Bored waiting - Had to go Shoot

sabotloader

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Well! It did not come yesterday and today was just a great day to shoot - so I grabbed the DISC ELite 50 cal and headed to the 'Rock Pit'.

Last time I went to the pit a couple of weeks ago and got about half way to the pit and buried myself in the rotten snow. So I was ready to give it another try. The weather has really been decent so I was sure the snow would have melted out by now.... Well, no quite but good enough that I could get through in 4 wheel drive.

My goal for today was to get some velocities recorded for the Lehigh/Bloodline 40 cal bullets from a 50 cal muzzleloader. The Elite has not been shot for accuracy in a long time - in fact I can not remember for sure when I did shoot it last.

One of my thoughts is... I know the velocity of a 40 cal bullet from a 50 cal rifle is going to be maybe 100-125fps less velocity than if I were to shoot it from a 45 cal rifle. I could not find where I have recorded velocities for the 40's from a 50 cal rifle and I wanted to see what they might be.

When I got to the pit - the plan was to shoot the 40-200 DOA first followed by the new/experimental 40-230 FT. I had also decided I was going to shoot my normal hunting load of 120 grains of T7-2f and the MMP 40x50 Deep Blue sabot.

The first two shots at the 50 yard target grouped OK with that hefty load, but I adjusted the scope for windage and elevation for the second two shots. Velocities were recorded for the 4 shots.

Then I switched over to the 40-230 gr. FT bullets. The last time I shot them in a 1-28 twist, I was shooting 110 grains of T7. When I showed Lehigh Dave the target his eagle eyes picked up on the fact that the 230's might have been yawing a bit with the 1-28 twist. So this time I was hoping the extra 10 grains of T7 would take the yaw or wobble out of the bullet. I think moving the bullet up and out of the barrel at 2050+ FPS seemed to cure the problem.

Next up I wanted to get the velocities of the .458-300 gr. DOA from the rifle. This is my elk hunting load and I just wanted to verify what I thought I already knew... But I was in for a real surprise, not in velocity but accuracy - it was terrible. I really do not know where my mind was but when I was loading the bullet - I was thinking wow! this bore is really tight - almost to tight but I just kept doing my thing. On the second load I even noticed that the petals were being elongated strectched and canted to side as I pushed the sabot through the crown. Then after the second shot which was a couple inches higher than the first one - Ireally be gan to wonder. thse bullets have always shot lights out for me. Loaded the third load and again struggled to get the sabot and projectile down the bore. Other than that nothing registered except it was awful tight. #rd shot did hit the target board but just off the paper. Now I was really bothered.

When I went back to the work bench - thinking What the HecK!!! - as I am looking at the box of bullets and the sabots... The light came on - BRIGHT - I was loading the 458 bullet in a HPH-24 sabot. That then explained why I was stretching the petals so much even as I stretched them and they started canting to the right it did not resgister... I could not believe it.

Well to finish up - I decided to try fixing the problem. I walked 4 clay birds down the end of the rock pit and placed them on the wall (100 yards). I had already pulled the target and put the chrono away. So I loaded up the rifle again only this time I used the Orange .458 sabots that I should have been loading in the first place. Loading went much better... gosh! I could not believe I did that... Black vs. Orange sabot should have been a big clue! Anyway last 4 shots - went just as they were suppose to - 4 shots - 4 birds.

Target.jpg
 

Travis Bertrand

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Sabot,
Awesome write up like usual, what program are you making the photos with? That's a good way to keep a record of every shot.
 
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sabotloader

sabotloader

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Sabot,
Awesome write up like usual, what program are you making the photos with? That's a good way to keep a record of every shot.

I am just dropping the pictures into Microsoft Publisher, working with them in there then making the picture you see in the post..
 
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sabotloader

sabotloader

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Looks like some good velocities.
Are you finding the BH 209 is faster than the T7?

BH-209 can give a boost in velocity of a projectile in some cases, really more dependent on the weight of the projectile. Usually with lighter projectiles you do not see much oa significant velocity boost with BH vs. T7 loading grain-for-grain (by volume). Projectiles greater than 250 grain in weight then BH starts to show the increase. Since BH is a smokeless 'progressive burning' powder, the longer the bullet stays in the barrel the moe efficient BH becomes and the better velocity boost you may get from BH.

The characteristics of BH allow it to develope pressure differently than real BP or or any of the other BP subs. With BH pressure in the bore at any given time is normally 10-15% less than T7, but it maintains this lower pressure for a longer period of time and in the end developes more total pressure over the length of the barrel. Then if the projectile is heavy enough it will really produce the higher pressure curve.

With BP or other subs, when you ignite them they burn rapidly to the peek pressure and then the pressure starts decaying rapidly as the powder burns out and as the projectile moves up the bore. With BH - not so much - the pressure lasts longer even though peek pressure is never as much.

With a 300 grain bullet bullet and like amounts of powder you will or can get about 100-150 fps more velocity from BH at the upper end of the powder loads. These two spreadsheets were built a few years back and show what I tracked through my chronograph. One table shows the comparison with a 200 grain bullet shot from a 45 cal Knight and the other a 300 grain bullet shot from a 50 cal Knight.

45VelocityTest.jpg


50calT7vsBHVelocity.jpg


This chart show the rise and fall of the pressure curves for the listed powders...

BpPressures1.jpg
 
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robby denning

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Awesome data! Can't wait till I have a few minutes to sit down and digest. I didn't get to chrono the BH in my T/C with 450 grain bullets, but by the kick (120 grain BH) something special was happening. Maybe this summer I'll get to check.

thanks, and very informative.
 
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