primers
- Thread starter sako2
- Start date
Changing primers can make a difference but 99% of the time you don’t have to start from scratch. I used to load a couple of rounds reduced by 5% to check safety then back up to my standard load. I always found accuracy pretty close. Then again I don’t compete and if I’m around 3/4 moa or so I’m usually happy.
What was your mean velocity and what did your standard deviation and extreme spread of velocities look like? I'm trying to get a sense of what percentage of the velocity these were. German Salazar's experiment along the same lines in .30-06, IIRC, never had the primer cause more than about 30 fps difference. In 223 Rem, primer choice caused Charles Petty to see a 4.5% difference in muzzle velocity (150 fps) which corresponded to about 5% difference in powder charge with his powder and bullet choice. So I think the 5% back-down rule of thumb is pretty reasonable for primer change except, perhaps, in smaller capacity rounds where the primer gas makes a more significant difference in start pressure. I would be inclined to knock charge down a full 10% in a 7.62×39, for example.
This variation will go down as case volume goes up and will vary with the powder. Primers are not all that consistent (the Courtneys measured 11% pressure wave SD off of CCI 200's), so you want to limit their influence on the load insofar as you can.
Laurie Holland did extensive primer field testing a few years back and published the results in Target Shooter magazine
here is a link to part 1 of the large primer test
http://www.targetshooter.co.uk/?p=1471
and part 1 of the small rifle primer tests
http://www.targetshooter.co.uk/?p=2613
here is a link to part 1 of the large primer test
http://www.targetshooter.co.uk/?p=1471
and part 1 of the small rifle primer tests
http://www.targetshooter.co.uk/?p=2613
Those are similar to the older tests German Salazar had up on his site (though not for the small primer 308 case) when it was still up. The counter-intuitive grouping differences will be due to different barrel times resulting from different ignition enthusiasm (that's my new primer specification term).
I dunno Nick, the more I studied this stuff the more confused I was getting. Then about a year ago I went with the KISS theory. Minimal case prep and concentrated on consistency. I stopped overthinking and my group sizes kept shrinking. My opinion is get a good barrel and the right cartridge in a decent stock with a smooth trigger then put the right powder and bullet in it and practice a couple of times a week and the small groups will come
This reflects my philosophy. Obviously you must work up to an accurate load properly, and obviously you can’t be sloppy about case prep. Otherwise, it’s almost as simple as you describe. And I never found that changing primers lead to a significant difference in accuracy, nor any concerning pressure signs. Then again I load fairly conservatively and don’t push envelopes, and the majority of my rifle reloading is with large case volume and lower pressure milsurp rounds.
Or, you can do what Eric Cortina does, as shown in a link Hounddawg put up here, and just buy a solution to a lot of the variables. He does this by buying Lapua brass to eliminate case prep and Berger Bullets to eliminate pointing or sorting bullets. Assuming these products are made for your chambering, you can do the same. I note Cortina has a Forster Co-ax press in the background in his video. He probably has Forster or Redding Competition Seating Dies or another method of seating that tends to eliminate runout so he can stop fussing with that. I find I also tend to buy a solution once I've identified an issue the right tooling will solve. Then I move on to the next thing.
A hobbyist can spend decades working out how to make his cars gain a few miles an hour, or he can figure out how to afford a Koenigsegg Agera RS and not have to think about engine mechanics at all. There is a mechanical reason for every mechanical event, even when things don't appear to make sense. Some of us are driven to try to understand them, even when it doesn't help us shoot any better. And some of us just like the challenge of making a silk purse out of a sow's ear, I suppose. But some are bored to tears by that kind of effort and just want to go driving. Some are switch hitters who do one in the summer and the other in Winter. It really just reflects personal preference in what you consider to be a hobby.
A hobbyist can spend decades working out how to make his cars gain a few miles an hour, or he can figure out how to afford a Koenigsegg Agera RS and not have to think about engine mechanics at all. There is a mechanical reason for every mechanical event, even when things don't appear to make sense. Some of us are driven to try to understand them, even when it doesn't help us shoot any better. And some of us just like the challenge of making a silk purse out of a sow's ear, I suppose. But some are bored to tears by that kind of effort and just want to go driving. Some are switch hitters who do one in the summer and the other in Winter. It really just reflects personal preference in what you consider to be a hobby.
You just have to spend the time and money where it counts.Too many buy fancy BS and debate how many grains of powder can be balanced on the head of a needle just to impress the guy at the next bench.
Hot rodding your own ain't cheap either. One of my most accurate rifles original cost was $75, it came with a busted stock and a bent barrel from a forklift accident. By the time I fixed it with a $400 barrel, $150 trigger, and a $400 stock and I could have bought a off the shelf Tikka and saved money.
The real bargains are used benchrest guns. You can pick up a used 6BR or 30BR with several thousand rounds left in the barrel for 1/4 to 1/2 the price of a new custom build.
Hot rodding your own ain't cheap either. One of my most accurate rifles original cost was $75, it came with a busted stock and a bent barrel from a forklift accident. By the time I fixed it with a $400 barrel, $150 trigger, and a $400 stock and I could have bought a off the shelf Tikka and saved money.
The real bargains are used benchrest guns. You can pick up a used 6BR or 30BR with several thousand rounds left in the barrel for 1/4 to 1/2 the price of a new custom build.
jetinteriorguy
New member
Another way to eliminate unnecessary things, listen to Uncle Nick.
stagpanther
New member
Changing primers? I don't even know where to find them these days.
I just made an order for comblock 7.62 nato primers as they are the only I could find.
I just made an order for comblock 7.62 nato primers as they are the only I could find.You may be surprised at how well some of those work. Board member Slamfire said the Tula primers are his secret weapon in .30-06, getting some sub-ten fps SDs; lower than Federal Match gives him. (Note these KVB-7.62 primers are not the KVB primers that did poorly in the Michael and Amy Courtney experiment; those were non-toxic primers with DDNT instead of lead styphnate in the priming mix. I am hoping they will repeat that work when the Federal Catalyst primers become available to test.)
In the meanwhile, the only issue I found with the KVB's is the cups are crudely ground to length on something resembling a belt sander (from the marks on the cup lips). This leaves burrs and causes them to require some effort to seat. You'll want to swage or ream your primer pockets, as you can crush one on a tight pocket like the ones in IMI brass.
In the meanwhile, the only issue I found with the KVB's is the cups are crudely ground to length on something resembling a belt sander (from the marks on the cup lips). This leaves burrs and causes them to require some effort to seat. You'll want to swage or ream your primer pockets, as you can crush one on a tight pocket like the ones in IMI brass.