Freeboring .45 acp


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Venado
July 17, 2009, 03:20 PM
I freebored my .45 acp, and love the results. Wondered if anyone else has had good results doing the same.

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rcmodel
July 17, 2009, 03:24 PM
Quite frankly, I've been building 45's for going on 40 years, and have never heard of anyone free-boring one!
Do tell us more?

Are you talking about real free-boring where you ream the rifling out a ways to give the bullet a running head start?

Or throating to handle a different bullet shape?

rc

Venado
July 17, 2009, 03:34 PM
Real free-boring where you ream the rifling out a ways.

rcmodel
July 17, 2009, 03:38 PM
Sounds like a Really Bad idea on a .45 ACP.

Nothing to be gained, but lots to lose.
*Like velocity, on an already velocity challenged round.
*Excess gas blow-by until the bullet gets to the rifling.
*Increased leading when using lead bullets.
*You would have to load hotter to get back to the same velocity you had to start with, etc.
*Bullet rattling down the bore with no guideance until it got to the rifling.

rc

Jim Watson
July 17, 2009, 03:52 PM
How far did you freebore it and what are the results you love?

Venado
July 17, 2009, 04:17 PM
freebored .5". Contrary to popular opinion, the freeboring actually made the "velocity challenged round", gain more velocity. I tested the whole process using Winchester white box 230 grn. rounds. Average before freeboring: 785 f.p.s. after freeboring: 811 f.p.s. for an increase of 26 f.p.s.

I have not had any leading while using lead bullets. Accuracy is great.

Did a test with two differant guns, one freebored one not. Loaded the non-freebored gun with Power Pistol under a 250 grn. rnl bullet until pressure signs were being seen in the primer. Loaded freebored gun using same components and was able to put 2.4 more grains of Power Pistol until the same primer signs were seen.

So the good factors are:
*increased velocity.
*good accuracy.
*ability to load a hotter load with less pressure.

raskolnikov_22
July 17, 2009, 04:32 PM
So the good factors are:
*increased velocity.
*good accuracy.
*ability to load a hotter load with less pressure.

An average gain of 26 fps isn't very much at all and plenty of .45s are already plenty accurate out of the box, so could it really have been worth the effort?

Not trying to be contentious, just asking.

Mr.P345
July 17, 2009, 04:43 PM
I don't see the point in this. Any possible gains gotten by reboring/freeboring a .45acp are going to be negligible. You may love the results on paper, but there is no way you can honestly feel or see a measureable difference by doing this. I can appreciate the hard work though.

Venado
July 17, 2009, 05:43 PM
Thanks for the feedback. I guess no one else has done this. That is what I wanted to know.

krs
July 17, 2009, 06:07 PM
I freebored my CZ52 approx .250".

But I called it "throat erosion" and changed the barrel, just today.

1911Tuner
July 17, 2009, 06:49 PM
rc...I think he means lengthening the existing freebore...or rather using a less acute angle as the rifling goes to full depth.

Kart barrels have very short leades and a sharp, abrupt entry into the rifling just ahead of the chamber. I finish ream every Kart barrel that I use, and I've found that it not only allows shouldered lead bullets easier chambering...it also helps the accuracy a bit and increases velocity a small percentage with jacketed bullets. It doesn't seem to make much difference in velocity or accuracy with lead bullets...but does aid in reliable chambering when they have a bit of shoulder protruding above the case mouth.

Venado
July 17, 2009, 11:23 PM
No, my freeboring is removing the rifling .5", giving the bullet a jump before hitting the rifling. If none of you have ever done this, how can you judge based on assumptions. I am basing what I say on facts. In fact we would have to do a disclaimer for myself and for THR, if I were to tell you all of the results.

"Did a test with two differant guns, one freebored one not. Loaded the non-freebored gun with Power Pistol under a 250 grn. rnl bullet until pressure signs were being seen in the primer. Loaded freebored gun using same components and was able to put 2.4 more grains of Power Pistol until the same primer signs were seen."

Some things to think about. .6 of a grain of Power Pistol is equal to an increase of 55 f.p.s. On paper, I have not chronographed it yet, an increase of 2.4 grains of powder over a normal load, would be equivalant to 220 f.p.s., with the same pressure as the base load. If that were possible, do you not think it would be worth the effort?

I am going to chronogaph the two loads to see what the differance is in velocity, and not just on paper.

jbaker
July 17, 2009, 11:37 PM
the real test would be to take one pistol shoot for accuracy and chrono it. Then freebore that pistol and do the same test agine. How did you freebore the barrel just curious?

