Fool Proof Practice

[SDDasher]

Is there a "Fool Proof" practice to measure accurately the distance from the base of a cartridge (face of bolt closed) to the lands in the barrel? I never feel completely sure when using the Stony Point that I have the exact measurement given just a thou or two makes a big difference when either jamming or jumping bullets. Sure wish someone would invent something to make it a "sure" thing.
Or am I being too precise about the significance of this and should just accept it as being close enough for gov't work?

 

[PhulesAu]

Accuracy is a good thing. But NOTHING is Fool Proof.

 

[Larryh128]

The best thing that I've done & someone might improve on it is to load a dummy round long, apply lay out dye (nail polish will work) & try to close the bolt. You are going to have marks if it's touching the lands. If it's stiff, set the bullet down, recoat & try until it just barely marks. As foolproof as I've found. A little messing around but government work doesn't pay well anyway.

 

[deadwooddick]

Boyd will be along shortly to explain it… but IF you use a cleaning rod and ONE bullet, you can get a precise measurement. You do need to know the freebore diameter as well as the land and groove diameters.

Of course, any "other" bullet (same box/lot/caliber/weight) that's used will NOT give you the same measurement as the one derived from the first example.

 

[Immike]

I guess I see it different than touch because I use jam for the zero and go from it with my measurements. I can reliability find it by soft seating several bullets and chambering each several times until they are pushed in the case as far as possible. I have been using wet moly for some time now and I can't get it to jam very far into the lands because the case doesn't hold on to the bullets like a bare bullet does. I have seated bullets until I can no longer see the rifling marks and have called it touching but it is not the fool proof way you are seeking. I log my load testing by the die setting and try to buy enough bullets of the same lot to last the barrel. My base of case to ojive measurement is what I watch for when I check my ammo.

 

[Raythemanroe]

I use (Stoney point) now Hornady, combine this with a Micrometer die and I think it is as fool proof as the bullets can let you be..I measure using the Stoney point tool and set my die up a couple thousandths long and then I work a dummy bullet like a go gauge. I take out the firing pin assembly and bump the bullet back a thousandth at a time until it falls without resistance and right it down..

 

[GSPV]

Why do you want to measure it? The important thing is to be able to find the right seating depth.

Here is my method:

1. I use inline seaters made from Wilson blanks with my reamer.
2. I incrementally seat a bullet deeper into the case till I find where the bullet is just kissing the rifling. I do this for each bullet/barrel combination. That dummy round gets labeled and, eventually, stored away for safe keeping with all the others.
3. Every bullet/barrel combination gets its own seating stem and top that is likewise carefully labeled. It actually gets a number engraved and that number is coded to careful notes. But, heh, give me some literary license.
4. I then use Skip Otto seating die shims to control seating into the lands. I never jump, so this works for me as is. If someone uses jump, they could just set the dummy round or seater stem to be some known reference off the lands. For example, 20 thou off.
5. I have a case built for the seater stems/tops. The shims that I'm currently working with go with them.

This seems a little crude. Like, why don't I use a micrometer top and keep notes? Because I've already tried and my current method is less error prone.

Now, this is a method for someone that likes inline seaters, is a target shooter, and had multiple bullet/barrel pairs in action.

Take that all for what it's worth.

 

[Keith Glasscock]

I use carbon on my bullets to see if they touch. Just hold the bullet in the flame of a candle for a few seconds.

BIG DUH ALERT: Only do this with dummy rounds!

This is not foolproof, but it works.

 

[pdog]

I use the Stoney Point with a case that has been fired in the chamber I am measuring. I drill and tap the fired case myself. I use a wood dowel from the muzzle end to push back on the bullet and allow me to feel the point of contact with the rifling. With a little practice for the consistent feel I can take five measurements that are within 1/1000 of each other.
pdog

 

[Centerfire]

Just my ideas on the subject.
1st get a wood dowel from the hardware store that will be able to be inserted into your rifle barrel from the muzzle.
Deprime all cases!
2nd measure the case you are using with the Stoney Point tool.
This is the case head to the datum. Write down
3rd measure a fired case from the chamber or 2 or 3.
This is the case head to the datum. Write down
Now see if they are the same or are you going to have to add to the Stoney Point case measurement to match the fired case dimension.
4th insert a bullet into the Stoney Point tool & insert into chamber.

