Confusion with OAL gage

dakota1 · Posted: Sat Jan 26, 2008 8:32 am Post subject: Confusion with OAL gage

Gun: is a Rem 700 BDL .270 Win
Measuring device: Stoney Point, compariter (sp), .270 ogive insert, digital caliper
Bullets: Speer 130 gr BTSP and Sierra 130 gr BTSP

When I measure the OAL length of the two bullets, in the stoney point gage, I get a difference of .037.
When I measure the length of the bullets alone, I get a difference of .0046.

Since the only variable in the measurement is the bullet, shouldn't the difference in the stoney point gage measurement be the same as the difference when measuring the bullets alone, when measuring, using the same caliper, comparitor and insert?

When measuring with the stoney point gage, I measured 10 different bullets of each manufacturer, threw out the high and the low, and averaged the remaining 8.
When measuring the bullets alone, I measured 5 different bullets of each manufacturer, and averaged the total.

What am I missing?

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

A lot of time shooting.......................................

ElyBoy · Posted: Sat Jan 26, 2008 10:13 am Post subject: Re: Confusion with OAL gage

Try weighing the bullets on your powder scale dakota.
That should tell the story.
I will bet that there is a difference.
I too check things like you do, and when I see disparities, I try my best to find out what causes them.
It makes a difference when you do go shooting.
As an example, I purchased some .41Mag Starline brass from Midway, and noticed at the range that the same reload using Starline brass compared to using Winchester brass seemed "hotter" with my Ruger Blackhawk 4 5/8" barreled pistol.

After using the caliper, weighing them etc., I found that the cases were a about .001" thicker on the Starline than the Winchester brass.
I dropped the powder charge by 1gr, and came up with a more accurate and easier load, with the same velocity.

Keep up the good work checking your bullets.
It keeps things safer, and like I said, the results will show at the range, and in the woods.

Eric

chambered221 · Posted: Sat Jan 26, 2008 1:42 pm Post subject: Re: Confusion with OAL gage

dakota1

wildswalker is right, your missing alot of time shooting, nothing wrong with haveing a better understanding of things though.

What you are seeing is common. Bullets are made in a die that forms them. That die wears over time. Most bullet manufactors will run a number of dies into the same production run. When they are packaged you end up with a box of bullets made off different dies. Therefor you get different ogive readings.[bullet comparitors read off the ogive]
Also keep in mind your seating die seats off the ogive. If ogive varies on the bullets, your OAL of a loaded cartridge will also vary.

As far as the OAL of the bullets themselves, hollow points have always varied. Benchrest shooters use a meplat trimmer to uniform them to the same lenght. Lead tips vary also, not as much from my measurements.
Plastic tipped bullets seem to be the most uniform.

Unless your match shooting don't worry to much about it. Its not one of those things that will shave a whole lot off of group size, if any.

chambered221 · Posted: Sat Jan 26, 2008 1:49 pm Post subject: Re: Confusion with OAL gage

Just reread your post, I think I missed what you was asking!!!!!!!!!!!!!!!!!!!! Embarassed

I hate when that happens!!!!!!!!!!!!!!!!!!!!!!!!! Mad

Pumpkinslinger · Posted: Sat Jan 26, 2008 5:47 pm Post subject: Re: Confusion with OAL gage

If I'm reading this right (remember, I work night shift and am rarely 100% awake...) Different brand bullets have different shapes. If you are measuring to the point where the bullet is the same diamter as the lands I would expect them to be different.

I measured a Speer .224 40 grain SP and compared to a Sierra .224 40 grain SP using a dial caliper and a Sinclair comparator.

OAL Comparator
Speer 0.505 0.266
Sierra 0.491 0.214

Difference 0.014 0.052

Now, if I've misread this question please excuse me for muddying the water!

ElyBoy · Posted: Sat Jan 26, 2008 6:29 pm Post subject: Re: Confusion with OAL gage

A guy can't figure that thinking take time away from shooting.
That is a pretty non-sensical statement.

For me, half the fun of shooting, is in my reloading room reloading, and trying to figure out how things either work of don't work.

