Oddball caliber & tight bore- what diameter bullets to use?

the possum · September 13, 2011, 03:26 PM

Greetings, all.

Some time back I got an old German Drilling (Nitro proofed), with the rifle barrel chambered for 9.3x72mm Rimmed. I've done a chamber cast to verify, and have brass. I've scrounged up load data from various places, and would really love to get this thing shooting again. A gunsmith who specializes in Drillings thought it should be just fine to fire from a safety standpoint.

However, I slugged the bore, and found it's rather tight for that caliber. It measures exactly 9.0mm (.354") just ahead of the chamber, and further down toward the muzzles it constricts to 8.9 to 9mm. (I suspect it got slightly dented out of round.)

Problem is, I don't know what diameter/size bullets I should be using, since it has such a tight bore. I want to take it easy on this old gun, and am concerned that 9.3mm bullets could cause undue pressures. I've been reloading for years, but in the case of rifles, have never actually slugged a bore & just bought readily available bullets made for that caliber. But in this case, I'm not sure if I should be looking for bullets of exactly bore diameter, or slightly oversized, or what.
If I could get by with .358" bullets, it would certainly open up a lot more options... maybe I could rig up something to swage them down a bit if necessary...

Some pics if you're curious:

Magnum Wheel Man · September 13, 2011, 03:47 PM

hmmm... maybe something like this... with lighter loads, just to get it shooting...

http://www.midwayusa.com/viewProduct...tNumber=254487

the possum · September 13, 2011, 04:05 PM

That thought did occur to me, but this round seems to have been meant for bullets more in the 200 grain range, and I don't have any load data for bullets that light. I may cobble something together like that eventually if I can't find any other answers, but it would be nice to get it shooting the way it was meant to. I'd love to flatten a coyote with it while quail hunting.

**Unclenick** · September 13, 2011, 04:15 PM

Hmmm. That gun is old enough that it could be a near custom bore. I would suggest it is intentionally 9 mm. If you have an actual indentation in the bore, I would see if it can be removed safely. If not, a 0.004" constriction could probably be hand-lapped out. What did you slug and measure the slugs with? Pure lead and an OD thimble micrometer with ten thousandths resolution is usually a good idea. Calipers can sometimes be off as much as a couple thousandths.

You don't have the chamber cast dimensions up. Are you sure it's a 9.3×72R S&S, and not a 9×64R (picture attached)?

Also, DKT bullets makes a 200 grain 9 mm that's in QuickLOAD's database. You can also get a custom mold made.

Jim Watson · September 13, 2011, 04:32 PM

If the GROOVE diameter is .354", I sure would not be shooting any .366" 9.3 bullets in it. That makes it pretty much a 9x72R, doesn't it? Which is what is included in the proof marks.

Montana Bullet Works has a 200 grain gas check .357" that would probably work.
http://www.montanabulletworks.com/358_Rifle.html

You could try a soft 200 gr .358" .35 Remington JSP.
It could probably be squeezed down to .355" in a Lee push through bullet sizing die in a stout press.

mkk41 · September 13, 2011, 04:41 PM

I'm looking at the 11th Ed. of Barnes Cartridges of the World , and the 9.3x72R (Sauer) calls for a .376 dia bullet.

I see the 9.3 and 72 stamped in the barrel , but I also see the 9mm stamped farther forward/center.

Perhaps a new rifle tube was added at one time? Sleeved?

I also see a 9x70R cartridge listed with a .354 bullet dia.

Slugging the bore is definately called for.

**Unclenick** · September 13, 2011, 05:25 PM

That's not a 9.3. It's a 9 followed by a small ribbon symbol. I'll have to look that up. But looking further forward on the barrel tells you Jim is right: it's 9mm on purpose.

the possum · September 13, 2011, 05:38 PM

Quote:

What did you slug and measure the slugs with? Pure lead and an OD thimble micrometer with ten thousandths resolution is usually a good idea. Calipers can sometimes be off as much as a couple thousandths.

I used some pure lead balls from my .36 Navy revolver. I actually did 3 separate balls- one halfway down the barrel from the chamber end, one all the way through, and then a couple months later I did another one all the way through after thoroughly cleaning the bore. I measured with calipers, so this is the groove diameter (max diameter of the slugs). I also used two different calipers.

