Primer Effects on Groups

[Grump]

I just re-tested one brand of primers and not only was the accuracy abysmal again (well, actually WORSE than before for a few groups), but the ES on velocity was like 71 and 91 fps.

That's what I get from ammo loaded on a progressive! Dillon measure (okay, it *was* 748 but that load still shot MOA at 200 yards with iron sights...).

So has anyone had such a dramatic difference as this? Charges are weighed, brass is full-prepped, and the established load with the different primers is more like no more than 34 ES on velocity, often mid-20s, and shoots 1.4 (worst) to .7 MOA, most at .8-9 MOA. BEST with the other primers was 1.75, and one was in the high 3.xs.

 

[ChrisGarrett]

Re: Primer Effects on Groups

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">I just re-tested one brand of primers and not only was the accuracy abysmal again (well, actually WORSE than before for a few groups), but the ES on velocity was like 71 and 91 fps.

That's what I get from ammo loaded on a progressive! Dillon measure (okay, it *was* 748 but that load still shot MOA at 200 yards with iron sights...).

So has anyone had such a dramatic difference as this? Charges are weighed, brass is full-prepped, and the established load with the different primers is more like no more than 34 ES on velocity, often mid-20s, and shoots 1.4 (worst) to .7 MOA, most at .8-9 MOA. BEST with the other primers was 1.75, and one was in the high 3.xs. </div></div>

It's not a lot to work with.

What was the charge weight with the 748 and what was your load density?

Generally, at least per Nosler's IV guide, cases that are more full tend to have lower SDs/ESs and shoot a tad more uniformly.

748 is also a ball powder and Speer, among other manuals, likes to use a magnum primer in all of their rifle data using ball powders, so maybe fiddle with the magnum primers and when using that powder?

Varying neck tension, as a function of uneven neck wall thicknesses can also increase ES and SD.

I load on a Dillon 550b, so I know it can throw +/- .2grs, but I've also polished up my main funnel housing and powder funnel to increase powder flow, but 748 meters like butter, so that shouldn't be an issue.

Make sure you work on your stroke, keeping the force, movement and timing the same, for each and every pull. On the down stroke, I'm now double tapping, just to make sure stuff leaves the measure and passes through the powder funnel and into the case.

At 100 yds, I've shot a 5 shot 338LM group with an ES of 200 fps and they all went in under the size of a quarter, so there's no rhyme or reason to that equation, at least at shorter ranges.

Chris

 

[Greg Langelius *]

Re: Primer Effects on Groups

Loading on a Dillon RL550b can be as accurate as most shooters can shoot to.

For any precision shooting work, I always weigh each charge.

I set up the Dillon measure to consistently over charge the case by at least .1gr (I know most of the charges would be slightly wrong anyway so ensuring they are all heavy simplifies the overall process).

I then dump the charge into the scale pan and immediately pinch out a fingerful. Trickling the fingerful back into the pan finds the exact correct weight. Excess powder is dropped into a small cup, the charge is returned to the case via a drop tube, then the case is returned to the press and advanced to the next station. With practice, it becomes natural and speedy.

Another cause for charge weight variance can be static elctrical charges imparted to the powder when the weather is dry. Bonding the press elctrically to an electrical ground can reduce this.

A loose baseplate can affect OAL and other dimensional criteria. So I adjust the plate's vertical play to a minimum degree, where it rotates with a very small amount of drag. If it drags, it's good; if it snags, it's too tight.

Do not be concerned about the vertical play in the toolhead. It never changes, so it's effectively the same as if it didn't exist in the first place.

Greg

 

[sandwarrior]

Re: Primer Effects on Groups

Grump,

Some truisms I've found. I'll rarely ever just dump powder for a load unless it's ball. Stick powder, no matter how good your powder dispenser is, simply does not uniformly stack itself in the powder dispenser. Ball powder does. Unfortunately, ball powder is very temp sensitive.

I find usually primers causing accuracy issues only when my load is a summer or winter load. Meaning, when working up a load in the summer, I do a ladder to see how the harmonics work with the barrel. If I sit in the middle of the 'sweet spot', come winter time and the difference in temperature, you go from a 'sweet spot' to a 'dead spot'. I'm assuming since you are in Utah where the altitude makes for pretty cool winters and hot summers you experience the same winter/summer phenomenon as I do. Typically we vary on an annual basis of 110-120 degrees.

By the same token as above, I work up Winter loads at the minimum of the 'sweet spot'. Come summer, I'm not taking a chance on popping primers.

That said, maybe you aren't getting enough pop with your primer? Which primer are you using? Winchesters and Remington tend to be hotter than CCI and Federal. Wolf small rifle (which is all I've used of them) is really consistent and hot. How a primer affects accuracy is simply putting the load above or below the harmonic equilibrium of the barrel. If the batch you have isn't shooting the same shot to shot in the same temperature, you may have a bad batch. Maybe your powder is going bad? How long has it been stored? What's it smell like?

