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

[Dragoon300]

You are very welcome.
I really don't think jump is that critical, just that too much is. As I have found in my 338's case it really isn't that critical (.010" - .090"), but Brian Litz designed the OTM Hybrids to accept more jump much as tangent ogive bullets do. In the case of the secant ogive Berger and Litz say it does matter. However, in my opinion you shouldn't go too far, the bullet bearing surface still needs to be in the case neck as the ogive contacts the rifling, if it isn't it can induce a lot of yaw entering the rifling and cause problems down range with group size.

 

[Mikecr]

What you really need to pursue understanding of is:
-What is seated land relationship actually doing to results?
Then:
-Why?
Then:
Can it be predicted, and manipulated -on paper?

If you list every response from shooters, and then consider their different scenarios and contradictions (failed tests), you'll end up scratching every item off the list, one by one.
For instance, most will suggest that it's tuning. Yet you'll find that those among them, who actually did full seating testing(rare), and initially found best CBTO OTL by ~20thou(example), are reporting same great results with that established CBTO 1500shts later and now ~100thou OTL. How was that seating about tuning again? Apparently not..
Then there is the 'what benchrest shooters do fallacy', with implications that their conditions with tiny little 6PPCs loaded for 75Kpsi+ are anywhere near applicable to those of us shooting hunting capacity cartridges.
So it may be useful that BR shooters wiggling bullets from 20thou ITL to 25thou ITL affects group shaping, but it remains that this is unlikely 'tuning'. Scratch that one off the list...
The BR shooter who declares "stop chasing the lands"/"I pity the fool", like this is a new discovery,, is actually right.
But he doesn't know why, or when his declaration is right & wrong.

I keep bringing up primer swapping because it is also a prerequisite condition (that is not tuning). And there is not a person alive who can explain why one primer provides better results over others with local testing. It's similar in that it's a problem to solve with exactly the same questions I began with.

On these things, I know mobs will never solve them. I can only wish I was intelligent enough to do so.

 

[asd9055]

What you really need to pursue understanding of is:
-What is seated land relationship actually doing to results?
Then:
-Why?
Then:
Can it be predicted, and manipulated -on paper?

If you list every response from shooters, and then consider their different scenarios and contradictions (failed tests), you'll end up scratching every item off the list, one by one.
For instance, most will suggest that it's tuning. Yet you'll find that those among them, who actually did full seating testing(rare), and initially found best CBTO OTL by ~20thou(example), are reporting same great results with that established CBTO 1500shts later and now ~100thou OTL. How was that seating about tuning again? Apparently not..
Then there is the 'what benchrest shooters do fallacy', with implications that their conditions with tiny little 6PPCs loaded for 75Kpsi+ are anywhere near applicable to those of us shooting hunting capacity cartridges.
So it may be useful that BR shooters wiggling bullets from 20thou ITL to 25thou ITL affects group shaping, but it remains that this is unlikely 'tuning'. Scratch that one off the list...
The BR shooter who declares "stop chasing the lands"/"I pity the fool", like this is a new discovery,, is actually right.
But he doesn't know why, or when his declaration is right & wrong.

I keep bringing up primer swapping because it is also a prerequisite condition (that is not tuning). And there is not a person alive who can explain why one primer provides better results over others with local testing. It's similar in that it's a problem to solve with exactly the same questions I began with.

On these things, I know mobs will never solve them. I can only wish I was intelligent enough to do so.

I hear you Mike. I think I might have a slight chance with bullet manufacturers. My instinct tells me bullet design makes a difference, some are more forgiving than others.
Thanks

 

[asd9055]

First of all, KUDOS to BERGER bullets. Philip responded to me within minutes of me posting the question. Though it is not the answer I was looking for, bullet design makes a difference, different starting point for each different design, but basically it is the whole system, cartridge, powder, bullet rifle. I could post the full reply here, but I am not sure
Again, BERGER great service

 

[Lenny Foffa]