JB

Venado
July 17, 2009, 11:46 PM
Used a Manson .45 caliber pistol throater. Cuts .001 over the diameter of the bullet. Did do accuracy testing before and after, but did not have a ransom rest, which would have been nice. Did velocity test before and after. The real gain is not just the 23 f.p.s more for a factory load, but the reduced pressure in loading hot loads.

NC-Mike
July 18, 2009, 09:43 PM
I'd venture a wild guess that the increased "pressure" is going out the barrel before the bullet, just as RC Model alluded too.

It would seem to me a .5" "free-bore" would be the same as severe throat erosion...

I can not see any other reason why you are able to load another 2.3 grains of power other than it escaping past the bullet in the free-bore.


This may be the same dynamic of accelerated throat erosion in a hot barrel. The barrel expands and thusly allows hot gases to escape past the bullet.

1911Tuner
July 18, 2009, 09:51 PM
I can not see any other reason why you are able to load another 2.3 grains of power other than it escaping past the bullet in the free-bore.

It's the long bullet jump into the rifling, and the increased volume of the cylinder behind the bullet that the gasses had to fill. I encountered the same thing when loading much-shortened .45 Colt brass in a Winchester Trapper carbine. I had to use a lot more Unique...I won't post how much...before the recoil level got even close to the levels of the old standby 9 grains.

The cases had been trimmed below .44 Special length, so it was a good amount of jump.

I will say that shooting the little carbine with 9 grains and a 250-grain bullet felt downright wimpy. Never did chronograph it, so I don't know what the numbers ran, but it was apparent that full pressures just never did develop until I bumped the powder charges up.

I'd venture a guess that with a quicker powder like Bullseye, the difference probably wouldn't have been so marked.

JKeefer
July 19, 2009, 08:53 PM
Venado:
Good for you. Innovation is how we advance..The 1911 has stalled in the accuracy dept.
in recent years. It is capable of more, and some of us are working to remedy the situation.. And you are not alone, some of us have been free boring to improve accuracy for quite a while now..Your findings are correct. It will improve accuracy, although, I have not been going quite that deep in the autos, but, some what deeper in revolvers. Don't use throathers. Have a custom reamer made specially for the process. Taylor Throating in revolvers has proven itself for decades, and many revolvers at Camp Perry last week proved it again. Nay Sayers at one time declared the world to be flat..!!
Stay curious and refuse to paint by the numbers...

Jerry

1911Tuner
July 20, 2009, 07:59 AM
Jerry doesn't post much, and he's not very well known...so I'll post a heads up here for those who wonder who he is...where he comes from...and what he does.

Jerry is busy building match-grade pistols in Ye Olde North State, and tends to think outside the box. He's chasing half-inch 50-yard groups, and from all reports...has been successful.

So, when he talks accuracy...Listen.

Venado
July 20, 2009, 10:21 AM
Jerry, appreciate the input. I also do not believe the world is flat. It has been said that the .45 acp is a "velocity challenged round". I am in this for the accuracy and velocity. The .45 acp case has more volume than either a .357 mag. or a 10mm. The thing that has held this cartridge back is the archaic input of SAAMI specifications. We now have the same guns shooting high pressure loads in .357 sig, and .40 S&W, but limit the .45 acp to early 1900 specifications. Thanks again for the input. Sometimes the negativity gets discouraging.

krs
July 20, 2009, 12:28 PM
I'm not a nay-sayer as I'm quite familiar with the process and possibilities in rifles. Benchrest shooters have been messing with 'jump' since the 1950's.

It's that the .45 acp headspaces on the case mouth that would bring me to hesitate to try it in one of my pistol barrels that shoot well enough to make them valuable to me as-is. That's my subscription to the age old "if it works, don't mess with it" credo.

But I'm sixty years old and haven't competed in many years. Were I doing that now I might just try applying what I've learned in rifle accuracy to pistols. In those days I spared no expense in my search for even one point on the scoreboards.

That said, Venado, you should understand that you are not the first new poster to come in with an idea but no established credential in this forum. As such you can't be surprised to find that there are people who might put you to the test in the form of negativity just to see if you know what you're talking about and will stand up in what you say under a little bit of sceptical scrutiny.

1911Tuner
July 20, 2009, 01:17 PM
Like krs, I've been aware of benchrest competitors playing with freebore in the quest of another nth degree of accuracy. I never gave it a lot of thought...mainly because the zenith of accuracy has never been my pursuit the way that weapon reliability has.