To trouble shoot this, you need to check each component one at a time. Work up a ladder in the cold. Then test the best load in the cold. If that isn't working go to new primers and repeat. If that doesn't work go to new powder and repeat first with original primer then new primer. If those options don't work then you have a brass issue or a rifle issue.

 

[deadnbrkn84]

Re: Primer Effects on Groups

I'm like the rest of you, I polished my powder measure funnel and I load all mine on a 550b but unless it's bulk .40 or bulk .223 loads all my precision stuff gets individually weighed because the stick powders just dont meter that accurately. I'm purposefully have them drop at about .3gr low, throw it on the scale and use the trickler to bring it up to the correct weight.

 

[arnie19]

Re: Primer Effects on Groups

I have seen primers make a big difference in groups .I would never change primers and load alot of ammo till i tested that primer against a known good load . Arnie

 

[boudin]

Re: Primer Effects on Groups

When I changed from Federal 210 GMM to CCI 200 primers in my 85 gr SGK load, I experienced a reduction in average group size ranging from 1/8-1/4" less than groups shot using the Feds.

 

[Beef82]

Re: Primer Effects on Groups

For my go to loads, RL15 w CCI200 1.1" w WLR .6"; Varget w CCI200 .5" w WLR 1.0" @ 100yds. Huge difference? No, but measurable and repeatable results. Enough that I decided to buy a pack of every large rifle primer I could find as time and weather allows.

 

[Grump]

Re: Primer Effects on Groups

Thanks for the replies.

Some people would get an F for reading comprehension if this were a class. I was *comparing* the velocity spread with one un-named primer with what I used to get with a progressive-loaded charge of WW-748. (That one was 43.0 grains, LC unsorted brass, and CCI 200 primers sending 168-gr SMKs or Hornady's clones out at about 2560 or so...still a recommended mid-range load if temperature sensitivity is not a factor).

Here's what was in the post:
<span style="font-style: italic"><span style="font-weight: bold">Charges are weighed, brass is full-prepped, and the established load with the different primers is more like no more than 34 ES on velocity, often mid-20s, and shoots 1.4 (worst) to .7 MOA</span></span>

Those weighed charges were from a ChargeMaster, then confirmed on a balance beam scale to +/- 0.3 gr based on my calibrated eyes.

I switched away from the Winchester primers on load development after re-barreling because of accuracy effects. I wasn't sure then, but now I am. It just held true for both Varget and 4064 last week. CCI seems to be the game. Lingering doubts about the legends of Federal and slam-fires in semiautos keep me from trying them out.

BTW, CCI BR2s do no better in this rifle--but it's a .75 to 1.0 MOA barrel/rifle anyway, my loads and FGMM 175s.

One load last week shot like Lake City Ball. I really don't want to spend my A-Maxes for that level of performance.

 

[crewchef]

Re: Primer Effects on Groups

Changing primers is like changing any other component, it's going to change how the load shoots. Would you put the same primer, powder and bullet in a different case and expect it to shoot the same? There are several good articles written about primer testing that describe how just primer changes can have a big effect on MV and pressures. If you want to test other primers, tweak the load a little to adjust to the primer.

 

[Greg Langelius *]

Re: Primer Effects on Groups

I concur fully. A load with a different primer is a different load, pretty much by definition.

I sometimes use Federal and CCI match primers for my match loads, but I use the same brand standard primer during load development.

My final testing stage substitutes the same brand match primer (and no other load alteration), to see of there's any appreciable difference. Often there is none; not just a little, but <span style="font-style: italic">none</span>. Usually, that last stage is performed using the ammo for an actual match, which s where load performance undergoes its greatest stress and scrutiny.

Under those circumstances, does it pay to use the match primer, post testing? If I'm loading for a 'whole ballgame' match, it does. For me, using the match primer also provides confidence, above and beyond providing raw performance. Honestly, I don't think you can win unless you have full confidence in your loads.

Often, during the match, there come a point when things start to fall apart. I know that I have to pause and take stock of the situation. Beyond that, I know that if I simply press on, my match is really not going to go anywhere good from there on. When performance changes, there's always a reason. If I can have confidence in my load, that's a big part of the situation that I don't need to be obsessing over.

In hindsight, the issue nearly always relates to shooting cadence. I shoot too fast, and often tend to get antsy and just try to get it over with when it's backfiring; which means I compound the problem by speeding up even more.

Often there's too much heat already in the system to allow sufficient cooling to occur before time expires. There's two ways to proceed then.

