dustinflint says

More expensive to feed, but worth it.
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cslcAl
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Re: dustinflint says

Post by cslcAl »

Here's a link for heat treated bullets.
There are more just use the search box at the top of the page.

viewtopic.php?f=2&t=9751&p=76576&hilit= ... ets#p76576

Al Foust
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Re: dustinflint says

Post by SteveD »

boats wrote:64,000 question ?

Boats
The $64,000 Question was a game show. The $64 question is, according to the Merriam Webster dictionary: a crucial question expressing the basic issue on a problematical subject.
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Re: dustinflint says

Post by SteveD »

I have not been back out to the range to take more measurements. I believe that the ones that I did take are very telling. I have been thinking of a way to better quantify, if not in the absolute then at least in the relative, the striking force of various bullet/cartridge combinations.

I'm thinking of taking the force gauge that I bought and building a fixture to hold it and a 12" X 12" piece of AR500 steel that I can clamp to the Rams rail and capture the force imparted by the bullets. I'm thinking that the plate would need to be mounted on slide rails that have bearings so plate would move only in one direction when struck.

Any help would be appreciated.
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Re: dustinflint says

Post by SteveD »

cslcAl wrote:Here's a link for heat treated bullets.
There are more just use the search box at the top of the page.

viewtopic.php?f=2&t=9751&p=76576&hilit= ... ets#p76576

Al Foust
Interesting read. Follows a trail similar to the one I am on. I would like to include heat treated bullets in the measurements.
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Re: dustinflint says

Post by SteveD »

I have a technical question pertaining to the bullet force measuring fixture I am working on. Perhaps someone with an understanding of Mechanical Engineering can give me some insight.

The part of the fixture that is struck by the bullet will move when struck. This will push against the force gauge and be measured as the force of the bullet. Does it matter what the moving portion weighs? If so, how much should it weigh?

It seems as though it should weigh not less than the highest force required to push over a Ram (my measurements so far shows that to be less than 15 pounds) and not more than the actual weigh of the Ram, approximately 55 lbs. The greater the mass of the moving portion the greater inertia it will have and it will present more resistance to the bullet. And since the Ram requires less than 15 pounds to push it over it seems as though the bullet striking a greater mass may distort the test results. The whole, force, work, mass consideration is outside of my experience.

Given that a 12" X 12" X .375" piece of AR500 weighs about 15 pounds the lower bounds is set there anyway. A fixture with 55 lbs of moving weight would be very difficult to work with but if there is a justifiable necessity within the laws of physics for it to have that much mass then that will be what I do.

I'm thinking of attaching the plate to rails that slide on ball bearings with the moving portion resting against the plunger of the force gauge, held in contact with some springs, just enough spring to keep the plate in contact with the plunger.

Keep in mind that the goal is to accurately measure the RELATIVE force that different bullets impart onto the Ram and not the absolute force although knowing the absolute force would be best.
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Re: dustinflint says

Post by OldRanger »

The mass of the fixture target definitely matters. To compare apples to apples the best way would be to attach your force gauge to something the same mass as the rams. But that would be impractical I think. If you attach it to a 15 pound plate then the readings you get would be much higher than when you hit a ram (about 3.8 times higher I think). But again, you will know relative to each other how different bullets and charges affect the force imparted. It will be interesting to see if faster bullets shatter and put less force out, or if that is just a myth.
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Re: dustinflint says

Post by SteveD »

I am not sure in this case what would be 'apples to apples'. The force I measured to topple the Ram was a little over 14 lbs. So is 14 lbs the appropriate weight for the moving mass? The Ram weighs 55 lbs. Does the moving portion need to weigh 55 lbs?

Either way the weight will be riding on ball bearings so the force required to move the mass if applied slowly will be very small regardless of the weight of the target. The bullet will be traveling at 1,600 to 2,000 fps so even 14 pounds will present a significant resistance to the bullet.

This is what I am stuck on at this point.
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Re: dustinflint says

Post by eeleater »

I believe there is a better way to address quantifying bullet effectiveness in knocking over rams.
This would address bullets of different weights/velocity, construction, and heat treating.
It would not address variables such as tilt of the ram, mud gluing the feet down, wind velocity and direction, etc.

