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Thread: Using small pistol primers in low-pressure cast .223 loads?

  1. #1
    Boolit Man
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    Using small pistol primers in low-pressure cast .223 loads?

    Hey everyone--

    From what I have read, small pistol primers have a slightly thinner cup than small rifle primers, meaning they can't be safely used at rifle pressures (you'll get pierced primers and or high-pressure failures).

    However, I don't have small rifle primers right now and would like to work up a few low pressure test loads using a Lyman 225415 55 grain boolit for my AR-15, to see if I can find the sweet spot for accuracy, reliable cycling, and no leading. These CCI 500 small pistol primers are what I've been using in 9mm since I first started casting. My favorite load with Bullseye in 9mm gets me to an estimated 28,050 CUP and I've never once had an issue with primers blowing out or anything like that.

    The highest pressure load for my test rounds here is 14 grains of IMR4227, which should only generate 23,200 CUP of pressure. I have even read that some precision .223 shooters use small pistol primers in their loads specifically because it improves accuracy, although that's anecdotal evidence at best.

    Am I safe to use small pistol primers in this situation?
    Currently in the process of developing the "perfect" cast .223 load for my AR-15. Click here to follow my progress

  2. #2
    Yup.
    The fact is, you are shooting low pressure loads, with light powder charges.
    .
    An old gun writes ( name escapes me ) used to shoot 22 Hornet, in his home state of North Carolina. He settled on small pistol primers exclusively, ..cause they were less disruptive to the powder burn, and gave better accuracy.
    .
    Were I to shoot cast in the AR, at low pressures, and sensible velocities, my first, and only choice would be the small pistol primer.

    Were I to ever shoot the 22 hornet again, my first choice in primers would also be the small pistol primer.

  3. #3
    Boolit Man
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    Still reading up everywhere I can find info. I'm not concerned about the pressure blowing out the back, but I am a little concerned about slam fires or piercing the primer. My AR-15 has a floating pin. As long as I seat the primer as deep into the pocket as it will go, I should be okay, right? And just make sure I have the gun pointed in a safe direction and firmly in hand when I close the bolt
    Currently in the process of developing the "perfect" cast .223 load for my AR-15. Click here to follow my progress

  4. #4
    Boolit Master


    mold maker's Avatar
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    Every primer maker produces both primers for pistol and rifle. They wouldn't go to that expense if they were interchangeable. Some may get away with swapping, but to advise doing it is questionable. Besides the data you develope won't be the same when you change back to the normal primers. There is a difference even between brands. Every book I have ever read warns against swapping any component for any reason period.
    To publicly discuss subjects like this increases the likelihood a novis will mistakenly do it in a condition that causes damage to a weapon if not the shooter.
    Information not shared. is wasted.

  5. #5
    Boolit Master
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    the difference between "rifle primers", and "pistol primers" is in thickness of cup, and thereby pressure containment capacity. pistol primers shouldn't be used over 25 KSI, and mag pistol not over 35KSI.

  6. #6
    Boolit Mold TemplarKnight's Avatar
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    It is not acceptable to use small pistol primers in place of small rifle primers for three reasons, two of which you have identified: 1) Pressure versus cup material = pierced primer; 2) Floating firing pin slam fires - pistol primers by the nature of their design are more "sensitive".

    The third reason is firing pin protrusion/firing pin indent. Given the major variables when the effects of headspace, temperature and eccentricity of blow are considered, the minimum industry standard firing pin indent for centerfire rifles, based on a 060" inch to .O8O" inch diameter approximately hemispherical firing pin is .017 inch while in handgun calibers the minimum runs from .009 inch to .011 inch depending on the actual cartridge, most small pistol being .009 inch and large pistol being .011. The few exceptions are the 22 Rem Jet CF Magnum, 221 Rem Fireball, 256 Winchester Magnum, and the 357 Magnum, all of which are call for the small pistol magnum primer which has a somewhat "tougher" cup. The issue here of course is the firing pin protrusion of your rifle being greater than called for in a handgun could be the cause of pierced primers as well.

    Given three possible sources of failure it would prudent to use what the industry has engineered to work correctly in the given application.

  7. #7
    Boolit Man
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    I'll have to agree with everyone here and I'll have to say thats probably not a good idea based on points highlighted above. I only had one slam fire but I'm more carefull then ever when I drop my bolt and that was using CCI SRP. Using SPP in AR paltform is going to be prone to slam fires I would think. Plus SRP have more charge if I remember correctly so I dont see how SPP would help here. I often use SRP in 357 Magnum with a mild load of of BH6 but thats like using magnum primers with even thicker cup. Not so sure i would go the other way around.

  8. #8
    Boolit Master
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    That slam-fire possibility with mil-spec systems caused CCI to release their mil-spec primers (#34 and #41) for general retail consumption.

    Remington has two small rifle primer types--#6-1/2 for 22 Hornet, 25/20, 30 Carbine, and 32/20 case sizes; #7-1/2 for 222, 223, and 222 Rem Mag case sizes.
    I don't paint bullets. I like Black Rifle Coffee. Sacred cows are always fair game. California is to the United States what Syria is to Russia and North Korea is to China/South Korea/Japan--a Hermit Kingdom detached from the real world and led by delusional maniacs, an economic and social basket case sustained by "foreign" aid so as to not lose military bases.

  9. #9
    Boolit Master

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    I have read that CCI small pistol magnum primers and small rifle primers come off of the same line and are one and same except for packaging. Do any of the other primer manufacturers do this?

