if you shoot "jammed" loads,

[762plinker]

Kinda sensitive, are we?

i asked what i thought was a simple question about neck tension when jamming,
ONE person posted a reply
i test all the time
to be clear looking for some basic info on neck tension when shooting JAM.

 

[RegionRat]

to be clear looking for some basic info on neck tension when shooting JAM.

The answers are not basic because "jam" means different things to different folks, just as neck tension numbers don't translate to seating force between different folks.

Try your current prep process first. Again with dummy rounds not live ones.
Then, try soft seating which means much lower seating force such that the bullet can slip.

In both contexts, you will want to play with levels of jam based on your experiments with loading dummy rounds first. Then live testing can follow with less drama.

 

[1shot]

I've had more luck than not while jamming. Since it's difficult to quantify how much tension you need I'll just say this. Use a bushing small enough to allow you to engage the rifling to the point where the marks are at least square before the bullet will move in the neck. I'd use a little more just to be sure. Once you have the bullets seated to that point and you start testing seating depth, you have really only one direction to work in...out from the lands. Depending on cartridge and bullet, I'd move no more than .003 at a time.

Part of the beauty of this approach is the simplicity, in that you can only go one direction. The rest is that possibly near 95% of the time, my best seating depth is between there and .010 off of touch. Several thou difference there but most often, it'll be between there and just touching, to narrow it down a bit more.

If nothing else, being jammed lessens your dependency on neck tension being identical because the neck will open up before the bullet can move. As with anything...test...test and test some more. Different bullet styles often prefer more or less jam, etc. Only one way to learn for sure and the internet is chock full of good intentions and little testing. Don't be that guy.

^^^^^^^^^^^^^^^^^^^^^^^^
I've been doing it this way for years. you start with a worst case scenario in terms of pressure, then start moving the bullets deeper into the case.

Lloyd

 

[boltfluter]

Most of my rifles, hunting rifles included, shoot best between .010 to .020 into the rifling with .002 neck tension. One outlier .22BR absolutely drives tacks at .060 in . All shooting moly coated bullets. Nothing I own, accuracy wise, can touch being into the rifling. But, you still need a little testing. Good luck and keep us posted!
Paul

 

[jimmymac]

The terminology in most of these threads is what leads to confusion for people, especially newbies. The term "jam" means different things to different people, while the term "touch" seems to be more universally accepted with a singular definition.

My definition of jam is exactly as the name implies and is in line with how @gunsandgunsmithing describes it. Jam has a singular meaning just like touch has a singular meaning. At any given neck tension, the bullet is jammed and cannot advance further. There are no degrees of jam. It is either jammed or it isn't. "Jam" is nothing more than a reference point opposite of "touch", which is the other reference point. I record them both for each bullet I use and go on from there fully knowing where I'm at for any given CBTO length.

I use both terms and they both have very specific definitions with no gray areas. I didn't come up with this. SR BR shooters have been doing it this way for years. It certainly simplifies life.

 

[AlNyhus]

I'd encourage the OP to work with what's more correctly called a 'jam seat'.

Find the 'T.P.' (touch point), seat the bullet longer than that and let the act of closing the bolt finish seating the bullet. Either the stripped bolt method or Mike Ezell's clever seating depth checker should be used to determine the 'T.P' rather than the Hornady modified case gizmo.

I start with .030 of 'jam seat' and a a neck sized .004 under what a loaded round measures regardless of the chambering. Assuming his powder charge is optimized already (big assumption), tweak the 'jam seat' first and the neck tension at the end.

On a new barrel or bullet, I tune with powder charge first, then 'jam seat' and finally neck tension.

It always works. -Al

 

[jimmymac]

Guys,
762plinker is an accomplished 600 and 1000 yard Benchrest shooter with 2 national titles.
He knows how to define “jam”

Sorry for my ignorance. If that is the case, I’m surprised by the question, and I mean that respectfully. If he doesn’t have use for my opinion, then maybe it will help someone else out there that has less experience than him. This concept seems ambiguous to some people on this forum.

 

[DaveTooley]

how much neck tension are you using ?
i am a jump shooter with little luck in jam.
i have a cartridge i may try jam based on some comments. i use lite neck tension, what do i need to do if g0ing to a jam load.
( guessing between .005 and .015 jam)
thanks

Seems like a pretty simple question to me.

Personally I err on the side of more neck tension. Less risk that way. If you have ever seated bullets where the body goes below the neck shoulder junction you know they act like an expander mandrel. So you can only get just so much tension.

 

[Fuj]

I can't be the only one here but I was testing some non VLD
7mm's with a light ,001 tension, loaded long, and closing the
bolt gave the final seating. Shot great with good SD's. Now
doing the same test with VLD's. the groups were like buckshot.
Other then that, I try to keep my current stuff at .003 and above
neck/shoulder junction and .006 in.

 

[Straightshooter1]

I'd encourage the OP to work with what's more correctly called a 'jam seat'.

Find the 'T.P.' (touch point), seat the bullet longer than that and let the act of closing the bolt finish seating the bullet. Either the stripped bolt method or Mike Ezell's clever seating depth checker should be used to determine the 'T.P' rather than the Hornady modified case gizmo.