Quote:

You don't have the chamber cast dimensions up. Are you sure it's a 9.3×72R S&S, and not a 9×64R (picture attached)?

I don't have a picture of the sulfur casting, and don't have my notes handy with the dimensions. But I do also have some loaded 9.3x72 ammunition from Norma and RWS, and the casting looks exactly like it, and the ammo fits perfectly in the chamber. I have not tried to fire it with the factory ammo though due to these concerns about the tight bore.

Quote:

You can also get a custom mold made.

Yes, but I'm hoping to get by on the cheap. The only reason I own this gun is because it went for less than $200 at an estate auction; I could not afford one at the normal prices they usually fetch, and do not currently have money for dies, molds, etc. The trap door is missing from the patch box; a new one costs more than I paid for the whole gun.

Quote:

That makes it pretty much a 9x72R, doesn't it? Which is what is included in the proof marks.

I don't know. ? The chamber is marked for 9.3x72 (note the tiny superscript 3 in the photo), and factory 9.3x72mm ammo fits perfectly, as mentioned above. But the barrel is stamped 9mm; someone postulated it was marked separately like this to indicate it has a tight bore. While googling, I did come across another drilling owner who has this exact same issue- a 9.3x72 chamber with a 9.0mm barrel.

Quote:

You could try a soft 200 gr .358" .35 Remington JSP.
It could probably be squeezed down to .355" in a Lee push through bullet sizing die in a stout press.

Thanks for the tip. I've never done anything like this either though- I'll have to do some more googling. If you happen to have any links on the process, I'd appreciate it.

Quote:

I see the 9.3 and 72 stamped in the barrel , but I also see the 9mm stamped farther forward/center.

Yeah, that puzzled me too, as mentioned above. As far as I can tell, everything is original, at least regarding the barrels.

Quote:

I also see a 9x70R cartridge listed with a .354 bullet dia.

Isn't that a bottlenecked cartridge though?

Quote:

That's not a 9.3. It's a 9 followed by a small ribbon symbol.

I realize my picture isn't the best, but I can assure you it's definitely a small number 3 after the 9 on the chamber. I assumed this meant 9.3mm, since as I mentioned, 9.3x72mm brass & factory loaded ammo fits perfectly, and is a perfect match to the chamber casting.

I was only able to find one reference to a 9x72mm rimmed round, which was essentially a 9.3x72mmR necked for a slightly smaller bullet, but I was unable to verify if such a beast officially existed: http://www.shootersforum.com/rifles-...5x54mm-ms.html

243winxb · September 13, 2011, 06:01 PM

Google found this, see post # 14 > http://forums.gunboards.com/showthre...ertus-Drilling

mkk41 · September 13, 2011, 07:26 PM

Yes , the 9x70R (Mauser) round is a slight bottlenecked cartridge.

Jimro · September 14, 2011, 06:10 AM

I have a 9.3x62 with a Lothar Walther barrel. A 9mm bullet will not travel freely down my bore. It is fine just in front of the chamber, but the rifling constricts as it approaches the muzzle. Still shoots commercial 9.3x62 ammunition just fine.

As long as your groove to groove diameter is .366 plus or minus a thousandths or two you should be good to go with a low pressure round like the 9.3x72.

Jimro

**Unclenick** · September 14, 2011, 09:39 AM

He says above that he's measured the slugs at .354" groove diameter, so it's a 9 mm bullet. I'm guessing the smith wanted to make a 9.3×72, but had 9 mm drills and reamers and cutting head for the rifling and didn't want to invest in making the slightly larger ones. Another possibility is if the original factory loads were paper patched lead, the the lead would be soft and be 8 to 10 thousandths under groove diameter, making the gun more tolerant of a light bore. I just don't know the history of the cartridge, and without dates that's just speculation on my part.

The Possum,

I looked closer (eyes getting old) and you are right that is a superscript 3. It looked like a symbol when I first blew it up.

The 9.3×72 R S&S is a bottleneck design, albeit a slight one. From QuickLOAD's database, I've put the two cartridges by that name below for comparison. The straight wall is the original black powder (non-nitro) version, and has a bigger bullet.

