Hare-Brained idea…

As I’ve stated before, I really like the idea of driving bands and all of the new bullets have got me wanting to try them (especially the barnes). I want to try them in my doubles, but just can’t bring myself to do it.

Let’s leave the pro’s and con’s of different brands/materials out of the equation for now, and focus on a means of measuring the differences… stay with me here.

So, as many of us often do, I’ve devised a plan to “prove to myself†that they are no more difficult (stressful on the barrels) than a conventional lead core bullet is.

How do I test it? Well, initially, hydraulic presses, electronic readouts, and thousands of dollars worth of equipment came to mind, but of course they seem a little impractical for the shade-tree gunsmith – especially for such a trivial exercise.

Plan B:

Start with a take off barrel, which I have, and thread a “cap†onto the barrel shank threads. The end of the cap has a threaded hole (of a diameter slightly smaller than the bore) and will accept a threaded bolt (in effect a, push-rod) that is the length of the barrel and, again, slightly smaller in diameter.

The idea is that a bullet could be dropped in the chamber, aligned to engage the rifling, and the bolt the length of the barrel threaded into the “cap†covering the shank threads.

A torque wrench is then attached to the “push bolt†and as the wrench is turned, it pushes the projectile down the length of the bore. The torque on the wrench starts low and is incrementally increased until a number of ft/lbs is determined that can push the bullet down the bore.

The same process is completed with other bullets, and presumably – the different amounts of measurable torque will be compared.

Does this make as much sense to you guys as it does me, or am i completely off my rocker?

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Originally posted by new_guy:
Hare-Brained idea…

As I’ve stated before, I really like the idea of driving bands and all of the new bullets have got me wanting to try them (especially the barnes). I want to try them in my doubles, but just can’t bring myself to do it.

Let’s leave the pro’s and con’s of different brands/materials out of the equation for now, and focus on a means of measuring the differences… stay with me here.

So, as many of us often do, I’ve devised a plan to “prove to myself†that they are no more difficult (stressful on the barrels) than a conventional lead core bullet is.

How do I test it? Well, initially, hydraulic presses, electronic readouts, and thousands of dollars worth of equipment came to mind, but of course they seem a little impractical for the shade-tree gunsmith – especially for such a trivial exercise.

Plan B:

Start with a take off barrel, which I have, and thread a “cap†onto the barrel shank threads. The end of the cap has a threaded hole (of a diameter slightly smaller than the bore) and will accept a threaded bolt (in effect a, push-rod) that is the length of the barrel and, again, slightly smaller in diameter.

The idea is that a bullet could be dropped in the chamber, aligned to engage the rifling, and the bolt the length of the barrel threaded into the “cap†covering the shank threads.

A torque wrench is then attached to the “push bolt†and as the wrench is turned, it pushes the projectile down the length of the bore. The torque on the wrench starts low and is incrementally increased until a number of ft/lbs is determined that can push the bullet down the bore.

The same process is completed with other bullets, and presumably – the different amounts of measurable torque will be compared.

Does this make as much sense to you guys as it does me, or am i completely off my rocker?

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Huh?

Just attach a strain gauge to your rifles' chambers, attach to an Oehler PBL, and shoot some reduced loads with conventional solids, and banded solids. That should give you some indicia without damaging your barrels.

George

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Huh?

Just attach a strain gauge to your rifles' chambers, attach to an Oehler PBL, and shoot some reduced loads with conventional solids, and banded solids. That should give you some indicia without damaging your barrels.

George

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Don't have a strain gauge, and don't have a PBL. Do have a drill press and torque wrench.

The idea is to measure the ft/lbs of torque necessary to push the bullet down the bore by applying that torque to a bolt that pushes the bullet.

Using a threaded rod, with measurements from the torque wrench, the results could - in theory - be compared.

In other words, I hope to find that it takes 35ft/lbs of torque applied to a bolt to push a banded barnes solid down the bore, and that it takes say... 40ft/lbs of torque applied to the same bolt to push a Hornady solid down the bore... with me now?

new_guy,

You idea sounds good to me, IF you are after relative values. I would strongly recommend using the SAME threaded rod for each test, and use a rod which has been well burnished before testing. By burnished I mean exactly that, threads which have been used enough that they are nice and polished (shiny).

Let us know what you find out.

Testing I have been involved with shows that Barnes "X" bullets without driving bands take ~ 40% more force (read with a load cell, you know that REAL expensive equiopment you are trying real hard to avoid) than a Sierra, Remington, or Hornday jacketed bullet. More interesting than that is the fact that with the jacketed bullets the force drops off dramatically after initial rifling engraving, this DID NOT happen with the Barnes "X" (again without driving bands). I won't share the data on driving band bullets we obtained, until after you post the results of your testing. I will tell you we saw a significant reduction in engraving force, as well as, the sustained force after engraving. They still weren't as low as jacketed bullets.

ASS_CLOWN

Yes, AC - you're with me.

I'm just trying to find two relative values from the same test. It could be how much water pressure is required, how many pounds of feathers, etc...

But your Load Cell sounds much more reliable than my practical method... do you feel that your results would save me some time?

Either way, I'll keep the group posted...

Now, who has a barnes banded solid in .375? As for any other bullets you want "tested" in that caliber PM me and I'll give you an address to which they can be mailed.

I know I've got some Woodleighs and Hornadys on hand...

