Free Bore

[deertroy1]

So while I'm waiting for a stock inletting tool to widen out my stock's barrel channel I decided to take some COAL measurements of my new McGowen 6mm Rem. barrel. I only tried a few bullets but in those I tried it is obvious this barrel has a lot of free bore. Bullets are going to have somewhere in the neighborhood of 0.100" of jump to the lands. While I prefer to be around 0.020" - 0.030". I have a new Cooper in 7mm-08 rem. that has a fairly long throat and so far I can't get it to shoot worth a hoot.

Would be interested in hearing some experiences people have had with barrels chambered with this kind of free bore?

[gbflyer]

I've found Barnes TTSX and also Hornady Eld's don't mind a big jump.

[RC20]

What is the length of your magazine?

[Nor Cal Mikie]

You'll have to set the OAL that will fit your mag. I single feed everything but my gas guns so I'am not concerned about OAL and mag length. All my chambers are cut with ZERO freebore. That way, as the throat wears, I can go to a heavier bullet and still reach the lands.
I start off with the lightest bullets I can get my hands on then go heavier as needed.
Nothing worse than having a long freebore, shooting your favorite bullet and the next thing you know, you can reach the lands and still have enough bullet contact in the neck.
Go short. You can always make the throat longer but you can't go shorter.
All my loads are built with the bullets stuffed .010 into the lands. And you would be really surprised just how fast the throat wears. Plan ahead!!

[deertroy1]

Don't think you have a choice of custom throat with the savage prefits.

[DanSavage]

Don't think you have a choice of custom throat with the savage prefits.

If you want a true custom barrel and have a little patients Apache throats and chambers the barrel of your choice to YOUR specifications.

I wanted a Bartlien full bull profile, 8 twist in 6 br norma throated to shoot the long bullets and that is just what I got. You send in a dummy round just the way you want it and he will take it from there.

I have a McGowan .223 with a 7 twist and it has a short throat so I can't really take advantage of the heavy long bullets. I could either buy a uni throater and make the throat longer my self by hand,, or wait til the throat gets shot out more. I've put 1000's of rounds on paper running barrels while there hot and throats don't seem to move hardly at all with me,, don't know why, maybe the cartridge design. I shoot .308's a .223, a pair of 6 br's and 6ppc.

[Nor Cal Mikie]

The one barrel that caused me to think back was a Shilen in 6 BR. Didn't specify what chamber I wanted. Came with a long throat. Had to start off with 60s and go heavier. Didn't take long before the throat wore and I couldn't reach the lands. Sold it to someone that wanted to shoot heavier bullets. From then on, I only order custom cut chambers.
Did pick up an A&B barrel in .221 Fireball from Midway that was on sale for a "very good price". Surprised to discover that it had a "very short throat". One of my better buys.
My guess is you will have a better chance now in chamber choices than a few years back. Never hurts to ask.

[RC20]

I would always ask to see if they can shorten the free bore.

You can always seat any bullets out past the listed COAL and close up that gap.

It obliviously has limitations once you get out too far. I think they call for I caliber distance for grip.

[deertroy1]

If you want a true custom barrel and have a little patients Apache throats and chambers the barrel of your choice to YOUR specifications.

I wanted a Bartlien full bull profile, 8 twist in 6 br norma throated to shoot the long bullets and that is just what I got. You send in a dummy round just the way you want it and he will take it from there.

I have a McGowan .223 with a 7 twist and it has a short throat so I can't really take advantage of the heavy long bullets. I could either buy a uni throater and make the throat longer my self by hand,, or wait til the throat gets shot out more. I've put 1000's of rounds on paper running barrels while there hot and throats don't seem to move hardly at all with me,, don't know why, maybe the cartridge design. I shoot .308's a .223, a pair of 6 br's and 6ppc.

Part of my reasoning to go with McGowen was availability. I'm in Canada and it can be difficult to source exactly what you want up here.

[65Whelen]

You just have to shoot it to find out. I had a Savage 22-250 with .090 free bore on Nosler 55g bullet at recommended COAL. I loaded up a bunch with .090 of free bore and a bunch loaded at .020 off the lands. The loads that we're .090 off the lands shot more accurately than the .020 off loads. I was getting 1/2 MOA with the .090 off lands, consistently.