Jimro · September 14, 2011, 11:11 AM

Well, I think that as long as you use a lead bullet at normal 9.3x72 pressure the bullet will get squeezed down to size just fine, however, swaging bullets down to .354 is cheap insurance.

It's only .004" of squeeze on a lead .358 bullet, so get the die and have fun.

Jimro

the possum · September 14, 2011, 01:12 PM

It's been several months since I actually took these measurements, so I decided to get out the calipers & did some playin' around.

The chamber cast seems to best match the regular 9.3x72mm R.

Also found another diagram here:
http://www.loaddata.com/members/sear...19&MW=&PM=&PT=
And according to post #14 at this link, mine should have a type E chamber.
http://forums.gunboards.com/showthre...ertus-Drilling

However, I got out the slugs from my bore again, and it looks like I was only remembering the minimum dimensions.

But if I keep checking around the circumference of the slug, I do get some bigger readings:

So, I measured 10 "random" measurements all around the slugs and averaged them. The average of one slug was .360" (at the muzzle) and the other was .362" (ahead of the chamber).

So, should I be using the absolute minimum measurements, or would it be better to go by the average of 10 measurements?

Jim Watson · September 14, 2011, 01:26 PM

You need to get lined up on the raised parts and get a measurement of GROOVE diameter. The Internet Confusion of bore vs groove diameter can make a lot more difference than clip vs magazine.

It is getting to look like you have a BORE of .354" and a larger GROOVE diameter correct for a true 9.3 and need .364" bullets.

**Unclenick** · September 14, 2011, 01:45 PM

He also said he had an oval muzzle. I think maybe that's what's changing the reading as he goes around. I'm thinking the out-of round maybe needs some correction and then maybe some lapping.

What your really want to do is determine cross-sectional area. It can be done with water displacement. A bullet should be possible to select based on that.

It does look like you've got the older case style and not the Sauer.

the possum · September 14, 2011, 02:24 PM

Quote:

You need to get lined up on the raised parts and get a measurement of GROOVE diameter. The Internet Confusion of bore vs groove diameter can make a lot more difference than clip vs magazine.
It is getting to look like you have a BORE of .354" and a larger GROOVE diameter correct for a true 9.3 and need .364" bullets.

Jim-
The rifling of this barrel was not cut with a round cutter- the pattern left from cutting the grooves resembles an octagon more than a circle. If I measure my slug right over the grooves left by the rifling, it is actually bigger than if I go across the flats (which would normally be the "raised parts" of a modern barrel).
And either the barrel is slightly out of round, or perhaps the rifling was cut one groove at a time & some are not quite as deep, because that's where the biggest differences in the measurements come from- Not from taking some measurements across the high parts vs. across the engraved valleys.

Perhaps a sketch will better describe what I mean-

The flats are the smallest & most inconsistent measurement. If I measure my slug right over the grooves left by the rifling, it's slightly bigger, and if I cock the slug a bit so the caliper jaws are just touching the corners, I get the biggest measurements. None of these are the actual bore diameter, since my calipers can't actually get down into the grooves left by the rifling.

Which one should I be using then?

**Unclenick** · September 14, 2011, 04:01 PM

That is most interesting. People tended to be more inventive with rifling at one time, and you seem to have a hybrid polygonal/land and groove rifling.

I still think we want to go by cross-sectional area. That is one of the ways in which SAAMI specs bores. It would still be better if you had a thimble micrometer that will give you ten thousandths ($20 at Harbor Freight) but we'll have to do some averaging anyway, so let's go with what you have:

List all four distances across the flats.

List all four distances across the lands (your bigger numbers).

List all four flat widths from land to land.

Measure across the lands at one spot, the slide a thin but fairly rigid feeler gauge (say 0.01") into the land engraving and measure the diameter from the outside edge across the bullet to the lands and report that.

Measure the width of the feeler gauge and report that.