My goals are geared more toward the practical/general purpose approach. Pickup truck instead of a highly tuned Gran Prix racer way of thinking.

As to my theory on why freeboring has a positive influence on accuracy...

The added jump softens the violent initial punch of acceleration, and lessens bullet deformation. Any other thoughts?

JohnBT
July 20, 2009, 01:58 PM
The 1/4" freebore in my Rohrbaugh R9 hasn't helped my shooting any. :)

Seriously though, freebore has been linked to bullet tumbling.

www.acbsystems.com/boards/rohrbaugh/basefile/tumbling.htm

"...it can probably be imagined therefore that not every bullet of every type will engage the rifling with absolute symmetry, per the example above. This then also explains why there are occasions also where a perceptible degree of bullet tumble is seen after exit from the gun."

What little I know about match accuracy involves rifles, not pistols, and requires placing the bullet at, or on, the lands. John

Venado
July 20, 2009, 02:04 PM
I hate to theorize on how things work, I just know they do. I also have firelapped my barrel, as well as the freeboring. My quest was not as much for accuracy as for velocity, but I got both.

rondog
July 20, 2009, 02:41 PM
I'm just happy to get out and shoot once in a blue moon.

JKeefer
July 20, 2009, 09:23 PM
The 1/4" freebore in my Rohrbaugh R9 hasn't helped my shooting any.

Seriously though, freebore has been linked to bullet tumbling.

http://www.acbsystems.com/boards/roh...e/tumbling.htm

"...it can probably be imagined therefore that not every bullet of every type will engage the rifling with absolute symmetry, per the example above. This then also explains why there are occasions also where a perceptible degree of bullet tumble is seen after exit from the gun."

What little I know about match accuracy involves rifles, not pistols, and requires placing the bullet at, or on, the lands. John >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Hello John;
Thanks for the link, but I can't give much credibility to data based on a 9 mm pocket pistol, which the designer free bored in hopes of preventing it from self destructing.
I'll give one more example, and everyone can decide what ever they chose. My only goal here is to share relevant information. On Sept. 2001 two competitive shooters won the National Championships with two 1911 9mm pistols that were freebored and set a world record that still stands today. Internal ballistics are somewhat complicated, but they do not discriminate between rifles and pistols..There is much more too it than chopping out some extra space in the bore..
Thanks again

Jerry

The Wiry Irishman
July 20, 2009, 10:48 PM
He's chasing half-inch 50-yard groups, and from all reports...has been successful.

An MOA 1911? I would love to hear more about this.

combatantr2
July 21, 2009, 08:00 AM
is it safe to freebore my glock??? :rolleyes:

JohnBT
July 21, 2009, 08:54 AM
"Thanks again

Jerry"
________

You'll get no arguments from me sir. I heard about you years ago when I didn't have any money and then when I finally got some I saw on the APG site that you were backlogged and not taking in new work.

I don't shoot pistols well enough to need one of your creations. I just like well made guns.

John

woad_yurt
July 21, 2009, 09:26 AM
My Star MOD 30MI has a bit of freebore from the factory. I didn't know that that process was also done as a later modification on other weapons.

I do know that my Star is one very accurate mofo. I wonder how much the freeboring has to do with that.

Every now and then, I get some info that makes me even more impressed with those Star guys. It's a shame they no longer make guns. They incorporated a lot of cool features into that gun.

Badger Arms
July 21, 2009, 10:04 AM
Snake oil in your bore will also work!

Seriously, there are DOZENS of things to do on a pistol before you mess with the bore to make it more accurate. Try lapping the rifling. That'll do essentially what you've said without possibly creating headaches. Don't have any problems with increasing the 'forcing cone' (so to speak) ahead of the chamber on a 45, but if a little is good, how about alot. Why not take out the rifling to halfway down the barrel? Why not take it all out!? Velocity will jump alot if you do that, right?

Where do you draw the line? I think the manufacturers have it about right now. Not that there isn't room for an opinion, but I'd like something other than 15 posts and your word. It doesn't work out in my head that lengthening the freebore on a .45 pistol will increase accuracy with a variety of bullets. Maybe a longer bullet or one seated backwards, but half an inch is lotsa jump.

... oh and remind me NEVER to buy a used gun from you.