I am also learning a lot after 44 years of reloading. I Hunt, but also shoot bench rest. I measure all my Jam or Jump from the Ogive of each bullet. Careful notes in a ledger for rifle and bullet /powder and Primer , is a must for me. The Jam or Jump you select will , of course , change from Bullet to Bullet. I need to shoot three shot groups for each change of COAL and OGIVE length. That tells me if any change I made actually matters. Even though Score Shooting is just One shot only in to one bulls eye . 10 times . I use a Completely Stock( Club Rules no Mods on the rifle for this game ) Medium Heavy Barrel Savage 110 in .308 for this "Score Shooting"Game. I will shoot 110 Grn Hornaday with a completely different COAL and OGIVE Length than the when I use the more tapered 115 Grn Berger Flat base Target Bullets. These are all being shot single shot. I have never used the magazine. All the loads regardless of bullet, are seated out to about 2/1000 to 5/1000 under touching lands and grooves , as measured from the Ogive, with my Hornady tools. I am sure they are all way to long to function in the magazine. I am making progress.

 

[Mikecr]

Cartridge and powder and load mean nothing to best seating.
You can do Berger's full seating testing with a bullet/barrel, and wherever tests as best will be so regardless of powder, load, or cartridge behind it. If Berger told you otherwise, they're wrong.

 

[asd9055]

Just so I don't misquote anyone, here it is. BTW it is from Philip at Verger Bullets, responded within minutes...KUDOS again

There are many different ways around the load development round. In regards to bullet design. I have found with TANGENT OGIVE bullets . That starting with the bullet on the lands. Then working back into the cartridge case in .005 increments works. For HYBRID OGIVE bullets : We suggest you start your bullet seating depth testing at .015" OFF THE LANDS and then WORK BACK INTO THE CASE in .005" increments. Information on the effects of bullet seating depth is here: https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf . Any bullet seating depth testing should be done using a starting powder charge listed. Once a good depth is found, adjust the powder charge back up slowly checking for pressure signs and accuracy until a velocity accuracy node is found.
VLD BULLET SECANT OGIVE SEATING DEPTH info for target and hunting bullets is here: https://bergerbullets.com/vld-making-shoot/ . The throat length determines how much you can set the bullet out of the cartridge . The type of bullet seating testing you do is determined by if you are using the MAGAZINE of the rifle or not : https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf
THE RIFLE ALWAYS DETERMINES BOTH THE BULLET SEATING DEPTH AND VELOCITY ACCURACY NODES. Hope this helps. If you have any more questions please feel free to contact us at any time!

 

[Doom2]

If you had read the responses you were told as much. By the who did you quote since you failed to give credit?

 

[asd9055]

If you had read the responses you were told as much. By the who did you quote since you failed to give credit?

This was from Berger. I was not sure if I should post his name. Yes, everybody mention parts of it. What you fail to see is that they start different designs at different distance off...
But again, nobody explained the what/why...only the how...I knew the how before I asked the question...I am not an expert, just eager to learn, but this is not my first rodeo...
Thank you
BTW I did say in the post before who replied and what company...so credit is given....I am a Registered Professional Engineer, I always give credit

 

[Doom2]

Sorry, my response sounded a little snarky and I apologize for that. As for credit, you did and I missed it.

Now I'm off to time out.

 

[Mikecr]

I agree completely with that quoted from Philip. He is only describing basic seating testing method.
You should understand that It does not counter anything I've stated, and it does not answer your initial questions.

 

[asd9055]

I agree completely with that quoted from Philip. He is only describing basic seating testing method.
You should understand that It does not counter anything I've stated, and it does not answer your initial questions.

Mike,
I agree with you. I came to the conclusion that unless I device and experiment and execute it my self, I won't get close to the answers. I will definitely think about it,

 

[Mikecr]

Intelligence is divided by numbers.
With this, mobs prove foolish, and every great problem is solved by an individual.
Can you solve it with intellect or excess resources? There it begins & ends...

 

[asd9055]

Intelligence is divided by numbers.
With this, mobs prove foolish, and every great problem is solved by an individual.
Can you solve it with intellect or excess resources? There it begins & ends...

I reached out to a company that does FEA (Finite Element Analysis). They have a rifle model already and do the harmonics barrel harmonics. I know it can first be modelled first and then confirmed by real data, however, I am not expecting a reply. I just do not have the expertise to built my own FEA even if I had the software.