Bullet Jump/Jammed - Is it the Bullet design or the rifle

[BountyHunter]

Personally, I think you are tilting at windmills and wasting effort. Engineers are afflicted with the desire to have things fit in a known model/formula and it does not work that way in real world. Every bullet, barrel, powder, primer, case combo is different and normally act differently. You are not going to find an accurate predictive "formula" that is accurate. Yes, bullet mftrs can give you some fairly accurate starting points for that style bullet, but you are going to have to physically test that specific combo with that rifle. Plus if you are testing for a magazine hunting gun, does not even matter at all and is meaningless as you will not be anywhere near the lands. There you should simply start at max magazine COAL and work backwards. BTW, not all BR guys shoot with bullets into the lands, that is an old school generalization. Cutting edge in the LR BR game is using labradars to tune for a known acccurate MV for that days conditions. Same thing Crane is doing is making sniper rounds to an exact known MV for each powder lot as a standard. That gives more consistent accurate ammuntion.

 

[asd9055]

Personally, I think you are tilting at windmills and wasting effort. Engineers are afflicted with the desire to have things fit in a known model/formula and it does not work that way in real world. Every bullet, barrel, powder, primer, case combo is different and normally act differently. You are not going to find an accurate predictive "formula" that is accurate. Yes, bullet mftrs can give you some fairly accurate starting points for that style bullet, but you are going to have to physically test that specific combo with that rifle. Plus if you are testing for a magazine hunting gun, does not even matter at all and is meaningless as you will not be anywhere near the lands. There you should simply start at max magazine COAL and work backwards. BTW, not all BR guys shoot with bullets into the lands, that is an old school generalization. Cutting edge in the LR BR game is using labradars to tune for a known acccurate MV for that days conditions. Same thing Crane is doing is making sniper rounds to an exact known MV for each powder lot as a standard. That gives more consistent accurate ammuntion.

Thank you for taking time to reply. I understand everything you are saying, and I never said you had to be near the lands. In fact modern research show the opposite.

The first V2 rockets in WWII did not go straight up and then to the target. The "Engineers" under Werner Von Braun had to understand why and fix it. Then, after the war, his team came to the U.S. and built the moon project.

This is where we are now with bullets. We have a greater understanding today than 40 years ago. We have a lot more different designs now than before. Tangent, secant, hybrid just to name the major ones. And we have lot more different objectives. Hunts within 300 yards, LR Hunts, ELR hunts, then we have the competition shooting and the various types. If you read Mark Gordon's articles, he is not looking for the perfect distance, because after 100-200 rounds the throat will be different. He is looking for the most forgiving node.

Speaking of Mark Gordon, I just heard back from one of his associates. Their research and testing so far confirms my initial suggestion that bullet design is the main factor. I will device my own testing and figure it out. It's a long a complicated process, and I do not have the right firearms right now. Yes, IT CAN BE PUT INTO EQUATIONS, I am just NOT capable of doing that. FEA people could.

Thank you all for your contributions. I wish you all Good Shooting at the Range, Successful Hunt in the Field!!!

ASD

 

[BountyHunter]

gotcha, but your equation will work for one rifle barrel (barrel steel is varied by lot also) and bullet, powder combo. Change anything causing new parameters and equation is out the window. When you say "bullet design is the main factor" of what? Guess my other question is "to what purpose" is all this?

BTW, weatherbys were designed for long jump due to speed not accuracy. Chamber a weatherby with standard throat and to headspace off the shoulder not the belt and it is extremely accurate. My first heavy gun LR BR rifle was a 300 weatherby capable of 10 shots in 5 inches at 1k.

 

[asd9055]

gotcha, but your equation will work for one rifle barrel (barrel steel is varied by lot also) and bullet, powder combo. Change anything causing new parameters and equation is out the window. When you say "bullet design is the main factor" of what? Guess my other question is "to what purpose" is all this?

You get it but don't get it!
Bullet jump is not the whole thing of tuning a rifle. Bullet jump is the first step. Bullet jump depends on bullet design, that is tangent, secant, hybrid or something else. That is the shape of the bullet.
The everything else you talk about, all the other parameters, that is the fine tuning. That is where all the other rifle parameters come in to play. That is where you play with powder and MV to fine tune it.
You must be familiar with one of the methods of tuning a load: OCW, Satterlee, Ladder Test or any combination or variation of those. Well if you do a bullet jump test before any of those, you will find a load that will be good when the rifle is new and after a few hundred bullets though it. That is the assertion.

 

[DUSTY NOGGIN]

this angle is cartridge specific .. some 1 degree, some 3 degree .. suggest looking up the cartridge you are referring to

i think a 3 degree can be an abrupt swage with a vld .. while not so much with a older spitzer type bullet profile ..

i just used this pic cause its the one in your first post

 

[asd9055]

this angle is catrigde specific .. some 1degree some 3 degree .. suggest looking up the cartige you are reffering to

i think a 3 dgree can be an abrupt swage with a vld .. while not so much with a older spitzer type bullet profile ..

i just used this pic cause its the one in your first post





View attachment 215427

Thanks Dustin!