Now with one hand on the dowel bring the dowel into contact with the bullet.
Now with the other hand on the Stoney Point mandrel capture the bullet between these two and you can move the bullet back and forth and will be able to feel when the bullet seats into the lands. Lock down the Stoney Point mandrel. Measure this
Do this several times with several bullets to confirm your measurement.

5th Now set your seating die to the correct measurement.

Note: I have always found that the cases supplied from Stoney Point are usually a few thousands shorter than the cases that come from my chambers.
Centerfire

 

[SDDasher]

Just my ideas on the subject.
1st get a wood dowel from the hardware store that will be able to be inserted into your rifle barrel from the muzzle.
Deprime all cases!
2nd measure the case you are using with the Stoney Point tool.
This is the case head to the datum. Write down
3rd measure a fired case from the chamber or 2 or 3.
This is the case head to the datum. Write down
Now see if they are the same or are you going to have to add to the Stoney Point case measurement to match the fired case dimension.
4th insert a bullet into the Stoney Point tool & insert into chamber.

Now with one hand on the dowel bring the dowel into contact with the bullet.
Now with the other hand on the Stoney Point mandrel capture the bullet between these two and you can move the bullet back and forth and will be able to feel when the bullet seats into the lands. Lock down the Stoney Point mandrel. Measure this
Do this several times with several bullets to confirm your measurement.

5th Now set your seating die to the correct measurement.

Note: I have always found that the cases supplied from Stoney Point are usually a few thousands shorter than the cases that come from my chambers.
Centerfire

Thanks, I do make my own Stoney Point cases from a fired case for each chamber so that I get a proper case to work with. I do use a wooden dowel down the muzzle to remove the bullet when inserted into the rifling using the SP. I will try your "capture" method and see if this is a more accurate way of arriving at the proper length.

Why do you want to measure it? The important thing is to be able to find the right seating depth.

You answered your own question and mine to boot. Measure is another way of saying find the proper seating depth as we all know that plays a large role in accuracy. However, putting accuracy aside for a moment, lets discuss pressure.
I am relatively new to the "Dasher" round and have spent several thousand rounds down range seeking the optimal seating depth, to control pressure in two separate Dashers. Adding sensitivity of powders to ambient conditions causing a rise and fall in pressure one can quickly observe the importance of getting it "right" if not for accuracy, for life of brass, which as we all know is not exactly cheap.
I thought if I had an accurate method of finding the rifling then I could work on the accuracy side of the equation as Quick Load is a pretty good primer on pressure when you either jam or jump. Just trying to save some range time and barrel/brass life.
What I am finding out is that Varget is not as Temp neutral as some would have you believe and H 4895 is sensitive to temp swings of twenty degrees or more. Here in the south it is not uncommon to shoot the first relay at 70 degrees and the third at 90.
I have Krieger barrels .236 chambers with .104 freebore in one and .155 in the other. I like to shoot 105 Berger Hybrids and Berger 108's using the H 4895 in the warm months. It is when it cools down the accuracy goes south and is not solved by just backing off. Accuracy falls off with backing down the load.

 

[BoydAllen]

I have the Hornady/Stoney Point tool, and I think that it takes practice with any tool to get consistent results. After a while, trying and measuring with the same bullet and chamber, you should develop a feel.

I also have the Sinclair tool, that I have more experience with, the one with the rod, action adapter, and stepped stop collars. With either one, all that I am looking for is something consistent that is reproducible that I can work in and out from when testing seating depths. It does not matter to me if it is exactly the point where contact is made. For the Sinclair tool, I use as much pressure on the rod as I can easily apply with the rod on the center of the pad of my thumb. With that pressure, I have no doubt that, depending on the ogive of the bullet (pointier ones will go in farther, more blunt less) that my starting point is some small distance into the rifling, but since my notes will include how I got my starting point, there is no problem.