My suggestion is to take an actual ram and suspend it to make a ballistic pendulum.
Ballistic pendulums were developed to measure the velocity of bullets. They do this by measuring the swing and rise of the pendulum after impact. The extend of the swing (and thus rise) reflected the energy, and with the mass of the bullet being known, calculation of the velocity was possible. This required the capture and retention of all of the mass (energy) of a bullet on impact. Blocks of wood were used as targets to do this. The results are thus not affected by bullet construction and the dwell time of the bullet as it disintegrates on the target.

https://en.wikipedia.org/wiki/Ballistic_pendulum
http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html

The goal is to use the swing (rise) of the target to measure the energy actually transferred to the ram by the bullet. This will vary by bullet construction and bullet dwell time.

This does not have to be done at 500 meters if the loads can be adjusted to provide the "on target" velocity we actually see at 500 meters.

To determine the center of mass of a ram as an aiming point, hold it horizontally and balance it on a short piece of conduit. Use this as the aiming point for the test. A hit here will move the animal straight back.

You do want the mass of the pendulum to be the same as an actual ram so he rate of the acceleration of the target is the same.

I would suggest first setting the ram on an actual stand at 200 meters. For several different cartridge/bullet combinations determine the minimum (on target) velocity for each which will consistently knock down the ram. (Use an optical chronograph)
Set up the ballistic pendulum using the actual ram, and measure the swing (rise) for the same combinations.

We are measuring the swing, but it is the rise above the resting height which goes into the calculations.
The measured swing will work for simple comparisons, but actually doing the math using the rise will provide more information

The swing (rise) should be the same for the different combinations. The energy actually required can then be calculated and compared to the that calculated by knowing the mass of the bullet and the optically measured velocity. The difference between the two is the energy used in the destruction of the bullet.

I would not assume that the "destruction energy" will be the same at all velocities. At some low velocity it will remain intact after it hits, and if the velocity is high enough, it will destruct before reaching the ram.
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Re: dustinflint says

Post by SteveD »

eeleater wrote:I believe there is a better way to address quantifying bullet effectiveness in knocking over rams.
This would address bullets of different weights/velocity, construction, and heat treating.
It would not address variables such as tilt of the ram, mud gluing the feet down, wind velocity and direction, etc.

My suggestion is to take an actual ram and suspend it to make a ballistic pendulum.
........................
Not sure how a ballistic pendulum would be better than what I am working on. It is a proven method for ascertaining bullet velocity when a fully absorbing stopper is used and your suggestion to substitute an actual Ram is reasonable but is considerably more difficult to accomplish and I do not have a facility at which I could conduct such measurements. A ballistic pendulum with an actual Ram would give an indication of the force that a bullet transfers to the Ram but I'm not seeing why it would be be better.

Perhaps it would be helpful to state clearly what I am looking to accomplish. I am looking to establish a baseline of the bullet applied force, 'Ramficiency' (sp) seems to be the term agreed on, of a 142 gr, Sierra MK launched at 2,600 fps and then compare other bullets to that 'Ramficiency' number. The other bullets are:

Lapua Scenar 139 gr
Sierra 123 gr MK
Lapua Scenar 123 gr
Sierra 123 gr MK
'Name not specified' bullet of solid construction, 120 gr.

If the numbers of the 120 gr solid bullet are significantly different (better) than the 142 Sierra, I would also look to try a 107 gr, 6mm version of the same solid bullet.

The 2,600 fps is my guesstimated muzzle velocity for a 142 from a 6.5 BR. I will adjust it when I have actual data.

I am working on a concept drawing of my Ramficiency meter (Ram-O-Meter) and will post it when I have it done.
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Re: dustinflint says

Post by eeleater »

I am interested in seeing your drawing.

"Alternative" would have been a better choice in terms.

A part of my thinking in bringing it up is the assumption that our silhouette community has better access to optical chronometers and rams than to force gauges and AR500 plate pieces. A modified ballistic pendulum is a simple device, which can provide a very direct measurement of the impact of a bullet on a ram. If someone does not want to do the actual math, they can compare the bullet/velocity combinations by just measuring the swing.
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Re: dustinflint says

Post by SteveD »

Ahhh yes, it would be a reasonable alternative.

You may have missed earlier in the thread that I had purchased a force gauge. I snagged it off of eBay. That is what I used to measure the 14.1 pounds of force required to push over a Ram.
Mark 10 digital force gauge reduced.jpg
I am looking for some AR500 locally. I would really only need one 12" X 12" piece but I will probably get two and build a symmetrical moving mass. (An engineer that I worked with always said "If you are building a one off, don't worry about over engineering it, just make it so that it will work and last.").

