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Post by ET on May 16, 2019 17:03:14 GMT -5
In my book it definitely is. Other than imparting a solid gyroscopic spin it produces a responsive ignition by containing more pressure at the start of the burn that helps the sabot base flair to seal the bore. Then pressure can really build up and accelerate the powder burn.
Add some slight compression to the powder with a little extra push and that load is just waiting for a good ignition source. Using this as a guide line has never let me down.
If anyone has some additional comments or thoughts feel free to chime in.
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Post by hunter on May 17, 2019 8:44:03 GMT -5
I agree with your thoughts on this, I always got better accuracy with tight fitting sabots
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Post by GMB54-120 on May 17, 2019 9:52:28 GMT -5
The majority of my rifles shot very tight sabots best. My NULA would be the only exception. It will shoot a Harvester short black better than pretty much anything tighter and its not very tight at all. Just like sabotless, a softer lead core and a thinner jacket can make sabots less fussy about fit. Solid coppers in general benefit more from the tighter sabots.
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Post by ET on May 17, 2019 16:23:09 GMT -5
I enjoy hearing that others have benefited when a good load resistance is employed. One other benefit I've experienced is the bullet/sabot does not easily move off the powder load when the ML receives an unwanted bump. But it's still prudent to check.
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Post by AJ on May 18, 2019 10:05:04 GMT -5
Loading pressure is a lot like torque on a fastener. Unless you are using something to measure the resistance, what is just right to one may be too loose or too tight for another. I have seen pressures vary as much as 5k psi using the same load when using easy to seat bullets vs needed 2 hands and a good grip to seat. I don't think any one is better than the other as long as you are consistent.
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Post by ET on May 18, 2019 12:48:51 GMT -5
Loading pressure is a lot like torque on a fastener. Unless you are using something to measure the resistance, what is just right to one may be too loose or too tight for another. I have seen pressures vary as much as 5k psi using the same load when using easy to seat bullets vs needed 2 hands and a good grip to seat. I don't think any one is better than the other as long as you are consistent. Good point about the peak pressure difference. This in turn also shows the difference of burn efficiency. I agree load resistance consistency is important to the load for repeatable results. Ed |
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Post by encore50a on May 18, 2019 14:55:55 GMT -5
 Only way to get perfect measurements  |
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Post by rpcw on May 22, 2019 2:56:35 GMT -5
Now that is fancy! Where can I get one?
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Post by encore50a on May 22, 2019 6:44:57 GMT -5
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Post by bluedog on May 23, 2019 6:57:41 GMT -5
Just get you a 'Powder Packer', I assume they are still made. I bought one of the early wooden versions made in the early 80's when I was still shooting Black Powder. I Still use it with either smokeless or BP substitutes. Spring loaded (calibrated to ?? pounds on one end, ramrod starter assist on the other). It may not produce the optimum ramrod pressure for smokeless (I don't know what that is) but it produces the 'same' pressure each loading. Easy to use and easy to carry.
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Post by lbahunter on Jul 13, 2019 17:50:26 GMT -5
In my book it definitely is. Other than imparting a solid gyroscopic spin it produces a responsive ignition by containing more pressure at the start of the burn that helps the sabot base flair to seal the bore. Then pressure can really build up and accelerate the powder burn. Add some slight compression to the powder with a little extra push and that load is just waiting for a good ignition source. Using this as a guide line has never let me down. If anyone has some additional comments or thoughts feel free to chime in. I know this thread is a few months old but...... Does a good load resistance help when using lighter weight bullets? Does bullet weight affect pressure more than load resistance? tight fitting lower weight bullet vs not as tight fitting heavier bullet? or am I way off base here.... |
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Post by ET on Jul 13, 2019 20:27:43 GMT -5
Ibahunter
Good questions.
First you need to understand what is happening with the specific parameters of a given load. Hope I can properly describe it.
Lets take 250gr bullet and sabot that has a load resistance of say 10lbs. Now we need a specific force to start moving that bullet/sabot load. Here the powder needs to start burning to build enough pressure to start this movement of a 250 grain bullet with a sabot that has an additional load resistance of 10lbs. Once the bullet starts moving the load resistance effect is now reduced and bullet weight plays a more major roll. The sabot's duty now is to seal the bore with it's flared base to contain the pressure behind the bullet/sabot load.
