.....MUCH more knowledagable than my self.

This is my situation.
My most accurate and all time favorite rifle is a 100% factory M700 Stainless/Synthetic in .338 Winchester Magnum. I am going elk hunting in a VG unit this year and I desided to give some .338 225grn Nosler Accubonds a try. As the Gods of accuracy would have it my rifle LOOOOOOVES them and shoots them at a level of accuracy far better than I could ever have hoped fore.

Now for the my question resulting from what I discovered while reloading the Accubonds.
I have since day one of my rifle reloading, I have always used a Stony Point bullet comparitore with my calipers to help determine and set my cartrage over all length. This part of my reloading procedure is the same every time. I use the SP/Comp to set and double check the first 2-3 reloads then off to the races. Well seeing as I was using a new bullet, I desided to measure every loaded round. I was quite amaized and surprised to find that the OAL was varying from 3.70405 to 3.708 and a few even as high as 3.711. I then reset the bullet seating die untill every reloaded cartrages OAL was 3.705 or what I always thought I was the OAL of my past reloads.

I at first thought this might be caused as a result of a batch of 50 count Accubonds that had some how sliped buy Noslers QC, but I as soon as I finished reloading these rounds I reloaded the same exact loading in 338wm, except I used 225grn Hornady Interloks, and experienced the same OAL length varience, although not quite as extream as with the Accubonds.

My question to those far more knowledgable than my self in reloading, is this varrience in in OAL length caused by inconsistent bullet length normal?

I ask this strictly to increase my reloading knowledge as went to the range to day and the above lads with both 225grn Accubonds and Interloks both produced SUB-MOA groups at 100 and 200yrds so obviously this varying OAL of the loaded cartrage had zero impact on my accuracy.

So what what gives? Based on this I would be lead to the conclusion that in in this particular M700 cartrage over all length has little if any affect on accuracy as long as I am with in 3.704.5 to 3.706 which was the minimum/maximum OAL varience I would allow.
And lastly, using a SP comparitore is this the actual cartrage OAL as I am reading it with my digital calipers?

Thanks for helping me out with this.
Arthur.

Art,

First off, although you ask the question as though you believe the OAL length variance is cause by bullet length variance.

For that to be the case then the variance in bullet length would be somewhat more than the 4-6 thousandths you are seeing if your die is seating off the ogive.

Probably this is just slop in the press and manipulation of it.

Lastly only a few bullets tend to be that particular about distance off the lands. Barnes notably Some gun/bullet combos work best with bullets close to the lands, some with them way far off. There isn't a rule. Well, there is, but your gun and bullet make it, not you. Generally you have to be careful with the close one not being too close for both safety sake and accuracy. So, for OAL do not exceed the distance to the lands you measure with the Stoney Point gauge. For bullets that never touch the lands you may well find that .020 variance is no big deal at all. For something like Barnes TSXs a variance of .005 has made a noticeable difference in my experience. I have seen Barnes bullets shoot best at .005 off the lands and I have seen them shoot best at .070 off in another gun.

On some guns with very long throats you cannot get close at all. With a gun shooting well pick a distance off the lands that will keep you off every single time and be happy.

You don't say which seating die you are using and that may be your problem. I spend more on my seating die than all the other dies combined and get an RCBS Competition or Gold Medal Match, a Redding Competition or a Forster Competition seating die. Those will seat your bullet to a more consistant depth.

What could be causing your variation is that your seater die stem is contacting the bullet curve at a point too far forward or even hitting the tip up in the middle of the seating stem. That means that the difference between where your seating stem bears on the bullet and where the ogive is as measured by your comparator varies, or at least that part of the curve varies.

As posted, IMO you have a cumlative measurment of press slop(that word sounds worse than I mean it) and manufacturing tolerances.
In the end however you are still ending up with just a few thousandths of varience.
I would make sure that in no case are they close to touching the lands and then load up a batch and shot them with the variences. It is after all hunting ammo and the proof of the pie is in the eating. And too, safety and reliability trump any .25 gain in accuracy you may get from creating bench rest ammo for a hunting situation.

quote:

Help with Loaded round OAL question for those....

Actually, it seems you have found for yourself that the OAL figures are far less critical than some folks believe. If a round fits and feeds from your magazine, chambers readily and you have no excess pressure signs, the OAL HAS TO BE OKAY!

Now, for variations in OAL, understand that small differences (of 3-5 thou) are really no difference at all, especially if you are actually reading the full OAL and not from the base to some point on the ogive. I only consider anything over 5 thou to be significant and that's still not much change.

Why does it change at all? Variations in neck tension, actual bullet diameter, thickness or hardness of the case neck, sloppy press linkages or turrets, etc, all make a difference in the pressure required to seat a given bullet to a given depth in a given case. If the bullet goes in hard, the pressure will compress the linkages, and their lubricant, more. The ram travel is reduced and the bullet won't be seated quite as deeply as it will be if the reverse is true. Consistant operation of the press lever helps but we can't stop it.

I love the Forster/Redding BR type seaters for improved concentricity but I've never found them to seat to any more consistant OAL than conventonal seaters.

Thanks to all for your help in sharing your knowledge with me.

Does anyone think that a press like the Foster Co-Ax would help minimize this OAL varience?

Again thanks to all for your help.
Arthur.

FWIW, the loads in question produced three 100yrd three shot groups from the bench that averaged out at .53" and two 100yrd three shot groups shot while sitting off of Stony Point shooting sticks that averaged 1.3".

quote:

Originally posted by ARTJR338WM:
...I have always used a Stony Point bullet comparitore with my calipers to help determine and set my cartrage over all length. ...

Hey Art, I do love it when the answers are relatively simple. Give the "Thingy" to someone you dislike, sell it to Woods or just Trash it.

Trust in the Seating Die to do it's job correctly with a consistent Seating Stroke as long as the Tip of your Bullets are not touching the inside of the Seating Stem. And you might be interested in trying the excellent, never-fail, time-proven, always-works OCL to ODL conversion process. Do it each time you open a New box of Bullets so you stay close to the same Lands distance as the Throat moves forward.

Great rifle in an excellent caliber.

Hot core said it. As long as it is shooting better than you could ever have hoped for. Throw that thingy away. The target is where the story is told.
Lyle