jump or jam

[Richard Coody]

just curious how many reading this forum jump or jam their bullets.

just target rifles now. we know if it is a hunting rifle or a repeater that needs mag length ammo jam is not on the agenda.

 

[BoydAllen]

Typically, I seat bullets into the rifling. Not all chamber magazine length combinations dictate jumping. Also when working with friends on custom projects, if they want to seat into the lands and use a magazine I take that into consideration in the design of the reamer.

 

[yotehater]

I like to just kiss the rifling where extraction isn't an issue if I don't fire.

 

[Sniper338]

I jump everything 10-30 thou depending what it likes. never jam though. aint fun when a bullet gets pulled outta the case on extraction because you didnt shoot and powder goes in every hole and orfice in the action and stock and everywhere else.

 

[Mozella]

I like to just kiss the rifling where extraction isn't an issue if I don't fire.

I conduct careful seating depth tests on all my target rifles and select the depth which produces the best performance. Sometimes that's a jam, sometimes it's a little bit of a jump, and sometimes it's a significant jump. The most important thing to realize is that it all depends on many factors and anything I do is unlikely to be the same for your rifle/bullet/powder/primer/caliber/action/barrel combination.

 

[Mulligan]

i shoot everything "IN"
CW

 

[texasbilly]

I shoot both jammed and not. It all depends on the purpose for the load. I begin with the determination of the maximum length for a given bullet to touch the lands. Then I decide if this is a target round, a practice round, or a hunting round. Target rounds tend to be jammed, or close to that, based on experimentation with that bullet and powder combination. Usually these tend to be at target (lower?) velocities, and offer the best ultimate accuracy. Practice rounds are not jammed and usually at the SAAMI recommended OAL for that cartridge. Hunting rounds must be at least short enough to go through the action and magazine, but most often are off the lands by .020-.030" if possible.

 

[Zero333]

Lately I been seating the bullets IN THE LANDS but NOT JAMMED.

In repeater rifles this doesn't feel any different than if the bullet was away from the rifling.
My live rounds that are in the rifling (but not jammed) eject no different than round that have the bullet jumping.

Some of the barrels I load for I can seat the bullet 0.030" into the rifling and not have it jam.

 

[JLT]

Both. Depends on the bullet/load. I let the target make the decision.

 

[Richard Coody]

Both. Depends on the bullet/load. I let the target make the decision.

me too.

i start jammed then back off in .005 increments.

i have found berger VLDs like a jam but i have also found very good accuracy nodes jumping them. some as much as .120+ off the lands.

now the berger hybrid i have found like a little jump. some as little as .005

i don't like to just kiss the lands. that seating depth just won't last. too much trouble chasing the lands. i have had success soft seating like John Whidden but you must have very good control of neck tension. for these i anneal every firing, final neck size with an expander mandrel and seat bullets with my hydro seater. only those with the proper seating effort are used.

 

[seymour fish]

me too.

i start jammed then back off in .005 increments.

i have found berger VLDs like a jam but i have also found very good accuracy nodes jumping them. some as much as .120+ off the lands.

now the berger hybrid i have found like a little jump. some as little as .005

i don't like to just kiss the lands. that seating depth just won't last. too much trouble chasing the lands. i have had success soft seating like John Whidden but you must have very good control of neck tension. for these i anneal every firing, final neck size with an expander mandrel and seat bullets with my hydro seater. only those with the proper seating effort are used.

Tangent 15 thou off, secant/ vld jam, for openers

 

[jimmymac]

me too.



i don't like to just kiss the lands. that seating depth just won't last. too much trouble chasing the lands. i have had success soft seating like John Whidden but you must have very good control of neck tension. for these i anneal every firing, final neck size with an expander mandrel and seat bullets with my hydro seater. only those with the proper seating effort are used.

No more trouble than trying to maintain .005, .008, .010, etc off. It's the same problem.