Dobe
July 21, 2009, 10:30 AM
Hello John;
Thanks for the link, but I can't give much credibility to data based on a 9 mm pocket pistol, which the designer free bored in hopes of preventing it from self destructing.
I'll give one more example, and everyone can decide what ever they chose. My only goal here is to share relevant information. On Sept. 2001 two competitive shooters won the National Championships with two 1911 9mm pistols that were freebored and set a world record that still stands today. Internal ballistics are somewhat complicated, but they do not discriminate between rifles and pistols..There is much more too it than chopping out some extra space in the bore..
Thanks again

Jerry That's good information. I remember when gun writers were claiming the 9mm was inherently inaccurate, possibly because of the tapered case. I enjoy hearing of those who go against the norm, and I wish the both of you the best.

Venado
July 21, 2009, 03:51 PM
I just got back from chronographing the two loads I refered to earlier. One in a non-freebored gun, and the other in my gun that has been freebored and firelapped. There was 155 f.p.s. difference between the two loads. Two reinterate what went on, I had loaded a load in the nonfreebored gun that was starting to show signs of pressure with the primer. It was a load by the book for a 240 grn. bullet, but I used a 250 grn., that is why the pressure signs. I then duplicated the load in my freebored gun, and worked up from there trying to duplicate the primer from the other gun. Then chronographed. The difference was 2.4 grains of powder and 155 f.p.s.

Venado
July 21, 2009, 07:12 PM
I hit two keys at the same time. Reiterate.

Oyeboten
July 21, 2009, 08:03 PM
Relationship of Bullet Diameter, to any specific Barrel's bore diameter....is often overlooked.


Barrels can vary a little...and for any given Barrel, an optimum diameter of Bullet, or diameter for Bullet type, should be possible...even if everything else remained the same.


The geometry of how the Rifeling begins, and where it begins, seems definitely important to my imagining the early stages of interior Ballistics.


Is the Rifeling indifferenly plowing grooves into the Bullet?

Or, does it oblige the Bullet to flow into it?


Bullet Alloy...hardness...how readily the Bullet upsets in it's initial phases of forward motion, to fill-out into the Rifeling...and the mechanical resistanes the Bullet is meeting as it does so...


Lots going on there in that first half-inch of forward motion...


So Venada, your Free-Boring...how does the Rifeling begin?Is it gradual, tapering? Or, abrupt?

JohnBT
July 22, 2009, 08:23 AM
"I just got back from chronographing the two loads "

I'm still paying attention, but right now I'm off to sit through a 3-hour staff meeting. I'm glad somebody is out having fun. :mad:

I'll read your post later.

John

Jim Watson
July 22, 2009, 09:01 AM
Hmm, freebored barrel makes possible heavier powder charges and higher velocity.
Let's call it a ... Weatherby.
Interesting it should work at the pistol level.

I wonder how far you could extend the smooth throat and still spin up the bullet for reasonable accuracy. Maybe you could invent the Paradox handgun, too.

Venado
July 22, 2009, 10:32 AM
Jim,

A person can get a lot more velocity out of the freebored gun. In fact that is what I am in to, the accuracy just came along with it. The two loads I chronographed were:

non-freebored: 963 f.p.s. /515 f.p.m.e.

freebored: 2.4 grns. powder difference 1118/694

That is with a 250grn. LRNGC

These loads did use a bullet lube that I made that probably helped out a lot.

This was just a test, I have gone way beyond with jacket bullets, but don't want to get kicked off here by saying just what has been done.

1858rem
July 22, 2009, 10:42 AM
wow! that is some amazing velocity man but please dont list the complete load some no one else tries it and gets hurt. i was backing off 255g cast bullet loads at 775 fps lol

ROBBY.1911
July 23, 2009, 10:25 PM
how can you say the .45 acp headspaces on the case mouth, when in reality it is positioned in the chamber by the extractor. iam no expert, just trying to learn something. the extractor grabs the round before anythng else happens. like i said, i'm no expert.

1911Tuner
July 24, 2009, 05:21 AM
how can you say the .45 acp headspaces on the case mouth,

Because it does. The extractor doesn't grab the round. The cartridge slides upward on the breechface and under the extractor during feeding...but the extractor doesn't bear against the forward part of the rim until the case is extracted.

Assuming minimum chamber depth and mid-spec case length...the case only has .005 inch deeper to go until the mouth contacts the chamber stop shoulder. Even if the static headspace dimension is .910 inch, and the case is .888 inch...or minimum spec...the firing pin will shove the case forward in the chamber until it contacts the shoulder...thus headspacing the cartridge.

The case will headspace on the extractor only if either the chamber depth is far out of spec, or the chamber is nearly so AND the case is minimum length or below. Even then, the chamber would be so far out of spec that the gun would fail the standard NO-GO gauge test.

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