SD and ES problems: primer related?

[Thebelly]

I'm seeing SD of about 25 fps and ES that hovers around 45-50 fps.

I've had a couple folks double check my loading processes, and the consensus is that all is in correct order there.

Caliber is .260 Remington. Gun is LMT MWS with factory 20" SS barrel. Load is 123gr Scenar, 42gr H4350, SSA brass, and Remington 9 1/2 LRP.


Assuming all the rest is as close to equal as I can measure, how much can the primer affect velocity?

 

[mdmp5]

All things being equal, especially the powder charge, the primers can definitely be implicated for larger than desired ES. If you work the same load, trying different primers, you may see different ES with different primers, and it should be repeatable.

 

[RHunter]

All things being equal, especially the powder charge, the primers can definitely be implicated for larger than desired ES.

Not only that but seating depth will throw your numbers way off.

For example when I use VLD's, the closer I get to the lands the smaller my ES as SD's are and my accuracy improves. Everything else is the same. It has to do with pressure and how the powder burns. Some guys will see accuracy improve by crimping rounds, it is because you get a higher initial pressure and this effects the rate of which the powder is consumed and when. Seems to make it more consistent round to round and that consistency affects your accuracy.

I'd definitely try to find some Federal match primers and try some rounds with a nice taper crimp and some without.. and try some with a couple different seating depths, you will see what I am talking about.

 

[M40_A1]

Large sample sizes give more precise and consistent SDs too. (10-rounds minimum, IMO)

 

[Thebelly]

Large sample sizes give more precise and consistent SDs too. (10-rounds minimum, IMO)

my sample size is an average of 50 rounds. I'll try a couple different types of primers to see if that settles it down.

Can primer seating depth have a role in this as well?

 

[jkonzal]

I'm not sure about primer seating depth (they should be bottomed out) but bullet seating depth can make a big difference. Have you played with that?

 

[RHunter]

my sample size is an average of 50 rounds.

That is overkill.

Can primer seating depth have a role in this as well

Possibly. But so can burs on flash holes, flash holes not centered, flash holes too small... Everything can affect your ES, it is all about consistency and learning all the little tricks to bring those numbers down. For most guys it has been years worth of trial and error, experimentation, changing this and changing that to see what makes the numbers better and what makes them worse.

Everybody here is giving you just a few aspects of fixing the problem. You need to take these points and do your own experimentation to see what works for you and your gun.

$20,000 worth of reloading experience can not be summed up in a couple posts. Some of the guys that have been doing it for 30 years have literally spent that much money discovering what it takes to get their ES numbers in the very low single digits. Making good ammo is not only a science, it is also an art.

If your sample size is 50 rounds you are going to go broke before you figure out how to get where you want to be. I promise you that.

 

[Thebelly]

I'm not sure about primer seating depth (they should be bottomed out) but bullet seating depth can make a big difference. Have you played with that?

I have not played with bullet seating depth yet. This is for a semi-gun, so the method used for a bolt gun (where the constraints of mag-length are less of a concern) can't be used.

What are the normal increments to be used here? .003" increments? They are currently loaded to 2.805".

 

[Thebelly]

That is overkill.



Possibly. But so can burs on flash holes, flash holes not centered, flash holes too small... Everything can affect your ES, it is all about consistency and learning all the little tricks to bring those numbers down. For most guys it has been years worth of trial and error, experimentation, changing this and changing that to see what makes the numbers better and what makes them worse.

Everybody here is giving you just a few aspects of fixing the problem. You need to take these points and do your own experimentation to see what works for you and your gun.

$20,000 worth of reloading experience can not be summed up in a couple posts. Some of the guys that have been doing it for 30 years have literally spent that much money discovering what it takes to get their ES numbers in the very low single digits. Making good ammo is not only a science, it is also an art.

If your sample size is 50 rounds you are going to go broke before you figure out how to get where you want to be. I promise you that.

Yep, acknowledge all, especially about the consistency thing. The part that chaps me is that I'm trying really hard to get the definitive answer about the hard science, but I HAVE to acknowledge that there is an art to it. The hard science tells me that there should be a definitive solution, at least to about the 80%-85% level. It's the rest that I'm starting to chase....hence the ART of it all.

I just had 50 rounds loaded up. A guy at the range had a Magnetospeed that he let me use. I didn't even look at the display until I was done shooting.

 

[Aimsmall55]

Your going to get higher speeds over the chrono with fgm primers. Like 15 to 25 fps more. In my experience, slightly higher spreads too. The Br2 is most likely going to knock
The Es and sd down but I've had some issues with them in ftf incidents.
The 9 1/2 LR is good to go. I shot them for years and never had a single issue.
But YES PRIMERS EFFECT VELOCITY !!

 

[Thebelly]

Your going to get higher speeds over the chrono with fgm primers. Like 15 to 25 fps more. In my experience, slightly higher spreads too. The Br2 is most likely going to knock
The Es and sd down but I've had some issues with them in ftf incidents.
The 9 1/2 LR is good to go. I shot them for years and never had a single issue.
But YES PRIMERS EFFECT VELOCITY !!

Excellent info, thanks!

 

[ZiaHunter]

Been loading for 40 years and still searching for the Holy Grail of low ES &SD. I can consistently achieve sub 9 fps SD's but still working on lowering them. Frankly, I haven't seen much variation in SD and ES between different makes of primers and case uniformity is the key. Neck tension, seating depth and charge weight variance have been the biggest variables. Variations in neck wall thickness will affect neck tension as well as brass hardness. Neck turning and annealing can help address those issues. Uniforming the primer pockets as well as deburring the flash holes is also recommended. Depending how deeply the bullet is seated in the case will affect pressure which in turn will impact ES and SD. Uniform seating depth within the case is important and there are several ways to address it. If you really want to get anal sort by bearing surface of the bullet and base to ogive. As you can see its just a matter of how much time, money, trial and error you are willing to commit to achieve low numbers.

