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How to educated guess pressure?

Discussion in 'Reloading' started by themighty9mm, Sep 6, 2013.

  1. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    Got back from the range awhile ago. Trying to figure out a load I like using aa2230. Its coming from a colt 6920 16inch barrel 1-7 twist. My load is 62gr ss109 using lc cases at a 2.225 oal, and cci 41 primer.

    With 24.4 gr of powder. From my pro chrono, I got 2886 fps on the high end, and 2855 on the low end. Hornadays manual says 24.0 is the max, my lyman manual says something like 26.1 is the max. I did not notice any pressure signs, but is there any way to get an educated guess, or even exact result as to what kind of pressure this is producing? A mathematical formula or something?

    I tried everything from 22.0 up to 24.4 same everything except the powder charge. And to get a similar velocity to what I'd like and best results with accuracy the 24.4 seemed to work best. But now it has me wondering if my pressure levals are still safe.
     
  2. F106 Fan

    F106 Fan

    8,033
    268
    Oct 19, 2011
    The hobby reloader has NO way to measure or estimate pressure. There are some signs of overpressure but by the time they show up, you are probably about 20% over.

    Read, starting on page 59 of Speer #14, about the voodoo of reading overpressure signs. If they can't do it, there isn't much hope for the rest of us!

    You can look for signs of difficult extraction, bulged cases, flattened primers but these occur when vastly overpessure. Except flattened primers. Federal primers will flatten in a light wind.

    So, take your reloading data seriously, decide on who you trust and go for it. Very few manuals publish pressure for their reloads. I might lend more credence to those who do. They might have actually measured something.

    OTOH, why load anywhere near max? If you need more velocity, change powders. The most accurate loads will be at mid-range anyway. Take a look at the Sierra load for the .308 175 gr BTHP. Their accuracy load has a muzzle velocity of 2400 fps and I only get about 2300 fps out of my 20" barrel. But it's superbly accurate!

    BTW, there is some instrumentation available to measure rifle pressures at significant extra additional expense.

    Richard
     

    Last edited: Sep 6, 2013

  3. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    This was more of an availability purchase. I was using ramshot tac. But my stash of that is pretty much depleted. I was kinda caught with my pants down. At least as far as rifle powder goes. Picked up some aa2230 at a spot on price and in a quantity that would keep me shooting for a bit. Never really ran into such vastly different data in my manuals before. So it got me thinking about the current question. In the hornday manual 24 is max, in the lyman 24 is pretty much low mid range IIRC
     
    Last edited: Sep 6, 2013
  4. Zombie Steve

    Zombie Steve Decap Pin Killa

    18,083
    18
    May 31, 2007
    Old Colorado City
    Your Lyman manual lists the pressures they got. SWAG from there.
     
  5. F106 Fan

    F106 Fan

    8,033
    268
    Oct 19, 2011
    You will always find a difference of opinion in reloading manuals. Sometimes it is because of slightly different components or different firearms. Certainly velocity will vary by firearm - my 20" .308 will always have less muzzle velocity than a 24" .308 for the same load.

    My definitive answer for rifle reloading is the Sierra manual. I have decided that they do more actual testing than any other manufacturer and they are the ones I am going to use. Now, I have no factual basis for that decision, it's just the one I made.

    Others use the Lyman manual and I think it's true that they have no entanglement with powder manufacturers. Speer is married to Alliant, for example, because they are owned by the same parent company.

    I don't think you'll get in trouble using the Lyman manual - it is a published source of load data. I also think that most of the manufacturers have backed off on max loads over the years. I suspect that Lyman is perfectly acceptable. I would still look for primer flattening (even with Federal primers) or difficulty in extraction.

    Or, I would use the lower value and keep the Lyman extra in mind in case I was worried about consistent powder drops.

    I don't see the motivation for running anywhere near MAX. Unless you are trying to shoot way far out, velocity isn't a big deal. Consistency is more important.

    Richard
     
  6. Zombie Steve

    Zombie Steve Decap Pin Killa

    18,083
    18
    May 31, 2007
    Old Colorado City
    Ok, I looked it up.

    I ran 69 grain matchkings up to 24.8 grains with AA2230, win brass, cci srp loaded to 2.260". It was right at max, and I got a few that showed pressure signs. Good velocity (was at 2,858 average from a 16" AR), but too close to the edge for my tastes. Switched to Varget and didn't look back.
     