Barnes TSX bullets are not drive band bullets, they are grooved bullets. There is a difference.

See this page for some information on the subject.

Gerard, it appears that you are associated with GS Custom...?

If so - maybe you already have the answer to my question? Any comments or observations?

I do the R&D for GS Custom Bullets.

When it comes to double rifles, especially older ones, I would not shoot anything other than jacketed lead and true drive band bullets in them. I have been gunsmithing since 1979 and have seen my share of trouble (expensive) with double rifles and hard bullets. According to Sabi Rifles, who are the appointed agents for Krieghoff doubles, they will not honour their guarantee if the gun was fired with bronze monometal bullets.

A jacketed lead bullet requires around 1200 pounds (roughly 10 000 psi on the base of the bullet) to get started through the throat of a barrel. A conventional copper monometal bullet takes around 1500 pounds and a drive band bullet will get going at less than 400 pounds depending on calibre. I do not have the numbers for bronze solids or grooved copper bullets and I am not set up to do a test of this nature at the moment.

Gerard....if I order some 470 flat nose solids from you....about how long is it taking to get them to the state? I'd love to try them, but I've read it takes 2-3 months? Thanks.

Gary B.

It's just past midnight here. I can check for you tomorrow.

Thanks!!....now get some sleep.

Gary B.

For those interested, I've refined the testing setup a bit.

Now i'll be pushing a projectile through a few inches of rifled barrel with a hydraulic bottle jack.

The jack is fitted with a gauge measuring the applied pressure in psi.

The gauges max out at 10K psi.

Does anyone have ANY idea how much pressure would be applied to a bullet in order to force it through a rifled barrel???

I just want to make sure i get the appropriately scaled gauge.

quote:

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Originally posted by Gerard:
I do the R&D for GS Custom Bullets.

When it comes to double rifles, especially older ones, I would not shoot anything other than jacketed lead and true drive band bullets in them. I have been gunsmithing since 1979 and have seen my share of trouble (expensive) with double rifles and hard bullets. According to Sabi Rifles, who are the appointed agents for Krieghoff doubles, they will not honour their guarantee if the gun was fired with bronze monometal bullets.

A jacketed lead bullet requires around 1200 pounds (roughly 10 000 psi on the base of the bullet) to get started through the throat of a barrel. A conventional copper monometal bullet takes around 1500 pounds and a drive band bullet will get going at less than 400 pounds depending on calibre. I do not have the numbers for bronze solids or grooved copper bullets and I am not set up to do a test of this nature at the moment.

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Sounds like great info, and my negate the necessity for my make-shift testing.

Can you post some more specific data regarding those findings? i.e. Caliber, bullets compared, etc?

That would be very helpful.

I was only interested in finding out how three different bullet types compare: Jacketed lead, copper monometal and copper drive band. We used a 270 barrel and a 5ton hydraulic press fitted with pressure guage. Bullets were a jacketed 150gr boat tail, copper mono 130gr and 120 gr drive band.

The results were so obvious, I went straight to pressure testing in a ballistic lab from there.

I have been shooting GS Custom flat nose solids in my double rifles for a number of years now, as has Johann Calitz..I have shot them in both english and Searcy guns..

Of note is I have had to up the charge a grain or two to bring the POI up and bring the velocity up to to match say Woodleighs, which tells me they develope less pressure than other bullets.

furthermore, they kill much better than a round nose, visably so....

The same senario applies to the NorthFork flat nose solid and cup points that I have used in my old 450-400 AN, and of late my 470 Searcy..Also the bridger flat nose solids (no longer available)..Bridger is supposed to be out again by another fellow, but I have not seen them.

I have not tried the Barnes bullet but I don't like the nose configuration on it anyway, so will stay with the others..

Interesting test, I have often wondered about now much the drag force on a bullet in the barrel contributes to overall pressure. One thought though, how does the breakaway force or quasi-static friction compare to the forces encountered when the bullet is being pushed by 20-40ksi hot gas? I would expect soft bullets (lead, copper jacketed lead) to obturate at these pressures whereas a monolithic solid probably doesn't upset much. What we need to do is put some longitudinal gages on the thinnest section of a barrel and measure the 'stretch' caused by the friction?
C.G.B.

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Originally posted by cgbach:
Interesting test, I have often wondered about now much the drag force on a bullet in the barrel contributes to overall pressure. One thought though, how does the breakaway force or quasi-static friction compare to the forces encountered when the bullet is being pushed by 20-40ksi hot gas? I would expect soft bullets (lead, copper jacketed lead) to obturate at these pressures whereas a monolithic solid probably doesn't upset much. What we need to do is put some longitudinal gages on the thinnest section of a barrel and measure the 'stretch' caused by the friction?
C.G.B.

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Makes sense to me... but I don't have access to a longitudinal gas maker! (just kidding)

I've thought about pushing them through extrememly thin (turned down) sections of barrel and measuring them, but I believe that relative values will paint a pretty clear picture. I guess I'm more worried about the force exerted on the barrel walls by a "harder" than normal (lead-cored) solid and i'm trying to deduce some interpretation of that force by the presumed friction varities i'll encounter from one "soft" solid to another "hard" solid.

Any other bullet makers located in the USA makin bullets with limited land/groove contact? I read volumes of info at Gerard's gscustom.co.za and also see the larger cal bullets are primarily African loadings.
I am working with a 45-70 and plan to work with .44 and the 444 marlins also.