Stoney Piont OAL Gauge?

16 July 2002, 18:34

Are these things any good? They seem like they could make life a whole lot easier.

Opinions please.

[ 07-16-2002, 09:34: Message edited by: LazoG ]

17 July 2002, 00:43

<toto>

Yes, works for me. fws

17 July 2002, 06:00

Bear in Fairbanks

Absolutely. Then measure your seating depth to the ogive.

17 July 2002, 06:05

Don Shearer

LazoG,

Sure, the Stony Point OAL gage works, but there is an easier and a lot less expensive way of doing the same thing.

To determine the maximum overall length of a cratridge, first, insert a full length cleaning rod with a flat tip (cut-off jag), from the muzzle so as to touch the bolt face. Place a piece of masking tape on the cleaning rod at the muzzle and with your pocket knife flat against the muzzle, make a cut in the masking tape. With a magic marker, mark over the knife indent and while it is still wet, wipe it off. This will leave a very fine dark line in the masking tape at the distance from the bolt face to the muzzle. Next, drop a bullet into the throat, hold it against the rifling with a short section of a rod or a pencil or whatever will keep it against the rifling. Then with the same cleaning rod with the flat tip, insert it into the muzzle and against the bullet tip. Again, with masking tape on the rod at the muzzle, make a small mark with the knife and do the same as before. Now measure the distance between the two knife marks on the rod and that is the MAXIMUM OVERALL CARTRIDGE LENGTH.

Now, with THAT bullet, load a dummy cartridge to that maximum overall length and then measure its overall length with a comparator. This last step is advisable because all bullets (eg. all Hornady 150 gr FBSP #3031) with exposed lead tips aren't the exact same length due to small deformations at the tip from handling or whatever. A method that is Cheap, Accurate, Repeatable.

Hope this helps,

Don Shearer

17 July 2002, 06:58

Zero Drift

The best things about the Stoney Point Gage is it provides you with a repeatable, accurate measurement tool. This is important for monitoring throat erosion in addition to proper seating depths. With the SP gage in conjunction with a competition bullet seater, you can accurately load to the thousands of an inch.

[ 07-16-2002, 22:01: Message edited by: Zero Drift ]

17 July 2002, 11:06

<bigcountry>

Little secret to using that bad boy. Use a dow or something to give opposite resistence. It will increase your feel for where it hits the lands greatly instead of just pushing on a bullet. When I just pushed on a bullet from the guauge, my AOL wasn't consistent as when I used the wooded stick so I was jamming the bullet into the lands.

17 July 2002, 12:12

HenryC470

quote:
Originally posted by LazoG:
Are these things any good? They seem like they could make life a whole lot easier.

Opinions please.

They do work, but they are subject to an error that Stoney Point doesn't point out in their manual (editing note: Yes they do point it out; it is discussed in the manual. I should have read the manual before firing off my mouth. H. C.) If the headspace dimension of the drilled-out Stoney Point case (it comes with the gauge) is shorter than the the headspace dimension of the case you make a reloaded cartridge with, your bullet will be that much farther off the lands than you intended. If the Stoney Point case is longer than what you're making reloads out of, your bullet will be closer to the lands than you think. You must correct for this error if you want to know how close your bullet's ogive is from the leade of the rifling.

It's easier to illustrate this with a specific case than to make a generalized argument, so here goes.

Let's say you took three fired rimless cases from your rifle (cases that headspace on the shoulder, assume headspace clearance ~0 for fired cases). Neck-size one of them (not pushing back the shoulder), and full-length resize the heck out of the other two, pushing the shoulders back 0.020".

Put one of the full-length resized cases on your lathe, and make a Stoney Point drilled-out case from it. Use your homemade drilled-out case with the Stoney Point gauge (you'll be pushing it into the chamber until the shoulder of the case makes contact with the shoulder in the chamber), and push the bullet in until it contacts the lands. Withdraw the case and bullet, and measure the length (overall length is okay, but length by comparator is better). Let's say the comparator gives you a length of 2.580" from the case head to the portion of bullet ogive that contacts the leade of the rifling.