  7. GIockGuy24

    GIockGuy24 Bring M&M's

    4,037
    5
    Jul 14, 2005
    With Amber Lamps
    The SS109 bullet is about the same length as the 68/69 grain bullets. I usually start with 68/69 grain load data for SS109 bullets. Their lighter weight does allow them to be pushed a bit faster than the heavier lead core bullets, which can allow the use of SLIGHTLY more powder but I'm not sure it's worth pushing it. Accurate Powder has M855 load data for A2230 for both 223 Remington SAAMI chambers and AR15 chambers.

    http://www.accuratepowder.com/wp-content/uploads/2010/09/WP_LoadSpec_7-2-13.pdf

    The load data for the Speer 62 FMJ lead core bullet works too. Some of the Lyman load data is a bit dated. The Hornady load guide seems to be one of the most updated for popular calibers, if you get the latest version.
     
  8. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    According to this information I am right in the middle ish, lyman I am on the low end. And I misthought earlier. It was the speer manual that stated 24.0 gr as the max. My hornaday manual shows no information. I have 3 manuals. I fallow them very closely. I tend to avoid the max. But following speers information, according to my chronograph. The velocities were pathetically slow and to me was just unacceptable. I'm not a speed freak by any means. My handgun ammo for the most part just barely functions my semi autos, but gives good accuracy. My rifle ammo has always stayed in the middle ish. I had never run into such drastically different info in my manuals before. Different information, yes. But not to the point of this.

    So between 3 loading manuals, a chronograph, 6ish years experience. I learned something... I think I need some more loading manuals
     
  9. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    I keep hearing this word swag. What on earth does it mean? I'm only 27 and have no clue what it means. I used to know all the cool kid words. Am I getting old? I even heard my son who is 7 say it.

    It does indeed list it. Guess I forgot about that part. Or started to discredit it due to the somewhat drastic difference in info.
     
  10. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    That velocity is pretty close, very close to what I am getting at 24.4, but am not seeing any signs of anything wild. Is aa2230 temp sensitive maybe? today was right at 93 degrees according to my iphone
     
  11. Zombie Steve

    Zombie Steve Decap Pin Killa

    18,083
    18
    May 31, 2007
    Old Colorado City
    Scientific Wild ___ Guess

    If the manuals are showing you different things, you need to remember that powder charge is only one part of the equation. Look at the brass they used, the primer, the test barrel (they are probably testing a 24" barrel and you're shooting a 16" barrel), bullet shape / weight, seating depth... all have an effect on the pressure (well, not barrel length... but it does impact velocity).

    What velocity are you looking for? My plinker 55 grain load only does 2,850... which is what PMC, American Eagle or Wolf ammo is going to get. You just aren't going to get to 3,000 fps with that bullet and a 16" barrel. Don't go chasin' nato loads with canister powders... particularly not with a fast burning powder like AA2230. I my opinion, 2230 is just about right for 50 grain bullets and below. Get into the heavier bullets and you want a slower powder.
     
    Last edited: Sep 7, 2013
  12. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    I was looking for something similar to m855. My thinking was I am using the same bullets, same cases, same primers. I believe at the same length aswell, though I failed to write down my xm855 length so I could be wrong on that.
    I chronographed xm855 at between 2861-2956. Relizing that this is nato spec ammo, I wanted slightly less velocity, seeing as they are using crimped in primers, and brand new brass. That is what I achieved at 24.4 gr. At 24.4 gr of aa2230 I achieved 2886 fps on the high end. That is basically what I got, slightly less than 855, and still apparently within a safe loading range. This was using the same barrel, very close to the same distance away from the chrono, and in very similar temperatures. My load also produced better accuracy than what I was getting from xm855. Now I have two published sources telling me I am on the mid to low end, source dependent.

    Again I am not seeing any pressure signs in the brass or the primers. But I still do not know what sort of pressure I am getting. Judging from my lyman 49th edition I am apparently under 50,400 c.p.u. (thanks for reminding me btw) with a barrel that is rated for 65,000 cpu IIRC. But how far under?

    I would love to go back to ramshot tac, but that simply is not an option for some time apparently.

    Something else I saw. Was aa2230 is very similar to ramshot x-terminator. At least as far as loads go. This powder (ss2230) just has me all sorts of discombobulated apparently.
     
  13. Zombie Steve

    Zombie Steve Decap Pin Killa

    18,083
    18
    May 31, 2007
    Old Colorado City
    The load you have is no slouch. If it's accurate, stick with it.

    Again, if you really want to push harder, look at varget, imr 4320 or if you like ball powders... AA2520.
     
