I am seeking advice on freebore length. I hear about it and its benefits, but I can't find how much is good or how much is too much.

I want more freebore to lower pressure, and to experiment with longer bullets and seating depths. The calibers in question are .458 and 7mm.

Thanks!

Ackley's position on freebore is that it does lower pressure, while at the same time lowering muzzle velocity. You can add powder to bring the velocity back up, and the net result is that you get about the same MV, for a grain or two more powder. His recommendation was, don't do it.

Well, two of the .458 bores has to be done. If I can't find any info or advice I will add about 1/4". In regards to the 7mm, I know accuracy will suffer if I go too far, but like I said before, I can't find ANY info on the subject.

The longest bullet plus .020" sounds about right to me. The only real push a long freebore has is from Weatherby, and they dropped the length of their freebore sometime back as well. In actual fact, you can load a little hotter with the longer freebore, while still maintaining sane pressure, the longer freebore effectively gives you more case capacity. So yes, you do have to use more powder to equal the velocity of less freebore, but you can also get more velocity from the combination (assuming everything else is equal, which it rarely is). I hope that made sense. - Dan

Beware of long freebore. Yup, you can use longer COALs (cartridge overall length), but surprise, surprise, your long cartridge will not fit in the magazine. Your rifle becomes a single shooter with your long ammunition.

I have a suspicion that manufacturers set magazine length or freebore length so that the longest cartridge that will fit in the magazine will be nowhere near the leade, thereby assuring that there will be no overpressure loads from bullets jammed into the rifling when the round is chambered. You can get around this by using a longer action for a shorter cartridge (ex: .308 length cartridge in .30-06 length action), but you must take responsibility for loading cartridges that are safe in your rifle. Normally the magazine acts as a filtering device that protects the chamber from dangerously overlength cartridges.

Right or wrong, most everybody who chases accuracy wants to get their bullets so they are just off, at, or into the rifling. Chasing the leade will cause you to perhaps use longer-than-optimal bullets.

In short, I'd rather have shorter-than-normal freebore for my handloaded rifles, because then I can get ultimate accuracy with ammunition that has the bullet nearly touching the rifling that will fit in the magazine. The disadvantage is that then anybody who fires factory ammunition in that rifle could be seriously injured. Rifles with wildcat chambers have to be looked after carefully to make sure they don't injure anybody, which is why any good gunsmith will not mark a barrel with a standard chambering if the dimensions at all deviate from standard. It works both ways: ammunition assembled for a .308 LT (long throat) might not be safe in a normal .308.

My general rule for custom chambers is to get at least one caliber of bearing surface in the neck of the cartridge, with the other end of the bullet just off the rifling. That allows for one caliber's worth of throat erosion before the bullet is out of the case, all this with the bullet I intend to use, and of course this neglects any consideration of the location of the cannelure, a matter of concern with a .458 that feeds out of the magazine...

Thought about getting more space for powder with a .458 Lott instead? The same chamber will still accept .458 Win too, though perhaps not a good idea to do too often.

ChevYota,

If you were to hire me to throat your rifle, I would have you send me a dummy round, with the longest bullet you wish to use, seated to where it will still work through the action. I would then set the throat length so that the bullet would just touch the lands at that length. You could then adjust and experiment with freebore, by changing seating depths.

Keep in mind a couple of things. 1) It is easier to remove metal than to replace it. 2) Long sloppy throats does not accuracy make, so keep it tight. And finally 3), unlike my ex, one size throat doesn't, well,... we'll save that one for another day.

Good luck,

Malm

The Brno Mod 21 and 22 are about as free bored as a rifle can get and I have yet to see one that would not shoot great, I doubt that anyone else has either....Weatherbys are free bored and many of them are tack drivers.

My Brono will seat a 7x57 half way to the cannalure and shoot and inch...It will shoot a 130 gr. Speer just as well and it has to jump a football field to hit the rifleing..

So, my point being, this theory stuff is just that, theory....

Malm, you have the best approach. Ray's suggested "theory" that freebore does not hurt accuracy is typical Ray BS. Try to find a Bench Rest shooter who uses one iota of free bore in their custom chambers. You will have a long and uneventful search. If we can't learn from the folks whose sole game is accuracy then we have our heads stuck firmly up our asses. I prefer to keep my head where I can see something other than what I ate.

[ 08-07-2003, 04:35: Message edited by: Customstox ]

chevota

You can get top accuracy with a long freebore but the rifle really needs to have the freebore diameter not much bigger than bullet diameter. I think this might be a reason why there is so much variation on the accuracy reported with Weatherbys. I have owned two 460 Wbys and like other owners have obtained extremely good accuracy with 500 grain Hornadys seated to the cannelure. This gives about 3/4" jump to the rifling.

While very fine accuracy can be obtained with rifles with long freebore in my experience they are more fussy to load for.

In conventional non Weatherby type chambers and when using brass that has a few thou headpspace quite often the best accuracy is achieved with the bullet maybe a 1/16th to an 1/8th inch off the rifling. Neck sized ammo seems to prefer being seated just next to or just into the rifling.

Mike

I think free bore is allright as long as the throat is cut parallel a long tapered throat is not good imo however with a parallel throat it does not matter.
My .500 AS has a staight throat and it shoots long or short bullets very good it is reamed to .510" same size as the bullets the only problem with this is if one want's to shoot cast (one thou oversized .511" ) it will not chamber.
So .510 heat treated is the norm.
Talk to Pac Nor

Regards martin

Chic,
Is everyone who disagrees or has had a different experience than you BS...

