NATO CCI 34 primers and load impact

[Uncle Duke]

I second the OCW method. For the loads I've used it, its made for loads that can deal with variations I may put into the batch. This is only for the guns I've really wanted to spend time on tweeking the accuracy. Much of my reloading, I'm just doing milsurp calibers for the fun of it.

I"m no wise old expert but going from 1.5" to 10" with just a primer change does not sound right though. If you have a good bullet, you should not vary that much unless there is something Really inconsistent about what you are doing or how you are shooting.

Scoped? something loose?

Also watching this thread with interest. Not at all discounting what OP notes here, as his target showed what it showed. But unless that chronograph shows data that's for some reason all over the map, and erratic to a point that would explain group size growth by a factor of 6 or 7? I also think there's likely something else going on here.

 

[Doco Overboard]

Maybe the primers are inconsistently seated. Priming cup and anvil pellet out of whack to non uniform primer pocket.

 

[Warpspasm]

I second the OCW method. For the loads I've used it, its made for loads that can deal with variations I may put into the batch. This is only for the guns I've really wanted to spend time on tweeking the accuracy. Much of my reloading, I'm just doing milsurp calibers for the fun of it.

I"m no wise old expert but going from 1.5" to 10" with just a primer change does not sound right though. If you have a good bullet, you should not vary that much unless there is something Really inconsistent about what you are doing or how you are shooting.

Scoped? something loose?

I agree. That's why I'm so confused. I was shooting irons and nothing seemed loose anywhere. I don't get it.

 

[Doco Overboard]

Flame column igniting inconsistently due to powder coating exposed to different temps/ duration. 10 inches is a lot though, makes me think mechanical problem.
Single load and then point muzzle straight up before leveling the rifle. See if there is an improvement.

 

[Magnumite]

Harder primer. Weak mainspring or something slowing down hammer fall might not have affected with the softer primer metal of the original load.

 

[Pinecone]

#34s are magnum primers.

There can be some very large changes in velocity from changing just primer brands, much less from standard to magnum primers.

I would work up the load again, following OCW and see what you end up with. I am betting an accurate load with less powder.

Another, less likely, possibility is a bad batch of primers. They may be very inconsistent. But working up the load will show this.

 

[BradMacc82]

I can say from first-hand experience that the #34's have been pretty reliable for me in .260 duty, although that's not to say you may have gotten an odd batch, it's possible I suppose.

120gr, 39.6gr Varget, #34, multiple brands of brass - it'll stack shots right on top of each other.
139gr FMJ, 43.3gr H4350, #34, mixed brass - same results, slightly different POA/POI.
142gr SMK, 43.3gr H4350, #34, mixed brass - tack driver, reliable/predictable as death and taxes.

 

[Biggfoot44]

You Really need to use your chrono, for ES and SD comparison between previous and new primers .

Magnumite's post #25 could be a real thing . Primers struck just barely hard enough to ignite can give inconsistent flames, in turn giving inconsistent ignition. ( Hence first suggestion, it will show up with significant velocity variations shot to shot .)

 

[Park ranger]

But 10 moa? .... Let someone else shoot the gun. If bet it goes away.

 

[Warpspasm]

But 10 moa? .... Let someone else shoot the gun. If bet it goes away.

LOL. 10 may me a bit of an exaggeration, but was about 5 or 6

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[Magnumite]

But 10 moa? .... Let someone else shoot the gun. If bet it goes away.

OP is a very capable shooter. His assessment is open minded. Let us know when find the gremlin, Warp.

 

[K-43]

OP is a very capable shooter. His assessment is open minded. Let us know when find the gremlin, Warp.

Yeah. When he has an accurate load, changes primers, then has an inaccurate load, it's not the shooter that changed.
You have to isolate what changed to figure out a solution.

 

[K31]

.

 

[BradMacc82]

LOL. 10 may me a bit of an exaggeration, but was about 5 or 6

That's still a pretty significant swing. Depending on the range to target, you'd be talking about a sizeable/massive deviation in velocity to get 5/6" of dispersion.

Personally, I haven't seen a shift that large just from switching to a diff't primer - even when going thru load developments, but I guess it couldn't be ruled out.

 

[Warpspasm]

That's still a pretty significant swing. Depending on the range to target, you'd be talking about a sizeable/massive deviation in velocity to get 5/6" of dispersion.

Personally, I haven't seen a shift that large just from switching to a diff't primer - even when going thru load developments, but I guess it couldn't be ruled out.

I may have figured it out. I measured the OAL using my comparator and the rounds were longer than my earlier loads and may have been touching the lands. I set them back and plan on hitting the range tomorrow.

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[BradMacc82]

Hopefully backing them off the lands gets it back into a reasonable pattern.

 

[Magnumite]

Staying tuned in...

 

[Warpspasm]

There is something else I just thought of, but don't THINK that would make a difference. My original, more accurate load, was done using Hornady 3039C bullets, but my less accurate load were done using Hornady 3039 bullets. As far as I know the same bullet without a cannelure. I thought I was buying the 3039C, but got the non-cannelure version instead. The shape of the bullet would be the same (I think) but I crimped these new bullets with a Lee factory crimp die and I did it with a heavier crimp to make up for the lack of cannelure in the bullet.

 

[Pinecone]

Yeah. When he has an accurate load, changes primers, then has an inaccurate load, it's not the shooter that changed.
You have to isolate what changed to figure out a solution.

Duh, maybe the PRIMERS?????

 

[Pinecone]

WOW.

Change in primers.

Change in COAL.

Change in bullet.

And you wonder why the load won't shoot?