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I am looking at 9mm barrel length. Thinking about putting a 5.5" or longer barrel in my carry XDm9. Currently I have the 4.5" Service model.

Looking here: BBTI - Ballistics by the Inch :: 9mm Luger Results

I notice that on average going from 4" to 6" barrel yields about 100fps in velocity gains. Is that really something or not? Is it worth it? My gun is only for conceal carry and its very accurate. Money is not really an issue but I don't want to spend the money if there won't be much of a benefit.
 

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I think more important is bullet design. Faster doesn’t mean better if the bullet doesn’t perform well.

Federal HST has shown to perform extremely well for expansion and consistently well bullet to bullet.

I’d look for expansion and penetration tests on your carry ammo in long barrels before I’d worry about fps.
 

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To me, 100 is not worth the added barrel length when it comes to CC. The chances you will ever use the gun for that purpose is slim. But, you should be carrying daily. That’s where you’ll want the comfort. Shoe placement will count more. And training.


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It only matters if your on the receiving end..
 

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I think more important is bullet design. Faster doesn’t mean better if the bullet doesn’t perform well.

Federal HST has shown to perform extremely well for expansion and consistently well bullet to bullet.

I’d look for expansion and penetration tests on your carry ammo in long barrels before I’d worry about fps.
My personal favorite
 

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It only matters if your on the receiving end..
Yes and no.

While the “receiver” really wouldn’t be able to tell the difference, 100fps can mean the difference between the bullet working properly (vis a vis expansion and/or penetration) and failing...and that can go both ways. A bullet can be too slow to work properly, and, say, fail to expand and/or over/under penetrate...but pushed to fast, and it can over expand, fragment, and over/under penetrate as well.

But...most modern defensive ammunition has a pretty wide velocity envelope where it will still function just fine.

Personally, going to @pbnationrc 's question...I think the drawbacks of the longer barrel as far as carry is concerned would outweigh any possible benefits.

If it were a HD pistol, or something like that? Then it might make a little more sense.
 

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Do you really think a "target, what ever that may be" cares if it is 100 fps faster or slower when struck? in self defense bullet placement means more than how fast or how slow the bullet travels. for arguments sake it only means more to the person pulling the trigger. 100 fps will not change how the bullet perform when it strikes an object. 500fps may.
 

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Do you really think a "target, what ever that may be" cares if it is 100 fps faster or slower when struck? in self defense bullet placement means more than how fast or how slow the bullet travels. for arguments sake it only means more to the person pulling the trigger. 100 fps will not change how the bullet perform when it strikes an object. 500fps may.
As pointed out above—yes, 100fps can make a difference between a bullet performing properly and failing.

A prime example is Hornady’s Critical Duty; if it is underdriven, it fails to expand...which is why such failures are very common with this load in short barreled carry pistols—it’s designed for duty pistols with 4”+ barrels. Quite often the velocity drop is right around 100fps...
 

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Failure to expand could mean the difference between a fight stopper and a pass through.

That said, keep popping til the threats start dropping.
 

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There are several ammo options for 9 mm that have good terminal performance from 3 inch barrels. IMO you're better off stocking up on quality defensive ammo and range fodder instead of a new barrel. If velocity will give you more confidence in your ammo, consider +P loads, being aware they also have more recoil and blast.
 

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I did some milk jug testing not long ago, and some of the JHP loads I tested did get more penetration from a 3" barrel vs 4", and it seems that the expansion from the longer barrel was somewhat greater, although relatively marginal.
 

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The only thing that matters, with HP ammo, is being OVER the velocity threshold to expand. Typically, with most HP ammo, it will expand over like 900 FPS or so. Generally, the faster the bullet, the more it has potential to reach MAXIMUM expansion. Think of it this way...

Fast and light bullets dump energy quickly over shorter distance.
Slow and heavy bullets dump energy over longer distance. (after they hit)

U want to kill varmints? Lighter, faster bullets are far better. This is why companies nickname the small stuff like "Varmint grenades" they dump everything in first ~5" of impact. Great for varmints. You want to shoot something thicker and want to make sure you go in deep? 147 grain is far better.
 

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Velocity by itself, hydrostatic shock, becomes destructive-deadly starting at around 2,200 fps. Below that a bullet designed for the velocity you are generating becomes more important than minor velocity or energy differences.
My short barrel guns run Speer Gold Dot Short Barrel ammo.
 

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The only thing that matters, with HP ammo, is being OVER the velocity threshold to expand. Typically, with most HP ammo, it will expand over like 900 FPS or so. Generally, the faster the bullet, the more it has potential to reach MAXIMUM expansion. Think of it this way...

Fast and light bullets dump energy quickly over shorter distance.
Slow and heavy bullets dump energy over longer distance. (after they hit)

U want to kill varmints? Lighter, faster bullets are far better. This is why companies nickname the small stuff like "Varmint grenades" they dump everything in first ~5" of impact. Great for varmints. You want to shoot something thicker and want to make sure you go in deep? 147 grain is far better.
Not entirely true.

A bullet that is overdriven can and will fragment and/or have the expanded “petals” peel back and flatten against the core, giving it a smaller frontal area to damage tissue...

And “energy dump” is pretty much a null term when it comes to terminal ballistics...sounds cool, but has no real meaning.
 

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And none of this is a yes/no good/bad discussion. Nothing works or doesn't work. It's all on a continuing range. At some velocity not opening is an issue, a range where it will open a range where it starts opening too fast at the expense of penetration, a range where it starts coming apart.

There is no scenario where 99 fps is bad and 100 fps more is good. In the grand scheme of things, in the normal ranges of hand gun performance, there is no scenario where 100fps is going to be the difference of you living or dying.. It's well withing the noise of all other considerations... And at the end of it all 200 fps doesn't mean crap if you don't hit a vital structure, and a underdriven bullet 200 fps slow hitting a femural or neck artery wins the fight. Shot placement beats fps and questionable hydrostatic effect every time.
 
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I would imagine that more velocity is a good thing when winter garments are worn. I admittedly have zero evidence to back that up though.....

I’m going to keep shooting until the bad threat ends.
 

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I am looking at 9mm barrel length. Thinking about putting a 5.5" or longer barrel in my carry XDm9. Currently I have the 4.5" Service model.

Looking here: BBTI - Ballistics by the Inch :: 9mm Luger Results

I notice that on average going from 4" to 6" barrel yields about 100fps in velocity gains. Is that really something or not? Is it worth it? My gun is only for conceal carry and its very accurate. Money is not really an issue but I don't want to spend the money if there won't be much of a benefit.
If your ammo doesn't expand from a 4.5" barrel, you're using the wrong ammo. For 9mm, a 4.0" barrel is plenty, and you've got a 4.5". Like others have pointed out, today's HP's are designed to expand from shorter and shorter barrels. The BEST ones will usually work with a 3.5" barrel or even less.

I would go with Federal HST's in either 124 grain or 147 grain. From tests I've seen the 147's are a little better but you can't go wrong either way. (check out the Lucky Gunner gel tests) The HST excels in EVERY caliber.
 
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