Now make reloaded cartridges out of the the two cases you've been saving. Seat the bullets in both cartridges so the distance from the case head to the portion of the bullet that contacts the leade of the rifling is 2.580".

Chamber the cartridge you made from the aggressively full-length resized case, closing the bolt as usual. Is the ogive of the bullet in contact with the leade of the rifling? No, it is not. The extractor will hold the case head against the bolt face. The shoulder of the case will be 0.020" off the shoulder of the chamber, and the bullet's ogive will be 0.020" off the leade of the rifling.

Chamber the cartridge made from the neck-sized case. Is the bullet's ogive in contact with the leade of the rifling? No, it is not. This neck-sized cartridge has the same overall length and same length by comparator as the full-length resized cartridge. The shoulder of the case is in contact or nearly so with the shoulder of the chamber, but the bullet's ogive is 0.020" off the leade of the rifling.

The error in overall length in both cartridges was equal to the difference in headspace dimension of the Stoney Point drilled-out case and a fired case from your rifle. If you use the actual drilled-out case provided with the Stoney Point gauge, your error in measurement will probably not be as large as 0.020", but the chances are vanishingly small that the Stoney Point gauge comes with a drilled-out case that has exactly the same headspace dimension as fired cases from your rifle.

RCBS sells something called a Precision Micrometer that measures the headspace dimension of bottleneck cases (editing note: Stoney Point sells one too. H. C.). For 30-06 and other rimless cases, this measurement is from the case head to something called the datum point on the case shoulder. You can use the RCBS tool to set your resizing dies so the case shoulders don't get pushed back too far, and you can also use the tool to correct the error in the Stoney Point gauge.

The amount by which your fired cases are longer or shorter in headspace dimension than the Stoney Point drilled-out case, that's how much longer or shorter your reloaded cartridge should be (in overall or comparator length) than what you measure with the Stoney Point gauge.

For example, if you want your bullet in contact with the rifling, and your fired cases are 0.005" longer than the Stoney Point drilled out case (as measured with your RCBS Precision Micrometer), you need to add 0.005" to the overall length of your reloads to have the bullet in contact with the rifling. If you want the bullet 0.010" off the rifling, measure with the Stoney Point gauge, subtract 0.010", and then add back that 0.005" in headspace dimension difference.

H. C.

[ 07-19-2002, 16:26: Message edited by: HenryC470 ]

17 July 2002, 12:16

<bigcountry>

He's got a point. Thats why you want to send Stoney Point a fire formed case so this won't be a problem. The do charge 10 dollars a think to modify a fireformed case.

17 July 2002, 13:33

Holmes

This is why I prefer the Sinclair OAL tools; they work with a fired case from the chamber being measured.

~Holmes

19 July 2002, 15:48

HenryC470

Well, shut my mouth and take my keyboard away. Stoney Point does discuss the variation in headspace issue, in their manual. The gauge is very easy to use, and I never did read the whole manual. I owe Stoney Point an apology.

By the way, Stoney Point's drilled-out 30-06 case is 0.001" longer than my fired 30-06 cases, so all the time I thought that my reloads put the bullet 0.010" off the lands, the bullets were really 0.009" off the lands. I have never bothered with the correction until now. I probably never will.

Stoney Point also makes a headspace that I didn't know about.

H. C.

19 July 2002, 15:54

jeffeosso

get it, send em a shot case or three, and use it for every bullet. It's FAST and it's EASY. It's not PERFECT, but what is?
jeffe

19 July 2002, 16:22

claybuster

If you get the automatic rifle version,,You can put it in your seating die and run the seat plunger in to get close to your seating depth in a hurry,really nice if you decide to load a couple of different weight bullets for the same caliber. If you're handy with a drill,and have a tap set you could make your own cases for it