Rookie question: pistol data vs. rifle data

Discussion in 'Ammunition & Reloading' started by Shopfox, Dec 12, 2019.

  1. Shopfox

    Shopfox Well-Known Member Supporter

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    I'm looking at reloading data for 44 mag, 300gr XTP w. H110 and magnum primers.

    Rifle loads range from 18.0gr to 19.0gr (Hodgdon manual), and 11.4gr to 18.4gr (Hornady manual)

    Pistol loads range from 18.0gr to 19.0gr (Hodgdon manual), and 17.5gr to 20.1gr (Hornady manual)

    Why would pistol loads from Hornady have a higher max?

    (I'm assuming it has to do with short barrel length, or pressure bleeding off in a cylinder gap, but I'm only guessing)
     
  2. Wambli

    Wambli Well-Known Member

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    Because on short barrels a lot of your H110 (slooooowwwwww burning powder) will be expelled out of the barrel unburned before reaching max pressure. This will give you a colossal fireball to no effect. In a rifle barrel you have room to burn all the powder giving you higher potential velocities but also potentially achieving higher pressures. Because of that you can play with the loads to go from pleasant to brutal more effectively.
     
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  3. Sniper03

    Sniper03 Supporting Member Supporter

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    As a rule you will find that somewhere in the middle of the loads will produce the best results! Only from experience! But IMO I think Hornaday has done much more research in the reloading and bullet field. So they get my vote for the most credible! And as was stated it depends on what weapon the tests and pressures were taken from. Assuming they both used the same powders. And other factors regarding the same specification of powder, including environment it was subjected to. (*Picking the Fly Sh**t out of the Pepper!) Barrel length as mentioned can result in varying results and recommendations.

    For example for our Army Match Ammunition or LE Sniper Rifle Ammunition. When we were on the line training or out on an operation for example. We always kept our ammunition out of the direct hot sun before loading it into the rifles. The high heat had a definite effect on the rounds impact point
    So one company could have tested under one condition while the other tested under another condition.

    03
     
    Last edited: Dec 13, 2019
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  4. Shopfox

    Shopfox Well-Known Member Supporter

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    I'd loaded and almost shot a complete box loaded at 19.5 gr. I don't remember why I'd thought it was a good idea or safe at the time. Maybe I'd looked at the T/C data? - I don't know.

    I later read that Underwood Ammo makes a +P+ 44 mag ammo, only for use in certain firearms. My CVA is on the "strong" list of acceptable firearms, so I'm a little less freaked about shooting 0.5 gr. over the max.

    On the upside, the 19.5 gr 300 XTP's sealed well, and burned clean, and looked no worse for the wear. Primers, headstamp, and sidewalls looked good. That said, I'll back them down to 19.0 gr....
     
  5. Sniper03

    Sniper03 Supporting Member Supporter

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    You are exactly on Point! One should always be aware of any stress, cracks or signs on the Casings of any round. As well as the Primes and Head Stamps after being fired. If one is exceeding on a load there are usually always signs. The other thing that years ago I learned before I had an incident. Was the criticalness of the "Overall" Case Length. And especially with Rifle Calibers! At first I did not realize that the cases of my 6.5 Grendel would stretch as much as they did with only one firing. But after reloading them noticed what I believed to be excessive pressure when I fired them. I was correct the Cases had stretched and was crimping the Case even more on the Bullet Canular when the Bolt went into battery! And the pressure was exceeding what it should have been. So that is also very important!;) So trimmed them to the proper OAC Length for the round and good to go!:)

    03
     
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  6. locutus

    locutus Well-Known Member Supporter

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    Remember that ALL reloading manuals are general guidelines, they are NOT holy writ handed down from on high.

    If you want to factory duplication loads, look at 3 or 4 manuals, start halfway between the max and starting charge, and work up your load in your weapon.

    You may find that YOUR max is a full grain or two less than the manuals, or a full grain or two more.