One is to take the time to cool down anyway, assuming some cooling is better than none. This approach renders the better results at the time.

The other is to proceed as before, recognizing that the match is no longer a matter of competition, but a learning opportunity. One can use the opportunity to see what sorts of POI trends might be developing on a repeatable basis as the system continues to increase in temperature. Scores at the time go into the toilet, but may provide insight that could lead to an alternative approach to barrel heating. But honestly, it's not going anywhere useful for me so far.

Bottom line, start slow, stay slow, check the barrel temp by hand frequently and when it's significantly warm, slow down even more and avoid the problem in the first place. A hot barrel changes the game, and affects the load's suitibility.

Greg

 

[sandwarrior]

Re: Primer Effects on Groups

Grump,

Even though I got an "F" for reading comprehension...cause I can't read your mind.... I'll further dispense what little bit of information I know.

The load you first talk about is using 748. You made no mention of Varget or 4064 in your first post. A lot of how well a primer works with a load is load density. Light-medium density loads tend to fluctuate more. High density loads fluctuate less.

I have found this with many primers in most loads. If you can, fill the case as much as you can. Up to the point it is either full or lightly compressed. A heavily compressed load tends to run into the same issue. The way a load compresses can make it erratic. Not necessarily dangerous, just erratic.

So, with load density being optimal here is what I've found:

Winchester- reasonably hot primers typical for igniting double base powders. Pretty consistent. I love using this for RE- powders.

Remington- Same as Winchester for output, but not as consistent. Because of the optima case loading however, my .308 Norma is shooting .5 MOA with these. If I had the Feds that I was using that might tighten up even further. I have noticed with some marginal loads that I get primer rupture. I use these as the shop had nothing else when I was looking for Large rifle magnum primers.

CCI-generally cooler than Win/Rem but more consistent than either. Again however, much consistency is gained with optimal case load. Not, what ever powder you've got that you can make work. Varget is the optimal powder IMO for the .308. 748 is definitely NOT a good powder to use in the .308 If you want Winchester powder for that use 760. You may or may not want to try a work up with a magnum primer.

Federal- I've found them to be very consistent. However, as you noted and I know several others have had ruptured primers. I agree, they aren't the best to use in a semi-auto where there is a chance of a slam fire. I do, and will continue to use these as bolt action primers.

Wolf- Pretty hot, and pretty consistent. I use these in my 5.56 to duplicate Mk. 262 loads with RE-15.

Again, load consistency helps the primer work at it's best.

 

[Grump]

Re: Primer Effects on Groups

Yeah, the 4064 load is lightly compressed. 42.5 and I'm limited to mag length by choice.

QuickLoad says the old 748 load is at about 89% load density. High ES but it was always MOA out of the gas gun.

Yeah, I saw the article that compared the same basic 168-gr .308 load with different primers and bullets and cases. Since this type of stuff doesn't seem to be tested and reported much these days, here it is: 40.5 IMR-4895, 168 SMK or clone.
Lake City cases, W120 (WLR) primers, changing bullets, 24-inch commercial barrel:

SMK 2626 fps, 52,200 CUP
Speer M 2625 fps, 51,200 CUP
Hornady NM 2625, 51,200 CUP
Nosler SBM 2624, 52,100 CUP

So, all the 168 clones are within +/- 1 fps, and within 1,000 CUP total spread.

That barrel was said to give almost identical velocities as a 22-inch M1A barrel also available in the testing. But there was no word on whether that meant within 10 FPS or 30 fps or some other number.

Same load, SMKs only, swapping primers:

W120 2626, 52,200 CUP
F210M 2622, 51,000 CUP
R9-1/2 2571, 45,500 CUP
CCI 200 2581, 45,500 CUP
CCI 250 2579, 46,100 CUP

Wow, magnum primers were 2 fps slower but 600 CUP higher pressure. ". . .the magnum primers produced noticeably better uniformity in both velocity and pressure." Total spread 6,700 CUP in pressure, over 55 fps.

Same load, back to W120 primers, changing cases and using SMKs:

LC 2626, 52,200
FC* 2586, 44,700
WW 2580, 45,300
RP 2589, 46,400

*I have reason to believe that current production FC cases are almost identical in case capacity as military LC cases. At least the recent ones I have are. My really old FCs are much lighter, much higher water capacity. I don't mix those two batches.

At the time of this test, the SAAMI CUP standard for .308 was 52,000. The 200 CUP over-pressure of some loads was deemed immaterial by the ballistician, who plowed through more than 700 test rounds. It was not stated whether every round was also pressure-tested.

So, I'm not really in a panic over swapping primers. If the velocities were 2625 or more out of my 22-inch barrel, I would be.

I was just interested in the accuracy effects anyone has observed or heard reliable reports on. For me, it's all about quantifying things.