I've been using a Stoney Point gauge for a couple of years now and I thought I would try and compare it to some other ways of determining an oal. So I used the method of slightly bending the mouth of a spent case and closing the bolt on a case and bullet that was marked with a black magic marker. The oal of the case this way was about .050 longer than I come up with when I use the Stoney Point gauge.
What could cause such a large variation, am I being too gentle with the Stoney Point comparator? Or is the mouth of the spent case bent too severely to measure properly.
When I use the comparator I try to stop when I barely feel the lands and I can get a very consistent measurement, usually 10 different measurements will not vary .010.
I was wondering if I am missing some accuracy be not getting close to the lands but a little hesitant to try something that is this far from what I been doing. Any opinion is welcome

It's not an opinion but a fact, that the case you use for the measurment does NOT conform to your chamber. The difference will be the same as between an unfired and a new case. To get more exact you must drill and tap a case fired in the chamber you are measuring. For those "new" cases, or to double check any measurement, I usually seat a bullet out about .010", paint the ogive with Marks-alot, chamber and check the marks on the ogive from the lands, then keep repeating while seating the bullet deeper until you have the exact contact you want from the marks on the ogive. Then use that as your dummy round and guide for setting up seating dies.

I used to use the bent case technique, but believe you have much more sensitivity with the stoney point guauge. Too bad almost all of my guns, the throat is so long, I couldn't ever touch them and still fit in my magizine.

Good point Bob338, I must say that I never thought about the size of the measuring caset hat Stoney Point sends with it.

Is there enough thickness in the base of a 270 case to drill and tap it and still have enough threads to function properly?

I ran across this problem recently with my .270 -- I couldn't get a consistent reading with the Stoney Point tool.

It takes a lot more force to push a bullet back into a case than to feel the "sticking point" with the Stoney Point gauge. In my .270 this may have been aggravated by the beginnings of wear on the throat and/or the streamlined profile of the Hornady bullet I was using; when I tried the blunter-profiled Speer, it worked fine.

The Stoney Point tool (which I love because it usually works great) just seems a little too sensitive on that particular rifle.

There will almost always be discrepancies between the methods. The comparator bushing measures a given diameter which will fall at various "lengths" on an assembled cartridge depending on both seating depth and shape of bullet.

The rifling will act as a comparator of sorts but of a different diameter than the tool hence the difference in lengths measured.

It's all rather irrelevant as the various methods are only to provide reference points from which to vary measureable amounts.

Bob338 is absolutely correct. For the modified case to be accurate, you must fireform your own case to be drilled and tapped, preferrably a case that's been fired at least three times without setting the shoulder back. If you can't drill and tap yourself, Stoney Point will modify a case you provide for $6.50. Just send them 2 cases along with your money. Even then, it takes a little practice to feel the initial contact point of the bullet into the lands. You can force a bullet into the lands as much as .025", so do a little practicing, and verify by blackening a bullet and running it into the lands and look for similar markings on the ogive when using the OAL gauge.

Most of the time, overall cartridge length is limited by the length of the magazine, so the point is moot. It's more important to be consistent. After finding your maximum cartridge length to the lands, back off about .010-.015" and keep all future seating depth controlled and uniform by using a comparator.

Simdow: I too was using the Stoney Point method but got fed up with discrepancies in measurements. I just received the guage that Sinclair sells. So far, I've found it to be quite a bit more consistant. Bear in Fairbanks

If you understand where the discrepancies are using the new cases, you can compensate for them.

I bought a tap which is either 5/16" X 32tpi or 36tpi (I believe the latter,) and drill my fired cases and tap them. The tool is amazingly accurate once the operator error is eliminated. As for the comparator for checking the bullets, that's all it is, a "comparator" for "comparing". As long as the measurement is consistent at the same point on any ogive, you have all you need.

I did the same and purchased a tap (5/16 - 36) and then drill and tap my own fired cases. I have found the stoney point to be very accurate, but it really helps to use a wooden dowel from the muzzle end of the barrel to help to feel the bullet into the lands.

Those are three of my OAL gauges, which work better than my Stoney Point OAL gage. They are consistant, accurate and quick.

Split a NK or FL sized case neck with a dremmel tool or hacksaw and deburr like in the pic, insert the bullet and chamber the round. Tension is perfect if it is split below the neck/shoulder juncture. It will offer enough tension to firmly contact the lands, but will not engrave and pull the bullet out when extracted. OAL's are usually consistant to about the thou, and done in just one or two chamberings.... denting the case mouth trying to accomplish the same results plain does not work, I've tried 'em all. The bottom of the list is the dented case mouth method, next up is the SP gauge, and the split case method at the very top for accuracy and consistancy.

The case is forced back against the boltface, unlike with the SP gauge (which is indexing off the shoulder), and headspace is zero in this measurement.

Try the split neck method and the SP gauge will set on the shelf from then on.

MSC has the 5/16 - 36tpi tap (pt# 04841367) for $10.47 if you do your own cases for the SP gauge.

Good luck with whatever method you use.

I've been splitting the necks of cases to measure but I saw the Stoney Point gauge and liked the idea just didn't like paying for something I thought I could make. I spent about 30 minutes in the machine shop and made my own and I also have my own cases that are drilled and tapped. Works really well.

