Changing primer improved accuracy by 1.5MOA is that even possible?

[Troutslayer2]

I finally got a new lot of RL26 and I wanted to try WLRM primers in my 280AI. I wanted to change over to them because the barrel is short and I often hunt in the cold- sometimes extreme cold. So I first loaded up a ladder with the new batch all with the WLRM. Went to the range and fired them and when I got to 2905FPS I shot the next 1/2 grain up, light ejector marks, so I came home and pulled the higher charges.

I reloaded 4 with BR2 primers and 4 with WLRM, same charge, same seating depth. HUGE jump, which I have been reading has been successful for some people.

Went back to the range and shot all over the chrono. The crazy thing is my AVG MV was exactly the same over both strings at 2886. My SD and ES were a bit better with the WLRM, BUT my group size shrank from nearly 2MOA with the BR2 to just over .5MOA with the WLRM.

I'm like, whoa, is this even possible? I'm still kind of in disbelief and wondering if there is something wrong with my mount, or my action screw. How can group size shrink that much when MV stays the same, the only difference being primer?

 

[MagnumManiac]

Yes, I ALWAYS try several primers with the same load while working up a load.
9 times out of 10, one primer will be far more accurate than the rest.

Cheers.

 

[LongWalker]

I haven't seen that big a difference but as MagMan said it's always good to try different primers to find your best load. What bullet are you running?

 

[Troutslayer2]

I haven't seen that big a difference but as MagMan said it's always good to try different primers to find your best load. What bullet are you running?

ABLR 168 grain. So far, the farther I move them from the lands the better they shoot.

 

[L.Sherm]

Some people just refuse to believe what a primer change can do.

 

[Mikecr]

It's big enough that re-working a load per primer may be called for.

Muzzle velocity itself means less to actual tune because bullet accelerations are not linear, and less consistent than velocities.
Picture a narrow timing window at the muzzle. If the bullet releases well in the window it hits near POIx. Slightly out of window = POIr,y,z, etc.. It helps if the bullet spends a consistent amount of time through this window. Enough to path align with POIx.
If the bullet is playing catch up, over accelerating to/through this window, it will likely release less consistently. Even while it reached same MV.
QuickLoad makes this stuff easier to see.

Shorter barrels create less dispersion. You might want the shortest barrel that you can consistently manage tune with, and meeting all other needs with chosen bullet. But longer barrels are easier to tune, and that actual tune is far easier to see.
For a relatively large cartridge like 280AI, I would want a ~28" barrel. I would pick a powder that burns up inside that barrel. And with that I would know when things are right -vs- wrong.

 

[Varmint Hunter]

When loading between 60-80gr of powder, in any given cartridge, I have occasionally switched from LR primers to LRM primers (or visa versa) to see if there was an improvement in group size. In the instances that I have done so I have never seen any significant improvement or degradation in group size.

More experimenting may change this outcome but so far that has been my observation.

 

[Greyfox]

I haven't used Winchester primers for several years, but I recall that they were labeled for std "and" magnum use. Interestingly, they produced similar velocity and accuracy to the Fed210M's and BR2 in my 308's. Of late, I have found that my primer changes will generally effect ES/SD more so then group size. Given your velocities are comparable, I wouldn't not rule out the 1.5MOA improvement with the switch, but would be suspect that something else is going on. I have not seen changes that great due to a primer change that produced the same MV.

 

[BHP9]

I've had a great number of Winchester primers that didn't go off, so I will not buy them again.

I've had great luck with CCI's but prefer Federal 210M's. You could always use 215M, which are a magnum primer.

 

[Mikecr]

I don't believe there is such an available thing as a 'better primer'.
And the notions I grew up with about compatibility with powder, rarely applies today.
When one isn't working, we haven't developed a load with it, and/or it isn't being seated to a sound standard, and/or the striking of it is less than optimum -for that primer.

 

[wonderman4]

It is all in the way the primers are seated and of course barrel timing.

 

[Philward]

I worked up a load for a friend's 7RM browning hells canyon long range, ladder testing and 2 different bullets and they ALL shot within about a 1.5" group. So I loaded a total of 27 rounds with the 168 nos ablr, 3 different primers (rem 9.5m, win lrm, and cci250) , and 3 different bullet seating depths. Total of 9 groups of 3 shots. All grouped the same but poi shifted slightly for some of them. I think Remington primers were about 1" higher than the others. The rifle may have big influence on which primers work better. This one apparently seems to shoot anything quite well. I may need to get one of them.

Edit:After looking back at the Target again I see that so loads and primers hit same poi. Must of been thinking of something else.

 

[del2les]

From decades of experimenting with BR and very precise varmint loads, I have seen simple primer changes reduce groups by half. BUT sometimes do nothing. Like so many things we try to improve groups, SD, ES, etc, it is only one factor in the tool box.

For larger capacity cases with slow propellants, a magnum primer "may" give more uniform ignition and improve the cartridges overall performance, or it may not. Again in the quest for "better", it is just a variable that one has to try.

 

[wv270wsm]

Yep sure can and will at times . You may even try a different powder that shot good before the switch just to see that just the primer switch caused it to spread out