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Using an auto pistol barrel find a MAX O.A.L with your bullet

Discussion in 'Handloading and Reloading' started by Walkalong, Feb 20, 2010.

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  1. nplaggie07

    nplaggie07 Member

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    Sorry to bring this thread back up but I have a question. I use this method mainly shooting lead. I ran into a problem when helping my brother load for his Sig 45acp.

    He wanted to load 185 grain hp/xtp. We pulled the barrel out and I started at max oal (1.275) and the round chambered and dropped out easily. The manuals I have all had a oal of 1.175 to 1.230. My experience with 180 lead bullets lead me to believe the round needed to be shorter to get a clean powder burn.

    I decided to seat them to 1.200 and use start loads. My question is what is causing the descrepancy between oals? Did I do the right thing in seating the bullet deaper or should I have stayed out at max? It didn't seem to make a difference on how deep the bullet was seated. They all chambered and dropped out of the barrel easily.
     
  2. joneb

    joneb Member

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    I settle on a COL that functions best in my firearms, finding a max COL is important when loading a bullet with or without load data.
    I will load 2 or 3 dummy rounds (no primer or powder) with no crimp at the max COL minus .01", and then manually run these in the firearm. I check for bullet set back and dings in the bullet, if these rounds cycle well in my firearms I have a workable max COL, if not I gradually decrease the COL.
    If I have load data for the bullet I'm using with a given COL, I will try to find a workable COL closest to it using the method above so I can determine a start charge.
     
  3. Walkalong

    Walkalong Moderator

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    Same here.

    Determine an O.A.L. that functions well, and (while taking into account the O.A.L. the manual used), go from there. AC

    Welcome to THR nplaggie07
     
  4. nplaggie07

    nplaggie07 Member

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    Thanks for the replys. Gonna try the rounds this weekend.
     
  5. UltraCdp

    UltraCdp Member

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    Walkalong,
    Just found this thread. Thank you for the great write up. May I ask what you use to polish your barrel with? It looks great.
     
  6. Walkalong

    Walkalong Moderator

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    Thanks. I did not do anything to the barrel.
     
  7. joneb

    joneb Member

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    I can't believe this thread is still not a STICKY :confused:

    Again, nice work Walkalong
     
  8. blarby

    blarby Member

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    I use this thread over and over.

    Its comin back around again.

    Thanks walkies !
     
  9. bds
    • Contributing Member

    bds Member

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    Yes, awesome thread ... a picture is worth a thousand posts. :D

    +1 for sticky.
     
  10. greybeard57

    greybeard57 Member

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    Very informative. Great photography. But I must be tired or dense or stupit or all three.

    Is the overall objective to get the greatest oal that will work in a given gun without actually binding on the rifling if it will cycle through at that length? Which, in affect, would make the oal given in the data the minimum oal which must not be gone under?
    I read the Lyman book and the Lee reloading book and that, combined with being in a bachelor course these days in college, makes me think my brain is being scrambled. I'm too old for CRS, I must have entered the senility stage.. :eek: :banghead::p
     
  11. Walkalong

    Walkalong Moderator

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    The idea is to see how long you can load a particular bullet and still chamber without the leade/rifling being engaged and interfering with the round chambering.

    After that you need to come up with an OAL that feeds and functions well. Knowing how long you go can speed that up and help avoid OALs that will be a problem.

     
  12. bds
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    bds Member

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    The closer the bullet's bearing surface (part of bullet base that rides the rifling) is to the start of rifling when chambered, sooner the chamber pressures will build when the primer ignites the powder charge.

    If the bearing surface is further away from the start of rifling when chambered, more high pressure gas will leak around the bullet before chamber pressure builds.

    More consistent chamber pressures will produce more consistent muzzle velocities/lower standard deviation (SD) which will lead to more consistent shot groups/accuracy.

    [​IMG]

    The not to scale picture above shows leade as space the bullet jumps from the case neck/chamber to the start of rifling. While shorter OALs will allow the finished rounds to feed/chamber reliably from the magazine, more high pressure gas will leak around the bullet when the primer ignites the powder charge as the bearing surface of the bullet base will take longer to engage the start of rifling and shot groups may not be as accurate as rounds with longer OALs.