Brandon

Currently have Stoney Point gauges and not pleased with them. They initially had a problem because the new RP brass they were using had significant neck runout and would not let the bullet touch the lands correctly. I was getting OAL readings that varied by as much as .075 which is crazy. My fix was to full length size the SP cases, expand the neck with a special expander to let the bullet slide freely. The OAL measurements came within .002 of each other after the fix. Stoney Point would never admit they had a problem. Seems a shame to buy something and then have to fix it.

I like the sounds of the split-case method mentioned above. That would cut down on the cost.
Ron

FlyDevil,

Cost for the SP OAL gauge wasn't really a big deal, getting accurate and consistant results was the main thing I'd never been able to get while pinching the necks, sizing them down a few thou, or other methods I'd tried. They either left the bullet in the throat, with no means to place it back into the case at the same length it was at, like the SP Gauge lets you do, or it was too tight and shoved it too far into the lands etc, etc...

The split neck method was tried after someone here suggested it, and when my SP gauge was giving me multiple erratic readings.

For purposes of monitoring throat errosion, I wanted to be within a thou or two CONSISTANTLY, so I tried the split neck method.

It worked so damn well, and is way, way faster too, I couldn't believe it, the SP gauge sets on the shelf and never gets used anymore. The split neck is just way more accurate and faster, I can never see going back. It wasn't a money issue. The way I see it, this time the best way was totally free, and that doesn't happen all to often either.

One note:
If you don't split the neck to "below" the neck/shoulder juncture, it will grip the bullet to tight there and won't work properly. It offers perfect tension if sized first and then split... it must be tried to belive how well it works.

Brent,
Have you tried using a little super glue to hold the bullet in the split neck? This would help keep the bullet in place when setting up the bullet seater.
Ron

FlyDevil,
I have a loaded dummy cartridge with each bullet I use to set the seating stem correctly, it's double checked with the SP Comparetor too. Never have used the split case to set the die, just to give me a length to the lands for a referance point. I think the CA glue could be a bitch to get loose, maybe not, and a pain to clean out, but that's just me... it would work, but you may not even need it. Like I said, all mine are dummied up with old cases and seated at the depth I "shoot" them at.

I have to agree with brent...i have a friend that uses the SP guage and he thinks its great. But i think it kinda sucks. i use the split neck method as well. I personally think it is more accurate than the guage. Get a bullet comparator from sinclair and use that for measuring to the ogive. Works great and only costs you one case for each caliber/gun.

I have a competition grade .308 rifle that i have used a NK sized cased for the split neck case...i use that case with just that gun. SOme people may feel that it is overkill to have a different case for each gun. But here is my thinking. LEts say you have 3 .308s. all might have slightly different chambers... maybe a few thousandths off. if you used on case for all three, your OAL may very those few thousandths, because the case didnt fit the same in all three guns. I take a fired case from each gun and use that, once its NK sized. If you save your split neck cases, you only have to make them once!

a word of caution. i use a dremel tool to cut mine... its a pretty rough cut, make sure you deburr like Brent said in order to not "scratch" your chamber. just my two cents.

[ 07-02-2003, 01:40: Message edited by: sharps-shooter ]

I know most folks love the Stoney Points, but for the reasons stated above a Precision Mic from RCBS is worth a look. A good bit cheaper, too, if I'm not mistaken.

RSY

Several problems with the Precision Mics. At one time I had about every one they make, but what do you do for the cartridges they don't make? I bought the Stoney Point tool for precisely that reason and after I learned to use it I sold all my Precisions Mics though I still have one in 22-250 that I'll gladly sell. The ability to use the Stoney Point universally was the biggest attraction to me. Secondly, the Precision Mics take so long to screw and unscrew the parts to get measurements. If you want to check ALL your reloads you have to alott a great deal more time with them.

The Stoney Point is like any tool, you have to learn how to use it and understand its limitations. There IS a learning curve. I wouldn't trade for mine for anything for the work I do with it. I also have the Sinclair tools, including the comparator. None are near as convenient as the Stoney Point is for me. For the guy that only messes with one or two rifles, the Precison Mics are great though a bit inconvenient, but for someone with several rifles, and/or in oddball cartridges, best stick with something convenient and universal.

Brent Moffit- I tried the split case thing on my 22 250 and first time stuck the bullet in the throat.This was a sized case and I used a dremel cutter to split the case.Also deburred the cut.

Wow, thanks for all the responses! I have since tried the split case method and I must agree with all the people that like this method. It's fast and extremely consistant. I've had no problems with the bullet sticking in the barrel yet.

I think I will try and resize my Stoney P. cases and see if they are a little more consistant that way, but it's nice to know more that one way to skin the same cat.

thanks

uper,
you may need to squeeze the neck together, keeping it round still, to increase the tension on the bullet a bit, the smaller calibers have less surface area in the neck and less grip as it's extracted. A little experimenting will show you the proper tension to place on it.

If you have the shoulder bushings for the Stoney comparator you can simply measure the Stoney threaded case against a fired case. If the threaded case is shorter from base to shoulder datum just add that amount when measuring a finished cartridge.

I agree with those of you who split the case neck and have found that to give the most reliable measurement. I also use the Stoney Point guage and find it's adequate, but not as precise as the former method. You definitely have to use the Stoney Point to acquire proficiency with it. It doesn't always come easily. Best wishes.

Cal - Montreal