S.P. OAL gauge & Comparator questions

[Nortonics]

I'm ultra new at this - actually ultra new in precision rifle shooting altogether. One good thing though is I read a lot and appreciate a complete understanding of what I'm doing, and man-O-man have I been scouring your web site and forum with all the truly excellent information they contain.

At this stage I'm just now about to produce my first ever rifle handloads for my first ever centerfire rifle, that being a new Savage 12BVSS chambered in Win .243. This gun will be primarily to introduce myself to accurate shooting. Yes I know, it's no 6mm BR rifle like the beauties you guys handle, but I think it will be a great starting point for me.

Okay, so tonight I'm getting down to learning just exactly what the maximum cartridge OAL is for this chamber, and as such I'm using the Stoney Point OAL Gauge and the companion Bullet Comparator & Insert set.

I'm totally golden as far as understanding how to use it, and have come up with a rock solid reading/measurement. But I'm a little confused about something. Reading the directions exactly from the Bullet Comparator & Insert set they indicate that upon attaching it to my Caliper I should close the jaws on the assembly,including the Insert) and then zero the caliper - okay, no problem there. Then open the jaws and measure my locked in place case gauge with my chosen bullet style in place while still attached to the OAL gauge - okay, no problem there too, and I fully understand the reasons for measuring at the bullet ogive and not at the bullet tip.

Now the questions. The length read on my caliper certainly is not the cartridge OAL as the reading I get is exactly 2.2175". Is that reading strictly used to slowly, little by little, close my seating die while continusouly pulling the cartridge from the press and using my caliper with the Comparator and Insert attached until I get to that exact same measurement reading listed above, then lock down the seating die once achieved the just go to town seating the rest of my loads? I presume so, but that actual measurement has just thrown me for a loop - guess I though I'd be reading something that was going to be the actual cartridge OAL instead. I measure the actual cartridge while attached to the OAL gauge only,from base to tip) and I get 2.690" +/- which certainly makes sense for an OAL touching the barrel rifling. Am I thinking this through correctly, or am I doing something wrong?

Then one more question concerning the cartridge OAL I'm trying to achieve. With the info above as a guideline, is it truly okay for me to create cartridges that just touch the rifling on this gun, for the purposes of best accuracy? The Stoney Point literature just short of screams that the handloader should be setting the bullet back from .020" to .040", of course for hunting loads that would be cartridge fed, of which I won't be doing - just one cartridge loaded at a time for me.

Thanks for any insight guys!

 

[Forum Boss]

I don't zero the calipers when using the Stoney Pt. OAL guage. If I had a dedicated set of calipers for that I might. I leave them set at zero with the jaws closed.

When it comes to loading length, I do measure off the ogive. I'll start a dummy round, deliberately seating 1/4" or so long,I can eyeball that).

Setting Seating Die
I'll measure the case from base to ogive using the caliper with the SP comparator tool attached. Note: I've previously written down a length for this particular bullet touching the lands. Let's say, at the initial seating die placment I'm .200 inches long. I will then crank the micrometer die down in a couple stages until I'm within about .015" of my desired load length,but still a bit long). Then I'll do a loaded round and check the length from base to ogive. If it's still .015" long, I'll move about 12-13 index marks, and test again,you won't always move exactly .15" from the marks on the die--sometimes it's more, sometimes less). Once I get within .001" I'll start loading the rounds, checking base to ogive of each finished round.

Sometimes you'll get one that seats a little long--maybe because the neck on that particular case is a little stiffer. I'll crank in .002 to .003 more stem depth and reseat that round.

Normally, with Scenar bullets, I can hold base to ogive length within .0015" or so.

 

[Aussie_bob]

Just a little add on just to clarify.
The reason you measure from base to OGive with the comparator is that that is the part of the projectile that will be contacting the lands, rifling)not the tip so it is this point that you want the .010 off or just on and a good thing is to batch all your projectiles first with the comparator so that you have all same length from base to comparator lengths on some projectiles that can be .010 out so would mean the difference of being .010 off ON or .020 Off.
Hope this helps.

 

[Forum Boss]

Also, if you start with a safe load, there is no reason not to start .015" or .010" into the lands. That way, as you are load tuning, you only have to work in one direction.

Additionally, many match bullets seem to perform best seated to contact the rifling. As long as you understand that seating into the lands can increase start pressure compared to seating away from the lands.,With short cases such as the BR however, you can actually have more average pressure jumping the bullet quite a bit than slightly jamming--that's because you are reducing the internal case capacity by pushing the bullet base deeper in to the case.)

