Stupid question please clarify

[londonhunter]

I shoot almost exclusively vld in 6 and 6.5

Up till now I load just touching or 0.002 behind the land

My question is simple

What does one mean when you jam into the land

I have never done that

Mine is a single shot break open rifle so extraction is never a problem

Surely if I load an oal longer than what I measured when the

action is closed the bullet will be pushed back to the chamber oal length and no longer

so what does one mean when loading +oal length ?

 

[mc223]

What does one mean when you jam into the land

Just that the projectile is at a depth that has engaged the rifling. Or past the start of the lands.

Adequate neck tension is required to jam, and in some situations removal of the cartridge with the bullet still attached is a job for a squib rod.

 

[MarkS]

londonhunter,

Just touching can cause problems, then one bullets touches and then next does not touch. I like to be into the land for VLD's 0.010" to 0.020" The bullet will need more grip to be held in place, most of the time 0.020" will not push the bullet back. I shoot most everything this way. Or I like to be out of the lands 0.005" or better. Be into to lands or out, not just touching.

Mark Schronce

 

[2506]

They now have found that the Berger VLDs will shoot waaaay of the lands just as good as jammed. You might try a ladder test of ten thousands off going all the way back to as much as 80 thousands or so off the lands.

 

[jo191145]

With a break open action loading into the lands may be problematic.
Just guessing as I don't have one..... might not be able to close the action too well. I'm sure you could get away with a little jam, just not much.

Depending on the shape of the ogive and neck tension a good bolt action can drive a bullet pretty far into the rifling without setting it back.

The definition of "jam" can vary depending who you ask.
Old school Benchresters consider jam the point when a specific bullet with specific tension begins to set back in the case.

Folks (like me) who use a Hornady COL tool can find "just touching" the rifling with ease. Any thing past that we consider jam.

 

[artbosco]

What does one mean when you jam into the land?

"JAM" can have a different meaning for different shooters. Essentially it's a starting point. Here's a sample:

Call me "old school" but to me any time you are are using the term, "Jam" means bolt closure is seating the bullet by .XXX".

For seating of say 0.020" into the lands, it is just that: seating "into the lands" (ITL) and is not the jam seating.

So if you tell me you are seating your bullets at ITL=.015" I understand you to mean they are engraving the lands by .015".

If you say your at Jam=.015" I understand you to mean the “bolt-closer” is jam-seating the bullet the last .015".

If you say your OTL=.015" I understand you to mean your "off the lands" by .015" with no engraving. ... Donovan Moran
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I like what Donavan said. "Jam" is a relative term. Saying ".010 into the lands" seems to be a more accurate description as to what is happening.

In 100-200 yard Benchrest, many of us have found that moving a bullet into the lands, at what first glance would seem like a ridiculous amount, is where many bullets, especially the "double radius" variety, like to shoot.

For instance, I tell shooters that, with the combination I shoot, I "make the marks appear twice as long as they are wide". I really do not know how far into the lands I actually move the bullet to achieve this ... I never measured it. I can feel the bullet lightly "crunch" as the bolt closes.

It is one of the strange quirks that appear when using [Vihtavuori N-133] 133 with this particular style of bullet. ... Jackie Schmidt
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Before one can tune a rifle, there must be a starting point. Many use the "JAM" length as a reference to start loading development.

By "JAM" I mean the maximum length that can be obtained ... without the lands pushing the bullet deeper into the case.

Once this is determined, one can tune by moving the bullet only one direction ... deeper into the case. I, like many, have found that many bullets shoot best when seated .008" or .010" off the jam.

After determining a starting point, let the conditions and the results on the targets dictate what tuning is needed.

Joe Krupa, Precision Shooting, August 2008, page 51, under: Where to Start.
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Jam
One of the things many of us have discovered with the current crop of double radius bullets, when using 133, is that they like to be jammed to the point that you can actually feel the bullet crunch into the lands when you close the bolt.

However, shooters who use these bullets, especially the Bruno BoatTail, with 8208, find that just off the lands to just touching works best.

With a standard .237 4-groove Krieger and 133, I jam the bullets to where the [marks appear to be about twice as long as they are wide.]

These seem tight, but remember, the portion of the bullet that contacts the lands is just about the same shape as the 1.5 degree lead. It really isn't 'tight' in the sense that the bullet is getting compressed more, the marks just sort of skim along the ogive.

