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Thread: Why does one load make my primers so flat with BP

  1. #1
    Boolit Man
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    Why does one load make my primers so flat with BP

    Why is my primer so flat with BP?

    The loads both 45 Colt, were shot from a Ruger New Vaquero 5.5” bbl.

    Load 1) - Starline brass, 260 gr 20:1 alloy bullet from a LEE 255-45-RF-DC mold, sized .452” with Emmerts Improved lube, 35.0 gr GOEX 2fg BP, CCI 350 Magnum primers.

    Load 2) - Same components except for the powder which is 9.0 grs of Hodgdon’s CFE-Pistol.

    The cases for both loads have had the primer pockets and flash hole uniformed.
    The condition of the spent primers differ between the two loads.
    The smokeless load, primer edges are still rounded, average MV 925 fps.
    The BP load the primers are flat with slight rivet heading at the edge, average MV 823 fps. Outdoor temperature about 22* C (room temp).

    Why the flat primer with BP?

    Both loads should be under the 14,000 psi SAAMI pressure standard.


    I was thinking that the load with BP the primer flash jet has to bore its way into the cartridge case through compressed powder. So maybe a lot of primer pressure is reflected back into the primer slamming the primer back against the firing pin bushing.
    The smokeless load the jet of primer gas has some where to go straight into a mostly empty cartridge case. This acts as a pressure relief so the primer doesn’t get thrust back as hard there by leaving the primer with rounded edges.
    Any thoughts on why the BP primers are so flat?

  2. #2
    Boolit Master

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    I am thinking the original 45 colt load with BP was a 250 grn round nose bullet, 28 grns powder in a balloon head case. What size did you uniform the flash holes to? Bigger flash holes allow for more pressure to impact the primer also. Also BP is a different pressure curve than smokless powders.

  3. #3
    Boolit Master
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    large pistol primers have never showed pressure signs in 45/2.4" using up to 100 gns powder, or 40/72 using up to 85 gns of powder.
    this is with compression, and sometimes with a paper wad under the primer.
    will be interesting to hear an answer to this one if discovered.
    keep safe,
    bruce.

  4. #4
    Boolit Master
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    I think you are right about the compressed BP blocking up the flash hole.........European military rounds with Berdan primers had flash holes specially dimensioned to maintain pressure in the primer pocket at max,until chamber pressure fell as the bullet left the gun.This is why the flash holes are so tiny.

  5. #5
    Boolit Master
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    I'm thinking that all the things mentioned may be coming in to play.

    I'll ask a couple of questions . . . not to "confront" in any way . . . just curious.

    I use Starline brass in my 45 Colt and have never had an issue with flattened primers with BP loads.

    You mentioned that you "uniformed" the flash hole. Why? And what did you "uniform" them to? I have never had an issue with the Starline 45 Colt brass with the flash holes just as they come from the factory - either smokeless or BP. Why did you feel the need to "uniform" them? Again . . . just curious.

    Magnum primers . . . again, just curious. I've always used standard large pistol primers and they all go bang just fine. Was there a reason why you chose to use magnum primers?

    I have some original 45 Colt balloon brass and there would be no way to get 35 grains of BP in to those casings. There is, of course, a larger volume space in the Starline 45 Colt brass. You mention that you used a load of "35.0" grains of 2F Goex so I am assuming that you are creating your BP load by weight and not volume. So . . . I'm wondering just how much compression is needed to seat the boolit where it needs to be to get it crimped.

    I'm not a competition shooter but I know that many concentrate on "keeping things exact" every time to keep things consistent. And that's fine. I love my BP pistol cartridges (38 Colt Short, Long, 38 Special and 45 Colt) by volume. i.e. on the 38 special brass, I have found that using a 38 Colt Long casting with a spent primer in as a dipper measure gives me the correct volume in the 38 Special casing to give ample compression to the powder when seating the boolit. Will volume measure be "off" at times . . . certainly due to differences in powder "lots" but what little variance there might be is not going to really affect anything - as long as it fills the casing to get a compressed load.

    Again, I'm not challenging what you are doing in any way . . . just curious about the flash hole change, mag primers, etc.

