Barrell and pressure?

Discussion in 'The Ammo & Reloading Forum' started by Gene Seward, Nov 10, 2008.

  1. Gene Seward

    Gene Seward Member

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    If the manual shows that the test barrell is 24 in. and I am shooting a 20" is there anyway of tellling or an educated guess as to how much more I can load in powder? I know not to "assume" anything and that is why I am asking. To me I am assuming that due to the 4" shorter barrell I can load the powder a little hotter. And as always, Thanks. I am soooo thankful for this board and all those that contribute.
  2. Terry_P

    Terry_P New Member

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    The length of the BBL doesn't determine the amount of powder to use. Stick to what is in your reloading manual for min to max loads and find the load that is the most accurate for you. The velocity loss from 24" to 20" BBL doesn't mean you add more powder to keep the velocity constant it means you lose velocity. In a typical rifle load for my rifles the most accurate load is usually not at max anyway and having the ability to put the bullet where I want it is most important to me.
  3. LDBennett

    LDBennett Well-Known Member

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    Gene Seward:

    NO!!!!

    The pressures the gun see's (the limit to load levels is how much the gun can take pressurewise without exploading) is dependent on a lot of things but powder quantity is the most important. The pressure levels are around 50,000 to 60,000 pounds per square inch, all pushing on the bolt of the gun. Add more powder and the pressure gets even higher. Add still more powder and the cartridge case splits sending those gases back into your face. Add more still and the receiver comes apart, sending shrapnel everywhere.

    The chamber has no idea of how long the barrel is and consequently the barrel length does not effect the pressure peak which occurs before the bullet has traveled 6 inches in most rifles. The longer barrel gives higher velocities to the bullet because the pressure pushes on it longer.

    Reloading recipes should not be modified and in particular the maximum load levels should NEVER EVER be exceeded. If the cartridge over all length is shorter than that specified in the manual then the pressure will rise. If a different primer is used the pressures may rise. If different bullets are used then those specified the presure may rise. If different weight bullets are used the pressure may rise. BE SAFE and follow the recipe.

    If you do change anything start you load developement all over again at the starting load level for bullets of that weight and for the recipe's powder. DO NOT be randomly changing things or you will get into trouble fast.

    LDBennett
    Last edited: Nov 11, 2008
  4. Gene Seward

    Gene Seward Member

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    I have all my loads well below the max., but I knew that a shorter barrell would drop the velocity. I guess what I was wondering is how much does the barrell length add or drop in velocity? Does the length effect impact height that much? I am going to have to invest in a chronograph to see the speed to find long range drop. I am at the point that I still like the group size better than how fast it is going. That is the reason I do not own a chrono. now. Do you know of a program to find the impact point of ammo. according to speed and weight of bullets/ bullet coeff.? Like I say all the time thanks again.
  5. LDBennett

    LDBennett Well-Known Member

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    Gene Seward:

    Most reloading manuals have balistic charts in the back of the book for their bullets.

    Any program that might be used that would fit on a home computer is not all that accurate. The ballistic charts in reloading manuals are run on giant computers then checked in the field. Go with the reloading manual for your bullets of choice for the best ballistic charts. But you must know the muzzle velocity so a chronograph reading of your load is necessary to get any accuracy.

    A very coarse rule of thumb is 25 to 100 FPS per inch of barrel. So you might see anywhere from 100 to 400 fps increase. It all depends on the cartridge and its efficiency in regards to powder usage. At some point in barrel length the bullets friction will overcome it and the velocity may even go down with barrel length increases. Most high velocity centerfire cartridges are a long way from that point at 20 to 24 inches but 22LR barrels get max speed from an 18 inch barrel, with most ammo.

    LDBennett
    Last edited: Nov 11, 2008
  6. JLA

    JLA Well-Known Member

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    careful killer. go loading more powder than necessary and you might turn that 20" rifle into a 20" stick o' dynomite...
  7. Gene Seward

    Gene Seward Member

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    LD that is what I was looking for. I have never varied from the manual and never loaded the max. for anything. I would rather get accurate than fast results anyday of the week. The loss or gain in barrell length is what I was wondering. How long have you been loading LD?
  8. LDBennett

    LDBennett Well-Known Member

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    Gene Seward:

    I bought my first reloading dies and components in about 1962. I reloaded then for 32 Winchester Special using my friend's single stage C-H press. The next time I reloaded was about 1986 or 1987 when I bought my next gun...a Taurus PT99 9mm pistol. I have added guns since then until I have over 50.

    For reloading after about 1986 I started with a Dillon Square Deal pistol press. I loved the concept of progressive loading as I truly hated the single stage process I used in the 1960's. I also learned then that I did not like casting bullets either so I have never done that in recent times.

    I next bought a piece of junk Lee Progressive that broke every time I used it so I could load 10mm. That got replaced by a RL550B Dillon progressive and I have that one to this day after over 20 years of use. The others are long gone but Dillon graciously took the Square Deal pistol press back for full value that was applied to the RL550B cost beyond the one year money back guarantee period. That's one of the reason I like Dillon so much. The other is that they quickly replace broken press parts and upgrade the press over time all for free (my press has been completley rebuilt twice in those 20 years, all for free). They help reloaders.

    I did some shotgun reloading for awhile but the Hornady press I bought also broke frequently and was so poorly designed that Hornady replaced the old design with a completely new press design. They refused any credit toward the new model for a trade back of their crummy press. That's one reason I don't like Hornady reloading products...no customer satisfaction efforts by them.

    I enjoy reloading and it is more than just pumping out reloads for me. I search out accurate loads for all my guns. I try various techniques and tools to make my reloads more accurate and to reduce my efforts. For example my case trimming is all motorized. I tried hand lathes, drill press case holders, but settled for the RCBS motorized trimming lathe and their motorized case preparation center. I use Lee Factory Crimp dies but like RCBS, Forester, and Redding die sets better than Lee equivalents. The Lee die sets that I do have are regularly being replaced with mostly RCBS die sets.

    I am a long time subscriber to Handloader Magazine and for a time to Precision Shooting Mag and try to keep up with the latest reloading techniques and tools. Over the years I have collected about 20 reloading manuals and refer to most of them for every new cartridge I add to my 30+ cartridges that I currently reload for.

    I think I am a qualified old fart reloader. But which part am I qualified for.. being a old fart or a reloader? You'll have to figure that one out yourself.

    LDBennett
    Last edited: Nov 12, 2008
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