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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Ross Smith posted this 29 October 2022

The only difference that I've noticed-not tested- was with magnum primers used to get compressed loads og FFg burning. Did very well.

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Little Debbie posted this 29 October 2022

Yes they do make a difference in accuracy in cast bullet loads using medium and fast powders.  I shot an exstendive test in my 6mm PPC with cast bullets comparing pistol and rifle primers.  The rifle primers shot measurably better with that load /,bullet combo.  I’ve seen this phenomenon on the target (not anecdotal) in many situations, primer type, brand, and lot makes an accuracy difference.
The current supply situation it’s tougher to get a variety of primers to test for best accuracy.  My current testing is to determine which loads I can substitute pistol primers for rifle. This is because I have more pistol primers than rifle.

 

My current rule of thumb is this:

Pistol primers work fine with pistol and shotgun type powders in rifle loads. When fine powders migrate into the flash hole you get vertical stringing. Store the rounds bullet  down and give a light tap on the round with the bullet down prevents this.

Rifle primers are best with rifle type powders 4198,4759, 4277, 4895 etc even in “light” cast loads.

 

I’m still trying to get groups consistently under MOA with cast bullets.  Trying different primers is a variable I always try in load development.

 

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Wm Cook posted this 29 October 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 sets a very specific range of variables with the wild card being the powder charge may need to be tuned to the primer. So I’ll avoid that one.

John can confirm this or not but taken at its lowest common denominator I think he’s asking (might be wrong, frequently am) that assuming you have a bread and butter cartridge like the .308 and you have a load developed that gives you a round evenly distributed 1 1/2” group using CCI, will the group suffer or improve if all variables are kept the same but the loader substitutes the CCI with Win, Fed, or Remington primers.

The biggest nut to crack is when you stretch the expectations such that you have two proven loads with the same rifle; one with fast and one with medium burning rate. And then do the primer comparison.

The thought of that gives me a headache. Great thread! Bill C.

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Qc Pistolero posted this 30 October 2022

I started asking questions when I was having problems with my 30-30 in competition having vertical stringing when the temp would go down at or below freezing point.Ed Harris suggested I'd use mag primers and it did help a lot.

I started using regular LR primers during summertime and mag primers when it was getting cold;my scores improved due to less vertical stringing(guess I should send a few $bills to Mr Harris).

Mag primers definitely have an hotter spark and should be taken into account not only for the type of powder they're being used with but also at what temperature they are going to be used.As far as I'm concerned,40*F is about when I switch to mag primers whatever the powder I'm using.

LP primers having a cup slightly lower than LR primers are not,according to my tests as accurate as LR primers.Besides having a lower temp spark,I think that some of the force of the firing pin is absorbed by the 2/1000'' shorter cup being driven to fully seat in the pocket.It always translated for me in that old buggaboo vertical stringing.

 

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RicinYakima posted this 30 October 2022

I shoot two early Stevens firearms; an 1865 rifle in 35 Stevens and a 32 Short pistol converted to CF. Both require Federal standard primers because the firing pin strike is so light. And Federal has the softest and thinnest cups. Both were made to shoot pure copper primer cups.  FWIW

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comprschrg posted this 30 October 2022

This is interesting to me. I'm not trying to be facetious. But initially I learned magnum primers had more heat/fire/umpf. Then through much reading , was informed only the cups were thicker to withstand more pressure.
Now ......back to magnum primers have more spark. As it may. Just today I was reading a different make was only the difference in say 1/2 grain of powder in load development. I am only a neophyte in this art, so please understand I'm trying to learn.

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Bud Hyett posted this 30 October 2022

Thought One: Based on experimenting a half-century ago, you can find a difference in primers. You might wear a barrel out getting there. 

I had only two centerfire rifles, a 788 .222 Remington and a 700 BDL .270 Winchester. Both shot sub-minute ten-shot groups. The .222 with Sierra 53 grain Match and the .270 with Sierra 90 Hollowpoint. Remington  standard primers in both rifles. Then I was given a carton of W-W 8 1/2 primers (wooden trays) to use.

I substituted these primers and the rifle did not shoot as well. The groups were minute and one-half and not going down, interesting. I raised and lowered the powder charge, no help. Then I moved to powder one burning rate slower and one powder rate slower raising and lowering the powder charge. Then I moved to powder two burning rates slower and two powder rates slower raising and lowering the powder charge.

Eventually I found a load shooting near the original. But I'd put over 500 test rounds through the barrel in the journey. 