Alternately to the last two, take a set of drill bits and find out which drill size just nestles down into the round bottom of the land engravings so it touches bottom and both sides at the same time. Measure across the lands without the drill in place and again with it in place. Unless the lands are very tall relative to their width, reporting those two measurements will get us the height of the lands. A set of numbered drill bits is probably needed to get as close as possible. Do what you can.

From the first 5 or the first three and the two in the last paragraph, I can figure out the cross section area about as closely as I expect is needed.

243winxb · September 14, 2011, 06:17 PM

Your drawing shows that your barrel has a groove diameter of .364" Bullet diameter should be at least .364" & .366" should work with a light load. If your sure you measured the groove diameter correctly from chamber to muzzle. A loaded rounds neck diameter should not be larger than .388" as shown by your chamber cast measuring .390"

243winxb · September 14, 2011, 07:25 PM

Quote:

But I do also have some loaded 9.3x72 ammunition from Norma and RWS,

Measure the loaded rounds neck diameter on the brass over the bullet. What do you get? The chamber cast is .390" - .364" bullet diameter=brass wall thickness of about .013"

the possum · September 19, 2011, 01:43 PM

I must admit I'm a little surprised to hear I should be going by the biggest diameter, considering most measurements I could take were considerably smaller. I would'a thought if I fired a .358" bullet, the parts that got swaged down by the .351" grooves would squish over to fill those little .364" points.

I suppose once I finally get this thing in proper working order I'll just have to do some experimenting on my own too...

**Unclenick** · September 19, 2011, 01:55 PM

If you list all the measurements I mentioned, I can draw the resulting form in my CAD software, which figure the area automatically for closed shapes. QuickLOAD's database then has the cross sectional areas typical for a round. It has .100688 in² for the 9.3×72. We can see how your barrel geometry compares to that number, which reveals how much metal you are swaging into how much area.

Jim Watson · September 19, 2011, 02:11 PM

Your drawing looks like an 8-sided version of Alex Henry rifling (7 sided in Scotland) which is very flexible as to bullet diameter. I can't explain the unevenness unless the barrel was dented by impact. It was no problem for an old line barrelmaker to hold dimensions much closer than that.

**Unclenick** · September 19, 2011, 03:14 PM

I just did a trial drawing using your average diameter of 0.3535" all around and made the assumption the little lands were about .9 mm diameter radii. The result has an area of 0.10059 in². Very close to QuickLOAD's 0.100688 in². If I alter the radii to 0.8 mm it's .101+change. If I use 1mm it's .099 something. This centers the circle at the apex of each corner, which might also not be true. A 1 mm centered just a little further out would produce a similar appearance and the right cross sectional area.

So, I think you basically have (whoever actually invented it) what amounts to polygonal rifling with the little corner radii added. Perhaps they were added to help mitigate gas bypass from failed corner filling or perhaps it's just that the originator didn't trust the polygon completely. Can't say. But I think it's pretty clearly intended for the standard 0.364" bullet.

the possum · September 19, 2011, 03:50 PM

Unclenick-
I gotta admit that's pretty danged cool. I really don't know how I'd actually measure all those dimensions accurately, which was part of the reason for my lack of response.

My idea was to take a known quantity of something soft/malleable & stuff it in the barrel. Then measure the length of the resulting plug and find the average area by solving for the diameter of a cylinder.

September 13, 2011, 03:47 PM	#2
Magnum Wheel Man Senior Member Join Date: July 26, 2006 Location: Southern Minnesota Posts: 9,333	hmmm... maybe something like this... with lighter loads, just to get it shooting... http://www.midwayusa.com/viewProduct...tNumber=254487 __________________ In life you either make dust or eat dust...

September 13, 2011, 06:01 PM	#9
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Google found this, see post # 14 > http://forums.gunboards.com/showthre...ertus-Drilling Last edited by 243winxb; September 13, 2011 at 06:04 PM. Reason: see post 14

September 14, 2011, 06:10 AM	#11
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	I have a 9.3x62 with a Lothar Walther barrel. A 9mm bullet will not travel freely down my bore. It is fine just in front of the chamber, but the rifling constricts as it approaches the muzzle. Still shoots commercial 9.3x62 ammunition just fine. As long as your groove to groove diameter is .366 plus or minus a thousandths or two you should be good to go with a low pressure round like the 9.3x72. Jimro __________________ Machine guns are awesome until you have to carry one.

