Different barrel lengths and commercial loadings.
http://rifleshooter.com/2014/04/223...s-chop-box-and-his-friends-rifle/#prettyPhoto
http://rifleshooter.com/2014/04/223...s-chop-box-and-his-friends-rifle/#prettyPhoto
Brownell's link to a study on bbl length in .223 and velocity
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R.W.Dale
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This backs up my long term assertion that case volume bore ratio is by far the most critical factor in how much a cartridge is effected by losing barrel length
Basically the more overbite the round is the more it's performance suffers in a shortened bbl
Basically the more overbite the round is the more it's performance suffers in a shortened bbl
Yep...I sold a 264 Win mag because the thing had a barrel long enough to poke an elk in the eye. When I did a comparison study for equal bbl lengths the 264 Win Mag wasn't much better than a.270 Winchester.
Cool article. For me it really reinforces that the 16" (and military 14.5") lengths are the most practical overall. 18" is the max I would personally go for a dedicated long range .223. The gain from 18-20 is negligible, just more length and weight.
gbw
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Very nice.
I wish they'd have continued back to a 1" barrel as a final base. Probably couldn't because it's illegal but it would be interesting.
I wish they'd have continued back to a 1" barrel as a final base. Probably couldn't because it's illegal but it would be interesting.
Here's another source with similar data in a variety of calibers.
http://www.ballisticsbytheinch.com/
Their data for .223 has barrel lengths ranging from 3" up to 18".
http://www.ballisticsbytheinch.com/
Their data for .223 has barrel lengths ranging from 3" up to 18".
Nice...thanks
dsink
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It kind of shows the old rule of thumb that you loose about 25 fps per inch holds true.
R.W.Dale
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bannockburn
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Bexar
Great article; very well written and documented. Thanks for the link.
Great article; very well written and documented. Thanks for the link.
I share strambo's perspective and it's part of the reason that I just built up a very nice 14.5" AR. It's freeing to have a small and light do-most-everything gun without giving up very much performance that I'm unlikely to notice or need.
But there are a few flaws in the experiment, one in particular is very critical.
Beyond the issue that it would have been more interesting and relevant to test a more AR-like firearm - a 1:9 or so, and a greater range of bullet weights (on the low and high end of weight).
But the big one here is that it ignores the opportunity of creating loads that are optimized for the barrel length (and bullet weight). Just as there are a growing number of commercial loads that cater to short barreled handguns (e.g. Hornady Critical Defense), using faster or slower burning powders designed to expire at the right moment of a bullets travel down the barrel. So it's not clear that, optimizing for powder type and barrel length you need to give up even as much as was found in the experiment. It would be very interesting to integrate the skills of a knowledgeable reloader who could do such optimizations to improve the experiment.
Interesting work though.
B
R.W.Dale
Member
Optimization of burn rate to barrel length is a false premise.
Optimal Burn rate is determined by case volume and pressure. The fastest loads in all but the most extreme cases from a long bbl remain the fastest loads even when fired from a short one.
Firearms are not rockets. All the propellant is burned within the first couple inches of bullet travel. It's the high pressure gas resultant from this conflagration that actually pushes the bullet. All a longer barrel does is let's this finite volume of gas push on the base of the bullet longer hence more velocity
So called "short barrel" loads are not so much optimized for the bbl length in terms of velocity but rather flash and bullet impact speeds.
Optimal Burn rate is determined by case volume and pressure. The fastest loads in all but the most extreme cases from a long bbl remain the fastest loads even when fired from a short one.
Firearms are not rockets. All the propellant is burned within the first couple inches of bullet travel. It's the high pressure gas resultant from this conflagration that actually pushes the bullet. All a longer barrel does is let's this finite volume of gas push on the base of the bullet longer hence more velocity
So called "short barrel" loads are not so much optimized for the bbl length in terms of velocity but rather flash and bullet impact speeds.
denton
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It's often said that all the powder is burned in the first few inches. This is not always so. Heavy loads of slow burning powder can burn for a foot or so.
MachIVshooter
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Not true at all. Been handloading a long time, played with just about every powder that is safe in given cartridge, and the chronograph most definitely shows that some powders are more appropriate for short barrels, others for longer tubes. For instance, the powders that give the best punch in a 4" .45 (Unique, WW231) provide lower velocity than, say, Blue Dot, when fired from a 16" carbine. Likewise, the Blue Dot or other medium magnum powders have much lower velocities than the faster ones in the handgun barrels, particularly under 5".
Rifles are no different. The loads that gave the highest velocities in my 22" varmint rifle were not optimal in my 12.5" SBR.
That's what I was just thinking...is there a "best" powder for the 16" inch bbl with cases loaded with 62-65 grain projectiles. In reverse a better powder for bolt guns that have 22" bbls.
R.W.Dale
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Comparing powders suited to a snub nosed revolver compared to a carbine is that Extreme I noted above. I have even done a thread on the phenomena. My findings are that except for an extremely short snubby that the "magnum" powders will still ALWAYS provide the highest velocity.
HOWEVER as barrel length decreases the disparity betwixt fast and slow powder velocities decreases to almost nothing. While in longer barrels the magnum ppwders outstrip the fast powder by a huge margin.
Rifles are even less different, your 12.5 is pretty much the rifle version of a snub noses revolver compared to a carbine. For barrels I've tested from 16-30" the best performing powders powders for velocity remain a constant.
There is a statistical anomaly with the 16.5" barrel length. They have a couple of the loads exiting faster. Taken into consideration with the rest of the data, that shouldn't be possible unless there is was tight spot in the bore. If so, it skews the findings
R.W.Dale
Member
The best powder in either situation is going to be something between H335 and VARGET
Varget usually outperforms h335 and tends to be more accurate, h335 is a lot easier to meter and is less compressed
Good...I've got two pounds of H335.
MachIVshooter
Member
Also very cheap when you score it as surplus pull-down (WC844). I use the heck out 844 in 5.56 and 7.62, because I was scoring it for $8/lb. Not the absolute best choice for either, but cheap and flexible matter when you're talking large volumes.
My statements were in general and not just limited to this article. The velocity difference between 16" and 18" is very small no matter who is doing the measuring.
Strambo, I agree the difference between 16" & 18" is small. It's not worth going from a 16" barrel to an 18". But the difference between the 18" & 20" is larger and the difference between the 16" & 20" is notable. To me, the 18" barrel is too short to be as effective as the 20" and too long to be as handy as the 16". I'd either go with a 16" barrel for a handy carbine or 20" for a rifle. I don't find the 18" length useful at all
TwoEyedJack
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That Remington UMC load is sure wimpy. With a 20" barrel it gives up 300 fps to the Federal load.
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