually I don’t see much change in velocity but like JLS group size changes.
Are you using the same lot of powder from your previous load?

No. I guess that could be it. Still seems like a big change.

 

[cahunter805]

Different lots of powder will definitely generate velocity changes like that. It’s part of the reason I buy 8lbs at a time.

 

[Brian in Montana]

I haven't done much in the way of real experimentation with different primers, but I have played around with it a bit enough to have seen a decent-grouping load become a very good grouping load and vice versa. Some primers burn a little hotter than others and I'm sure that effects the pressure spikes in a given load. Like everything, you just gotta try stuff.

I only load for 7mm-08, .308, and .270 win. I found this chart on line that indicates which primer burns coolest to hottest. I've started matching the slower burning powders I use to hotter primers; for example H4831SC with Winchester WLRs. But everything's kind of relative to something else. Its hard to imagine why you'd get that much of an MV increase with a switch of primers. Could be other things involved temperatures, maybe the distance your chronograph is set up from the rifle.

Anyway, here's the primer chart. I'm honestly a little reluctant to post it because I'm not sure how reliable it actually is.

 

[Bluejeep]

I play with primers everytime I develop a new load for a rifle. I have seen the smallest sd/es with CCI BR-2, and the highest with federal 205 (as far as large rifle primers go). In my personal testing, the federals had an increase of about 40 fps over the BR-2 and horrible sd/es.

I would say to see an increase of 100 fps with a primer change, something else also changed. Powder lot, ambient temperature, distance to Chrono, case mfg, bullet seating depth, bullet crimped/not crimped.

 

[mtmander]

I have had accuracy changes if I switched primers , I currently use Federal Premium Large Rifle for my .270 , .308