Different barrels and different bullets have their own seating preferences. If you prefer, you might want to start .020" away from "just touching".

 

[Bobs243Ackley]

Hi Tom,

One thing that I did want to add that might help, is that regardless of which method that you choose, either the measuring method from Stoney Point, or that Paul uses, you must consistently use that method for all further measurements to maintain the validity of these measurements. This is nothing more than a "reference" measurement that means nothing to anyone, except to you and your rifle! As long as you look at it in this context, you will be off to a good start to what I refer to as "post graduate precision reloading".

Cordially,
Bob Blaine

 

[jb1000br]

Looks like you got your Q answered...

Yup, just a relative measurement for your own use...

For max precision, I always start in the land 15-25thou...

the SP OAL tool is almost useless...best just seating a bullet long, then keep seating deeper until the land marks dissappear.

you can mark the bullet with black sharpie to see the land marks, or twist it in some steel wool...or both...works for me.

YMMV,
JB

 

[Forum Boss]

I'll go along with Jason that the Stony Pt. tool may not be perfect. However, I do find it gives me a repeatable measurement to "hard contact"--the point where the bullet just sticks without engraving. I think Jason's point is that this may already be past initial 0.0" contact. As long as you understand that fact...

To get a good baseline. I'll take one bullet and measure it using the dummy case and one bullet 3 or 4 times. Then I will repeat the procedure with three or four more bullets from the same box,but usually just measuring once per bullet). This gives me at least three numbers for one bullet and three more base to ogive lengths. With that data, I'll take an average, and I'll write that number down in my load book. Every couple of months I'll repeat the procedure and that tells me how much the throat has migrated.

Once you have your baseline number for a particular bullet, you adjust your seating depth,longer) to move into the lands or,shorter) to jump the bullet.

If you have trouble extracting the bullet when using the SP tool, use a wood dowel inserted through the muzzle or drop a one-caliber undersized bullet down through the muzzle while holding the rifle muzzle up.

 

[Hipshot]

Tom,

I started precision shooting with the exact same rig as you now have. After the barrel lost accuracy,1500 firings) I rebarreled to 6BR.

Anyway, using match VLD bullets you want to start close,.010) in front of the lands and work up powder a bit at a time to find the best group on a consistent basis, then with that powder, primer and case load, shoot more loads while seating the bullets further out. I was able to shrink groups when the bullets I was using,and still do, the 105 Berger VLD unmoly'd)were just touching the lands. I use both the SP and an RCBS mic casegauge to ensure my OAL to the ojive is correct. Don't increase powder as you move the bullet further out because at the point of the bullet touching the lands the pressure will spike. I found that the .243 can be accurate but is much more finicky than the 6BR. I think the case is too large,long and narrow) for the caliber.

The conversion from .243 to 6BR for the Savage is a piece of cake. However, you will have to go through the process of working up loads all over again,that's the real fun part.)

For the record, I zero the SP before measuring, and record the data. That method makes it much easier to detect things like throat erosion or a batch of bullets with slightly different dimensions.

 

[jb1000br]

Unless your SP modified case has ZERO headspace in your chamber, the measurement will be even less accurate.

JB

 

[Nortonics]

Guys, thanks so much for all the insight! You all have most certainly answered my questions on this one - even printed out this entire thread to re-read on getting back home tonight. Very helpful info to help me be sure I'm not getting myself into trouble with these first ever rifle handloads. I'm sure I'll have more questions as time goes on, but thank goodness for that wonderful thing called a search engine so I don't need to chew your ears/eyes off with the same questions asked over and over already.

Once again, thanks so much all...

 

[Nortonics]

I get it, I get it, I GET IT!!!

You guys are the best!

I've just been spending the last hour reading and rereading this entire thread while experimenting with everything you guys have been saying, and now I totally get it!

Batch measured all my bullets/projectiles using the Comparator to learn which ones have the longest 'base of bullet to ogive' in the batch,thanks Aussie_bob).

I can then take that longest bullet/projectile measurement to determine my maximum 'cartridge Length to Ogive,LTO),thanks gunamonth) that will be safe without going past the lands on all handloaded cartridges in that batch.

And that the as long as I'm using safer/non-maximum/closer to the lower fps loads with the above info I can go right to the lands or even a little bit past/into the lands and work my way in one direction,out of the lands) until I find the best accuracy,thanks Moderator). Although I think I'll start in the opposite direction and move toward the lands little by little just to be safe, as a newbie should.

To the idea of just using the OAL gauge to get close, then just seat the bullet a little long to begin with and using the sharpie colored bullet and keep seating little by little until the land marks disappear,thanks jb1000br).