  10. #10
    Boolit Man
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    Quote Originally Posted by dondiego View Post
    I have read that CCI small pistol magnum primers and small rifle primers come off of the same line and are one and same except for packaging. Do any of the other primer manufacturers do this?
    Maybe I'm misinformed but I was under the impression that rifle primers have thicker cup then magnum primers. I might be wrong though.

  11. #11
    Boolit Bub
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    Quote Originally Posted by TemplarKnight View Post
    The few exceptions are the 22 Rem Jet CF Magnum, 221 Rem Fireball, 256 Winchester Magnum, and the 357 Magnum, all of which are call for the small pistol magnum primer which has a somewhat "tougher" cup. The issue here of course is the firing pin protrusion of your rifle being greater than called for in a handgun could be the cause of pierced primers as well.

    Given three possible sources of failure it would prudent to use what the industry has engineered to work correctly in the given application.
    Several reloading manuals I use call for Rem 7.5 primer for 221 fireball which is called Benchrest RIFLE primer on the box not small pistol magnum. I've also seen it called magnum rifle primer. I've had these primers pierce in my Remington 700! Never seen that with CCI or S&B.



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    Last edited by dimaprok; 02-02-2018 at 05:55 AM.

  12. #12
    Boolit Master Walkingwolf's Avatar
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    Be careful of long arms with floating firing pins such as the AR. They could discharge when the bolt slams forward.

  13. #13
    Boolit Mold TemplarKnight's Avatar
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    I would question what you read regarding CCI small pistol magnum and small rifle primers being one and the same. Industry primer sensitivity testing protocol requires the small pistol primer (standard or magnum) and the small rifle (standard and magnum)pass a "fire/no fire" sensitivity test protocol where the small pistol primer shows as being decidedly more sensitive. Reference "Ammunition Making" by George Frost for more information on the subject. Frost held executive engineering positions with Winchester-Western Ammunition and CCI. The book is out of print now but is good read for those that are interested and can find a copy.

  14. #14
    https://ballistictools.com/articles/...d-diameter.php

    See if this will help with your question

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  15. #15
    Boolit Master Hick's Avatar
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    Depends on the rifle. When a slam fire is a potential you need to look out (AR-15). With an ordinary bolt rifle it depends on the shape of the tip of the firing pin. My cz-527 works just fine with small pistol primers in light cast loads -- but its not semi-auto and there is no slamfire concern.
    Hick: Iron sights!

  16. #16
    Boolit Master






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    nope marek is correct and I got it right form the person who answered the phone for cci. Same exact primer in different packaging. Now that was probably 15 years ago and they might have changed but I seriously doubt it. As a matter of fact in this day of budgets and cost cutting id bet not many if any companys are going to produce two different thickness of cups. Federal primes are the easiest to ignite proably from the hardness of the metal they use in there cups. Ive shot fed small rifle primers in my sixguns and they seem as easy to set off as there pistol primers. Now I don't doubt for a minute that a primer like the cci mil spec primers are a bit harder.
    Quote Originally Posted by marek313 View Post
    Maybe I'm misinformed but I was under the impression that rifle primers have thicker cup then magnum primers. I might be wrong though.
    Soldier of God, sixgun junky, Retired electrical lineman. My office was a 100 feet in the air, closer to God the better

  17. #17
    Boolit Mold TemplarKnight's Avatar
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    Quote Originally Posted by Hick View Post
    Depends on the rifle. When a slam fire is a potential you need to look out (AR-15). With an ordinary bolt rifle it depends on the shape of the tip of the firing pin. My cz-527 works just fine with small pistol primers in light cast loads -- but its not semi-auto and there is no slamfire concern.
    Per my previous comment: The third reason is firing pin protrusion/firing pin indent. Given the major variables when the effects of headspace, temperature and eccentricity of blow are considered, the minimum industry standard firing pin indent for centerfire rifles, based on a 060" inch to .O8O" inch diameter approximately hemispherical firing pin is .017 inch while in handgun calibers the minimum runs from .009 inch to .011 inch depending on the actual cartridge, most small pistol being .009 inch and large pistol being .011. The few exceptions are the 22 Rem Jet CF Magnum, 221 Rem Fireball, 256 Winchester Magnum, and the 357 Magnum, all of which are call for the small pistol magnum primer which has a somewhat "tougher" cup. The issue here of course is the firing pin protrusion of your rifle being greater than called for in a handgun could be the cause of pierced primers as well.

  18. #18
    Boolit Master Jack Stanley's Avatar
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    I do it all the time , except I load for bolt rifles not the AR .

    Jack
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  19. #19
    Boolit Master wistlepig1's Avatar
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    I have been using SP primers in my Hornet for years with Max loads of LiLgun with No problems.

    ďA liberalís paradise would be a place where everybody has guaranteed employment, free comprehensive healthcare, free education, free food, free housing, free clothing, free utilities, and only law enforcement has guns. And believe it or not, such a place does indeed already exist: It's called Prison."

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  20. #20
    Boolit Master Forrest r's Avatar
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    I wouldn't use federal sp primers in a ar, too soft. But I do use s&b small primers for the mag revolver loads, semi-auto's & small rifle/ar loads. They go on sale a couple times a year for $20/1000 with free shipping. The old s&b box vs the new style.
    [IMG][/IMG]

    As you can see s&b states on both boxes for rifle, pistol or revolver cartridges.

    The only time I've ever had an issue with pierced primers is when using cci lp magnum primers with pistol powder loads in a 308w. But the 308's bolt's internals have been highly polished, moly treated & set for 60/1000" protrusion while using a extra power spring.

    What actually gets most reloaders in trouble is when they use primers like the s&b small primer or rifle primers in mousefart loads for their semi-auto's. Too many of those loads and the slides face ends up flame-cut.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check