1911Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
3,446 Posts
Discussion Starter #1
NO this is not some whine "is 5 inch better than 4 inch" because we all know the only real difference is the one inch longer sight radius, plus the 5" is a little heavier.

What I was looking for early this last Summer was the change in velocity between the 4" and 5". Conventional wisdom tells us that the 45 is a big, slow slug that takes a lot of barrel to get it going. I wanted to know how long it needed to be.

I did searches everywhere I could think of to see if anyone had an answer. If they do, I couldn't find it. In the first 250 threads on this forum, only one dealt with velocity vs barrel length and that was for a 357 revolver. At the same time I DID find that there were a lot of reviews done and published by Shooting Times that included chronograph results with various guns and thus various length barrels. Since they were there to establish how that individual gun performed, I gave more credence to those reports, because they were not attempting to prove anything about velocities but simply report them.

After finding three separate reports I started making copies of the web pages so I would not have to "find" them again each time I wanted to refer to the data. After finding five, I decided to put them into a single web page. I color coded the entries so that the table would be easier to read. It's at http://www.w0ipl.net/Vel-45ACP.htm

My conclusions (that I offer, and ask your input on) are:

1) There is very little difference in velocity of the 4" barrel, compared to the 5". In fact, for a few +P loads, the 4" is slightly faster. I consider less than twenty feet per second difference to be effectively the same.

2) Even the 3" is only about ten to fifteen percent down from the 5"

What did I miss? :scratch:
 

·
Registered
Joined
·
1,158 Posts
I don't think the difference is a velocity issue at all, but more of a reliability issue. That being the original mode of the JMB system was based around a barrel length of 5".
 

·
Registered
Joined
·
1,261 Posts
I have had a Colt Combat Elite & a S & W 1911 and in comparing velocity wise with my Kimber Compact SST with a 4 inch barrel the difference isn't worth worrying about. the 5 inchers had a higher velocity no more than 30 or 40 fps over the Kimber. with all of the variables involved the longer sight radius is the big difference
 

·
Registered
Joined
·
3,446 Posts
Discussion Starter #4
LastRites said:
I don't think the difference is a velocity issue at all, but more of a reliability issue.
OK . . . . . . . With multiple 4" Kimbers and one 5" TLE, I have had far more problem with the TLE than with all of the four inch ones combined. To me, the four inch are at least as reliable as the five inch.

Back to the point of this thread, I was curious about 4"bbl vs 5"bbl velocity. Turns out there is virtually none. :cool:
 

·
Registered
Joined
·
5 Posts
I remember reading that the pressure in a 45acp fired though a 1911 pattern barrel peaks within the first 0.5 inches of travel down the barrel. Sorry but I forget where I read this so you shouldn’t take it as gospel. This would, however, explain the relatively small differences between the barrel length and muzzle velocity.
Hope this helps.
 

·
Super Moderator
EDC: SIG P938.
Joined
·
22,288 Posts
If you cut an inch off a 5" barrel, I think you will lose less than 5% in velocity.
I don't have a 4" gun, but 200gr loads go about 6% slower in 3.5" than in 5", and about 4% faster in 6". Some barrels are "faster" than others, and I suspect you could find a 4" barrel that gave higher velocities than some 5" barrels. I think a lot of people want all the velocity that they can get, believing more is better, and if you are absolutely devoted to bullet expansion, then there may be some merit in that. Bullet designs from the '70s and '80s tended to need all the velocity they could get, for reliable expansion, but I think the art and science has advanced to the point that bullets can be designed to expand within a specific velocity range and set of conditions; still no guarantee that you will meet those requirements at game time.
 

·
Registered
Joined
·
3,446 Posts
Discussion Starter #7
lgb12b10 said:
I remember reading that the pressure in a 45acp fired though a 1911 pattern barrel peaks within the first 0.5 inches of travel down the barrel. Sorry but I forget where I read this so you shouldn’t take it as gospel. This would, however, explain the relatively small differences between the barrel length and muzzle velocity.
I'm not doubting your word, but I am a bit skeptical. If the pressure peaks in the first half inch, wouldn't it then stand to reason that a three inch barrel would produce identical or slightly higher velocities than a four or five inch one? Everything that I see says that the three inch barrel produces a lower velocity (for a given manufacturer and bullet-weight ammo) than the four or five inch ones. This implies to me that the pressure is continuing to rise with the bullet beyond three inches down the barrel. :)

I've also seen examples of high speed photography where there are particles of burning powder coming out the end of a pistol barrel that was longer than four inches. But then again, I can't see that fast so how could I tell? :cool:
 

·
Registered
Joined
·
816 Posts
It's like asking would you prefer to be struck by a 3/4 ton pick-up or a 1/2 ton pick-up. I suspect that either one is going to leave a mark.
 

·
Registered
Joined
·
2,071 Posts
The burn rate and the amount of powder used determines when the pressure peaks... Fast powders may peak at the .5" mark like you say...but slower burning powders will peak farther out...thats how they get higher velocity, they push longer.

