OAL Gauge

[JimFromTN]

I have been using an OAL gauge every time I change bullets. I could be using it wrong but it does not really seem like it helps that much. Am I doing something wrong?

 

[Mortis]

An OAL Gauge is designed to meet SAMMI Specs on a specific caliber. It has nothing to do with what the rifle likes.

If you are seeing a varied impact pattern downrange by bullet weight set to that OAL gauge, what you are actually seeing is the effect of 'bullet jump' from case to rifling. Reduce the bullet jump and your groups should tighten up.

Two factors in reducing bullet jump.... 1: the finished round has to fit in magazine. This is the real limiting factor. 2: the finished round should be just off the rifling, but not actually touching. If you are out too far, and actually contact the rifling as you close the bolt, some rifles will 'hold' the bullet in place as you try to extract an unfired round, thus pulling the bullet from the case and dumping powder all into your action.

Now.... I'll let the more technical types tell ya more....

 

[Guest]

I guess it depends on what tool you're using and how you're using it. If you mean you're using the stoney point style OAL gauge and a modified case to tell you the distance to the lands with each bullet, I'm not surprised you're getting similar results - especially if you're using a bullet comparator to measure the distance to the lands. That measurement should not change, of course. But, once you have the distance from the bolt face to the lands reliably measured, you can use that measurement with any bullet in that rifle, as long as you measure to the ogive of the bullet with a comparator. And if you're setting everything at the same OAL with a comparator, the difference will be in the true overall length of the bullet, casehead to tip.

Mortis' comments on magazine fit are spot on. No sense in making a single shot out of a repeater. As for the distance from the lands, I do not have one single rifle in my safe that shoots best up close to the lands. I start at mag length in all rifles (or length .010" off the lands, whichever is shorter) and work back from there. So far, in all my personal rifles, mag length is shorter and I've worked back from there to find the accuracy node.

 

[joelkdouglas]

I have been using an OAL gauge every time I change bullets. I could be using it wrong but it does not really seem like it helps that much. Am I doing something wrong?

Jim,

Welcome to the forum.

I also use an OAL gauge when I change bullets. I use the Hornady version, but I'm sure the Sinclair or other versions are just as capable.

I keep a log of load data in a binder (along with used targets, conditions, barrel times, etc.). In that binder I have a spreadsheet where I annotate OAL using a particular bullet to the lands in my rifle. I normally annotate the length both in total OAL and length to ogive.

All the OAL guage gives you is a known length of cartridge until you hit the lands. You still have to figure out what your rifle likes, but it does provide you a good starting point. I normally start at 0.015 off the lands, and vary powder combinations. Once you get a load close with powder, you can also play with OAL (I seat deeper, not towards the lands), seating in by 0.003 or whatever increment you choose, to see if that results in something your rifle likes.

Some load bullets to touch the lands, and in some cases individuals load beyond the lands (sometimes annotated as "into the lands"). I don't do this, but that's just personal preference.

What cartridge are you loading for / shooting?

v/r
Joel

Note: edited for correction to starting length. I normally start 0.015 off lands, not 0.0015 off lands.

 

[JimFromTN]

I use the hornaday OAL gauge. I typically seat the bullet .02 off of the lands.

I am loading 300 win mag rnds.

 

[Mortis]

Not to insult ya here..... but I need to ask this question....


What's your load data...

Bullet Make, Weight, powder (make and weight)

Sometimes it's just the wrong powder with the right bullet or wrong bullet with the right powder... etc....

The rifle wants what the rifle wants....

 

[joelkdouglas]

I use the hornaday OAL gauge. I typically seat the bullet .02 off of the lands.

I am loading 300 win mag rnds.

Sorry, can't help you with any load suggestions. I only load for and shoot a 30-06.

As for OAL, so long as the rounds function through your magazine, 0.02 off the lands is fine.

What have you loaded up so far? You could also post a request for suggestions for 300 WIn Mag loads in a new topic. There are mostly good dudes here, and I'm sure some of them load the Win Mag.

 

[Oldtrader3]

Ogive tangent datem is the important dimensions and distance from lands is the critical dimension, not how log or short the COAL is. Noslers need higher COAL then Accubaonds generally.