  14. steve4102

    steve4102

    2,310
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    Jan 2, 2009
    Accurate 2230 has changed over the years. It is now identical to Ramshot X-Terminator, has been since 2005.

    Most published data out there is old and should not be used with the New 2230.

    Use Ramshot/Accurate data, not old Lyman or Speer.

    You rifle is a 5.56 and you can safely load to 5.56 chamber pressures(62K). Ramshot/Accurate have pressure tested data for the 5.56 using 2230/X-T. They list Start=22.8gr and Max= 25.3gr for both 2230 and X-t.

    To answer your original question, no, there is no accurate way or formula for the handloader to measure actual pressures without pressure testing equipment.

    That said there is a computer program that can calculate/guesstimate pressures and velocities for you, it's called Quickload.

    Here is what QL says about your load.

    Code:
     Cartridge : .223 Rem. (SAAMI)
    Bullet : .224, 62, IMI FMJBT SS109
    Cartridge O.A.L. L6: 2.225 inch or 56.52 mm
    Barrel Length : 16.0 inch or 406.4 mm
    Powder : Ramshot X-Terminator
    Predicted data by increasing and decreasing the given charge,
    incremented in steps of 2.0% of nominal charge.
    CAUTION: Figures exceed maximum and minimum recommended loads !
    Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
    % % Grains fps ft.lbs psi psi % ms
    -20.0 76 19.52 2318 740 30787 8635 88.5 1.065
    -18.0 78 20.01 2375 776 32847 8915 89.8 1.036
    -16.0 80 20.50 2432 814 35018 9188 91.0 1.008
    -14.0 82 20.98 2489 853 37322 9453 92.2 0.979
    -12.0 84 21.47 2546 893 39776 9709 93.3 0.950
    -10.0 86 21.96 2604 933 42390 9955 94.3 0.922
    -08.0 87 22.45 2661 975 45173 10190 95.2 0.895
    -06.0 89 22.94 2718 1017 48138 10413 96.1 0.869
    -04.0 91 23.42 2775 1060 51299 10623 96.9 0.844
    -02.0 93 23.91 2832 1104 54669 10819 97.6 0.819 ! Near Maximum !
    [B]+00.0 95 24.40 2888 1149 58266 10999 98.2 0.796 ! Near Maximum ![/B]
    +02.0 97 24.89 2945 1194 62106 11165 98.7 0.773 !DANGEROUS LOAD-DO NOT USE!
    +04.0 99 25.38 3001 1240 66209 11313 99.1 0.752 !DANGEROUS LOAD-DO NOT USE!
    +06.0 101 25.86 3057 1287 70599 11444 99.5 0.731 !DANGEROUS LOAD-DO NOT USE!
    +08.0 103 26.35 3113 1334 75299 11557 99.7 0.710 !DANGEROUS LOAD-DO NOT USE!
    +10.0 105 26.84 3169 1382 80337 11650 99.9 0.691 !DANGEROUS LOAD-DO NOT USE!
    Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
    Data for burning rate increased by 10% relative to nominal value:
    +Ba 95 24.40 3019 1255 69078 10819 100.0 0.739 !DANGEROUS LOAD-DO NOT USE!
    Data for burning rate decreased by 10% relative to nominal value:
    -Ba 95 24.40 2713 1013 47742 10646 92.3 0.870
    
     
  15. PCJim

    PCJim Senior Member

    2,950
    1
    Aug 4, 2008
    FL
    Quite interesting charted data. I could help note that Quickload accurately predicted the OP's stated velocity.
     
  16. fredj338

    fredj338

    21,708
    925
    Dec 22, 2004
    so.cal.
    As noted, short of having a pressure system, the Quikloads is as close as you'll get, but still not precise. Stay with book data for safety reasons.
     
  17. steve4102

    steve4102

    2,310
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    Jan 2, 2009
    Quickload can be very accurate. For example,

    Ramshot data for the 223 Rem with 55gr Hornady FMJ list the following.

    Code:
     55 HDY BT-FMJ Start=22.4 2,976fps, Max= 24.9 3,278fps 54,466psi, 2.200OAL , 24 inch barrel
    Plug this into QL and we get this. Almost identical.