    As Walkalong posted in this thread and illustrated well with many pictures/barrels, using the barrel drop test to determine the max OAL and then determining the working OAL that will reliably feed/chamber from the magazine for your particular pistol will ensure more accurate loads.
     

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  13. orionengnr

    orionengnr Member

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    I have had that blue drawing/diagram showing the case seating depth for several years; have shared it, have consulted it regularly...it is great info.

    The remainder of the thread seems to show that there is a huge difference in .45acp barrels--far more than I have seen.

    The first pic with the dark grey "Precision Bullet" looks as if the "shoulder" of the bullet sits proud of the case by 1/4" or better. That is a huge amount.

    The later pics show it seated deeper. But in order for me to get to the point where the "blue background" diagram of the case sitting flush with the barrel or a bit less...I need to have the bullet seated a lot deeper--just a smidge of the shoulder sitting outside the case. Call it .030 or so.

    That works both with my Dillon Case Gage, and passes the "ker-plunk" test with the barrel of any of my 1911s.
     
  14. 1SOW

    1SOW Member

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    RF Wobbly "PUSH TEST" method for finding max "usable" oal in straight-wall semi-auto loads:


    There are several ways to do this, but here's my method.... Fit a new bullet into a fired case. (No powder; fired primer.) If you try 2 or 3 bullet/case combinations you'll end up with 1 or 2 where the bullet is a snug "push fit". Set the bullet out to an OAL of like 1.300". Any OAL longer than what you need. Working with your barrel REMOVED from the gun, slide this "test cartridge" into the chamber. At some point it will stop going into the chamber. In other words, whatever the bullet is striking is keeping the test cartridge from going all the way in. At this point, if you continue to push, the bullet will slide back into the case until the mouth of the case comes to rest on the end of the chamber. So whatever the bullet was striking has pushed the bullet back into the case. Follow?
    Finding%252520OAL%2525201.jpg
    Finding%252520OAL%2525202.jpg



    Now, slowly and carefully withdraw the test cartridge and measure its new length. Do this with other bullets and other cases until you start to see the same number again and again. That measurement is your exact chamber length for that bullet in that barrel. Now of course we need a set-back distance off the rifling, so subtract at least .015" from that number to obtain your maximum OAL.

    Finding%252520OAL%2525203.jpg
    Finding%252520OAL%2525204.jpg


    So let's assume your test cartridge keeps giving you a number like 1.177". We subtract our setback and get 1.177" - .015" to equal 1.160". You see I've backed off an additional .002" because 1) it's simply easier to read on a caliper, 2) the chances of finding a load for 1.162" is impossible, whereas 1.160 is probably pretty good, and 3) we're talking less than a human hair, so gee whiz give it a break!

    With an OAL like 1.160" you can use any load for 200gr jacketed that is equal to or shorter than. So the load for the 1.155" from Hodgdon will work nicely. Can you follow all that? I hope so. Now you are armed with EXACT knowledge of your firearm and don't have to guess any longer.
     
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  15. greybeard57

    greybeard57 Member

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    OK, I guess. :neener: ;)

    No, This is really seriously good info! :)

    I followed you up until this. MAN! I really must be dense! I understand the equal to or shorter than part. What I'm not picking up on is whether or not I maintain my OAL at the set point I determined from the push tests? In other words, ALL my built ammo will end up at the same length (per my chamber dimensions) and the loads that can be safely used will be ANYTHING which will fit into a recipe that calls for a OAL SHORTER than that? (not going over max of course) :banghead: Am I getting close? :confused:

    I have a 4.0 GPA but I'm feeling SOOO stupit right now.

    Thanks for the assumed patience BTW. :)
     
  16. 1SOW

    1SOW Member

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    greybeard57
    If the longest your chamber will accept is -say- 1.160", subtract about .015" and that gives 1.145" as the longest SAFE OAL for THAT GUN's chamber with THAT particular bullet. 1.145 is the MAXIMUM OAL you can use and be sure of no problems

    THEN any load manual recipe for an OAL "at 1.145" OR Shorter will run smoothly in THAT guns chamber with THAT particular bullet.