    I would suggest that you try an experiment. Load up som using the Starline brass just as it comes from the factory - no changes to flash hole or primer pocket. Use a standard pistol primer. Load by volume . . . not by weight.
    An45 Colt casing is pretty spacious . . . . figure the seating depth of you boolit and measure it and mark it on a casing. Then load by volume so that you have your powder above the full seating depth of the boolit mark by say an 1/8" or so - that should give you all the compression of the powder load that you need so that there is no open air space. Seat your boolit, crimp and then shoot them and see what the effect is on your primer. If it looks normal . . . then you know that you need to think about changing something - possibly not changing the flash holes - possibly changing to a standard primer?

    Then, if you feel you need to use a magnum primer . . . load some up without changes to the flash hole and use a magnum primer - shoot them and see what the effect on the primer is.

    I agree with everything that has been said . . . and I'm no "expert" . .. but I do think there can be some issues that arise with "over compressing" the load as well. It needs to be a safe compressed load for sure, but not overdone either as you can compress so much that if you pull the boolit, you'll have to scrape the powder out as it is one hard mass. Balloon cases that were originally used prevented that somewhat. Personally, I think that sometimes folks worry too much about having a hot enough primer (or percussion cap) and a large enough flash hole. Think about a flintlock - everyone likes to have a big shower of sparks to ignite the powder in the pan, but all it takes is one spark aimed at the powder to make it ignite. One can also reason that a smaller flash hole concentrates the flash to the powder.

    Just some thoughts and hopefully you can experiment and see if you can figure out what is causing the primer to flatten out like you describe. It's all part of the learning process in what works best in your particular gun. Good luck and I look forward to reading what others think and if you can figure it out.

  6. #6
    Black Powder 100%


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    The 45 Colt load was 40 grains of BP with the 250 gr. bullet, it was down loaded by the military with the 28 gr. loading to give easier firing.
    Shooter of the "HOLY BLACK" SASS 81802 AKA FAIRSHAKE; NRA ; BOLD; WARTHOG;Deadwood Marshal;Bayou Bounty Hunter; So That his place shall never be with those cold and timid souls who neither know victory nor defeat; 44 WCF filled to the top, 210 gr. bullet

  7. #7
    Boolit Master Dan Cash's Avatar
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    Quote Originally Posted by cajun shooter View Post
    The 45 Colt load was 40 grains of BP with the 250 gr. bullet, it was down loaded by the military with the 28 gr. loading to give easier firing.
    The 28 grain load was the S&W Schofield load in a shorter case and a 220-230 grain bullet. A baloon head case will hold more propellant than a solid head case. My Starline .45 Colt cases will just barelly let me load 38 grains of 2fg under a 230 grain bullet. It is a stomper but does not flatten primers. No idea why this happens for the OP.
    To paraphrase Ronald Reagan, the trouble with many shooting experts is not that they're ignorant; its just that they know so much that isn't so.

  8. #8
    Boolit Man
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    I uniform the flash holes to achieve uniformity through out my entire lot of cartridge brass. It was something I do to all my rifle brass and when I got into handgun shooting in 2016 when I retired I just continued to do the uniforming procedures on all my revolver brass.
    I don't know what the standard is for primer holes I suspect every manufacture has a preferred size within a SAAMI size range.
    I measured my flash holes using the shank of a number sized twist drill, then measured the drills with my digital caliper.
    My #46 drill which should measure .0810" according to my Starret drill size guide, but my calipers say the drill measures .0795".
    I have some Starline nickel plated 45 Colt cases (for the bling effect in the ctg belt) that I have not uniformed. These measure/feel the same fit with the #46 drill shank inserted in their flash holes. I have some new Hornady 357Mag brass and they measure .077".

    I loaded 35.0 grains of GOEX 2fg BP because I wanted to get the feel of this old cartridge doing its thing
    I figured that from a modern solid head case that 35.0 gr might be close pressure wise to a 40 grain load in the more voluminous balloon or semi balloon head case.
    My powder charge was dispensed by weight from a digital scale. My understanding is that volume type dispensers are calibrated to the weight of 2fg powder. I am sure that volume to volume between different powder brands their would be a slight actual mass weight difference between the brands. But 35 grains of fuel weighed is the same for every brand, the volume the weight occupies will be slightly different between brands but I suspect it will be very close.

