Help determining best OAL for my rifle

[iXanadu]

Hey guys,

Thanks to everyone that helped me work up a plan of attack for my first foray into reloading for a rifle. I have all my components, and am ready to start working up my load. I need a little help understanding the OAL for my rifle.

Caliper: Mitutoyo
Rifle: Browning X-Bolt .270 win
Components:
Nosler AB 130gr
Winchester brass fired in my XBolt
Powder H4831sc (not that it matters for this topic I don't think.)

Nosler recipe calls for oal of 3.320.

I cut a grove in one of my once fired brass and inserted a bullet a little long and carefully closed the bolt. The bullet is snug but movable by minimal pressure (I can seat it deeper with caliper). Several iterations resulted in different values from 3.3890 to 3.4000 with 3.990 coming up pretty frequently. Why in the world I'm seeing that much of a swing I don't know. I even notice a 2/1000 of a swing just rotating the casing - I suspect operator error.

I've read/watched information that suggest 2-5 thousands off the lands.

Where should I start? I'm thinking 3.3850.

I'll ask the next question even if it is pre-mature. I'm going to start with Nosler's "minimum" 55gr and work up, watching for pressure signs, velocity and accuracy.

What do I concentrate on first, powder charge or OAL?

Sorry to be such a noob, but there is no way around it except to ask and do it. I promise to pay it forward.

 

[joelkdouglas]

I think there are two methods.

Method 1: http://www.eabco.com/Berger%20Bullet%20 ... ethod.html

Method 2: http://riflemansjournal.blogspot.com/20 ... depth.html

You'll note Salazar says to seat bullets 0.02 off the lands for conventional tangent ogive bullets, such as Accubonds, Partitions, Custom Comps, etc.

I normally do some pressure testing (powder variance) while seating bullets 0.02 off the lands, find a good powder node, and then use the Berger method to see if I can tighten the groups up. In my tests it's not uncommon for Partitions to shoot best about 0.09 off the lands.


I think with H4831 and the 270 you'll find some good results quickly.
Good luck!

 

[Sas874runner]

I have always started ABs .060" off the lands. The AB seems to like the jump in most rifles. My 30-06 shoots .75" at .060" off the lands. My 270 is real happy .110" off the lands and my 300 rum sittin pretty at .122" off the lands. Some people have gotten good results closer to the lands but I never have started to see groups closer than .060". When I measure that way I start with the shortest length to be on the safe side. And if you look at the nosler length .060 jump would put you at 3.325". Sounds like a starting point IMO. Cup and core bullets I start .010" off lands

 

[hubcap]

I use .100 to .110 off the lands with 130,140 and 150 AB,s. If the X-bolt has a removable mag. you may not be able to load longer than 3.340. Just a thought.

 

[sask boy]

I have my 130gr. ABs loaded & the OAL @3.340"!!
My MOA is .5 if I do my part.
Blessings,
Dan

 

[rick smith]

My rules for bullet seating: has to fit and function from the magazine box, has to have enough bullet in the case to stay straight in the case during cycle and can't be jammed into the lands. There is no magic being close to the lands just a starting place for seating. For cup/core bullets I start 10-15 thou off the lands, monos start 50 thou off the lands. The reason your measurements varied was probably due to the lands holding the bullet as you extracted the case. You can find out for sure by coloring the bullet with a sharpie and looking for marks from moving in/out of the case. Once you determine your length make a dummy round at that length spin some 4/0 steel wool around the bullet, hand load the round into the chamber and close the bolt. As you extract the case use your fingers to prevent the case/bullet from hitting the chamber or receiver. Now look under magnification at the bullet for land marks. Rick.

 

[DrMike]

Choose an OAL that works through your magazine. If a magazine will permit me to build a load 0.010 to 0.020 inches off the lands, I will do so for initial testing. I work up a load that covers charge from a minimum (usually 10 to 5 percent off maximum charge) to the maximum. These are tested, watching for signs of pressure. The test load that gives me a velocity with the lowest standard deviation will be reexamined, testing for OAL if necessary. As a rule of thumb, for field loads (hunting), I do not like to have the cartridge tight to the lands. There is too much danger of a jammed round or a delay in chambering in the midst of the hunt, which would mean a lost animal. Nothing more disturbing than pulling the bullet and dumping powder in the magazine in the middle of your hunt. If the purpose is accuracy at the bench or competition, then I have no problem even kissing the lands if that is what it takes. As a rule of thumb, cup and core bullets (Partition, Ballistic Tip, Custom Competition) give high accuracy when they are seated close to the lands. Monolithic bullets (E-Tip) appear to enjoy a longer jump to the lands. The AccuBond is somewhat of an anomaly, appearing to enjoy a longer jump to the lands than would have been imagined, because it is a cup and core bullet.

 

[iXanadu]

All,

Thanks for all the feedback. The thread that inspired my interest in this round was posted by Rovert a year ago. viewtopic.php?f=4&t=17744

His research resulted in a very tight group of BT's and AB's using RL22 and an OAL of 3.320. I know that where the lands are on his rifle is different than mine, so I have a PM to him to see if he knows how far off the lands 3.320 puts him. What I do know, is that he, and several of the members that participated in that thread seemed to feel that the AB's like a little jump. Since I've only loaded 9mm handguns, this was counter-intuitive to me, were getting closer to the lands tightened the group.

Going in to this I know I wanted to have a little jump, but I was surprised when my guns is showing a 3.3890 lands position. Hard for me to decide to start at the recipe's 3.320, or go 3.340, 3.350?