 

[Thebelly]

Been loading for 40 years and still searching for the Holy Grail of low ES &SD. I can consistently achieve sub 9 fps SD's but still working on lowering them. Frankly, I haven't seen much variation in SD and ES between different makes of primers and case uniformity is the key. Neck tension, seating depth and charge weight variance have been the biggest variables. Variations in neck wall thickness will affect neck tension as well as brass hardness. Neck turning and annealing can help address those issues. Uniforming the primer pockets as well as deburring the flash holes is also recommended. Depending how deeply the bullet is seated in the case will affect pressure which in turn will impact ES and SD. Uniform seating depth within the case is important and there are several ways to address it. If you really want to get anal sort by bearing surface of the bullet and base to ogive. As you can see its just a matter of how much time, money, trial and error you are willing to commit to achieve low numbers.

At this point, I think if I can calm the ES down to about 25 and the SD down to low teens or ~10, then I'll be comfortable. Right now, I'm just really struggling with the 'is it me or my ammo' ? Of which, I have absolutely no one else to blame because I loaded the ammo with my own two hands.

 

[RHunter]

^^^^^^^^^^^^^^^^^^ that pretty much sums it up right there.

 

[Thebelly]

It seems that the load for my gas gun isn't well like by my bolt gun.

I had to load to mag length (2.805") for the gas gun, which was pretty bad when shot through the bolt gun. The bullet was jumping 0.060" before it hit the lands. The ES was 41fps and the SD was 15.

I loaded up 10 bullets where they only jump 0.015". This allows for reliable functioning in the AICS magazine. Tomorrow will tell the tale with the new load. We'll see what the chrono says!!

 

[opeagle]

I'd try a different chrono. Not saying the first one wasn't right, but do you have a secondary test to confirm?

 

[Chanonry]

Been loading for 40 years and still searching for the Holy Grail of low ES &SD. I can consistently achieve sub 9 fps SD's but still working on lowering them. Frankly, I haven't seen much variation in SD and ES between different makes of primers and case uniformity is the key. Neck tension, seating depth and charge weight variance have been the biggest variables. Variations in neck wall thickness will affect neck tension as well as brass hardness. Neck turning and annealing can help address those issues. Uniforming the primer pockets as well as deburring the flash holes is also recommended. Depending how deeply the bullet is seated in the case will affect pressure which in turn will impact ES and SD. Uniform seating depth within the case is important and there are several ways to address it. If you really want to get anal sort by bearing surface of the bullet and base to ogive. As you can see its just a matter of how much time, money, trial and error you are willing to commit to achieve low numbers.

OK so there are some big learning points for me in this discussion. I can play with primer and seating depth easy enough. Neck tension consistency is less clear. I had never bothered to turn necks as I don't have a tight chamber but this thread would suggest that this may be worthwhile from a consitant tension viewpoint ? At the moment I body size the case and then neck size but this will still give tension variations??

I should expand the neck on a mandrel, turn all the cases to the same thickness and then go from there. Have I got that right??

Thanks for the input ...

 

[Thebelly]

I'd try a different chrono. Not saying the first one wasn't right, but do you have a secondary test to confirm?

Nope, just the one chrono.

The effects seen down range matches what the chrono says, though. As in, plug the data in to a ballistic solver, and I should see 'xx' mils of drop. In practice, yes it drops the right amount.

 

[opeagle]

What distances were you "truing" at to make this determination?

Just trying to think through your issue.

 

[Thebelly]

What distances were you "truing" at to make this determination?

Just trying to think through your issue.

Trued the curve at 750 yds and 1k yds with two spotters. So, me plus two were watching what the bullets were doing.

 

[Thebelly]

It seems that it was an issue of bullet seating depth, or more specifically I believe neck tension to be a part of it.

Using brass that is once-fired through this gun, the shoulder was bumped back 0.002" and we loaded to have a bullet jump of 0.015" into the lands. This produced the following:

Min: 2866
Max: 2881
Avg: 2874
SD: 6
ES: 15

Load was 142 SMK, 42.5 H4350, SSA brass (see above), Remington 9 1/2 LRP. See above for seating depth.

I'm happy with that.

 

[opeagle]

That's great in my book. Glad you figured it out, isn't reloading both enjoying and frustrating? I think so.

 

[Thebelly]

That's great in my book. Glad you figured it out, isn't reloading both enjoying and frustrating? I think so.

I'm still having this problem with my gas gun. Today's SD and ES were damn ridiculous!! SD of over 40 and an ES of 65. Ugh!!!

 

[deadnbrkn84]

Consistency! Neck tension plays a huge role!

 

[6brshooter]

I have reloaded for 20+ yrs, i can only relay my experience. I have found pocket uniforming, fh deburring, consistent nk tension, and proper powder charge all do more then primers for low es)sd. I have only used br2&br4 in that time frame with the exception of 1k rem 6 1/2 bought last year. Paying attention to the my listed items, i have never had much difficulty getting lo teens es and 3-7 sd. Keep in mind that an ar gas system adds one more kink to getting very consistent numbers

 

[deadnbrkn84]

See now I will go the other way... That picture was taken with my standard loads. I do none of the above, and I use standard winchester brass. I deburr the flash holes (on new brass), and I chamfer the necks when I load. That's about the extent of it. I use .002 neck tension and I use the carbide expander ball. Seems to be working out for me.

That all being said I've only been reloading for about 4 years so I don't have nearly the experience that the gentleman above me does. What I did learn I learned from bench rest shooters, because no one knows accuracy like they do.