For the Stoney Point tool, I try to use as little pressure as will give me consistent results, and add the difference in shoulder to head length of a fired case and the Threaded case to the measurement, noting that that was done. Recently, for one of my PPC barrels the difference was .006. Whatever tool you use, having a wood dowel that is small enough to be used for both .22 and 6mm, and long enough for my longest barrel has always been a good idea. I managed to somehow break my last one, which suggests that next time I should get several, given that they are inexpensive, and that I am unlikely to stop making small mistakes.

 

[284driver]

http://www.midwayusa.com/product/190644/frankford-arsenal-cartridge-overall-length-gage

$15 bucks. Boltface to bullet tip. Of course your bullets will vary lot to lot and even bullet to bullet. I always use one bullet out of a box to get my seating depth set up until that lot is exhausted.
Stoney point stuff leaves a little to be desired in the accuracy department in my opinion.

 

[284driver]

And the image depicted isn't quite the way I use it. Just read the instructions if you get one. They are simple. I measure outside to outside then subtract the thickness of one clamp to get my oal.

 

[remo101]

Larryh128 has the best method. My father taught this method to me when I was 9 .I`am 70 now and I still do it this way .Always works .I`ve tried other ways but always come back to my old way.BOB

 

[sixshooter1948]

Split the neck of a sized case with a jeweler a saw and then soft seat. Works great.

 

[K22]

I use the a homemade tool that is similar to the Frankfort Arsenal tool. I purchased two nylon spacers with 1/4" diameter holes at Lowe's, drilled and tap for a No. 8 nylon screw. I slip the the spacers over a cleaning rod with a jag whose tip has been ground flush and use the tool like the Frankfort tool measuring the difference from the end of the barrel to the bolt face and the end of the barrel to a bullet carefully inserted into the lands using a pencil eraser end to hold the bullet in place. Work well and is precise enough for me.

 

[SDDasher]

I gave the capture method a go and after a few tries seem to have it down to just touching without sticking. As Boyd and others observed it is a "feel" that takes some practice and patience.
Thanks for all the replies and help.

 

[polebilly]

Take a case fired in the rifle to be measured, use a large enough bushing die to size the neck just tight enough to keep the bullet from falling out. Carefully apply a very small dab of JB Weld inside the neck of the case, insert bullet just enough to stay in the case and slowly chamber the round. Leave in chamber long enough to set up ,usually 6 or 7 hours. Now you have a round that you can use a comparator to measure and keep for your records without concern that it will pull out or fall deeper into the case. Just be careful with the epoxy. I'm a klutz and have yet to glue a round inside a barrel. I measure throat erosion this way. Next time you want to measure just heat the case neck with a lighter and remove bullet then repeat the above directions.
I do this because I got tired of having to insert and measure a half dozen times to get a semi accurate reading.

 

[chrislb]

I used to have problems getting consistent readings using the Stony Point tool until I figured out how to 'tune' it up and to modify the way I used it ... This is what I did ....

First of all, this is a mass-produced tool and the center rod is an injection molded plastic part ... as it comes out of the injection molding machine, there will be a thin line of 'flash' along both sides ... this causes excessive friction and means you have to push the rod harder when taking measurements, thus shoving the bullet an unknown distance into the throat ... Soooo take some 320 grip wet-or-dry paper and lightly sand the 'flash' off for the entire length of the rod.. While you're at it, lightly sand the domed end (that pushes on the base of the bullet) to make sure there's no trash on the end that would make the readings inconsistent.

When you put the rod back in (dont forget to clean the sanding residue off first!) you'll notice how much smoother it slides.

Now ... when taking a measurement, set the rod well back in the dummy case and drop your bullet in and make sure you can slide it in and out of the modified case smoothly. Lightly lock the rod so the bullet is seated deeply in the case. Slip the whole shebang into the chamber until the case stops in contact with the chamber shoulder then withdraw it about 1/8". Now unlock the clamp screw and VERY GENTLY ease the bullet up against the rifling and then slip the case back into contact with the shoulder and lock up the screw as in the directions. The reason for this long-winded process it to give the bullet enough freedom of movement as it is engaged with the rifling and give you the opportunity to precisely 'feel' the moment it comes into contact with the rifling.

Using this modification and this method, I am able to take repeated readings (I always take 5 and throw away the longest and shortest before averaging the remaining 3) to within .001"

Hope this helps!