 

[284winner]

Every barrel wants a different bullet seated differently for the best accuracy is my answer. I tried jumping in several hunting guns and some don't like it. Especially with bergers. I definitely don't like pulling the bullet when extracting so in all my hunting guns, I jump. A hunting rig doesn't typically require nearly the accuracy as a bench gun. Half minute to one minute usually makes hunters pretty happy. You can jump most bullets and achieve that. Amax bullets love to jump and I've never seen one inaccurate that I've jumped sometimes as much as .130. All labeled hunting bullets are very jump tolerant as well. To jump or not to jump is a decision I leave up to my particular gun I'm developing for. It's that simple for me.

 

[Richard Coody]

Every barrel wants a different bullet seated differently for the best accuracy is my answer. I tried jumping in several hunting guns and some don't like it. Especially with bergers. I definitely don't like pulling the bullet when extracting so in all my hunting guns, I jump. A hunting rig doesn't typically require nearly the accuracy as a bench gun. Half minute to one minute usually makes hunters pretty happy. You can jump most bullets and achieve that. Amax bullets love to jump and I've never seen one inaccurate that I've jumped sometimes as much as .130. All labeled hunting bullets are very jump tolerant as well. To jump or not to jump is a decision I leave up to my particular gun I'm developing for. It's that simple for me.

if you read the first post in this thread it is about target rifles. i purposely excluded hunting rifles and repeaters. i don't load either with a jam and expect after one bad experience most would quit doing it too.

 

[284winner]

if you read the first post in this thread it is about target rifles. i purposely excluded hunting rifles and repeaters. i don't load either with a jam and expect after one bad experience most would quit doing it too.

Sorry I missed that part.

 

[500Stroker]

just curious how many reading this forum jump or jam their bullets.

just target rifles now. we know if it is a hunting rifle or a repeater that needs mag length ammo jam is not on the agenda.

What every makes small groups at 600 yards.

 

[longbow]

Lets see pretty simple. five shots of each, 10 thou jam, touching lands,10 thou jump,20 thou jump. Your going to see right there what your gun likes. Then fine tune your load and test three makes of powders. Just takes time shooting, you cant learn that on the forums.

 

[Richard Coody]

now for my point with this thread. just wanted some who shoot jams to pipe up and let those who live in fear of the jam realize it is a pretty common practice with target rifles.

one further question for those with extensive experience shooting jams. Do you or have you experienced an overpressure event when going from jump to jam?

personally my load stays pretty much the same with no pressure signs.

 

[dmoran]

Do you or have you experienced an overpressure event when going from jump to jam?

Chronograph data can answer the extent of pressure variation very well.

For me, its common that I see some variation in pressure/velocity at all increments of seating depth. Going from say .010-OFF to .010-IN typically I won't see much variation, and definitely not an "overpressure". But going from a bigger jump of say .025-OFF to a harder jam like .025-IN, I would expect to see more definite variation in pressure/velocity, but still not an overpressure.

The only times I can attest to experience overpressures came from seating long bullets deeply into a case, and when seating with a hard enough jam that there is resistance in bolt closer. In both scenario's I have seen some dramatic variations.

My 2-Cents
Donovan

 

[seymour fish]

now for my point with this thread. just wanted some who shoot jams to pipe up and let those who live in fear of the jam realize it is a pretty common practice with target rifles.

one further question for those with extensive experience shooting jams. Do you or have you experienced an overpressure event when going from jump to jam?

personally my load stays pretty much the same with no pressure signs.

Richard, I for one do not ever go from jump to Jam, for the reason you list. Wasted time and backtracking to insure safety if you intend to flirt with “in the lands” to jammed. To add fuel, like a square mark, and have not yet had a bullet pull ejecting a live round, with a VLD. Jumping gets all the press, Bergers emphasis on hybrids extreme “jump ability” having perhaps some influence. Fashions change. What works, works. Each to his own, said the old lady when she kissed the cow