Do Primers Affect Group Size?

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John Alexander posted this 29 October 2022

I'm sure that primers make a difference when inappropiate primers are used such when regular primers are used when mag primers are needed to ignite heavily coated slow burning powder.

My question is do different brand primers affect group size when used with fast or medium burning rate powders and at the velocities of normal cast bullet velocities.

I have always been agnostic (promiscuous may be a better word) about primer selection using whatever was handy. It seemed to me that if they went bang they were all the same. I once tried the Federal 205M primers used by 99.9% of jb bench resters but couldn't see any improvement. I recently used some of these in a load and rifle that I have good records on.  Nine 5-shot groups with 205M averaged substantially worse than usual with this load.  I am skeptical but will try to repeat and see what happens.

Anecdotal evidence abounds about one primer or another causing either better or worse groups, but have there been any serious tests that have found repeatable differences in accuracy with different primer brands?

John

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John Alexander posted this 02 December 2022

I think John Carlson's  last post sums it up nicely.  It will take a lot of testing to get answers that generally apply.

It seems from the experiences reported in the posts above there lots of situations where all primers don't produce the same result. How rare, or how frequent, these cases are will take more testing -- that probably won't ever get done.

The posters to this thread have given us a lot to think about and may inspire more testing.

Thanks to all who contributed.

John

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John Carlson posted this 23 November 2022

A "serious" or valid test needs to evaluate only one variable.  In the case I described I actually made 5 tests.  Each test compared a five shot group using the Federal primer with a five shot group using the CCI primer.  The loads were identical in every other respect. 

To be valid I will need to be able to repeat this test achieving the same results'

HOWEVER

No matter how many times I repeat this test it can only prove that there is or is not a difference in accuracy using this cartridge in this rifle using these two primers. 

A definitive answer to John's original question will require a bunch of tests using different loads in different rifles comparing a different pair of primers (if you can find them).

John Carlson. CBA Director of Military Competition.

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John Alexander posted this 22 November 2022

Not familiar with the term, but think I may be the OP so will try to answer.

Off the top of my head it seems to me that a serious test that advances what we know requires at least two features.

One is to be planned ahead of time and designed to answer a specific question about a limited number of variables.

After the shooter thinks he has found the answer to the specific question asked, enough additional groups are fired to confirm that the answer is real and not just an artifact of the group to group variation that most of us badly under estimate.  

A couple of years ago I wrote a Fouling Shot article on my thoughts on running a good experiment.  I am away from home for Thanksgiving so can't say what issue it was in.  Will look it up when I get home if anybody wants to take a look.

I would be interested in what others think is required to qualify as a serious (probably valid) test.

John

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Shopdog posted this 22 November 2022

I'm curious,what's the OP's criteria for a "serious test"?

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John Carlson posted this 22 November 2022

Finally got some weather conducive to something other than practicing reading the wind.  I've been considering the use of Large Pistol primers and had a batch loaded up.  Rifle is the Howa 1500 in 7.62x39.  Ive never been able to consistently squeeze anything better than ok from this rig and wasn't surprised today.

The load was the Lee 312155 bullet over 14.8 gn of Buffalo Rifle. 25 rounds with Federal 215 primers and 25 rounds with CCI 350 Large Pistol Magnum primers fired in alternating five shot groups.  Results as follows.

                                             Fed                  CCI

Average group size               1.877               1.851

Average velocity                     1508               1484

Max velocity spread               50                     70

Standard deviation                  20                     26

While the chrono data may hint at a difference there doesn't seem to be an advantage.  I do happen to have another 50 cases primed so I'll just have to decide what to match them up with and wait for another nice day.

 

John Carlson. CBA Director of Military Competition.

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Wm Cook posted this 14 November 2022

Lucky 1 said: “ I just try to be optimistic on double strike primers and refer to it as "dry fire practice ".

Thanks. Laughed my butt off. It’s happened to all of us and we all have that same dumb look on our face when it goes click instead of “bang”. Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

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Ross Smith posted this 12 November 2022

double strikes might be ok for plinking but not for hunting or self defense. Also the double strikes occurred with 2 different rifles not just one.

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Lucky1 posted this 12 November 2022

I just try to be optimistic on double strike primers and refer to it as "dry fire practice ". Maybe that's from too many years of muzzle loaders.