So...to get the most fps out of a 4 inch barrel, without wasting powder, burn rates should be just on the slower end of the fast powders, for example Unique, which is a popular choice, Power Pistol may also fit in here (I'm gonna find out soon). This is just my theory...but I have been reading up on it because I'm about to start reloading for a 4.25 inch 45 acp. I'm not sure this will help anybody but its what seems to be the popular idea.:)
 

·
Registered
Joined
·
5 Posts
I follow what you guys, w0ipl-Pat and ridgerunner665, are saying and I’m certainly no expert in internal ballistics.

Here’s the post I read. http://yarchive.net/gun/pistol/1911_barrel_length.html

Before I go on, I definitely am not saying or implying that the pressure has dropped to zero over atmospheric pressure after peak pressure has been achieved.

If we’re looking for why the difference in barrel length has unexpectedly small differences in muzzle velocity I humbly offer the following:

Overall, there are 3 forces at work on the bullet once it is fully in the lands and grooves as it travels down the barrel: the force due to the pressure from the burning powder and the frictional forces of between the bullet and the barrel and air resistance.

If the bullet is gaining very small increments in velocity for each inch of barrel length then the frictional forces must be close to the force on the bullet from the burning powder. Other wise, if the pressure and hence the forces, continued to build you would have to see much greater differences; you know, the old F=ma thing from physics.

This also would explain why some barrels are “faster” than others even if they are shorter for a given load; they have less friction between the bullet and barrel. But that’s probably really obvious.

Anyway, I don’t think we are disagreeing as much as we are coming at this from a different perspective / view point. And in the end, shooting guns is a lot of fun and, for me at least, it’s even better if it’s a 1911.
 

·
Registered
Joined
·
3,446 Posts
Discussion Starter #11
lgb12b10 said:
Here’s the post I read. http://yarchive.net/gun/pistol/1911_barrel_length.html

(snip)

Anyway, I don’t think we are disagreeing as much as we are coming at this from a different perspective / view point. And in the end, shooting guns is a lot of fun and, for me at least, it’s even better if it’s a 1911.
Great information, and I agree with the last - totally. :cool:
 

·
Registered
Joined
·
2,793 Posts
Nice table accumulated by the O.P.

ONe thing, the O.P. never specified the platform.
However, not surprizing to assume the 1911 platform,
and I caught this but thought it might be about
5-inch vs 64-inch vs 3 inch WHeeelguns.

FY* - the sight radius of a 3" S&W Model 25 is
just an 1/8th of an inch longer than a 5" 1911.
 

·
Registered
Joined
·
15,319 Posts
Why YOUR six-inch shoots slower than your 5-inch, but HIS 5-inch is faster still.....

.....forget the 4" and 3".....

I suggest the barrel, not its length, the critical factor in velocity variations.

I've chrono'ed (no, not at 'matches') a fairly significant number of guns, and conclude that the barrel itself affects velocity due to its actual (vs 'guessed') bore size, shape, and interior suface condition, to include shape and height/depth of its grooves and lands.
I believe-but-cannot-prove that the chamber itself plays a significant role in velocity.
I am not so sure about 'headspace', but still consider it a potential contributing factor in velocity.
 

·
Registered
Joined
·
3,446 Posts
Discussion Starter #14
Randall M said:
ONe thing, the O.P. never specified the platform.
However, not surprizing to assume the 1911 platform,
and I caught this but thought it might be about
5-inch vs 64-inch vs 3 inch WHeeelguns.
Humm, I just thought that titling the page with "45-ACP" (which stands for 45- Auto Colt Pistol) defined it. Looks like I was wrong.
 

·
Registered
Joined
·
3,446 Posts
Discussion Starter #15
Just for grins I contacted Alliant powder to see if they had any information on how fast the peak pressure was reached. Their reply was:

I have no idea how far the bullet moves before peak pressure is reached.
My guess is there is no correct answer because it likely changes
depending on what powder is being use. Thanks for your interest in
contacting us and have a nice day.

His Name
Consumer Service Manager
Alliant Powder Company

:) I take that as "Go away kid, you bother me." :)

So much for going to the source. :biglaugh:
 

·
Registered
Joined
·
15,319 Posts
or

Maybe it's because his gun is different than your gun, so what happens in his gun is different than what happens in your gun, so the information is moot.
Or maybe his components are different.
Or his test environment.
Or his tooling.
Maybe.
 

·
Registered
Joined
·
2,793 Posts
"Full Size" 1911 5" Bbl. Len.
5" minus the case length of .898 = 4.1" of rifling

S&W 625 5" Bbl. len. of rifling

My pref. on the 1911 platform is the full size
it just feels right, it's what I had on watch in the
USN - I would rather have a 4" Bbl on my 625
with the 5" it seems just a bit muzzle heavy.
 
1 - 18 of 18 Posts
Top