Thought Two:

Primers (design philosophy):

  • Federal and Winchester are designed to throw the flame forward and ignite the powder column from the center outward.
  • CCI is designed to throw the flame outward at the back of the powder column to ignite the powder column to burn progressively forward to the front.
  • Remington throw the flame in a 45-degree angle to ignite the center and burn both outward and forward.
  • With the shorter, fatter, sharp-shouldered cases in use today, the CCI primer is gaining more usage.
  • I find when switching there is a load with a slightly faster or slightly slower powder that will shoot consistently as the first load.
  • Therefore, I standardize on a primer for a load and work forward. 
  • Federal or Winchester for long cases (.e.g., 30-'06), Remington or CCI for shorter cases (e.g., 6mm BR)

 

Farm boy from Illinois, living in the magical Pacific Northwest

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M1fuzz posted this 30 October 2022

Now this isn’t scientific by any means but, over the years I have found that if everything is the same in a cast load in my military bolt action rifles by using Winchester Large Rifle Primers will always tighten up the group not by much but, you can tell the difference.

Now, using a CCI 34 primer makes the groups smaller in one of my M1 Garands I use for cast. I have made a repro early to mid 60’s M16/AR15. That rifle seems to group the tightest using CCI 41’s.

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Fitzpatrick posted this 30 October 2022

Over the last couple of years I have been forced to try different primers in different calibers . I have come to the conclusion that if I work up the load you can achieve the same group size with in reason , I did have some hang fires in 308 based wildcats that I tried small primers in but even then using pistol powder solved most of that. Of course accuracy is in the eye of the beholder , if I can get a load to group at around a inch at a 100 yrds  that is a good hunting round . But in the end I think if loads are developed with a primer that you have on hand you can achieve acceptable results , with the exception of bench rest competition . and all my testing reloaded primers was also used with the same accuracy 1 moa  and continued shooting and enjoyment thou this time of no components

 

  just my two cents  James

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comprschrg posted this 30 October 2022

Thank you Bud. And M1fuzz. I'll be copying those posts to my notebook, then going back to the side line.

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Rich/WIS posted this 30 October 2022

Not an opinion on accuracy (me and my rifles are not good enougn to tell) but did notice that had occasional delays in ignition with ballpowders and standard primers.  I use magnum primers with Ball C2 and Win 748, standard with others.  Noticed the delay when shooting with electronic ear muffs, most went bang when the firing pin hit but a few there were a few where you heard a click-bang.

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JeffinNZ posted this 30 October 2022

Depends.  

My Hornet is fussy with primers depending on powder.  Stick powder not so much.  Ball powder, will only shoot with Winchester primers presumably as they are hotter.

I tend to think small cartridges can be picky about primers.  Large cartridges, no.

Cheers from New Zealand

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Wineman posted this 30 October 2022

I have shot 308 Win in an Ishapore 2A1 using Winchester LP primers, a 312299 and 15.5 grains of Alliant 2400. First shot pierced the primer, stopped there and broke that ammo down. Accuracy was good, but hard on the gun.

Dave

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Tom Acheson posted this 31 October 2022

For my CBA benchrest match guns, I’ve been using small rifle BR primers since 2005. Accuracy testing each time I changed to a different chambering, had me using R-P 7 ½ or FC 205M primers, depending on the chambering. For my revolver loads using large primers, I’ve found most brands do OK. Interesting that there are now some 45 ACP cases that use small pistol primers.

 

However, for my black powder cartridge loads, I’ve seen a trend of accuracy improvement where FC 150 (large pistol) match primers, along with a disc of wax paper dropped into the case before the powder goes in, is working well. Supposedly the wax paper softens, diffuses or spreads the primer “flame” to optimize ignition. Other shooter’s have commented that the shorter pistol primers (in the primer pocket) contribute to peening of the face of the breech block. In doing this for the past 5-years, I see no evidence of that in my rifle. It’s a C Sharps Model 74 chambered in 40 cal. 2 ½.

 

Tom

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Hornet posted this 31 October 2022

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?  Yes.

Oh, you want a little detail? Picky, picky.. Example: Remington 799, .22 K-Hornet, 1:12" twist, NOE 225-60-RN, 17 BHN, 59.5 +/- 0.1grain,  fireformed WW Cases, 5 shot groups,  AA1680 powder 9.3,9.5,9.7,9.9,10.1grains, WSR vs WSP, alternating groups between primers.   Result: groups using WSR were more rounded and visibly averaging smaller than the WSP groups. Repeated a few days later using WSR vs R-P 7-1/2, same powders charges. Result: R-P 7-1/2 groups clearly better than WSR groups. Annoyingly enough, the R-P 7-1/2 primers used were the old copper-washed version. I ran out and changed to the current brass-finish ones and groups got significantly worse, back to matching the WSR. Really need to retry with R-P vs Fed 205M some day.