Scott Ingle

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Ross Smith posted this 12 November 2022

Some primers made in a central european country that are on the market here required two strikes of the firing pin to go off today. Yes that will affect the group.

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Bud Hyett posted this 10 November 2022

There is a huge amount of thought and data here. In my summation, there is a difference when changing primers. My final thought is expressed above, choose a primer and stick with it. My selection criteria is based on case shape and primer availability. The powders are in a narrow burning rate band. These powders work well.

Perhaps I do not have Military rifles that are accurate enough to select primers. They shoot Federal and Winchester the same. After much work, the primer and powder charge is interchangeable between the two rifles. The bullets are different for nose diameter and seating depth.  

My Plain Base CPA Steven 44 1/2 rifles are much more accurate and will select primers. I'm still working a load for each rifle, but limited by primer availability. (I have a good stock of Remington 7 1/2 primers that are also needed for prairie dog shooting.) 

I need to determine the charge for each rifle, they like the same powder. I research the load data within each Fouling Shot with the addition of my own testing and records. By the way, this powder is AA 4100 or Ramshot Enforcer that are rumored to be the same powder.

In aerospace there is a saying, "There comes a time when you shoot the engineers and begin production." 

Farm boy from Illinois, living in the magical Pacific Northwest

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Wm Cook posted this 10 November 2022

John asked “ will different brand primers affect group size when used with fast or medium burning rate powders and at the velocities of normal cast bullet velocities.”

That seems clear enough. If I had a competitive load worked up with Rem 7 1/2 primers and was using a powder that ran somewhere between Unique and let’s say 4198 I could answer his question if I compared ten shot groups one each of Rem, Win, Fed, CCI. Which I haven’t done. I’m guilty of ignoring primers as a variable.

I’m set up that I could do it but the next couple range trips are promised to compare accuracy with the variable being bullet weight deviation. And I still got three more weeks of R&R with this new knee before I can even do that.

Maybe I’m wrong but I think what John’s asking is a simple pass fail test. Do different primers effect group size at nominal cast bullet velocities. Take care, Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

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lotech posted this 09 November 2022

John-

You  mentioned in your original post about different primers used with fast and medium burn rate powders at normal cast bullet velocities.To begin such testing and do it right where the results provided truly useful information, you'd probably have to narrow your parameters even more, say pick one appropriate fast powder per series of tests. Using every suitable primer (I don't know how many that is offhand), it would still be necessary to do some fine tuning of powder charges with each primer, then shoot as many five-shot groups as it would take to satisfy either normal curiosity or obsessive fanaticism, whichever one your tendencies lean toward. 

This would be an incredibly huge task and one that's probably never been done. As Dave Scovill, the former long-time editor of HANDLOADER and RIFLE magazines put it one time when describing a compex and time consuming handloading project that might eventually develop into an article: "It's  like chewing a piece of gristle that gets bigger as you chew it." And it doesn't taste good either. For those who aren't familiar with Scovill's work, he did some pretty detailed cast bullet handloading projects, but that was many years ago. 

Many of us have tried the lazy way to find the best primer but often fool ourselves with the simplicity. We develop a very accurate load with one primer, then switch primers only and don't touch the load itself. The informatiom obtained is of dubious value at best. Working up a load with each primer is of real usefulness, but that's a lot more work. 

 

 

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Ken Campbell Iowa posted this 09 November 2022

Ricin sez " Breach sitting is a different animal than shooting from a case.  "

but isn't breech seating just a better fit ... ? 

rule ( lonely rule ) 1 ... fit 

*************

i guess there a couple " suggestions " also ... twist and reasonably clean burn of powder ...

ken

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4060may posted this 09 November 2022

I noticed there was no mention of Wolf, or Fiocchi, I have shot a lot of Black Powder Cartridge, Both Silhouette and paper

Wolf primers in my rifle 40-60 Maynard RB, 38-50 Rem Hepburn, 40-72 CPA, 38-50 Rem CPA, all of these give me vertical stringing with Wolf Large Pistol primers, the current wisdom at the time and I guess still is Pistol primers and BP work better, I went to Fiocchi Large Pistol primers, the SD was OK, but the group was round and tighter than Wolf, I also used Federal LP, better SD but the group was no better, this is at 200-300yds

Tried Mag primers both Rifle and pistol, WLRM, and F215, worked OK is pistol primers were not available.

picked up some Fiocchi, small rifle primers, green colored priming compound, found out later these were green primers, 1500 to the brick was 29.00, no longer available I was told by the importer, used them anywhere a small primer was needed, .357max, mag, 32-20, both rifle, shot well with the powder I used, 7625, loaded some .357 max for deer with 180gr XTP bullets and WC680, almost a full case, Fioccchi small Rifle Primers would not light the powder up, left the powder yellow and in a clump

In the Schuetzen game with Breech seated PB bullets and SR4759,Rem 2 1/2 primers was the standard, never worked for me...

