Whitehorn

All things being equal how much 'ballistic' performance do you lose by shortening the barrel by 4 inches. How would this affect the performance of non magnum calibers like: the 308, 30/06 and 270.. Thanks.

bigcountry

Well, alot in that spot. If you were talking about dropping from 33" to 30, almost nothing. But you are in a sweet spot from 18" to 26". I have seen 120fps drop going from 24 to 20. Depends on your load and powder also. Some slow powders are building pressure greatly at that point. Some fast powders have starting to drop pressures. Don't get me wrong, pressure is still building but not as fast.

USMC PMI

What is the purpose? If you are making a short, easy to carry brush gun you may have a drop in FPS but it will not cripple the short range effectivness of any of the calibers listed. Just curious why you would make such a drastic change in barrel length at, as BC stated, the sweet spot.

Nomercy

One thing I've got to comment on, BC is right about it making a lot more difference at that bbl length than at others, but his observed drop of 120fps is pretty conservative, I've seen drops of 300fps going from a 20" to a 16.5" from a .300WM, the .30-06 I tried did about the same, a ~250fps lost...

Just figured I'd point that out, since 120fps on a .30-06 is only like a 4% loss, but what I'd seen was around a 10% loss. It really just depends on where your load's "sweet spot" is. The sweet spot is really the point where the bullet reaches its maximum velocity, OR, where its acceleration levels out...at first, the bullet is going to be accelerated slowly, then very quickly it will begin to accelerate VERY quickly, then eventually it will level off and begin to decay again. The sweet spot is where it levels off. Drop bbl length below that point and you start cutting out a LOT of power.

That said, I don't really know that I'd worry about losing 10% of my power from a .30-06, heck, even at 10% velocity lost, it's still going to have around 2200-2300ft.lbs of energy (about what it'd have at 100yrds is what it now has at the muzzle), which is still more than a .30-30 has at the muzzle!!!

Truth be told, it may be possible for a handloader to achieve nearly identical results in either bbl, as long as the sweet spot isn't too far ahead of the muzzle, just by changing powders. Loading a faster burning powder might let you bring the sweet spot back into your bbl without increasing your pressure beyond the rating of your rifle. You might look into this should you decide to go ahead and chop your bbl.

Whitehorn

I am just curious myself since I see rifles offered in these diffrent barrel lengths. My current rifle is a 270 model 70 classic LT with a 24"... Certainly doesn't feel too long for me and I'm very happy with it.

bigcountry

USMC. I thought about building a 338win mag with a 20" barrel for elk and moose hunting. I find very long barrels (~26") to be in the way with really thick hiking like I do in Newfoundland. A short handy barrel would work out good I believe.

Virginia7

For a "short" 338Win.Mag, how about 23"? I don't know, but I wish they would settle on
different lengths for std. and magnum rifles. Personally, I like 23" for magnums, 21" for the standards (270, 280, 308, 30-06), and 19-1/2" for carbines (not 18-1/2").
Yeah, I know

Anyway, concerning the orig. post, shortening from 24" to 20" in the std. cartridges noted shouldn't be too bad. I'd expect a loss of about 100 to 150fps, depending on the
cartridge.
The 308Win. seems to hold it's own pretty well down to 20". I found the following noted by Finn Aagaard in his book, "Hunting Rifles & Cartridges". He tested various loads using a 308Win.: "The results of the chronographing were quite interesting. The five different factory loads recorded velocity losses varying from 20fps to 35fps when the barrel was shortened to 20" ..... In contrast, shortening the barrel a further 1-1/2" to 18-1/2" produced velocity losses that averaged 71fps. The average total velocity loss for 12 different loads when the barrel was cut from 22" to 18-1/2" came to 96fps. It seems therefore that one would lose almost nothing by shortening a 308 barrel to 20", but that cutting it shorter does exact a price."

USMC PMI

BC Great minds think alike, I had the same idea in mind. A quick handling, short, light rifle to hike with, heck most of the time you wont shoot to 200 yards hunting anyway. This is a good post though, it seems that the general "handling" of rifles is rarely discussed. Certainly a shorter barrel would improve handling.

USMC PMI

You have me thinking now (I know scary thought) I may take on a project along these lines. I am thinking a center fire rifle, short barrel (18" - 20"), maybe in semi-auto since accuracy is not the main objective and to make short range follow up shots a breeze (I own no true hunting rifle in semi-auto so diving into new a new area on this one). I will say for deer size game out to 200 yards max. Something to take along on hikes through heavily wooded and rugged moutain terrain. Scoped but not over powered, max something in 3 x 9 with the widest field of view possible. I think I will go with a used rifle so caliber may be determined for me, but I think I would prefer something in .30 cal in one form or another and most likely not a Mag, that would just be blowing power out the end of the barrel. Most likely I will cut and re-crown the factory barrel, again since accuracy is not the main objective and to stay within a budget. I am just forming this idea, any suggestions? Anyone out there use such a creature?