Longer OAL = Safer?

ckc123

ckc123

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I've see it mentioned that a longer OAL is safer (Assuming the rifling and mags support it). But I have a quesiton.

Assuming you are going for the same power factor, you would also need to increase the amount of power to account for the larger volume of space in the casing.

So if the same velocity is desired, would not the internal pressure be the same?

and if the internal pressure is the same, then whould it be safer?


The only "safer" thing I can think of would be the powder variance. +/- .05 grain would be safer in a larger load, then is a smaller one.
 
More volume = lower pressures, or equal pressures at higher velocities.

And yes, a longer OAL will buy you a *tiny bit* more volume.

That may be offset by the pressure increase due to the earlier engagement with the rifling though.

Same with Moly. Less friction=less pressure=less velocity. But as you add powder to increase velocity, you find that the velocity increases at a faster rate than pressure does. Therefore, you can safely get a tiny bit more speed out of it at the same pressure levels (while burning more powder)
 
My own chronograph testing has shown that as OAL is increased,the velocity increases as well.This is most likely due to the shorter jump to the lands,and increased pressure, as with less speed,it is more difficult for the rifling to engrave the bullet.
 
Powder burn rates (of some powders) can be affected by pressure, and that of course is affected by the aforementioned lead.

Example I witnessed at the range at dusk, was some 44 mag loads I did up with H110. for My wifes '96 Ruger (That's a rifle) Same load, but one was jacketted, one was cast bullet of the same weight. We fired a good number of these rounds, and the results were consistent.
The cast bullets sounded different, and had very little muzzle flash. The jacketted loads were very loud, with three feet of flash.
The jacketted loads also printed three inches higher on the target at a hundred Yards.
 
That is the beauty of loading your own. We can set the length for power or accuracy. When we go for longer OAL, close to the lands with same amount of powder, we create more room inside the case and pressure goes down a bit, creating less velocity.

My idea of loading close to the lands is we need very good accuracy and I only do it with lite bushing, only neck sized with very little pressure on neck, so the bullet goes inside the barrel best centric I can allow, minimizing vibration.
 
When we go for longer OAL, close to the lands with same amount of powder, we create more room inside the case and pressure goes down a bit, creating less velocity.
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I have to ask if your answer is based on theory,or if you have actually chronographed loads that were identical except for differences in overall length.The theory about the increased volume in the case resulting in lower presuure is common,being closer to the lands means that the bullet has less velocity when it strikes the lands making it more difficult for the rifling to engrave the bullet.My own chronograph testing has shown that this actually more than makes up for the extra volume inside the case,resulting in more pressure and velocity with a longer overall length..
 
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So assuming that I want to keep the same velocity regardless of OAL (for IPSC), then the only difference due to +/- OAL, would be having the bullet closer to the lands and groves, when feeding. this should in theory can be tuned to give me better accuracy? (Eg matching close as I can to the groves, but not to far and be touching them (and increase the pressure a bit).

correct?
 
I have to ask if your answer is based on theory,or if you have actually chronographed loads that were identical except for differences in overall length.The theory about the increased volume in the case resulting in lower presuure is common,being closer to the lands means that the bullet has less velocity when it strikes the lands making it more difficult for the rifling to engrave the bullet.My own chronograph testing has shown that this actually more than makes up for the extra volume inside the case,resulting in more pressure and velocity with a longer overall length..
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My experience and tests I have conducted with different bushings seating bullets almost on the lands.
I never set bullet right on lands for my hunting loads using regular full/neck siez die. :)
 
Yes bushing, little steel or titanium rings most of reloaders use for sizing neck to obtain desired tension....however some people may use that for dif reasons :|
 
Yes bushing, little steel or titanium rings most of reloaders use for sizing neck to obtain desired tension....however some people may use that for dif reasons
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I was trying to understand the connection between bushings and overall length.I still don't see it.:confused:
 
I dunno, I find it varies with my guns, proving nothing useful. Further, since I cannot measure pressure, I get no help there, either. (What if pressure goes down AND velocity goes up? Pressure does not equal velocity, especially given that the capacity does not hold constant with our OAL tests)

So we're back at square one. It may or may not have an impact, there are no rules of thumb (other than closer to the lands generally = more accurate), so you're stuck with the 'try-it-and-see' approach.

You're asking for proof of the theory, which would require access to a lab and expensive equipment that none of us have access to.
 
Good call Prosper, but why wouldn't higher pressure lead to higher velocity? all that pressure has to push something somewhere.
 
savagefan said:
Good call Prosper, but why wouldn't higher pressure lead to higher velocity? all that pressure has to push something somewhere.
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Not necessarily, All depends on the pressure curve and its duration. A fast burning powder may develop higher pressure initially but its duration being short lived may not get you the velocity of a slower powder with a longer duration of that pressure even if it is lower pressure. i.e the bullet may not accelerate as quick in the barrel with slow powder but it keeps accelerating longer after the initial energy of the faster powder which may start the bullet faster but burns up and pressure falls off sooner. Many things can affect this, a bullet seated at the lands may take more pressure to start than one seated off the lands, but it also can work both ways, using more pressure to start it may mean it dosen't have as much pressure by the time it gets to the end of the barrel. You never what it is going to do and it varies with the bullet seating, case capacity change due to seating and the burning rate of the powder. You won't know till you try all the combos of the components possible in an individual rifle. No two will be the same.
 
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