Ray,

Look who's calling the kettle black..............Your one of the first to call something BS if you disagree........Just remember..............Opinions are like assholes and everyone got one including myself.

No Ray, just basically you. I like a difference of opinion. Don't care for the throw out an answer at any cost type of approach.

[ 08-07-2003, 10:36: Message edited by: Customstox ]

Ray hasn't didn't say anything I can disagree with. Seems like his point is that regardless of what every one will tell you, his rifle shoots great with little or much freebore.
That is valuable input to the original question.

That said, I'm having my chamber cut for a dummy round, since that does seem to get good results.
Also, the case I'm using is so damn big it won't need high pressures.

So, chevota, which chambers are you talking about? Is this a hot-rod 458 Winchester or 45-70 and a 7mm-08, where the pressures are really a limiting factor, or are you talking 450 Rigby and 7mm STW, where you're going to blow out your shoulder before your brass?

Bwana-be

I think what Chic is saying is that Ray's answer is not qualified in any way.

Ray's answer is indicating "it does not matter a fuck if the rifle is freebored" and that is totally wrong. Ray's answer is like someone saying "I have 4 rifles and none of them are bedded etc. and they all shoot well so bedding rifles is bullshit" or "I have three Model 70 factory guns and they all shoot well so that proves custom barrels are bullshit"

Mike

For what it's worth, I set up all my Weatherby chambers to allow .070-.125 bullet jump or freebore. My Lott chambers might allow as much as .600 freebore.The ID of my magazine box will not allow the loaded rounds to clear the box and touch the lands. While I will agree that the closer to the lands the bullet is,the better, this is not always practical. Somebody may want to shoot factory Weatherby rounds in this chamber and you'll need the freebore to allow this. Accuracy has always been excellent if the barrel, action work, scope mounts, loads and shooter was up to par.

I think what I said was some guns shoot with freebore and some don't...and that all the Brnos I have shot did well with their freeboreing...

I agree with Ray in that some rifles with considerable freebore will indeed shoot well, and some won't.

I have a Model 70 .458 Win. Mag. (factory-original barrel) with considerable freebore, and this rifle will shoot five-shot groups of just a little over an inch with regularity.

I also know of a fine custom .375 H&H based on a Brno barrelled action (built in the 1960s) that is a superb one-inch gun, and it has the typical, generous Brno freebore as well.

Of course, many Weatherby rifles, complete with freebore, do shoot amazingly well, but some of them won't. I think Weatherby's freebore too often gets blamed adversely effecting accuracy, when in reality other barrel (or other) defects are the real problem.

For example, I was visiting an excellent, accuracy-oriented riflemaker one time. He was in the process of building a custom rifle on a Mark V action. Originally, this rifle was a .270 WBY, and the client who owned it said it never did shoot well. Out of curiosity, the riflemaker pulled the factory barrel, then sawed in two lengthways just for the purpose of examining the rifling first-hand. I got to look it over myself, and there were so many obvious defects (including skips in the lands!) that it was no wonder that gun didn't shoot. It was the gunmaker's opinion that freebore was the least of that rifle's problems, and as a layman, I'd have to agree.

In general, and here's where I agree with Chic, FINEST accuracy is GENERALLY achieved if the bullet is seated close to the rifling - say .0025" to .0030" off. The target shooting and varmint shooting communities have established that as a guideline long ago. Even so, it's not a hard and fast rule.

One of my friends has a .300 Win. Mag. built on a pre-64 Model 70 .30-06 action with a somewhat unusual amount of freebore. If my friend were to seat the bullets just off the lands as per conventional wisdom, the cartridges would be too long to fit in the magazine. So he seats them so that the cartridges just fit in the magazine box without binding, which is the only practical solution. And that rifle shoots like crazy anyway.....

AD

[ 08-07-2003, 21:23: Message edited by: allen day ]

I agree with you Allen and thats basically what I said....Most of my guns shoot better just off the lands, but I doubt that for hunting it is really that critical in most cases....

Thanks everyone, you've been a big help! Now I have an idea of what to expect and where to start.

I have several guns I want to do this mod to, 45-70, 450 Marlin, 458 Lott, 7mm STW, and maybe some others, but it would be too much to by a bit for every caliber so I'll just get the 458" for now. I always like to load long to ease pressures but maintain power, especially in small cases like 9mm, 357, 44Mag etc., but I usually run into the lands before I run into a feeding problem. I also like to play with heavier bullets so I'm forced to sacrafice case volume due to the lack of freebore.

chevota,you don,t see above post

Regards Martin

Martin, what did I miss?

Chevota: The key imo is a parallel throat meaning the part of the chamber from the the case mouth to the rifling,this part has to be cilinder shaped.
It is the same or .0005" bigger than the bullet diam sort of like a section of smooth bore or false muzzle in the BP days.
Most freebores have a taper to them (not good) a parallel freebore however forces the bullet to engage the rifling straight.
In this case it does not matter how long the freebore is .100" or 3".
The only drawback is like I stated if you want to shoot cast bullets (cast bullets are normaly shot .001" oversized) the cartridge won't chamber due to the oversized bullet.
One can deepseat (not for me) or size nominal size and heat threat the bullet, this will work if you don;t push the speed over say 2000 ft/sec
Pac Nor made the barrel for my .500 and it shoots good with 450gr/550gr cast,550/600/and750 gr jacket bullets.
For more info on the throat/freebore thing look in the A Square reloading manual.
Hope this helps
Regards Martin

Thanks, yeah I read that part, makes perfect sense to me. I don't know what size my throater will be until it arrives since the lady I ordered it from had no clue other than one 45 was for a pistol, the other for a rifle. If it's too big I'll grind it down to size.