How much can you jam?

[savagedasher]

I have found the same . But with the lead angle of the reamer I feel any thing less then .020 jump is still jam. From touch to jam can be in excess of .030 depending on bullet shape and lead angle if the reamer and how it is found.
I shoot a compressed Using the number on QL 108% full .Using a 14'' long drop tube and a slow pour my bullet stay seated. I only size .150 of the neck for seating also.
A friend not using a long drop tube with the same load same chamber when the bullets moved forward his primers showed excess pressure. The ones that the bullet moved forward with less compression and jammed all showed over pressure on the primers.
I fell any thing less then.020 off is not a problem. .020 forward pressure go up. How much, enough for it to show on the primers. Larry

Sounds isolated and unique to your own circumstance and to one cartridge, charge level, and reloading technique.
Donovan

Thanks for the complement But I'm not Unique.
PO Ackley was. He talked about pressure change when seating to jam. My first time with it was in 1957. I built a 300 Ackley. I had worked a 200gr bullet to near max jumping .030. Flat but not flowing primers. Moved the bullet out to soft touch. First shot I blew the primer had to hammer the bolt open. Went back to .030 jump every thing was fine. Went back an pulled the bullets all the powder drops were fine. Bullet weigh and size was fine. Loaded two with .005 increase each back to touching The .005 no change .010 long or .020 off Slight change in primers but still good. Let the barrel cool. Shot the .015 off prime showed excessive pressure. Shot one .010 and had hard bolt lift the primer was flowing. Went back to the .030 jump and it was just like always
Just run the numbers on QL I had a 98.2 fill with 58236 psi at .030. The bullet .030 out or touching the lands
has 97.5 fill with 57430 psi
I should of lost 900psi but had a huge increase. .030 to .020 hardly none..020 and less big changes.
When I said .020 it was based on the primers.
I find the same results on other cases that is loaded near max. Any case under near max pressures won't show.
Thanks for calling me Unique. Thanks to PO Ackley or I never would of known. Larry

 

[Tim Singleton]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

 

[savagedasher]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

Tim Your target look great. I assume your shooting a PPC with 133 . 30.1 isn't hot to some. Some of the best shooters are shooting 30.3 and 30.4 But they are jumping in excess Of .015. I get the same result as your target shows with the use of a tuner.
When the turner was set I had 5 - 2 shot targets all in .009 to .113 With a savage and 105 bullets. none had as much vertical as you did. But I shot in a 5 to 7MPH wind without flags. Great target . Larry

 

[Tim Singleton]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

Tim Your target look great. I assume your shooting a PPC with 133 . 30.1 isn't hot to some. Some of the best shooters are shooting 30.3 and 30.4 But they are jumping in excess Of .015. I get the same result as your target shows with the use of a tuner.
When the turner was set I had 5 - 2 shot targets all in .009 to .113 With a savage and 105 bullets. none had as much vertical as you did. But I shot in a 5 to 7MPH wind without flags. Great target . Larry

We short range guys actually want to tune in a half bullet of vertical at 100. That tune fights the wind better than a round hole or a flat tune. In the example seating depth target the .010 off jam with the middle load of powder is what I would start the match with.
I don't have enough neck tension with my .262 NK to load anymore than 30.1 to compressed it will push the bullet out. Since this target I've went almost 100% to LT32.
When you say the guys shooting 30.4 of 133 in a ppc are jumping in excess of .015 at that point they are still in the lands leaving marks on the bullets. That would not be considered jumping by me. There are a few who go on deeper in the case and truly jump but they are in the minority.
IMO a 2 shot group wouldn't help me evaluate a barrel.

The point of posting the target was to give the OP and anyone else who cared to use it a structured way to determine seating depth. That barrel was an ok barrel not a big match barrel.

 

[LHSmith]

I assume your shooting a PPC with 133 . 30.1 isn't hot to some. Some of the best shooters are shooting 30.3 and 30.4 But they are jumping in excess Of .015.

While it is possible a few may get best tune with a jump on some barrels, the overwhelming odds are best tune comes with the bullet in the lands EVEN when running charges which seem in the upper stratosphere to some......they simply have found actions (or had them tweaked) that are unique in their ability to shoot hotter than normal loads. What amazes me is how they get that much powder in the case, so seating the bullet deeper is not conducive to maximum powder charge capability.

