Finding OAL

[arizona hunter]

I just read a useful article in the July Guns/Ammo mag. It was written by John Haviland, in it he describes a way to determine your OAL for a particular bullet/cartridge.

Previously I had read of coloring a bullet with a marker or "smoking" it with a candle, but I was never really satisfied with the results, and therefore could not trust them.

Haviland says close the bolt, then put a cleaning rod down the muzzle until it stops. Now mark this point in some way ( I used tape). Now, take a case and lightly fit a bullet into it--way out beyond what the OAL will be, now slowly close the bolt. Take the rod again and lower it into the muzzle, now mark the spot were it stops. The distance between the two marks (for me, between the insides of the two pieces of tape) is the max OAL for that bullet. Interesting thing, is that when I measured the distance between the marks, it was also the same length of the cartridge. This is the MAX OAL for that bullet.

For my 30.06 with Barnes XLC 180's I was .050 off the lands (what Barnes suggests). How I arrived at this was using the "smoking" method 4 years ago, and they shoot great, but I still wondered if I was close to the OAL.
With my old 1942 6.5 x 55, I now know why some loads shoot poorly when loaded at 2.889 instead of out to 2.995 to 3.100-too much jump to the rifling.

All this was very interesting to me this morning before going to work; for some of you it's old news and some others don't care. But I shared this in hopes that some other reloader (besides myself) will find it useful.

Make this a great day.

[kingudaroad]

It seems to me that the end of the cleaning rod touching the tip of the bullet can have some deviation. Measuring to the ogive with a Stoney point tool and a comperator would be the way to go if you are trying to be precise.

Of course that means a $30.00 investment.

[TimRB]

...Or if you don't want to spring for a comparator, you can use an appropriately sized piece of tubing, too. It just has to be something with a hole in it that's square on both ends. Oh, and short enough that you can get the whole claptrap into your calipers.

I might point out in passing that one drawback to the OP's method is that bullet length can vary quite a lot. Measure a few just to be sure that you're not injecting an error.

Tim

[Shoney]

The comparator method is the only valid way to determin Max OAL, in order to test how many thousandths off the lands you want to be. Do you really trust the eyeball method when dealing with thousandths?????

Just for git and shiggles, determine the max OAL by Guns/Ammo method in you rifle with a spire point bullet. Now! Load a round nose bullet to the same max OAL, and try to chamber it.

[Bullet94]

I believe the cleaning rod method could work if you set your seating die with the same bullet you used in your dummy cartridge and only for the brand and weight bullet you used.

I like to use this method that the benchrest guys use (copied from another forum) -

There are some pretty universal rules about seating a bullet. You first seat the bullet to a given depth and then work up with the charge. To do otherwise might lead to a pressure excursion. Do you know how to read pressure in a rifle case??? If the radius of the primer is gone,the bolt lifts hard,you can see the extrusion of brass back into the elector hole,see the machine marks on the bolt face in the brass or the primer flat falls out of the case the load may be a bit hot. BUT, this can and will happen regardless of where the bullet is seated if you tip the powder bottle too much. Here's a very easy way to develope a load:
1)-Set the bullet into the lands(if you can reach them) as much as the neck tension of the case will allow.
2)-Start with a minimum listed powder charge-10% for the bullet weight
3)-Work the powder charge up till the groups get as small as they will get.
This depends on the rifle.
4)-After getting as small a group as the rifle will shoot at the jam,back the bullet off.002/.003 at a time and see if the groups improve.Depending on the rifle they may or may not.
5)-If you decide on trying another bullet back the powder down and go back to the jam length and start again.
What this saves is guesswork. If the bullet is seated HARD into the lands then the only way to go with it is shorter. If the bullet is seated HARD into the lands and you have a safe working load pressures will NOT increase as the seating depth is shortened. If you, at any point,. get pressure signs, STOP. Back off the powder and start up again and see if it repeats. Be aware that a load shot at 70 degreesF. may not be a safe load at 100 degrees F.Back a load off when you change ANY part of that load including changing lots of the same brand of powder. Never assume anything;prove it to yourself. There is not really a lot of rocket science in rifles; experience is much more important

[mrawesome22]

Take an empty case. Cut a vertical slit in the neck, barely into the shoulder, with a hacksaw. Barely seat the bullet you want to use in this case with your hands. Chamber this round in your rifle. Eject it with your hand covering the ejection port. Take it out and measure it from base to tip with your calipers. This will give you MAX OAL (over all length) for that bullet. In other words, this bullet is touching the rifling. Now you can experiment with different seating depths. I've found that my rifle's usually give best accuracy .030" away from the rifling. But you'll just have to experiment as to what shoots the best out of your gun. This method works very well and you don't have to waste money on a Stoney Point guage.

[DBotkin]

That's what I did.

[Bullet94]

mrawesome22
Take it out and measure it from base to tip with your calipers. This will give you MAX OAL (over all length) for that bullet. In other words, this bullet is touching the rifling. Now you can experiment with different seating depths.

If the bullet is just touching the rifling how can this be MAX? Wouldn’t Jam length (HARD into the lands) be the MAX OAL? Wouldn’t you get better results if you measure using a bullet comparator than measuring from the bullet tip? I see a lot of variance when measuring from the bullet tip. Haven’t we been over this before?

[T-Bear]

But you for forgot to include the part where he says to cut a vertical slit with a hacksaw into the top of the case. This way there is jamming the bullet into the lands. With the slit there is a very very very slight pressure holding the bullet.When you do eject the casing go real slow so as to not distrub the OAL.

[30Cal]

Knowing where a spire point contacts the lands is interesting, but it doesn't tell you what to do with other bullets.

I guess I do it the easy way.

I seat a bullet (out long) in a sized case. Stuff it into the chamber using your thumb. If the cartridge doesn't drop out of the chamber by gravity alone, then the bullet is in the lands. Seat it 0.005" deeper and repeat until it does drop out on it's own. That's where your lands are. I doubt a dedicated gage is any more accurate.

Ty

[Shoney]

mrawesome22: I've tried this, and depending on caliber, the problem with this method is that the lands can grab the bullet and pull it slightly out of the case when it is extracted. This can be solved by putting a dab of super glue on the bullet and leaving it the chamber for 10 min. However, I never did care for the risk of supergluing a bullet in my chamber.

30Cal: This is the next best method to a comparator, but it is still guesswork. It is not useable for a different bullet, as it must be repeated with the various bullets.

[T-Mac]

Thanks, but.....I like my Stoney point OAL guage.
I'd recommend one to anybody wanting good accuracy.

[mrawesome22]

Haven’t we been over this before?

LOL Too many times buddy, too many times.