OAL variation

ezzy6.5

Well-Known Member
What sort of variation do you guys get in your seating depth? I just measured some of my .270 loads and was suprised to see quite a difference in the length.
I measured between 71.72mm to 71.84mm does this seem like a lot?
bullet is a 130gn gameking, case is full length resized and trimmed to length. Dies are redding, press is a rockchucker.
Any thoughts?
 
Ezzy

71.72 millimeters = 2.82362205 inches 71.84 millimetres = 2.82834646 inches

2.824 inches to 2.828 inches is pretty good in my book. I try to get less than +-2 thou with respect to the nominal OAL I am going for.

Well done. JCS
 
I've known a very long time that OAL is difficult to maintain consistency within +/- .002". You cannot rely on the bullet OAL being consistent for this, nor indeed your cases - unless you have very carefully sized and trimmed them to exact length.
Even so, the use of a comparator is the most reliable measuring device and provided the cases are indeed exact to matching OAL, careful & very consistent pressure on the ram lever just lightly touching the final point of the seating die, should yield the optimum consistency of OAL, more often than not, to within +/- .001"
It's a slow process, but does work.......but the question is:
Can you shoot to within the accuracy the rifle/crtridge combination will give?
Do you really need this close tolerance level? :old:
 
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I've known a very long time that OAL is difficult to maintain consistency within +/- .002". You cannot rely on the bullet OAL being consistent for this, nor indeed your cases - unless you have very carefully sized and trimmed them to exact length.
Even so, the use of a comparator is the most reliable measuring device and provided the cases are indeed exact to matching OAL, careful & very consistent pressure on the ram lever just lightly touching the final point of the seating die, should yield the optimum consistency of OAL, more often than not, to within +/- .001"
It's a slow process, but does work.......but the question is:
Can you shoot to within the accuracy the rifle/crtridge combination will give?
Do you really need this close tolerance level? :old:

Sorry, but why does case length (trimmed or not) affect OAL?
 
Sorry, but why does case length (trimmed or not) affect OAL?

Trimming changes the length of the neck that grips the bullet and trimming adds burrs to the end of the neck which are then removed. All work on the neck has an impact on the consistency of the neck tension on the bullet. In my brass prep I attempt to get consistent necks (length & tension) and necks that are burr free. Regards JCS
 
It depends on how you are measuring Ezzy.

If you are measuring to the tip of the bullet, then .005" tolerance is acceptable as the actual length of the bullets will vary this much.

If you are using a comparator and measuring to the ogive, then (In my opinion) .005" is rather excessive and you may need to look at
your bullet seating methods and/or dies.

However, Deeangeo is absolutely right. If the rifle/bullet combination accuracy is as you want it, then carry on as you are and enjoy it
 
Trimming changes the length of the neck that grips the bullet and trimming adds burrs to the end of the neck which are then removed. All work on the neck has an impact on the consistency of the neck tension on the bullet. In my brass prep I attempt to get consistent necks (length & tension) and necks that are burr free. Regards JCS

I agree that neck tension is important but length of case will not affect to OAL to ogive - only the amount of bullet in the case, so therefore gives differing tensions?
 
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Measuring with a comparator from ogive will give a more consistent OAL as bullet lengths vary considerably, also it will help ensure you maintain the correct distance from the lands you want to achieve.
Cheers, :old:
 
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If you want to get a more consistent measurement use a comparator and measure all your bullets base to ogive length
and batch them, you will find even match bullets vary as much .005", I have done this several times and it is a total waste time especially with a hunting rifle, you are better off tweaking your powder charge a couple of tenths of a grain.
Robert.
 
.... differing tensions?

Differing tensions will mean that when you seat the bullet, it goes into the neck to different depths. Do a trial, take 4 short cases and 4 long cases and seat bullets in them without adjusting the seater and see what differences in OAL you get (all other things being equal). Regards JCS
 
Do a trial, take 4 short cases and 4 long cases and seat bullets in them without adjusting the seater and see what differences in OAL you get (all other things being equal). Regards JCS
+ 1 absolutely correct JCS.

I re-load ammo. to a close tolerance to maintain consistency so that good accuracy is much more reliable. The pay back is in the field when stalking. I can't shoot now, as well as I could when younger. However, I'm not a target shooter and doubt that I could shoot to the level of accuracy I hope my ammunition may provide. As long as I achieve 1/2" MOA at 100 yards I'm happy.
Cheers, :old:
 
.... differing tensions?
Differing tensions will mean that when you seat the bullet, it goes into the neck to different depths. Do a trial, take 4 short cases and 4 long cases and seat bullets in them without adjusting the seater and see what differences in OAL you get (all other things being equal). Regards JCS

This..

Quote

I agree that neck tension is important but length of case will not affect to OAL to ogive - only the amount of bullet in the case, so therefore gives differing tensions?

Unquote

..was intended as a statement - not a question - and agrees that different amounts of bullet in the case will give different tensions.

Sorryo, but my engleeeesh she is not so good ;)
 
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i know from personal experiance that you will send your self crazy measureing oal measureing.
for hunting ammo.+/- 4" good enough.
i know i had alot a lot better results when i changed to neck bushing die.more consistent neck tension.
and spent more time on my case prep,all the small thing will change the end results .it really depends what you want from your ammo.
bob
 
:oops: i measure each one of my loaded rounds to ensure the length from the head to the ogive is within 1.5 thou... I have trimmed all of my cases to the same length, turned the necks for concentricity and then weight batched them.. i check 10 bullets out of the box for length to the ogive also.. :oops: :oops: :oops:
 
:oops: i measure each one of my loaded rounds to ensure the length from the head to the ogive is within 1.5 thou... I have trimmed all of my cases to the same length, turned the necks for concentricity and then weight batched them.. i check 10 bullets out of the box for length to the ogive also.. :oops: :oops: :oops:

You should be embarrassed. You make the rest of us look slovenly with your fastidiousness. What do you do if they are out of that 1.5 thou range? Toss them? What kind of loading gear do you have? ~Muir
 
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