September 14, 2011, 11:11 AM	#13
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	Well, I think that as long as you use a lead bullet at normal 9.3x72 pressure the bullet will get squeezed down to size just fine, however, swaging bullets down to .354 is cheap insurance. It's only .004" of squeeze on a lead .358 bullet, so get the die and have fun. Jimro __________________ Machine guns are awesome until you have to carry one.

September 14, 2011, 01:45 PM	#16
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	He also said he had an oval muzzle. I think maybe that's what's changing the reading as he goes around. I'm thinking the out-of round maybe needs some correction and then maybe some lapping. What your really want to do is determine cross-sectional area. It can be done with water displacement. A bullet should be possible to select based on that. It does look like you've got the older case style and not the Sauer. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 13, 2011, 03:26 PM	#1
the possum Senior Member Join Date: November 6, 2004 Location: Southern Illinois Posts: 555	Oddball caliber & tight bore- what diameter bullets to use? Greetings, all. Some time back I got an old German Drilling (Nitro proofed), with the rifle barrel chambered for 9.3x72mm Rimmed. I've done a chamber cast to verify, and have brass. I've scrounged up load data from various places, and would really love to get this thing shooting again. A gunsmith who specializes in Drillings thought it should be just fine to fire from a safety standpoint. However, I slugged the bore, and found it's rather tight for that caliber. It measures exactly 9.0mm (.354") just ahead of the chamber, and further down toward the muzzles it constricts to 8.9 to 9mm. (I suspect it got slightly dented out of round.) Problem is, I don't know what diameter/size bullets I should be using, since it has such a tight bore. I want to take it easy on this old gun, and am concerned that 9.3mm bullets could cause undue pressures. I've been reloading for years, but in the case of rifles, have never actually slugged a bore & just bought readily available bullets made for that caliber. But in this case, I'm not sure if I should be looking for bullets of exactly bore diameter, or slightly oversized, or what. If I could get by with .358" bullets, it would certainly open up a lot more options... maybe I could rig up something to swage them down a bit if necessary... Some pics if you're curious:

September 13, 2011, 04:05 PM	#3
the possum Senior Member Join Date: November 6, 2004 Location: Southern Illinois Posts: 555	That thought did occur to me, but this round seems to have been meant for bullets more in the 200 grain range, and I don't have any load data for bullets that light. I may cobble something together like that eventually if I can't find any other answers, but it would be nice to get it shooting the way it was meant to. I'd love to flatten a coyote with it while quail hunting.

September 13, 2011, 04:32 PM	#5
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	If the GROOVE diameter is .354", I sure would not be shooting any .366" 9.3 bullets in it. That makes it pretty much a 9x72R, doesn't it? Which is what is included in the proof marks. Montana Bullet Works has a 200 grain gas check .357" that would probably work. http://www.montanabulletworks.com/358_Rifle.html You could try a soft 200 gr .358" .35 Remington JSP. It could probably be squeezed down to .355" in a Lee push through bullet sizing die in a stout press.

September 13, 2011, 04:41 PM	#6
mkk41 Senior Member Join Date: December 4, 2004 Posts: 283	I'm looking at the 11th Ed. of Barnes Cartridges of the World , and the 9.3x72R (Sauer) calls for a .376 dia bullet. I see the 9.3 and 72 stamped in the barrel , but I also see the 9mm stamped farther forward/center. Perhaps a new rifle tube was added at one time? Sleeved? I also see a 9x70R cartridge listed with a .354 bullet dia. Slugging the bore is definately called for.

September 13, 2011, 07:26 PM	#10
mkk41 Senior Member Join Date: December 4, 2004 Posts: 283	Yes , the 9x70R (Mauser) round is a slight bottlenecked cartridge.

