Cartridge OAL

[RayB]

A couple of weeks ago I posted about Head space and OAL of cartridge. Quite a few of you straightened me out. When I asked about the OAL of cartridge for a particular gun and how to measure it, I received several answers. The one in particular was to load an extra length round with the bullet seated loosely then extract it slowly and measure the OAL. To be sure this was done properly I did this 6 times. Using the same bullet each time and came up with the same dimension each time, within .001" So my question is; How much of a bullet jump should I have? I realize that extra pressure is created if the bullet is touching the lands when fired, so how much relief should I give it?

 

[theleo]

However much the bullet needs to be accurate. Some bullet and rifle combos like no bullet jump what so ever, some may like .003 or a bit more. This is where playing with the seating depth comes into play. Find a bullet, powder, primer combo your rifle likes and then play with the seating depth to get the last bit of accuracy out of it that you can.

 

[sugarmaker]

Kind of depends on the bullet. Load 5 rounds at .005, 10,15 20 and slow fire groups with the same load chain. Look at groups... There will be the answer. For hotter loads like long line ammo on an AR, you may find you have to chase the lands pretty often as they erode, esp if you are under .005 setback

 

[higgite]

I've slept since 2 weeks ago, so i don't remember your other thread.
What type of firearm?
What type of action?
What type of bullet?
What caliber?
Target shooting?
Plinking?
Bad guy shooting?
Big game hunting?
Small game hunting?
Varmint shooting?
All of the above?
None of the above?
Details, details, details.

 

[Blue68f100]

Decades ago when I started hand loading you would start at 0.020" and work from there. These days with mfg moving the lands so far forward to prevent this, all bets are off. Apparently you have a gun in which you reach the lands. Makes tuning a load a lot easier. This is the last step I do in working up a load.

 

[Reloadron]

Determining Bullet Seating Depth is a pretty good read on the subject. Unfortunately there is no magic number as has been covered. The actual number will depend on your rifle, your chamber and your loads. Change the load, bullet or really any of the loading variables and all bets can easily be off or skewed.

I have seen benchrest guys literally use the bolt to seat the bullet. They start the bullet and literally use the bolt to run the bullet into the rifling and call that good. There are also those who find the elusive sweet spot .005, .010, .015. .020 or more off the lands.

How much does it matter? Really depends on the rifle and the rifle's chamber. On some rifles the difference is great enough to warrant screwing around with it and on others there is no discernible difference. One of my most accurate bolt guns is a .308 Winchester with a throat so long I don't even bother looking to come off the lands but just load to the manual for a given bullet. Your mileage may vary.

Ron

 

[RayB]

Remington 700 in 7MM Mag., 150 gr. Nosler ballistic tip, primarily Big Game. My main concern is over pressure, I can play around a little bit to work on the accuracy, just didn't want to do something wrong right off the bat.

 

[ericuda]

Ray you may be overthinking this. What is your goal, a 200 yd shot at a mulie or a 600 yard shot. Stick with published loads and play around a little up and down with charges until you get what you want. It will help if you add what game and your location on profile. The ballistic tip may not be a good load to start for big game and the 7 mag. They hit hard and reach out as far as i need in my areas with good old gamekings.

 

[Reloadron]

Remington 700 in 7MM Mag., 150 gr. Nosler ballistic tip, primarily Big Game. My main concern is over pressure, I can play around a little bit to work on the accuracy, just didn't want to do something wrong right off the bat.

I tend to agree with ericuda in that you may be overthinking this a little.

I would just load to 3.290" COAL and see how the rifle shoots. You are looking at a hunting rifle application.

Ron

 

[merrill]

I use the SWAG method of determining COAL. Mark bullet with Sharpie and when there are no more rifling marks on bullet, I'm good to go.

 

[steve4102]

Remington 700 in 7MM Mag., 150 gr. Nosler ballistic tip, primarily Big Game. My main concern is over pressure, I can play around a little bit to work on the accuracy, just didn't want to do something wrong right off the bat.

Set your OAL to the longest you feel comfortable with.

It should fit the mag and have adequate neck tension. The rule of thumb is one bullet diameter seating into the case. So, in the 7Mag .284 inches. This is of course not written in stone, just a rile of thumb.

Start low and work up. Now, when you adjust your OAL you will be reducing OAL and also Reducing Pressure.

In a bottle necked round the shorter the OAL the less the pressure, so if you start long, going shorter with the same charge will not cause a pressure issue.

 

[Walkalong]

I agree that you don't need to worry about loading close to the lands.

Load to fit your mag, with good neck tension, then quit worrying about OAL and work up a good load tha shoots a decent group, and more importantly, puts the first shot where you want it.

 

[spitballer]

Obviously a lot of variables factor into deciding distance to lands, but since consistency generally means accuracy then consistency is key. FWIW I've found that bullets either need to be into the lands or away from the lands. Apparently pressure rises so quickly as the bullet enters the lands that it's just not practical to try to seat one or two thousandths off them. Kind of like a flap-type stopper that wants to slap shut against a bathtub drain, best to close up the gap or stay off of it altogether. In my case I always seat into the lands, but I'm using a bolt action rifle with soft, varmint-style bullets. I doubt I would do it with FMJ's unless I really needed the starting pressure.

 

[TimSr]

I realize that extra pressure is created if the bullet is touching the lands when fired, so how much relief should I give it?

I don't have the answer, as I don't get that precise, but I think what the OP really wants to know is the minimum distance between the bullet and the lands that he should attempt, and I'm seeing a lot of different numbers.

 

[trentcwwilson]

I'm glad I stumbled upon this. I always wondered about "seating off the lands".

 

[bob4]

A lot of great advice here. Not sure if it was mentioned but since your loading for hunting you do not want to touch the lands. Reason being you have a good chance of having to unload that rifle. Don't want that bullet stuck in the lands and powder landing in your rifle.
I try and stay .010-.015 to be safe.

 

[trentcwwilson]

So for target shooting(when you're definitely going to take the shot, loading to the lands is feasible idea?

 

[bob4]

If that's where that rifle shoots well, people do that.

 

[spitballer]

So for target shooting(when you're definitely going to take the shot, loading to the lands is feasible idea?

it should be noted that although many individuals use autoloaders for target shooting, they may not be suitable for seating into the lands. If you mean a bolt action rifle then yes, because at a rifle range you are operating under controlled conditions and normally (but not always ) can anticipate a cease-fire.

 

[Newtosavage]

After reading about seating close to the lands, and trying many combinations of it in my Ruger 7x57, I eventually figured out that the gun shot best with the bullet seated NOWHERE near the lands. Go figure.

 

[LiveLife]

Despite our discussions and chrono data, ultimately it's the holes on target that truly matter.