Change of primer affecting accuracy?

[Flyfishnm]

First off, this is my first post so thanks to everyone for all the great knowledge I have gained lurking around this site.

I am fairly new to reloading and have been working on load developement for my grendel. Specifically using 108 grain scenar pills, imr 8208 sbr, and/or ramshot tac.

Took the grendel out and tested the new loads and ended up narrowing it down to 29.4 grains of Ramshot Tac. This gave me a 1/2" group at two hundred yards! We'll this got me excited, so I went home and loaded a bunch of these thinking I had finally solved this equation.

Took a bunch of these to shoot the next day with a chrono and am now getting 1 1/2 to two inch groups.
In the original test loads I was using cci br4 primers. The new loads I used cci 450 magnum small rifle primers.

Question is, will the change in primers affect accuracy that much?

I guess the 1/2" at 200 yards could've been a fluke as I am definitely not a 1/4 moa shooter.

Also, I was getting a wide variation in fps. From 2590-2703. Could be the scale I'm using though, it is a bit touchy

 

[BigDMT]

Primers most definitely will effect accuracy that much and even more in some instances. Primer type and consistency is a critical part of the accuracy recipe. Switching primers on a load can effect the results as much as switching bullets or powder type.

Pull all your rounds apart and reload with BR4s as they should have been and your good groups will come back.

 

[Flyfishnm]

Will do. I figured there would be some effect, I just did not realize how significant.

 

[Flyfishnm]

Also, what is the best/safest way to remove non fired primers?

 

[SS427]

Sounds like you learned a valuable lesson about changing one component in a developed load. It can change the accuracy of the load.

Before I took those loads all apart, I would consider a few things. Are you using wind flags? If not you are chasing your tail, and I would never conclude the primer made that much difference in the load until I ruled out wind as a factor. Any big environmental changes such as temp or humidity? Those too can be a big factor. How many 1/2 groups did you base your opinion on that your load was a 1/2 inch load? Even a monkey pulling the trigger can get lucky once with a load that typically shoots two inch group.

1/2 inch at 200 yards is pretty decent if you can do it consistently. Sounds like a good start.

 

[Flyfishnm]

It was just one group with that particular charge. I tested eight other charges moving up in .3 increments.
The wind was not a huge factor.

Changing the primer like that was definitely a noob move. Especially getting towards the upper end of max charge. Didn't find any excessive pressure signs though. Live and learn.

 

[Steve Blair]

Even changing lots of the same primer can affect the tune. Some primers, like Russian SRM and CCI 450, have similar characteristics, but are far from interchangeable.

 

[Flyfishnm]

I'll give it another shot with the br4 primers next weekend. I'll let you guys know the results.

As far as the varying fps goes, I know it's not normal to have more than 100 fps variation from one cartridge to the next. They were shot right after one another so it's not like they were sitting in the heat for an extended period.

Only other thing I can think of is my electronic scale is a p.o.s. I am very careful when I measure and follow the manufacturers directions. Maybe I got lucky on the first test group and actually had the precise charge weight I was looking for.
I have a hornady gs-1500. Maybe it's time to upgrade.

Or maybe it's the chrony. Are these accurate/dependable?

Wow, so many variables to consider for a new guy.

 

[Erik Cortina]

Accuracy is about consistency, do not change a thing once you find a load that shoots great. Now you will understand why shooters post an ad wanting to buy bullets with a specific lot #.

I would blame it on the chronograph before I blamed it on the scale.
What kind of chronograph do you have?

 

[Flyfishnm]

It's a chrony f1. I really hope it's the chronograph. If it's not and I'm not getting accurate charge weights then all the time and effort of the last month or so is null and void. :'(

 

[spclark]

Changing to a magnum primer certainly might cause an otherwise good load to perform erratically. If you can trust your scale (brand? model?) try again with BR4's before you change anything else.

I shot 6.5 Grendel for 3 or 4 seasons & given the (relatively) small case capacity you don't need a true magnum primer.

 

[artbosco]

Also, what is the best/safest way to remove non fired primers?

Push them out v-e-r-y s-l-o-w-l-y with a decapping or F/L die.

 

[Patch700]

It's a chrony f1. I really hope it's the chronograph. If it's not and I'm not getting accurate charge weights then all the time and effort of the last month or so is null and void. :'(

What distance are you placing the chrony from the muzzle?... I know they recommend 10' but my experience with the chrony's is unless you're using a big boomer or something with copious amounts of muzzle blast they are just too finicky at the 10' mark. Even when I'm running 6.5x284 stuff over one I'm able to get it as close as 18" or better without getting errors (30-31" barrel)..

 

[jsthntn247]

Even changing lots of the same primer can affect the tune. Some primers, like Russian SRM and CCI 450, have similar characteristics, but are far from interchangeable.

Just ran out of the silver wolf large rifle primers and had to go to the newer wolf large rifle primers with a gold cup. There is definitely a difference.

 

[Flyfishnm]

Ok, so I got out today with the br4 primers and the groups tightened up quite a bit. Better, but Still not 1/2" at 200 yards so I will probably chalk up the 1/4 moa group at 200 to a fluke.

Also loaded up some more of the same charge with the cci 450 primers and am getting consistently 100 more fps with these primers and no pressure signs. Right around 2700 fps with 97.4 grains of Ramshot Tac and 108 scenar, which makes sense looking at Alexander Arms load data for the Grendel. They've got the 108 scenar at 2760 fps with 29.7 Ramshot Tac and CCI 450 primers.

Also, took the advice of members here to set up the chrony and it seemed to work pretty good.

I tried 2 five shot groups at 200 yards with the 2700 fps loads. They lined up almost in a straight line vertically, within a two inch span. Is this a tight enough vertical dispersion to try to tweak by adding 0.1 grain or so and adjusting seating depth? Or should I try for tighter groups before I try adjusting seating depth?

Thanks for all the replies so far, they have been a great help.

 

[Flyfishnm]

That's 27.4 grains not 97.4!

 

[Flyfishnm]

Fail. Stupid thumbs.. 29.4 grains

 

[AckleymanII]

Primers can make a difference, big difference at times. We load right at the rifle range, can see immediate results.

When getting down to shaving off .040 off the group, I have seen changes from going to a 7 1/2 to a CCI BR-4 and vise a versa. Again, Winchester and CCI 450's will have different ignition characteristics.