Eric

Dawgdad · Posted: Sat Jan 26, 2008 7:06 pm Post subject: Re: Confusion with OAL gage

Dakota1,

Your readings are perfectly normal. I see this much variation in Hornady match HBPT .224, 75 grain bullets. The .005 variation from Ogive to tip is within the machine tolerance of most manufacturers bullet making presses. If you us a caliper to measure COAL from case head to tip of bullet and set the ones that are the same OAL aside, you will see this .005" variation with your comparitor on the same set of loads that were very tight with previous measurement. As was stated in an earlier post as long as that is the max variation you probably will not shoot good enough to see the difference. In the service rifle 600 yard stage where x counts make the difference between winning and losing it matters that the jump from Ogive to rifling is the same every time.

Most seating dies have a Donut shaped seating stem that will hit the ogive of most all except the very long A- max VLD type bullets. Once you set a die to give the proper Ogive - OAL it is counter productive to measure OAL to tip anymore. Unless you do not have a comparitor then you must.

dakota1 · Posted: Sat Jan 26, 2008 8:11 pm Post subject: Re: Confusion with OAL gage

Both measurements, COAL, and length of the bullets themselves, was done with a comparator and ogive insert. The tip of the bullet did not come into play. The COAL difference between two bullets was .037, yet the difference between the bullets themselves was only .0046.

Since all results were measured from the ogive, and the bullets being the only variable, why wouldn't the difference between the COAL be the same as the difference between the bullets alone?

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

I tend not to pizz up ropes nor fret things beyond my control, and can control bullet sameness via sourcing a known quality.......

The question is, how do they shoot....and that alone can answer many what if's/if then's.

Seat for mag box function and rock on........................

woods · Member Joined: Oct 15, 2005 Posts: 89

dakota1 wrote:

Both measurements, COAL, and length of the bullets themselves, was done with a comparator and ogive insert. The tip of the bullet did not come into play. The COAL difference between two bullets was .037, yet the difference between the bullets themselves was only .0046.

Since all results were measured from the ogive, and the bullets being the only variable, why wouldn't the difference between the COAL be the same as the difference between the bullets alone?

The difference could be that on one hand you are measuring from the ogive to the base of the bullet and then when measuring the COAL you are measuring from the ogive to the base of the case.

A comparator does not measure where the bullet is full diameter. For instance on a .308" bullet the comparator may measure where the bullet is only .293". There can be a variance in the curve of the ogive from where the comparator hits it to where it first measures full diameter. If the ogive curve is the same between those 2 points on different bullets then you should get the same measurement for seating depth.

However, as long as you are getting the same measurements on the same type of bullets then you are OK and need to go with it.

At times the Stoney Point can be very frustrating. Mad

That is why I also use a stainless rod from R-P Products (318-424-7867).

You insert the rod down the muzzle to the bolt face and lock the outside collet

then use the stoney point to insert the bullet and hold while you set the inside collet to the bullet tip. Then measure between the collets.

This will give you the COAL for that particular bullet. It is simpler than the Stoney Point and fool proof which helps me out. Then take the bullet out and measure with the comparator. Do that on 3 more bullets and you can get real close.

Vince · Posted: Sat Jan 26, 2008 11:51 pm Post subject: Re: Confusion with OAL gage

wildswalker wrote:

A lot of time shooting.......................................

I tend not to pizz up ropes nor fret things beyond my control, and can control bullet sameness via sourcing a known quality.......

The question is, how do they shoot....and that alone can answer many what if's/if then's.

Seat for mag box function and rock on........................

Gidday Wildman...how are you and the kids mate?

You had me a bit confused with your first post mate...but your second one has. I think, sorted me out.

Correct me if I am wrong, but is what you are saying...."the differences you have identified don't mean squat...get out, do some shooting and its the end result in the field that means something"?

Cheers, Vince

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

We're humped up with winter and a fair bit of Lake Effect, temps are in the teens down to zero, colder at night........

The kids, as always, are chompin' at the bit to yank on steelheads and burn powder. The Boy told me last night he was gonna slay some cottontails today for supper tonight......