    A chronograph, IMHO is a near absolute necessity for anything hotter than target loads.
     
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  7. PeeJay1313

    PeeJay1313 Well-Known Member Supporter

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    chronograph... New thought. To be continued..
     
  8. Shopfox

    Shopfox Well-Known Member Supporter

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    I remembered the logic of why I used 19.5gr... the factory ammo box had 1150 fps. Looking at the Hornady manual, only 2 pistol loads were below max at 1150fps: Win 296, and H 110.

    Perusing Hodgdon's site today, I read this about pistol loads vs rifle load applications - and why their load data is the exact same for both from them:

    "The first thing to remember is that the chamber dimension does not change based upon application. A 223 Remington chamber is the same whether the gun it is in is a handgun or a rifle. The chamber dimension determines the pressure. So, the pressure is the same when fired in that chamber in a rifle or a handgun. The barrel length has no impact on the chamber pressure and hence the reloading data (powder charge and pressure).

    The length of the barrel will change the actual velocity you observe. In general as the barrel gets shorter than standard the velocity will lower, and as the barrel gets longer than standard the velocity will increase. This does not change the reload data (powder charge and pressure), just the velocity."

    Supporting that interchangeable view 1 step further, I looked at the 44 mag pistol and 44 mag rifle section of my Lyman manual. When the same powder and bullets are used (at least for H 110), the min and max loads are the same. In the first sentence of the rifle data for the 44 mag, "Pressure limits for this cartridge are the same in rifles or handguns".
     
    Last edited: Dec 14, 2019
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  9. Wambli

    Wambli Well-Known Member

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    I’ll retract what i posted before. It was based on old information so I apologize. I got curious after your post so I checked with some friends that are true reloading experts and they showed me conclusively that peak pressure occurs within the first inch or so of the barrel. Thanks I learned something new and got myself a lengthy education on modern reloading using computers!
     
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  10. Shopfox

    Shopfox Well-Known Member Supporter

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    I think I found my answer by reading up on companies selling "hot" 44 magnum ammo. They explain in which guns their ammo is safe to shoot and why it's safe.

    Hornady uses data based on actual firearms, not universal receivers, so the divergent results make sense from them in light of this:
    http://garrettcartridges.com/garrett44mag.html

    Per Garrett, "Revolvers, by virtue of their long chamber throats, allow the use of longer cartridges than can be used in other firearm types. In response to this, we have designed our bullets to move weight forward, thus utilizing the long chamber throats of the revolver as storage areas, as opposed to their normal function as empty pre-barrel pathways. This is the defining characteristic of our long weight-forward Hammerheads, which exhibit long noses and unusually short bullet bases, resulting in increased gunpowder capacity in the cartridge case. By so doing, we are able to generate more power than can be safely generated by using conventional bullets, with their characteristic short noses and long bases. An inspection of the loaded revolver clearly demonstrates our weight-forward approach, as our long bullet noses dramatically fill the chamber throats."

    From Shooting Sports USA, "Some shooters have the chamber throat extended to fit a wider range of bullet designs, and a lengthened throat itself helps to reduce pressure."

    In a nutshell, revolvers (at least the one used by Hornady), have long chamber throats, and long chamber throats reduce pressure. It follows that more powder can be used in revolvers than rifles to achieve the same pressure level.
     
    Last edited: Dec 16, 2019
  11. Wambli

    Wambli Well-Known Member

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    Well Shopfox, I can tell you one thing, this is NOT a rookie question. I've learned more reloading science trying to understand this one subject than in decades of reloading. I'm glad I have access to some very smart folks that explained this to me. Thanks for sending me down this path. We've come a loooong way since I started reloading a few decades ago, that's for sure. I remember when I started hot-rodding .45 Colt, having to "guess" what recipes would yield desired results and not blow me up in the process. Now we have a bunch of computer programs that take all the guesswork out of any combination of components you can think of.
     
    Last edited: Dec 16, 2019
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