Similar testing with the RCBS 22-055-FN (Cramer hollow-pointed version) showed a similar pattern with IMR 4227 in doses of 9.8, 10.0, 10.2, and 10.4 grains and those used R-P 7-1/2, WSR and Fed 205M with the Fed 205M clearly best. Disappointing since the .222 and .223 also prefer the Fed 205M in similar testing in loads around 2100 fps with SR4759 and use large quantities of them. I may need to try a faster powder for the R-P's to work (got lots of them).

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RicinYakima posted this 5 weeks ago

I'll ask this question; I have lots of small rifle primers and less than 100 small pistol primers and none available locally. I want to load some cast bullets in my Savage 22 Hornet. I have lots of 225438s cast and and looking for a light load I can use with SR primers. Any help out there?

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Wm Cook posted this 5 weeks ago

Rick here's some numbers that I just pulled off my computer this week.  I was hoping to get out once more this year to give these loads a try. So I was getting my ducks in a row for the next range trip.  All 5 shot 100 yards, mixed Fed and Rem SR. Wasn't smart enough then to shoot 10, 20 shot groups..

So I thought these were the best of the powders and loads to look at again.  I also tried Lil Gun, 2400, 5744 and W231 and they didn't shoot as well.  Some of those groups were real ugly  Some over 10".  But I was shooting velocities from 700 to maybe 1300 fps.  Bill C

 

 

 

 

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RicinYakima posted this 5 weeks ago

Thanks Bil!

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Hornet posted this 5 weeks ago

I was reading Ness's Practical Dope on the .22 and he mentions that H. Guy Loverin said to seat the 225438 to NOT touch the rifling. He recommended 3.0 Grains of Unique for squirrel, etc and said they'd gone as high as 10.5 grains of 2400 (2750 FPS!!). Something to think about.

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RicinYakima posted this 5 weeks ago

I did also. But it was published in 1947, before they made the cases 10% thicker and reduced the case volume. I'm going to start with your loads and work my way up in the Savage 23D. Ken Waters liked 3.3 grains of Unique also with SR primers. 

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Hornet posted this 5 weeks ago

They also dropped the SAAMI maximum pressure spec back quite a ways. Bases on current published loading data being at least a couple of full grains below the 10.5 , I don't even want to think about what the pressures must have been with those loads. Sharpe listed loads just as scary high. Things changed a lot when some places actually started pressure testing.

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Glenn R. Latham posted this 5 weeks ago

Ric, I did a primer test in my Lyman Mini Sharps 22 Hornet last year.  Load was 9.0 IMR4227 and the bullet was the Lyman 225415.  Evidently the bullet is too long for the 16" twist as the "composite" group of all 60 shots at 50 yards was 14"!  But here's the numbers:

Primer   Velocity   SD

WSP      2333      40

WSR     2434      44

Rem 6-1/2  2321   55

Rem 7-1/2  2315   48

Fed 205    2285  43

Fed 100  2318   34

I've been using WSP for most of my loads.

Glenn

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Wm Cook posted this 4 weeks ago

About primer selection: I'll follow this tomorrow with data from the Nationals to see common threads to primers, cartridges and class.  As a lead in I'll say that selection of primer is distinct to each class but not distinct to cartridge.  I'll try to post tomorrow.

I apologize to John in advance for the diversion on the thread but I thought this might help some folks.

Regarding 225438 / Unique.  This is just a raw data dump sorted by charge weight.  If you're working with Unique and 225438 this'll give you some idea the velocity ladder I found with the couple of bottles of Unique I had used over the last bunch of years.  As I ran the velocity up I was getting too many fliers which I know could have been caused many things.  I settled on a low velocity load as the path with the least resistance.  And I was shooting a suppressor so it made a nice pop sound. 

As usual the standard cautions should be applied.  Take care, Bill.

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Hornet posted this 4 weeks ago

Nice data accumulation !!! I like the documenting of group size variation with the same load. It kind of illustrates the sheer joy of load development with cast in the Hornet.

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John Alexander posted this 4 weeks ago

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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RicinYakima posted this 4 weeks ago

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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Wm Cook posted this 4 weeks ago

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.

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John Alexander posted this 4 weeks ago

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 4 weeks ago

“ 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.

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RicinYakima posted this 4 weeks ago

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

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4060may posted this 4 weeks ago

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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Ken Campbell Iowa posted this 4 weeks ago

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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lotech posted this 4 weeks ago

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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Wm Cook posted this 3 weeks ago

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.

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Bud Hyett posted this 3 weeks ago

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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Ross Smith posted this 3 weeks ago

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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Lucky1 posted this 3 weeks ago

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.

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Ross Smith posted this 3 weeks ago

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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Wm Cook posted this 3 weeks ago

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.

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John Carlson posted this 2 weeks ago

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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Shopdog posted this 2 weeks ago

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

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John Alexander posted this 2 weeks ago

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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John Carlson posted this 2 weeks ago

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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