I owe 'em a winter survival weekend...but we're waitin' for colder temps to make things a tad more sporty.

Spent primers alone, can determine what makes a difference or not......

Much voodoo can be conjured up to complicate the process and many thrive on that willingly.

I'd rather just shoot 1/2 MOA or better out there a fer piece, and, can/do that less complicating things for myself.....

Find your lands, know you mag box max COAL, seat for unihibited function and rock on.....

Bad bullets with fugged up weights/ogive dimensions don't get much attention, nor get bought twice again, here.

On a side, never saw that bother me 'nuff to worry about it either...

Ain't hard...............................

Vince · Posted: Sun Jan 27, 2008 7:37 am Post subject: Re: Confusion with OAL gage

wildswalker wrote:

We're humped up with winter and a fair bit of Lake Effect, temps are in the teens down to zero, colder at night........

The kids, as always, are chompin' at the bit to yank on steelheads and burn powder. The Boy told me last night he was gonna slay some cottontails today for supper tonight......

I owe 'em a winter survival weekend...but we're waitin' for colder temps to make things a tad more sporty.

I'd rather just shoot 1/2 MOA or better out there a fer piece, and, can/do that less complicating things for myself.....

Find your lands, know you mag box max COAL, seat for unihibited function and rock on.....

Bad bullets with fugged up weights/ogive dimensions don't get much attention, nor get bought twice again, here.

Ain't hard...............................

I'd rather just shoot 1/2 MOA or better out there a fer piece That makes a lot of sense to me, as does Find your lands, know you mag box max COAL, seat for unihibited function and rock on. This is basically the way I work out my loads. I select a starting load, use factory specs for OAL, confirm that the rounds fit the magazine then start shooting. Onlt thing I don't do is seat the bullet just off the lands.

Same same with bullets that don't deliver the goods...they simply do not get bought again.

Single hole groups, and fractions of MOA are fine, however all I am seeking is acceptable accuracy for hunting out to a maximum of around 300 metres...and even that is extending beyond what I would realistically shoot. As you say...its the shooting that shows the viability of a load, regardless of what has been done prior to pulling the trigger.

Having said that...there is a place for all the "mumbo jumbo"...Bench Rest, Long Range (600 metres +) target shooting or similar shooting disciplines.

make things a tad more sporty....Ohhhh, you're a hard man
Very Happy

When you say survival, what sort of things do you teach the kids?

Fishing is a great way to relax...I love it. Only problem I have is I never catch anything...all I ever seem to do is fatten the fish up with my bait for the next guy to catch. Laughing

Did you get your "underground mutton" (aussie slang for rabbit) for supper? Nothing better than a nice rabbit stew/casserole or marinated rabbit back strap pan fried. mmmmm

Cheers, Vince

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

I tweak powder charge first, then seating depth second....have never found that to fail me.

Single hole groups interest me none, unless they can be repeated all months of the year.

1/2 MOA at 100 yards is neat to look at on paper, but a 2 1/2 inch group at 500 or 600 yards is hard to argue with when fired out of a light weight or standard weight hunting rifle MPAJ, or off backpack/bipods/bipods + backpack......

I don't play the benchrest game with my hunting rigs, nor own an OAL gauge/comparitor. I am however, guilty of finding lands with a black marker..........

Dakota's BDL 700 in 270 win. is no doubt a long throated bastid anyway, mine was. Seating for mag box confines rules out kissing lands and it can be said many Critters have died over the ages with the 700/.270/130 Speer/Sierra combo less any worry over a few thousandths of bullet dimension.

Loading OCW busts a lot of myths.......

Yankin' on steelheads leaves little room for relaxation as it's an exercise in hand to hand combat with a dose of cold water survival throwed in......despite that, it remains my favorite type of fishing.

The Boy is sleeping in this Sunday morning and have never seen that hold him up. Would expect him to get around soon tho' and grab a rifle. We've an 18" base with a light snow falling now. Good tracking weather and the cottontails will be easy to spot in the underbrush....

The kids teach me................................