Now lets take that same load and add 20lbs load resistance. It now takes more pressure to start the bullet/sabot movement. That extra pressure build up adds more accelerated burn rate to the powder at the start of movement with an end result of higher peak pressure.
The powder here is chosen for it's burn characteristic. Accelerated burn rate for a given weight load.
So load resistance is more for starting a burn that will produce a good accelerated burn rate at the start.
As for your other referencing questions I don't have an answer.
Ed
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Post by reloader22 on Jul 13, 2019 21:56:02 GMT -5
I have noticed that load resistance is very important with slow powder high velocity loads. I have also noticed that a very loose sabot/bullet combo and using mild doses of 4759 are very accurate and can be pushed down the barrel with no swabbing between shots.
By high velocity I mean H4198 in heavy doses behind 250-325 gr bullets. Unless using HCR sabots and .458 bullets, super high loads do not seem to be consistent.
Using the same HCR sabots and .451-.452 bullers and low doses of 4759 (yes I have many pounds of it) gives very good consistency and good groups. Very quick and easy to reload with no patching.
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Post by lbahunter on Jul 14, 2019 11:48:33 GMT -5
ET sent you a pm
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Post by edge on Jul 16, 2019 7:37:16 GMT -5
SNIP... Unless using HCR sabots and .458 bullets, super high loads do not seem to be consistent. If by high, you mean high load resistance, it is my belief that you get sabot distortion/stretching when load resistance become too much. edge. |
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Post by ET on Jul 16, 2019 8:14:16 GMT -5
SNIP... Unless using HCR sabots and .458 bullets, super high loads do not seem to be consistent. If by high, you mean high load resistance, it is my belief that you get sabot distortion/stretching when load resistance become too much. edge. Most definitely about unequal sabot/distortion with high load resistance without a bore guide. IMO by using a bore guide to keep the ramrod centrally located should equally distribute any stretch or distortion onto the sabot. Also I believe with the use of a bore guide it aids in the concentric placement of the bullet. Ed |
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Post by reloader22 on Jul 18, 2019 19:17:56 GMT -5
What I meant was a high performance load. A .451 bullets in a tight sabot combo does not shoot as consistent as the same weight bullets in .458 in a tight sabot. I'm talking H4198 loads and Re7 loads where speeds are 2500 fps or more.
Low doses of 4759 and almost any combo, light, loose or tight shoots really good. Not sure how you measure sabot stretch based on load resistence or if we assume there just is some
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Post by ET on Jul 19, 2019 6:54:49 GMT -5
What I meant was a high performance load. A .451 bullets in a tight sabot combo does not shoot as consistent as the same weight bullets in .458 in a tight sabot. I'm talking H4198 loads and Re7 loads where speeds are 2500 fps or more. Low doses of 4759 and almost any combo, light, loose or tight shoots really good. Not sure how you measure sabot stretch based on load resistence or if we assume there just is some Assume? Let's see what effect compression, surface tension does and include elasticity and temperature. Compression forces the sabot petals to conform to the bore. If the loading force applied is not centered then conformity is not even, so now we have distortion. This compression now also creates surface tension (friction) that will try to hold onto the sabot petals when it is forced to move. Here is where elongation or what we call stretch will occur. Add elasticity that is a characteristic property of the sabot and is influenced by temperature. This also adds to the amount of distortion and stretch that occurs. In effect there are numerous factors here that contribute to distortion and stretch. Ed |
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Post by encore50a on Jul 19, 2019 9:12:28 GMT -5
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Post by reloader22 on Jul 19, 2019 20:00:37 GMT -5
ET,
How is this measured?
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Post by ET on Jul 19, 2019 21:32:09 GMT -5
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Post by reloader22 on Jul 20, 2019 5:43:37 GMT -5
Could you measure the sabot before loading? Then push the sabot down the barrel with no breech plug with a loose fitting bullet and then repeat using a very tight fitting combo. Measure and compare?
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Post by ET on Jul 20, 2019 6:20:31 GMT -5
Could you measure the sabot before loading? Then push the sabot down the barrel with no breech plug with a loose fitting bullet and then repeat using a very tight fitting combo. Measure and compare? Now that is an interesting concept. You would have to create an exact reference stop point that say a BP could provide. MMP sabot has a more rigid base with it's step design for bottoming. The big problem would be insuring the sabot petals remain against the bore wall and not move inward. Possible-maybe, accuracy-questionable if the right conditions aren't met. Ed |
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