September 14, 2011, 01:12 PM	#14
the possum Senior Member Join Date: November 6, 2004 Location: Southern Illinois Posts: 555	Aarrrrgh! It's been several months since I actually took these measurements, so I decided to get out the calipers & did some playin' around. The chamber cast seems to best match the regular 9.3x72mm R. Also found another diagram here: http://www.loaddata.com/members/sear...19&MW=&PM=&PT= And according to post #14 at this link, mine should have a type E chamber. http://forums.gunboards.com/showthre...ertus-Drilling However, I got out the slugs from my bore again, and it looks like I was only remembering the minimum dimensions. But if I keep checking around the circumference of the slug, I do get some bigger readings: So, I measured 10 "random" measurements all around the slugs and averaged them. The average of one slug was .360" (at the muzzle) and the other was .362" (ahead of the chamber). So, should I be using the absolute minimum measurements, or would it be better to go by the average of 10 measurements?

September 14, 2011, 01:26 PM	#15
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	You need to get lined up on the raised parts and get a measurement of GROOVE diameter. The Internet Confusion of bore vs groove diameter can make a lot more difference than clip vs magazine. It is getting to look like you have a BORE of .354" and a larger GROOVE diameter correct for a true 9.3 and need .364" bullets.

September 14, 2011, 04:01 PM	#18
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	That is most interesting. People tended to be more inventive with rifling at one time, and you seem to have a hybrid polygonal/land and groove rifling. I still think we want to go by cross-sectional area. That is one of the ways in which SAAMI specs bores. It would still be better if you had a thimble micrometer that will give you ten thousandths ($20 at Harbor Freight) but we'll have to do some averaging anyway, so let's go with what you have: List all four distances across the flats. List all four distances across the lands (your bigger numbers). List all four flat widths from land to land. Measure across the lands at one spot, the slide a thin but fairly rigid feeler gauge (say 0.01") into the land engraving and measure the diameter from the outside edge across the bullet to the lands and report that. Measure the width of the feeler gauge and report that. Alternately to the last two, take a set of drill bits and find out which drill size just nestles down into the round bottom of the land engravings so it touches bottom and both sides at the same time. Measure across the lands without the drill in place and again with it in place. Unless the lands are very tall relative to their width, reporting those two measurements will get us the height of the lands. A set of numbered drill bits is probably needed to get as close as possible. Do what you can. From the first 5 or the first three and the two in the last paragraph, I can figure out the cross section area about as closely as I expect is needed. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 14, 2011, 06:17 PM	#19
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Your drawing shows that your barrel has a groove diameter of .364" Bullet diameter should be at least .364" & .366" should work with a light load. If your sure you measured the groove diameter correctly from chamber to muzzle. A loaded rounds neck diameter should not be larger than .388" as shown by your chamber cast measuring .390" Last edited by 243winxb; September 14, 2011 at 08:12 PM. Reason: added text

September 19, 2011, 01:43 PM	#21
the possum Senior Member Join Date: November 6, 2004 Location: Southern Illinois Posts: 555	I must admit I'm a little surprised to hear I should be going by the biggest diameter, considering most measurements I could take were considerably smaller. I would'a thought if I fired a .358" bullet, the parts that got swaged down by the .351" grooves would squish over to fill those little .364" points. I suppose once I finally get this thing in proper working order I'll just have to do some experimenting on my own too...

September 19, 2011, 01:55 PM	#22
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	If you list all the measurements I mentioned, I can draw the resulting form in my CAD software, which figure the area automatically for closed shapes. QuickLOAD's database then has the cross sectional areas typical for a round. It has .100688 in² for the 9.3×72. We can see how your barrel geometry compares to that number, which reveals how much metal you are swaging into how much area. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 19, 2011, 02:11 PM	#23
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	Your drawing looks like an 8-sided version of Alex Henry rifling (7 sided in Scotland) which is very flexible as to bullet diameter. I can't explain the unevenness unless the barrel was dented by impact. It was no problem for an old line barrelmaker to hold dimensions much closer than that.

September 19, 2011, 03:50 PM	#25
the possum Senior Member Join Date: November 6, 2004 Location: Southern Illinois Posts: 555	Unclenick- I gotta admit that's pretty danged cool. I really don't know how I'd actually measure all those dimensions accurately, which was part of the reason for my lack of response. My idea was to take a known quantity of something soft/malleable & stuff it in the barrel. Then measure the length of the resulting plug and find the average area by solving for the diameter of a cylinder.