Other shooters use different methods with these bullets and 133, but this is where the best agging capability seems to be. ... Jackie Schmidt

P.S. If you move down this page you'll see what a "double radius" bullet, referred to above, looks like: http://precisionballisticsllc.com/aboutus.aspx

 

[BBTC48]

Seeing a rifling mark that can be judged as twice as long as it is wide means it was extracted to be examined. Has it ever been marked to see if upon good contact with the rifling, is there any rotation of the bullet inside the neck to any degree, say if it was soft seated (low neck tension). ?? Could that even happen. ?? It would seem to me that if there is a condition present whereby a bullet remaining in the throat when trying to extract the cartridge, you know, the kind where the powder spills out everywhere. That when the bolt handle is rotated closed, there could be a sticking of the bullet independant of the bolt / brass rotation and would cause greatly varying OALs when fired. ?? Just sayin`....???

 

[BBTC48]

Here's a PS...the rub here is stating it's a single shot, presumably an Encore or other. As such, the headspace is of prime concern since it is set by the amount of sizing done to make the brass just fit perfectly flush with the end of the barrel. The gap between the barrel and frame determines the headspace. This needs to be known. If (as in my case) this gap is .0015" then with a flush fit my headspace is just that,...0015". If you seat your bullet out to jam, you have lost ALL your headspace and will be creating undue pressures. Bad JUJU ! That's if the action will even close properly and lock up properly. Might be prudent to reconsider this jamming stuff with this particular weapon. All of my T/C singles seem to enjoy a .005-.008 thousands jump.
Good luck
Bill

 

[londonhunter]

Fantastic and thank you for all your precious opinion and experience
Yes my rifle is like the encore
I will now measure the head space first before I try jamming
It has been grouping well up till now shooting 0.005 off the measured OAL length using a Stoney point gauge
I know there is more to come hence I asked the questions
I have some Bench rest and f class friends in Canada and they all suggest jamming but they don't shoot a break open single shot rifle
I have other custom action bolt gun
I will now venture into jamming with the above advice
thank you again

 

[BoydAllen]

IMO the correct use of the word jam (which is widely misused) is the specific length that a bullet will be pushed back to, with the neck tension that is being used to actually shoot the round. It is the maximum that a bullet can be seated to and NOT be pushed back as it is chambered. Different barrels, neck tensions, whether or not a bullet is coated, etc. all make a difference in the amount that a bullet may be seated into the rifling. Once a bullet has been seated long and chambered to push it back, that length is recorded, along with the seater stem plus cap measurement of the arbor press type (Wilson type) seating die, and they are the used as a reference for all seating depth measurements, representing the maximum that can be achieved with that set of conditions.

When you read that someone is seating their bullet .003 off of jam, the mean that they are seating to a length that is .003 shorter than the measurement that I have described above.

More recently, instead of saying that they are seating a certain number of thousandths longer than the point where the bullet just makes contact with the rifling, as in .005 longer than touch or into the rifling, reloaders have taken to writing that they are seating so that the bullet is "jammed .005". I think that this is not the correct usage of the term.

My reference in all of this is what I have read, over many years, in old issues of Precision Shooting Magazine, going back to the days when the entire magazine was printed without color, and its subject material was more narrowly focused on Benchrest, and conversations with knowledgeable competitors, with long experience. I would also like you to consider that when Benchrest shooters speak of seating a certain number of thousandths off, or shorter than jam the definition that I have given you is the only one that would make sense.

As to the question of whether seating your bullets longer than the point where they touch the rifling will be advantageous for a particular application, only testing will tell. I would suggest that you remember that seating bullets to touch or longer will raise the pressure produced, and so you should drop back with you powder charges and do a work up at the new seating depth. Also, trying a new seating depth, primer, or neck tension, without doing a little exploring as to what powder charge may give about the same velocity as the load that has previously given best accuracy is a common error, given that there is some thought that accuracy is related to velocity.

 

[BBTC48]

Even if you are not dealing with a T/C, whether it's a handy rifle or whatever, Mike Bellm's website will explain quite explicitly just what you need to know about break actions with relation to headspace and chambers for the safe (and accurate) operation of these type weapons. it would be to your benefit to give his stuff a long thorough read so we don't have any problems with a fellow shooter. All my experience with T/C singles will not even let you close the action properly if your seated too long or not sized down correctly. A .005" long seating will make you force (SLAM) the gun shut to get it to lock-up and that's just not a good condition. This is not at all like the world of bolt guns so more knowledge will help you to make good decision. Please, safety first. Good luck.
Bill