How to educated guess pressure?

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

  1. 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.

    Wanna kill these ads? We can help!
  2. Loading...

    Similar Threads Forum Date
    Glock Announcement #3, Educated & Non-Educated Guessing General Glocking Jan 14, 2013
    Those undereducated overpaid NFL football players - look what one did now The Okie Corral Dec 21, 2014
    How do I get educated in the physics of this?? Reloading Nov 17, 2013
    puns for the educated mind The Lighter Side Jul 23, 2013
    How Did the Educated Become So Ignorant? Political Issues Jun 3, 2013

  3. 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.


    #2 F106 Fan, Sep 6, 2013
    Last edited: Sep 6, 2013
  4. 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
    #3 themighty9mm, Sep 6, 2013
    Last edited: Sep 6, 2013
  5. Zombie Steve

    Zombie Steve Decap Pin Killa

    Your Lyman manual lists the pressures they got. SWAG from there.
  6. 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.

  7. Zombie Steve

    Zombie Steve Decap Pin Killa

    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.
  8. GIockGuy24

    GIockGuy24 Bring M&M's

    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.

    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.
  9. 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
  10. 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.
  11. 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
  12. Zombie Steve

    Zombie Steve Decap Pin Killa

    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.
    #11 Zombie Steve, Sep 7, 2013
    Last edited: Sep 7, 2013
  13. 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.
  14. Zombie Steve

    Zombie Steve Decap Pin Killa

    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.
  15. 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.

     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
  16. PCJim

    PCJim Senior Member

    Quite interesting charted data. I could help note that Quickload accurately predicted the OP's stated velocity.
  17. 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.
  18. Quickload can be very accurate. For example,

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

     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.

     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
    #17 steve4102, Sep 8, 2013
    Last edited: Sep 8, 2013
  19. 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.
  20. Uncle Don

    Uncle Don Wood butcher

    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.
  21. 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
    #20 themighty9mm, Sep 8, 2013
    Last edited: Sep 8, 2013

Share This Page

Duty Gear at CopsPlus