The Ram rail at the Ben Avery is an inverted railroad rail and has a nice flat bottom, now top, that is about 6" wide. I can sit the fixture on top of that an clamp it to it to prevent it from moving. No feet or legs or leveling mechanism required, just a base with ball bearing rollers on top for the moving mass.

Silhouette shooters over the years have spent countless amounts of money, directly and indirectly trying to figure this out. They've tried different bullets, different cartridges, new barrels, various wildcats, more velocity, less velocity etc, trying to solve this. Lots of fun to be sure but we still do not have a way of determining definitely if a particular bullet/velocity/cartridge combination is any better than another. I don't mind putting forth a little effort and money to perhaps come up with way of quantifying the difference.
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Re: dustinflint says

Post by thauglor »

If you shoot at a movable target that then impacts the force guage, you are measuring the force the target gives the guage, not the bullet on the target. Then you still have to guess how the force the target imparts on the guage correlates to the bullet on the target. Still not directly measuring the bullet force.

I think the best way to see what is the force being imparted by the bullet, the ram/target has to be connected to the force guage directly, with the force guage body not being able to move.

You would have to hit it towards the center to get the correct force reading I think; as off center shots would add torque to the target and possibly skew the force readings.

I think the idea of reduced loads (within safety) to bring the distance in and be more accurate is great.
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Re: dustinflint says

Post by SteveD »

In the concept I have in my head (and half way in a Visio drawing) the plunger of the force gauge will be in direct contact with the target at all times using just enough spring force to keep it there. The force gauge can be zeroed to eliminate any force applied by the spring.

I am not looking to measure directly the force of the bullet, only the force of one bullet relative to another.

Does bullet "A" transfer more energy or less energy to the target than bullet "B"?

I would propose to use the measured force at 500 meters of a Lapua Scenar 123 launched from a 6.5 BR (at whatever velocity I can get from it at an acceptable level of accuracy) as the baseline, Index of 1.00.

Working up reduced loads to fractional distance testing would be feasible but would add a layer of complexity to the testing. Using full loads at full distance would allow anyone to test their Ram loads easily.
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Re: dustinflint says

Post by eeleater »

You may want to contact Mark-10 about this application for that gage.

You had earlier mentioned the 142 Sierra MK, so I did some calculations using it.

A 142 Sierra MK at 2600 fps traveling 31200 inches per second is to be used.
An individual posted a 142 Sierra MK is 1.377 inches long ( http://www.65grendel.com/forum/archive/ ... -2750.html ).
31200 inches/second/1.377 inches/bullet length = 22658 bullet lengths/second. If we were shooting a paper target the time it would take the bullet to pass through the paper would be 1/22658 seconds.

The Mark 10 webpage Force Gage Comparison Chart ( http://www.mark-10.com/instruments/forc ... gauges.pdf ) shows sample rate of the economy model of 500/second, going up to 14,000/sec for the top model.
It may not be able to sample fast enough to capture the data.

The dwell time on a ram will be greater than 1/22658 s. I tried searching for measured dwell times on targets, and found this.
https://www.researchgate.net/publicatio ... AMIC_TILES

They are using 7.62 APM2 at 830 m/s (2723 f/s) being shot against ceramic plates of varying thickness. They also calculate the dwell time of the steel core. The steel core is 1.087 in of the 1.374 total bullet length. Figure 10 has the core dwell times with the dwell time increasing as the aluminum backing thickness increases. Figure 6 is from a different study, but shows the dwell time of the tip vs. the tail of a "steel rod" of unspecified length. The tip to tail dwell time was some 80 microseconds ((80/1,000,000 or 1/12500 second).

I could not find the dwell time of the 7.62 APM2 bullet on steel armor plate.

If the gage sample rate is an issue, having the plate move would help vs. having the plate and gage fixed together.
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Re: dustinflint says

Post by SteveD »

Sorry, I am working and don't have time to review all of that until later.

The target is 55 lbs of moving mass pushing against the plunger of the force gauge. The force gauge is fixed to the base. What the force gauge would be measuring is the movement of the 55 lb mass rather than the dwell of the bullet.
Last edited by SteveD on Mon May 16, 2016 2:36 pm, edited 1 time in total.
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