To consistently using just one method to keep validity straight - in this case using the Comparator to measure the OAL gauge readings as well as the finished cartridge coming out of the press,thanks Bobs243Ackley).

To the practical experience with the exact same gun,thanks Hipshot).

And now I can see that if I really wanted to get crazy I could seat each and every bullet that measures a little differently in this batch right to the exact same spot in the barrel if I wanted to readjust the seating die to each and every different bullet length - maybe when I get as good as Tubb, eh? Right!

I think I hit every one of you guys above!

Most seriously though, thanks a bunch all of you - I love it when a plan comes together!

 

[Bullet94]

Aussie_bob QUOTE -
“Just a little add on just to clarify.
The reason you measure from base to OGive with the comparator is that that is the part of the projectile that will be contacting the lands, rifling)not the tip so it is this point that you want the .010 off or just on and a good thing is to batch all your projectiles first with the comparator so that you have all same length from base to comparator lengths on some projectiles that can be .010 out so would mean the difference of being .010 off ON or .020 Off.
Hope this helps”.

I’m not sure what you mean, but since all your bullets will be seated in your seating die they all will be the same distance from or into the lands,unless you move your seating stem). Any difference in bullet length,from the base to Ogive) will be pushed into the case by the seating die since your seating die seats from the Ogive. Any difference in bullet length from the Ogive to the tip won't matter as far as seating depth is concerned because this part of the bullet won't touch the lands.

Here are a couple links you might find interesting -

http://www.benchrest.com/forums/showthread.php?t=28867

http://www.benchrest.com/forums/showthread.php?t=27109&page=1&pp=15&highlight=seating+depth

 

[Aussie_bob]

Bullet94,
If you go through a box of projectiles and measure over all length they are all very close but base to where you engage the lands which is where the comparator is measuring can vary .010 which also means that it is .010 different from tip to comparator length and seeing as how most seaters seat from close to the tip and not from down where your projectile will contact the lands you will have this discrepancy that is why i batch my projectiles buy comparator length and check the OAL so that when i seat them they should be all the same length to where they will contact the lands.
Hope this helps to understand what i was talking about Some people even trim all projectiles to exactly the same length i dont gothat far as i have found the couplr of tho arnt worring me as yet maybe it has more affect at long range.

 

[Bullet94]

Throw away the Stoney point stuff and get one of these –

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-600&type=store

You don’t need anything else.

 

[jb1000br]

Through away the Stoney point stuff and get one of these –

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-600&type=store

You don’t need anything else.

I have both, and i think the nut is a PITA compared to the SP comp...though if you are going to throw yors away, do send it to me instead...

batching bearing surface is to keep velocities similar, not seating depth...

JB

 

[Bullet94]

jb1000br

All right keep your Stoney Point comparator but throw the Stoney Point OAL tool away.

 

[Bullet94]

Aussie_bob
Now you have got me thinking about seating depth and bullet variances. I posted a question on another forum. Check it out and see what you think. –

http://www.benchrest.com/forums/showthread.php?t=32947

 

[Clarence]

Where do we start?
If and that is a big IF you have a GOOD chamber,not factory)why not let that $10,000 chamber do the work for you as it should,note: you WILL chase the throat anyway) by seating the bullet long way lond and close the bolt with NECK tension of no more than .002. That of course considers that you have qualified your base to ogive of the bullets within .001 batches.
Do remember to start the loading process low and work up as the long seated bullet will raise pressures.

Clarence

 

[Nortonics]

Just wanted to make additional mention of a really good article located here on the web that further illustrates the issues involved here and has helped me to better understand it all:

Realguns.com: Gauging Success - Minimum Headspace and Maximum COL

That article has helped me to better understand why the Stoney Point comparator along with a Stoney Point OAL gauge factory modified cartridge,non fireformed) can lead to erroneous readings because of rifle chamber headspace issues.

Now I can see how important it is to use a fireformed cartridge with the Stoney Point OAL gauge.

And thanks so much gunamonth for divulging your method of creating a personally created fireformed case for use on the SP OAL gauge - your method is brilliant, and is exactly what I'll be doing!

 

[chino1969]

The Stoney Point tool is a good tool if you know how to use tools and have an understanding of headspace. If you use the factory modified case, you will be off some in your measurement because that case was not fireformed several times in your chamber. Ideally, you should fire cases several times in your chamber until you can feel the case as you close the bolt with the firing removed. Send two of these cases to Stoney Point and they will modify the case to fit their tool; the price is minimal. This modified case will give you an accurate measurement.
Regards,
Chino69