 

[asd9055]

Got this from accurateshooter.com

Bullet design differences I am talking about. Just two examples here

 

[Dragoon300]

The bullet design is one of the factors you have identified, there is another, chamber design. The dimensions, angles and headspace of the chamber, then if you want to consider barrel harmonics the profile and then likely the material. Finally the cartridge case design.

 

[asd9055]

The bullet design is one of the factors you have identified, there is another, chamber design. The dimensions, angles and headspace of the chamber, then if you want to consider barrel harmonics the profile and then likely the material. Finally the cartridge case design.

Just curious, do you just read the last line and then post or followed the whole thread...because everything you are saying has been discussed

 

[Dragoon300]

I've been following it all the way, don't want to cause any hurt feelings. There may be many more things to consider than what I stated. I do still believe the closer to the rifling the better, unless your bullet is not seated concentric and parallel with the bore. Or the chamber is too big. In that case maybe mire jump allows the bullet to straighten out before entering the rifling but, I doubt it.

 

[Alex Wheeler]

I have been reloading for hunting and hand guns 35 years. I did not realized how little I knew until I started following and participating in forums like LRH, Nosler, Accurateshooter and snipershide, to name a few.
I don't want to get into OCW, Ladder and all those other subjects for load development. I just want to focus on bullet seating depth (jump or jammed)
I am familiar with bullet seating depth process, and I posted a link here before, but the engineer in me wants to understand more.
So here is the question I pose to the greater and more experienced group:

Is it the bullet design, i.e. tangent vs. secant that determines the jump/jammed, the caliber/cartridge (we know Weatherby cartridges are designed for extra long jump, the rifle (way the chamber and throat, barrel, lead come together) or a combination of all

Second question. Do you have a cartridge. let's say 6.5 Creed (pick one that applies to you) that you use a different seating depth for different rifle (same bullet)
I am trying to understand the physics/mechanics behind it

Its the barrel. I chamber a lot of long range Benchrest barrels. Many competitors own their own reamer, stick with the same barrel make and have enough components on hand of the same lot to last many barrels. I can send out barrels of the same make, from the same bar of steel, with chambers so close you dont have to adjust the die, that will see the same lot of bullets, powder, and primers and one barrel may prefer to be in the lands, the next, off the lands.
Now its also true that once you figure out a reamer, MOST of the barrels you chamber will like a similar seating, not all. Thats to do with the lead angle, not the lead angle on the print, but the actual lead angle the reamer cuts. There are tolerances. Order another reamer exactly the same and you will have to learn it again.
I have seen no preference for a bullet shape to prefer one or the other. As many guys are jumping vlds as are jamming them. Same goes for the tangents.

 

[asd9055]

Its the barrel. I chamber a lot of long range Benchrest barrels. Many competitors own their own reamer, stick with the same barrel make and have enough components on hand of the same lot to last many barrels. I can send out barrels of the same make, from the same bar of steel, with chambers so close you dont have to adjust the die, that will see the same lot of bullets, powder, and primers and one barrel may prefer to be in the lands, the next, off the lands.
Now its also true that once you figure out a reamer, MOST of the barrels you chamber will like a similar seating, not all. Thats to do with the lead angle, not the lead angle on the print, but the actual lead angle the reamer cuts. There are tolerances. Order another reamer exactly the same and you will have to learn it again.
I have seen no preference for a bullet shape to prefer one or the other. As many guys are jumping vlds as are jamming them. Same goes for the tangents.

Alex,

You definitely have a lot more expertise than I. I am not talking about to total fine tuning, but the "bullet jump" or "bullet jam". And I know if you ask completive shooters you will get many opinions. Who can argue with success, right?
On the other hand, when at least one major bullet manufacturer suggests doing a bullet test, start at one distance for one bullet design and another for a different bullet design, there must be something to do it. Combine that with the work of Mark Gordon and I think we have something there that needs to be tested in a controlled environment.
People say "I feel" this, I think "that"
My answer and final line on the subject is to quote from W. E. Deming: In God we trust, everybody else bring data.

Good Shooting Everyone!

 

[BountyHunter]

Its the barrel. I chamber a lot of long range Benchrest barrels. Many competitors own their own reamer, stick with the same barrel make and have enough components on hand of the same lot to last many barrels. I can send out barrels of the same make, from the same bar of steel, with chambers so close you dont have to adjust the die, that will see the same lot of bullets, powder, and primers and one barrel may prefer to be in the lands, the next, off the lands.
Now its also true that once you figure out a reamer, MOST of the barrels you chamber will like a similar seating, not all. Thats to do with the lead angle, not the lead angle on the print, but the actual lead angle the reamer cuts. There are tolerances. Order another reamer exactly the same and you will have to learn it again.
I have seen no preference for a bullet shape to prefer one or the other. As many guys are jumping vlds as are jamming them. Same goes for the tangents.

Alex,

Cannot argue with engineers. It ABSOLUTELY MUST fit into a spreadsheet or formula for them to believe it. He will wear out 500 barrels and still be no closer as you again pointed out the variables change with each barrel, primer, powder and bullet lot. Great for the industry though.

 

[Dragoon300]

Alex,
I agree completely with what you said about the reamers, steel and manufacturing tolerances. In your experience, where do you prefer to seat the bullet? And, what do you see as a practical limit of jump?