 

[savagedasher]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

Tim I would like to see a target done with 2 shots .but a aim and bullet impact +++. Aiming at a +with the cross hairs. The impact of the two bullets will show the impact change to the aim. Your target does it for me but some will miss what your target tells. Using a tuner I call it a round square. Very small changes from the point of aim. I find powder changes relates more to vertical. Bench rest shooting is different then long range .
Your bore is always clean the bullets a hand made and good shooters read the changing condition. That art wins more matches then a good tuned bullet.
I shot 2 nbrsa matches at manatee . The gun was tuned where I could shoot in the low .100 in good conditions. Late Friday afternoon I ask my camping neighbor Billy Stevens to try my gun. He had 4 in a small hole he waited for a wind change and shot the fifth.. I still have the target .068 In the match I had the second small and the third biggest. The shoot was named the Winds of Manatee for a reason. I found out. Larry

 

[Tim Singleton]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

Tim I would like to see a target done with 2 shots .but a aim and bullet impact +++. Aiming at a +with the cross hairs. The impact of the two bullets will show the impact change to the aim. Your target does it for me but some will miss what your target tells. Using a tuner I call it a round square. Very small changes from the point of aim. I find powder changes relates more to vertical. Bench rest shooting is different then long range .
Your bore is always clean the bullets a hand made and good shooters read the changing condition. That art wins more matches then a good tuned bullet.
I shot 2 nbrsa matches at manatee . The gun was tuned where I could shoot in the low .100 in good conditions. Late Friday afternoon I ask my camping neighbor Billy Stevens to try my gun. He had 4 in a small hole he waited for a wind change and shot the fifth.. I still have the target .068 In the match I had the second small and the third biggest. The shoot was named the Winds of Manatee for a reason. I found out. Larry

Billy is definitely one of the best. I still think I can squeeze that last one in. Wish it in. Can't put on the brakes and wait for my condition to come back. But I'm slowly making progress at it.

 

[savagedasher]

I sure would hate for someone like myself a couple years ago. To read this and avoid finding Jam and working seating depth from there for fear of over pressure.
Working light loads and moving up in powder in conjunction with seating depth change is the common method used by the top short range benchrest shooters in the world.
Especially when the OP is attempting to tune a 6br not some PO wildcat or heavy magnum hunting rifle

Finding the Jam length with a particular bullet and neck tension. The point at which the bullet is just pushed back into the case is the Jam for that combination.
Loadi a light then medium then hotter powder charge at that loaded length shooting 3 shot groups. Then repeating while moving the bullet deeper into the case each time by .003 until you see on paper what that barrel likes is the method many of the best in the world find a seating depth
Seating depth changes,down the sheet. loads increasing across the sheet
This barrel shot well from a light to hot load at .010 off Jam giving the widest tune of the test

By no means was I smart enough to come up with this method it was taught to me

Tim I would like to see a target done with 2 shots .but a aim and bullet impact +++. Aiming at a +with the cross hairs. The impact of the two bullets will show the impact change to the aim. Your target does it for me but some will miss what your target tells. Using a tuner I call it a round square. Very small changes from the point of aim. I find powder changes relates more to vertical. Bench rest shooting is different then long range .
Your bore is always clean the bullets a hand made and good shooters read the changing condition. That art wins more matches then a good tuned bullet.
I shot 2 nbrsa matches at manatee . The gun was tuned where I could shoot in the low .100 in good conditions. Late Friday afternoon I ask my camping neighbor Billy Stevens to try my gun. He had 4 in a small hole he waited for a wind change and shot the fifth.. I still have the target .068 In the match I had the second small and the third biggest. The shoot was named the Winds of Manatee for a reason. I found out. Larry

Billy is definitely one of the best. I still think I can squeeze that last one in. Wish it in. Can't put on the brakes and wait for my condition to come back. But I'm slowly making progress at it.

What is funny My 11 year old Grand Son Set our first 300 yd dirty bid record small group. Last week we shot IBS targets at 1000 yds he had the small One 10 shot target and small total both target group. He shot when the sight was right.. So much for playing the wind and mirage . Larry

 

[ELR LVR]

I only found long high number Tangent Ogive bullets benefit from Jam.
Ogive Radius is expressed in number of calibers of the bullet used to represent the curve of the front taper.
So a high number is less steep, a more sharper sleeker bullet
, As opposed to a more blunt Secant type low number ogive
Within High Ogive Radius such as Sierra SMK and Berger VLD's...
......The taper is so gradual it almost matches the 1.5 degree angle of the Leade
So lets say we call it .060" jam
Well it is not like jamming it into a flat surface
if we see .060" mark engraved onto the bullet this may actually be less of a jam effect.
it is more like sliding it into a taper that matches the taper of the bullet's ogive.
It is likely the longer bullets benefit more by lining them up into the freebore and starting them off straighter to begin with than shorter bullets to help them stabilize
A shorter bullet does not need as much help to stabilize since the shorter we go the closer we get to a round object
and a round object like a cap and ball does not need to be stabilized to prevent a tip from nodding/nutating or even tumbling, a tumbling ball is simply a spinning ball and has no effect on its aerodynamics, as far as its center of pressure is concerned.
However a tumbling long bullet or even a nodding bullet has more air resistance hitting its side every time it nods up or nods down effectively lowering BC when this happens. and creates vertical stringing.
A round ball can spin and still be stable on its trajectory course
So the longer the projectile the more help we can get getting it started off stable and remaining stable throughout its flight the better.
Jamming a bullet with a more blunt Ogive is more like jamming it into a wall which is why I believe it may build pressure too quickly or create pressure spikes off the bat or even create unwanted barrel harmonics from jamming it.