[jim_k]

Start loading with your longest round, and shorten the seating depth by 0.030-0.040" for each batch of five. Shoot them off a very good rest, like a front tripod and a rear bag. One OAL (seating depth) will outperform the others, probably significantly, and hopefully will also have a very small vertical dispersion component (this is the main thing you're after in this part of the test). If you are lucky, that group may also be the highest on the target relative to the POA. If you want to maximize the results, you can drill down on the seating depth in 5-10 thousandth increments. When you've found the best OAL, go back and load groups of 3-5 rounds with varying amounts of powder, but all at the same OAL. If the first test used 30.0 grains of powder, use 28.6, 28.8, 30.0, 30.2, and 30.4 for the powder test, and see if the width of the group tightens up. When it all comes together, take that show on the road.

[deertroy1]

Start loading with your longest round, and shorten the seating depth by 0.030-0.040" for each batch of five. Shoot them off a very good rest, like a front tripod and a rear bag. One OAL (seating depth) will outperform the others, probably significantly, and hopefully will also have a very small vertical dispersion component (this is the main thing you're after in this part of the test). If you are lucky, that group may also be the highest on the target relative to the POA. If you want to maximize the results, you can drill down on the seating depth in 5-10 thousandth increments. When you've found the best OAL, go back and load groups of 3-5 rounds with varying amounts of powder, but all at the same OAL. If the first test used 30.0 grains of powder, use 28.6, 28.8, 30.0, 30.2, and 30.4 for the powder test, and see if the width of the group tightens up. When it all comes together, take that show on the road.


This is exactly what I'm going to do!

[RC20]

I would do shorter movements. I think Berger has a regimen of .010 movements to see. That's what I stick with.

[m12lrs]

Remington and some of the other manufacturers have gone to a longer throat as Weatherby has done for years. Weatherby did it because they believed it resulted in better accuracy but over the years that was pretty much debunked. Fast forward to today and for completely different reasons, the free bore is back. Remington to a large degree can keep pressures down, or extend the margin as it were with people doing the long range shooting and loading a little beyond published to get out there. Berger rethought it and with todays bullets, it works out just fine to make the jump and in fact, a lot shoot much better that way. I have a Rem 700 LR with a very long throat, factory. I have loaded the bullets out to where they didn't fit the mag and they didn't shoot all that well. I loaded them back .08 or so to fit the mag and they are dead on accurate.

I guess you could say, Weatherby has come full circle and been saved by the bullet!

Roy did it for velocity. With that long jump he could higher velocities than his competition. Roy had no problems with accuracy.

Same thing the military did with the .223 to 5.56. Only difference is the throat. Longer jump, more powder, higher velocity.

[gbflyer]

I've never owned a rifle or found a bullet that grouped more consistently with a long jump. I must be missing something somewhere along the way.

[RC20]

Berger has a procedure that goes with .030 jumps (I had that listed at .010 previous comment. )

They have found some guns will use as much as .150 to get an accuracy point.

Its worth exploring. I have found some spots that are good one day and not so the next.

Moving them back out settles that down to more consistent (in my guns)

Its not that .030 is spot on, but it will show from one to the next its better and then you can split between it on either side and see where its happiest.

[deertroy1]

I've never owned a rifle or found a bullet that grouped more consistently with a long jump. I must be missing something somewhere along the way.

I'm like you. I've never had a rifle that shot better with a long jump. I have a new Cooper in 7mm-08 Rem with a long throat. Most bullets have to jump around 0.070" or more to fit the mag. Try as I may I can not get that rifle to group at all!

[Deadshot2]

Berger has a procedure that goes with .030 jumps (I had that listed at .010 previous comment. )

They have found some guns will use as much as .150 to get an accuracy point.

Its worth exploring. I have found some spots that are good one day and not so the next.

Moving them back out settles that down to more consistent (in my guns)

Its not that .030 is spot on, but it will show from one to the next its better and then you can split between it on either side and see where its happiest.

The Berger procedure was written up for VLD's because so many tried them and gave up because they didn't shoot well using the same "tactics" as they used with their tangent ogive SMK's (and their clones).

One of the first things the writer says is "think outside the box". With all the changes in bullets recently that's probably excellent advice.

[gbflyer]

I'm like you. I've never had a rifle that shot better with a long jump. I have a new Cooper in 7mm-08 Rem with a long throat. Most bullets have to jump around 0.070" or more to fit the mag. Try as I may I can not get that rifle to group at all!

I put together a 7-08 for my wife and son (I shoot it more than they do but don't tell[emoji41]). I've had really good luck with Sierra 120gr Pro Hunters. Never tried them on game, very consistent on paper.

[RC20]

The Berger procedure was written up for VLD's because so many tried them and gave up because they didn't shoot well using the same "tactics" as they used with their tangent ogive SMK's (and their clones).

One of the first things the writer says is "think outside the box". With all the changes in bullets recently that's probably excellent advice.

Agreed, but what works for one may work for another and always (pardon the pun) worth a shot!