    I chose to use magnum primers for 2 reasons. Researching loading the 45 Colt ctg. I used the Book SHOOTING SIXGUNS of THE OLD WEST by Mike Venturino. I copied a load that he found to work the most accurately in his gun. CCI 350 Magnum primers and 35 gr of GOEX 2fg and a bullet that weight at least 250 grs. This load was the winner of his accuracy testing. So thats where I decided to start my testing.
    My own reason for using the magnum primer is to ensure better ignition of this large charge of compressed powder. Yes a std primer will work but a mag primer lowered the ES in my testing with smokeless powders in my 357 Mag so I suspect it will do the same with BP.

    About the powder column height: I dump 35.0 grains by weight into a starline case. I tried to reduce the column height by using a long drop tube, and adding vibration. I have a buzzing little vibrating tool I can rub up and down the case side I could see the powder granules dance and settle down lower. But in the end using the drop tube and vibrator was very time consuming, I didn't see enough powder column height reduction over just using my "Saturn" brand aluminum funnel to warrant using them.
    The funnel with its little bump in the neck swirls the powder nicely to almost the same height that the drop tube and vibrator achieved.
    I use a steel compression plug mounted in the expander die body to compress the powder. The first time I loaded a 45 Colt ctg I tried to use the bullet to compress the powder, what a mess was made of that bullet nose! I would have to drastically reduce the powder quantity so as to not distort of soft ~BHN 10 bullet. I read a compression plug is what I needed and orders one from Buffalo Arms.
    That compression plug is amazing,I have no doubt I easily could put more than 40 grs into a 45 Colt case using the press with a compression plug.
    I measure the length of the bullet shank, base to crimp groove. I compress the powder down to that level. I try to be right on, but I usually over shoot the compression length a few thou, so at the most there could be a small 0.007" air gap under the bullet. For all I know between the time I load the ctg and firing the powder may have puffed back up to press on the bullet base.
    One time I dropped a case with a compressed powder charge and none fell out. I wanted to know how hard packed it was so I dug it out. That was a trick, a screw driver just bored a hole in the powder column leaving a ring of powder around the case sides. I tried again, twisting a close fitting but not too tight drill bit into the powder. While hold the case upside down the drill bored the 2fg turning it to dust. The deeper I drilled the easier it got till a whole clump of powder fell out and the case was empty. This little experiment let me know that the powder down at the flash hole is not packed as hard as at the top of the powder column.

    Poster Country Gent mentioned the pressure curve, I never seen a piezo electric pressure trace from a ctg fired with black powder but I suspect is a very fast burn like TiteGroup smokeless.
    I think the packed ctg case gives the primers jet stream no where to go so the primer is slammed back against the recoil shield, then the ctg case is move backward to reseat the primer as the bullet starts to move (equal and opposite reaction). Considering how much blow back fouling is on the out side of the ctg cases I don't think the case sides do much expanding to seal gas tight. If they did seal tight right away I think I would be getting some case length growth which I don't get.

    The next time I load the 45 Colt I'll try standard non magnum large pistol primers to see it the primers still get hammered as flat.
    My prediction is that it will still be flatter than the smokeless primer but not as flat as the mag primer.
    Last edited by greenjoytj; 07-14-2018 at 05:57 AM. Reason: Spelling, grammar

  9. #9
    Boolit Master
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    I have loaded 40 grains weighed in the Winchester 45 Colt cases behind the same 255 grain Lee boolit cast of 20 to 1 lead mix and sparked with a CCI large pistol primer.

    First thing that struck me was WOWWW what recoil.

    Second thing was the accuracy AND the regulated impact in relation with my second gen Colt SAA with 7.5 inch barrel

    Thirdly i now know the why of the reduction in powder for a more managable handle with the old thumb buster [ maybe this is where that term came from].

    But i don't remember my primers flattening and I'm bettin i woulda seen them and taken note if they did so.

    Oh and the powder i used in this experiment was Ol E 2F.
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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