    So if Hogdon says load at 1.142"--no problem--you're good-to-go.

    Hope this makes sense.
     
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  17. SpentCasing

    SpentCasing Member

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    So the OAL in the book is a lowest point? If I do the test stated above, with my G17 bbl, My max COAL is longer than SAAMI spec. (1.169)

    So does that mean that this particular bullet (124gr XTP) is safe from SAAMI max spec all the way down to what Hornady states in thier book (1.060) in my bbl?

    I also have Hornady 124gr HBFP bullets and they state in their book OAL is 1.050.

    This OAL stuff is really confusing me. I want to go by the book, but the book lists really small OAL it seems especially compared to other books I have. I can safely go higher than suggested OAL but never lower, correct?
     
  18. Walkalong

    Walkalong Moderator

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    SAMMI puts out a max OAL, not a minimum. Load books log what OAL they test a bullet at. Increasing that OAL will decrease pressure, while decreasing that OAL will increase pressures. This has nothing to do with feeding or fitting, which is what this exercise is about.

    In .45 ACP a .030 decrease in OAL will not increase pressures much, due to the large capacity of the case and the low pressure it operates at. An .030 decrease in 9MM can increase pressure a great deal, due to the small case and the high pressure it operates at.

    Basically, yes, as the pressure is safe at the OAL they tested at (1.060), and increasing it anywhere from that to a Max 1.169 will only decrease pressures.
     
  19. bds
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    bds Member

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    No. The OAL in the book is the OAL that was used to test the average maximum chamber pressures for that load data.


    Not quite, The listed OALs in published load data are not "suggested" OALs but simply OALs that were used for the test barrel fixtures (and not real pistols) to measure average maximum chamber pressures. Different pistols/barrels may require shorter/longer than listed OALs to reliably feed and fully chamber the finished rounds.


    Not practically. Glock barrels have longer leade (see pictures below) and more gradual start of rifling than many barrels and will allow longer than SAAMI max OAL. Even though longer than SAAMI max OAL may pass the barrel drop test, it does not mean the round will fit the magazine and/or feed/chamber from the magazine when the slide is released. I usually start with SAAMI max OAL when I conduct my barrel drop test outlined in this thread.

    [​IMG]
    Glock barrel
    [​IMG]


    For semi-auto pistols, using book OAL WILL NOT ensure the listed OAL will reliably work with your pistols/barrels/magazines. For any new bullet you reload for your pistol, you should conduct the barrel drop test to determine the max OAL and function test to determine the working OAL.


    How about some easier step-by-steps?

    Note: For the barrel drop and the function tests, I use .021" added to the bullet diameter for the taper crimp. So for .355" diameter bullet, I use .376" taper crimp.


    Determine the max OAL:
    - Remove the barrel from the pistol and clean the barrel, including the chamber
    - Using a dummy round (no powder/no primer), start with the SAAMI max OAL and incrementally decrease the OAL until the dummy round falls in the chamber freely with a "plonk" and spin without hitting the start of rifling
    - This OAL is your max OAL


    Determine the working OAL:
    - Put the barrel back in the slide and reassemble the pistol
    - Lock the slide back
    - Load the max OAL dummy round in the magazine and insert in the pistol
    - Release the slide without riding the slide
    - If the dummy round won't fully chamber reliably, incrementally decrease the OAL until it does
    - This OAL is your working OAL


    Conduct powder work up:
    - Reference all available published load data from powder and bullet manufacturers for the given bullet weight and nose type and establish the lowest start-to-max powder charges
    - If the working OAL is longer than published OAL and the bullet seating depth is shallower, use the published start/max charges
    - If the working OAL is shorter than published OAL and the bullet seating depth is deeper, consider decreasing the start/max charges by .2/.3 grain.
    - Load 5-10 rounds of .1-.2 incremental charges from start-to-max charges using the working OAL
    - Range test to determine the powder charge that starts to reliably cycle the slide, fully feed/chamber rounds from the magazine and reliably extract the spent cases (depending on the bullet/powder combination, this may happen either at start-to-mid range load data or mid-to-high range load data)
    - Continue the range test while monitoring the accuracy trend. The powder charge that begins to produce accurate shot groups is your lighter recoil/range practice/plinking/target load (depending on bullet/powder combination, this may happen either at mid-to-high range load data or high-to-near max load data)


    mid-range target load vs full-power max load:
    - Some powders with faster burn rate than W231/HP-38/Unique/Universal will start to produce accuracy even at mid-range load data at slower velocities. I use these powders for slower velocity target loads.