    Code:
     Cartridge : .223 Rem. (SAAMI)
    Bullet : .224, 55, Hornady FMJ-BT w/c 2267
    Cartridge O.A.L. L6: 2.200 inch or 55.88 mm
    Barrel Length : 24.0 inch or 609.6 mm
    Powder : Ramshot X-Terminator
    Predicted data by increasing and decreasing the given charge,
    incremented in steps of 2.0% of nominal charge.
    CAUTION: Figures exceed maximum and minimum recommended loads !
    Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
    % % Grains fps ft.lbs psi psi % ms
    -20.0 76 19.92 2655 861 28642 5567 90.4 1.303
    -18.0 78 20.42 2717 902 30568 5729 91.6 1.269
    -16.0 80 20.92 2779 943 32624 5885 92.7 1.237
    -14.0 82 21.41 2841 986 34820 6034 93.8 1.205
    -12.0 84 21.91 2903 1029 37140 6177 94.7 1.173
    [B]-10.0 86 22.41 2964 1073 39592 6312 95.6 1.140[/B]
    -08.0 87 22.91 3025 1118 42205 6438 96.4 1.108
    -06.0 89 23.41 3086 1163 44992 6556 97.2 1.078
    -04.0 91 23.90 3147 1209 47965 6665 97.8 1.048 ! Near Maximum !
    -02.0 93 24.40 3207 1256 51139 6764 98.4 1.020 ! Near Maximum !
    [B]+00.0 95 24.90 3267 1303 54529 6853 98.9 0.993 !DANGEROUS LOAD-DO NOT USE![/B]
    +02.0 97 25.40 3326 1351 58153 6931 99.3 0.966 !DANGEROUS LOAD-DO NOT USE!
    +04.0 99 25.90 3385 1399 62028 6998 99.6 0.941 !DANGEROUS LOAD-DO NOT USE!
    +06.0 101 26.39 3443 1448 66177 7053 99.8 0.916 !DANGEROUS LOAD-DO NOT USE!
    +08.0 103 26.89 3501 1497 70623 7097 100.0 0.892 !DANGEROUS LOAD-DO NOT USE!
    +10.0 105 27.39 3558 1546 75393 7129 100.0 0.869 !DANGEROUS LOAD-DO NOT USE!
    Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
    Data for burning rate increased by 10% relative to nominal value:
    +Ba 95 24.90 3402 1413 64891 6642 100.0 0.925 !DANGEROUS LOAD-DO NOT USE!
    Data for burning rate decreased by 10% relative to nominal value:
    -Ba 95 24.90 3079 1158 44461 6734 93.8 1.081
    
     
    Last edited: Sep 8, 2013
  18. steve4102

    steve4102

    2,310
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    Jan 2, 2009
    A lot of times that easier said than done. Load data varies from one data source to the next often times it is impossible.

    For example.

    Hodgdon data. 223 Rem, 60gr Hornady V-Max, 2.250 OAL.
    Varget Powder, Start=25gr, Max=27.0gr.


    Hornady Data. 223 Rem, 60gr Hornady V-Max, 2.250 OAL.
    Varget Powder, Start=21.7gr, Max=24.9gr.

    It is not uncommon to find a situation like this where the Max charge in one manual is less than the "Start" charge in another. Same bullet, same OAL, same powder, yet completely different results.

    As I said, staying within book data is often time difficult if not impossible. Quickload is certainly not perfect, but neither are the loading manuals.
     
  19. Uncle Don

    Uncle Don Wood butcher

    1,389
    125
    Jan 24, 2004
    Midwest
    I agree that there is no way to actually measure it, but there are signs that I personally look for and follow to keep it in check. In reality, I don't worry about it a great deal because I almost never load to maximum. Getting to old to continually get beat up by recoil.

    1. Primers that start to flatten or pimple around the firing pin strike.
    2. Leading where I didn't have it before using the same bullet and lube.
    3. Faster burning powders than are necessary for the load.
    4. Any type of obvious scuffing of the case head.
    5. When re-sizing seems to take a little more effort than it did last time I sized the same cases.

    Probably forgot one, but as another poster said - by the time these rear their head, it's already too high, but certainly a warning that something isn't right.
     
  20. themighty9mm

    themighty9mm

    3,096
    5
    Sep 19, 2008
    MO
    And this is exactly where I ran into issues. Of my three manuals, the two that had relevant info in them are in a very similar situatioin to as you described. Though I did not see any pressure signs in the cases or primers. I have decided to back off the powder charge, and in this case ignore the lyman data. (Even though the lyman data shows I am well within what is acceptable) Instead I will listen to speer. With the quickload showing near identical velocities, and telling me. "hey, you are pushing the upper limit, watch yourself". I will go ahead and listen to it as well. As it also apparently seems to support what speer is telling me.

    I did not know about the quickload program before. First time I had heard of it
     
    Last edited: Sep 8, 2013