Anyway thanks for all the comments. I'll start loading up next week once I fire some factory loads and generate some brass. If all else fails, I'll start at the recipe and go out from there.

 

[Sas874runner]

Some rifles have long throats that cause you to load very very long depending on where you want to be of the lands. My 270 with 140 ab oal touching the lands is 3.522" it just depends oj what the rifle likes. Only way to know is ask it.

 

[hubcap]

All,

Thanks for all the feedback. The thread that inspired my interest in this round was posted by Rovert a year ago. viewtopic.php?f=4&t=17744

His research resulted in a very tight group of BT's and AB's using RL22 and an OAL of 3.320. I know that where the lands are on his rifle is different than mine, so I have a PM to him to see if he knows how far off the lands 3.320 puts him. What I do know, is that he, and several of the members that participated in that thread seemed to feel that the AB's like a little jump. Since I've only loaded 9mm handguns, this was counter-intuitive to me, were getting closer to the lands tightened the group.

Going in to this I know I wanted to have a little jump, but I was surprised when my guns is showing a 3.3890 lands position. Hard for me to decide to start at the recipe's 3.320, or go 3.340, 3.350?

Anyway thanks for all the comments. I'll start loading up next week once I fire some factory loads and generate some brass. If all else fails, I'll start at the recipe and go out from there.

Have you checked your detachable mag to determine the longest it will take. I have a remmy clip that will not take over 3.340. I load no more than 3.330 so they feed correctly. Far as I know browning factory clips are the same. If I,m correct your looking at a very reasonable bullet jump of about .050 to .060. Factory ww 130 PP,s are loaded to 3.290 aprox. You are probably using considerable bullet jump with your factory ammo.

 

[RiverRider]

Measuring with a comparator attachment on your caliper will probably yield more consistent results. I used to believe otherwise, but not anymore.

 

[BD1]

Measuring with a comparator attachment on your caliper will probably yield more consistent results. I used to believe otherwise, but not anymore.

That's my experience also. To also add to the commentary about AB jump, I've had better results with the bullets seated deeper as well.

BD

 

[iXanadu]

Sorry for late reply. How do I measure OAL with a comparator? I have the Hornady comparator set and am trying to understand how to use it for neck size measurements.


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[ScreaminEagle]

If you are going to work up to a max load, do it with the bullet jammed into the rifling! Cook up a load that is max for your gun, then jam the bullet and you will create a possibly dangerous pressure spike.

 

[Dr. Vette]

Sorry for late reply. How do I measure OAL with a comparator? I have the Hornady comparator set and am trying to understand how to use it for neck size measurements.


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I'm not sure what you're getting at, since the comparator has nothing to do with neck size unless there's something I really know nothing about.

See photos below.

First, install comparator on calipers, and zero it out.
Next, note the two cartridges, one with a Sierra bullet and one with a Berger, both are 7mm Wby.
Now see how the distance to the ogive (CartridgeBaseToOgive or LengthToOgive) differ between them. This is just for examples so you see that different bullet shapes result in different CBTO/LTO measurements.

Your goal when loading is to the the CBTO/LTO measurement to be exactly the same for each round.

 

[hubcap]

Dr.Vette. Thanks for posting the comparator info. I have never used one of those.I just learned a new trick. :grin: :grin: :grin:

 

[Dr. Vette]

Dr.Vette. Thanks for posting the comparator info. I have never used one of those.I just learned a new trick. :grin: :grin: :grin:

You're welcome.
Works great, and helps get each of those loads exactly the same length.

Other than when trying to fit into a magazine when first setting up a load I never measure OAL (i.e. base to tip). It's CBTO/LTO only.

Sometimes I'm anal enough I sort bullets by the distance from their base to ogive, and put them in marked baggies for loading. :shock: I have no clue if it makes any difference, but it keeps me busy on a snowy evening.

 

[hubcap]

Well, I would not call it anal. It is called eliminating another possible variable. Loading each bullet exactly the same distance off the lands can,t be a bad thing. It is kinda like weight sorting cases. I always do that. Certainly weight sorting won,t make a crappy load shoot good. I think it makes an accurate load the best it can be.

 

[iXanadu]

Dr. Vette:

We were talking different comparators, and even then I got it wrong. I have the Honrady Headspace comparator kit. While I'm still trying to determine exactly how to use this I now know that you were describing a oal comparator, that basically measures from ogive to end of case.

I'm still accumalating brass so I'm still in the research phase of this load. In the Nosler 7th edition, 130gr AB/BT's are described having an 3.320 0.A.C.L. I always took that to mean from overall cartridge length or rim to tip. Not that I know about a oal comparators I definitely want one, but how would i translate 3.320 oacl, to a measurement from ogive not tip of bullet?

 

[Dr. Vette]

Not that I know about a oal comparators I definitely want one, but how would i translate 3.320 oacl, to a measurement from ogive not tip of bullet?

I load one up at an OAL of 3.320, for example, using the calipers w/o the comparator to measure it. I then install the comparators, measure base to ogive of that load, and off we go.

However, that will not tell you distance to the lands, which is probably what you want. You need to use the tool you own (OAL gauge):
http://www.hornady.com/store/Lock-N-Loa ... ght-1Each/
to find the distance to the lands, and then set the base to ogive using that number.

So, if the distance to the lands is, say, 3.450 you can set the base to ogive at 3.420 and say you're 0.030 off the lands.

Does that make sense?