    - Some powders with slower burn rate than W231/HP-38/Unique/Universal will produce optimal accuracy at high-to-near max load data. I will use these powders for higher velocity full-power loads.


    Using mixed range pick up brass and max loads:
    If you use mixed range pick up brass to reload, you may want to consider this, especially if you have barrels with less than fully supported chambers.

    The spent cases you pick up at the range or purchase may have been reloaded several times and you do not know the condition of the brass strength, mealiability, etc. For these reasons, I reserve known once-fired rounds I saw go from factory boxes to the pistols for max loads to shoot in 40S&W Glocks. For me, I use mid-to-high range load data for mixed range brass with unknown reload history. I may be too cautious doing this but have not experienced any KaBoom in my 9mm/40S&W/45ACP Gen2/Gen3 Glocks with factory barrels the past 18 years even with using faster burning powders like Bullseye/Titegroup/Clays/Promo/Green Dot/WST/N320/W231/HP-38. YMMV

    I hope this helped.
     
    Last edited: Apr 11, 2013
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  20. SpentCasing

    SpentCasing Member

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    Thanks to everyone who took their time to create and respond to this thread. It's seemed to help a lot of people, myself included. This is why I love this site. Keep up the good work!
     
  21. highway2082

    highway2082 Member

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    My OAL with .45 is with mgazine not chamber?

    Lyman says 1.275 OAL. When I use Berry's Premium Plated 230 gr. JHP they are way to long? If I seat shorter will that not change pressure with the 5.5 grains of W231? Can I seat until mags feed or recommend pull and lower powder? Respect/FD
     
  22. Walkalong

    Walkalong Moderator

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    1.275 is the SAMMI max OAL for .45 ACP. I seat round nose bullets to fall between 1.260 and 1.265 OAL. Others use a slightly longer or shorter range.

    The Berrys 230 Gr HP is going to have to be loaded shorter than that due to the shape. I cannot find a pic of it and do not remember what it looks like. I don't remember them making a 230 Gr HP. I seat the Berrys 200 Gr HP at 1.200.

    Yes, seating the bullet shorter will increase pressures. Start out with around 4.7 Grs W-231 and work up. You should not start with 5.5 Grs no matter what OAL you use.

    Welcome to THR

    Berrys 230 Gr RN
    [​IMG]
     

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  23. ASCTLC

    ASCTLC Member

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    People like me greatly appreciate your taking the time to detail this information for us Walkalong! It sure simplified my way of determining seating depth followed by a plonk test for verification.

    Andy
     
  24. gamestalker

    gamestalker member

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    Tilos, I've used your method, but without the pencil. I used a dial caliper down the barrel, which completely eliminated having to measure the pencil. It seems as though using the pencil adds one more step?

    Sorry Walkalong, I'm not trying to impede your message, which by the way is some really nice work, and will most certainly help many reloaders to fine tune their seating methods.

    GS
     
  25. 918v

    918v Member

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    The Leade/Throat/Freebore (people use these terms interchangably)

    DIAMETER

    is also very important, something that everyone left out.

    The above picture shows the case, the bullet shank, and the bullet nose. Notice how some of the bullet shank sits in the "leade". This is so that the "leade" can align the bullet with the bore for accuracy.

    Typically, the "leade" diameter is larger than the bullet shank diameter. Sometimes, however, the "leade" is the same or smaller in diameter:

    Case in point- I had a Wilson CQB .45 ACP with a .452" "leade" diameter. It would not allow .452" #68 SWC rounds to chamber at 1.250" OAL. They had to be loaded to 1.200" or shorter. That's stupid. That's alot of lead shaving. So I resized the bullets to .4515" and I was now able to use the correct OAL.

    Many times what causes problems is not that the "leade" is too short. It's just that the "leade" is too narrow and the bullet ogjive is stopping against the beginning of the "leade".
     
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