I start with .030 of 'jam seat' and a a neck sized .004 under what a loaded round measures regardless of the chambering. Assuming his powder charge is optimized already (big assumption), tweak the 'jam seat' first and the neck tension at the end.

On a new barrel or bullet, I tune with powder charge first, then 'jam seat' and finally neck tension.

It always works. -Al

Hmmmm??? Seems to me it should be noted that ".004 under what a loaded round measures" is going to have very different self seating results with necks of different thicknesses. Like necks turned to .010" vs necks that are .014 in thickness . . . as well as the difference in caliber ID of the neck. A 6mm with a neck thickness of .010" vs a 7mm with a neck thickness of .010 is gong to have a very different self seating jam result.

I only point this out for the OP or any other newbie to jam seating (like myself) to take into consideration.

 

[762plinker]

Seems like a pretty simple question to me.

Personally I err on the side of more neck tension. Less risk that way. If you have ever seated bullets where the body goes below the neck shoulder junction you know they act like an expander mandrel. So you can only get just so much tension.

thanks dave,
all of my competition chambers/reamers put the bullet above the neck/shoulder junction..and you know why.

 

[Link]

I jam until I get the lil square land marks on the Ogive. Then measure from the ogive to head. I call that measurement square jam. Then work in and out of the lands. KISS for me.

 

[762plinker]

so IN simple english and very different to some comments, JAM is any amount forward of TOUCH.
.002 IN,.005 IN AND .010 IN are all DIFFERENT amounts of jam INSPITE OF COMMENTS made here.
i want to test in .001 to .015 jam. and was asking about guidence on what increase in neck tension
( either from bushing or mandrel size) was used by others

 

[RegionRat]

What ends up happening to some folks the first times they experiment with higher jam values, is that if they run light neck tension some of their bullets slip deeper into the neck, and some end up getting a bullet stuck.

As long as you have a fairly sturdy round to begin with, you will get out of the gates without drama.

Not everyone knows their actual seating force, so they assume their neck prep produces adequate grip on the bullet, but it really depends on your current prep process.

Some guys start down this road with moly coated bullets and that makes it easy to have a bullet slip or get stuck just due to the friction coefficient.

I don't have strong opinions on how the definition works, but mine is more like yours in that jam is anything longer than a touch using the stripped bolt method, and you can have several fine steps of the amount of jam just based on your hardware and bullet choice.

Eventually, you find yourself putting too much effort into closing the bolt, or, you get to where the bullet can get stuck if you try to unload. I've never needed to go that far. YMMV

 

[jimmymac]

so IN simple english and very different to some comments, JAM is any amount forward of TOUCH.
.002 IN,.005 IN AND .010 IN are all DIFFERENT amounts of jam INSPITE OF COMMENTS made here.
i want to test in .001 to .015 jam. and was asking about guidence on what increase in neck tension
( either from bushing or mandrel size) was used by others

You can consider it however you want, but in my opinion that really isn't the case at all. It is also the same reason why people get confused whenever jam gets discussed. By not figuring out where jam is (i.e., no further forward at a given neck tension), you'll never know what your max CBTO is. Maybe you don't care. I care because I want that reference point in my records to allow me to know what parameters I'm working with.

Choosing a bushing that is about .003 or .004 smaller than your chamber diameter isn't a bad place to start, but I'm sure you already got that out of this thread which is why I originally diverged and started discussing terminology. Good luck to you sir.

 

[gunsandgunsmithing]

so IN simple english and very different to some comments, JAM is any amount forward of TOUCH.
.002 IN,.005 IN AND .010 IN are all DIFFERENT amounts of jam INSPITE OF COMMENTS made here.
i want to test in .001 to .015 jam. and was asking about guidence on what increase in neck tension
( either from bushing or mandrel size) was used by others

Much of the whole subject of touch and jam is based around terminology. I even make a tool for it. Ultimately, we do what works and the terminology only matters on the internet. We're all still talking about into or out of the lands by some amount. How much is the subject of lots of internet threads but hopefully we all do what works best in our rifle as opposed to what we read online. It's just a reference point for just that..discussion. As long as you have a method that gives consistent bto measurements, it doesn't really matter what that number is or how you got there.

Of course neck tension matters as to how far it will allow you to push the bullet into the lands before it moves in the neck. We covered that and I'm sure you understand that well.

 

[762plinker]

so jumping right in
i did plus .005 with the base brass and bushing..no issue
then did .010 the same way .no issue
then jumped down one size in the bushing, and did .015..no issue
so gonna load some up and see what happens

 

[RegionRat]

Good Luck and in for the range report!

ETA: Are you shooting a fresh barrel or one with lots of rounds on it?

 

[AlNyhus]

so jumping right in
i did plus .005 with the base brass and bushing..no issue
then did .010 the same way .no issue
then jumped down one size in the bushing, and did .015..no issue
so gonna load some up and see what happens

What issues did you think you might see?

 

[Dgd6mm]

762, I've been following your thread since you posted it yesterday morning.
Always wanting to learn something.
On your. 005 and your .010 jam I assume your using the same neck tension that your using jumping.
You stated it was lite neck tension.
For the .015 you stated you went down 1sizein bushing.
My question, on all three jams what neck tension are you using?

Thank you
Don Dunlap