Burn rate charts are nice to look at, but do not give pressure curves for particular cartridges

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RicinYakima posted this 09 November 2022

Breach sitting is a different animal that shooting from a case. 

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Wm Cook posted this 09 November 2022

“ There may be just one hard rule as Ken says.” Agreed,

With the right bullet fit and if you have a half dozen powders you’re comfortable with and enough of the same primer (Fed, Win, Rem or whatever) to keep you in business you can count on getting the most accuracy the barrel will give you.

But then I get my shorts tied up into a knot. How can the PBB agg right on the heels on unrestricted classes, run 550 - 600 fps slower, most all using a 32 Miller or a derivative there of, all using a very similar weight bullet but the two powders used in the PBB class lie on top of one another on the burn chart. Sorry for whining. Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

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John Alexander posted this 08 November 2022

Thanks for taking the time to ferret this out and post it. Interesting bunch of data points. To me this says that a fairly wide range of burning rates can produce competitive results in the same case and bullet weight. Not too surprising. The fastest pistol powders have won quite a few CBA matches, some in cases five times optimum size, and If I remember correctly Col. Harrison was a proponent of very slow powders like 4831 for cast bullets. 

I think we have a bunch of facts and principles about CB shooting( such as "slower powders give the bullet a gentler push and reduce deformation and aid accuracy" or "JBs are harder and shoot better than CBs so harder CBs should be better") that the actual cast bullets have apparently not read about. The older I get, the more it seems that the correct answer to almost all CB questions is " that depends on the situation."  There may be just one hard rule as Ken says.

That is part of the fun and challenge of our screwy hobby. If a shooter finds that more frustrating than entertaining he should consider jacketed benchrest where the exact recipe is handed to you on day one. Then you can go forth and pretend to be able to tell how a rifle and load are shooting by looking real hard at a single three or five shot group.

Yeah, I know this isn't contributing to answering the question posed in post #1. But that was a hard question.

John

 

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Wm Cook posted this 07 November 2022

If everyone was using the same cartridge and the same primer and all had custom barrels, shooting similar bullet weights, similar velocities, would you not expect that there would be some symmetry to the burn rate of the powder they used?

With that in mind could anyone explain to me why of the eleven 30 BR's that competed in the 2021 KC Nationals last year there was a such wide burn rate between powders.  I could understand it if there was a variety of primers being used but nearly all were using Fed 205M's.

  • All competitors shot the same cartridge, 30BR.
  • Nine of the 11 competitors used Fed 205M's.  So the field was almost exclusive using the same primer.  The exception was one using Winchester and one brave soul using Win SP.  He shot a .915 100/200 yard grand agg by the way using that small pistol primer.
  • But of the 11 competitors there were 6 different powders (no surprise there) but the range of powders was far greater than I had expected.  The powders ranged from the fastest being N133 and the slowest being Varget.  Maybe not an extravagant spread but far further apart that I would have guessed.
  • On my burn rate chart that put 44 other powders between the fastest and slowest powder used by last years 30BR shooters.  .
  • There seems to be no rhyme or reason as to bullet weight and powder choice.
  • There seemed to be no apparent relation to barrel length with one Unrestricted Pistol shooting N133 (fastest powder) but the other two were shooting Varget (slowest powder).

Thanks for any help.  Bill C.

A “Measured Response” is as effective as tongue lashing a stuck door.

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RicinYakima posted this 04 November 2022

Yes, it is only in the last 20 years that I have been keeping data, mostly because I didn't know anyone else cared. 

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John Alexander posted this 03 November 2022

It isn't just the Hornet or just cast. All calibers and all levels of accuracy. from 0.2 to 40 minute of angle, have variations in accuracy similar to these for any one load.  It shows up in any group match. If this seems unbelievable see the article on tuning in Fouling Shot #275.  We seldom see this because very few shooters do what Bill presented above (multiple results of one load) -- but maybe we should think about it.

John

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