Long range load development at 100 yards.

[Erik Cortina]

I think the last two look good. Both groups are horizontal so seating depth should bring them in nicely.

 

[trailrider121]

Thanks Erik.

 

[drjjl]

I've been reading thru this post and really like the idea of this method. Fairly new to reloading, but have done my research and am very thorough. I am a bit confused about the initial seating depth...sorry if it's been answered. Are we jamming the bullet .02" or jumping .02" initially? For example if our jam is 2.00" are we starting out with the OAL of 2.02" or 1.98"? Some of the posts seem to indicate a jam and other see to suggest a jump. Everything else makes perfect sense. Thanks in advance..I really enjoy this forum!

 

[spclark]

Are we jamming the bullet .02" or jumping .02" initially? For example if our jam is 2.00" are we starting out with the OAL of 2.02" or 1.98"?

Doesn't really matter as you have to start somewhere; I typically choose 0.020" off the lands for adjusting load parameters, then move in and out 0.005" incrementally to see if anything changes dramatically. Most of the time that 0.020" is where I keep it.

Keep in mind my shooting preferences are for sling & iron sights off a shooting mat so if you're into benched-gun or F-Class what you settle upon may very well deviate from what works for me.

 

[savageshooter86]

Believe Erik does jam -0.020

That's what I've been doing and it works

 

[spclark]

Believe Erik does jam -0.020

OK so I'm confused by what I see as a contradiction in that statement:

JAM to me means 'forcible contact' or seating bullets to a COAL that puts the ogive onto the lands with some amount of force when chambered.

Putting a – sign before a dimension would to me indicate seating short of that length or OFF the lands.

Assuming a COAL of 2.25" with a dimension of 1.875" as the "just touching" point of ogive to land contact, 1.870" would be 0.005" off the lands while 1.880" would be jammed 0.005", right?

 

[savageshooter86]

JAM I use is point where bullet gets pushed in case when chambering. I find that point where it doesn't move bullet on dummy round(takes a couple times of adjusting coal to find that exact point) and use that as my JAM length. Then I subtract -0.020 from that as my start point for testing

 

[Brians356]

Are we jamming the bullet .02" or jumping .02" initially?

Jumping 0.020".

How would you go the other direction.? "Jam" means literally hard against the lands. To go .020" farther in that direction puts the bullet well into the rifling. If you forced the bolt closed, the bullet would most almost certainly seat deeper into the neck rather than enter the bore.

 

[Brians356]

Believe Erik does jam -0.020

Putting a – sign before a dimension would to me indicate seating short of that length or OFF the lands.

That is correct. In this context the "-" indicates subtract .020" from the cartridge length. I.e. increase bullet jump.

 

[JohnMill]

I preferred Erik's pretty (very) concise explanation of how to establish bullet jam and that is how I'm going to do it from now on. It certainly does work.

John

 

[expiper]

Trailrider,,,,,as all ready stated the last two groups are excellent ,,,,if you are off .020 I wuld load 3-5 longer and touching and 3-5 shorter at .040 off ,,,,If you dont see any improvement stay where you are (and watch for subltle wind changes),,,you would be in a window,,,,as Rodney Dangerfield said in Back to School,,,,"YOU are there"........Roger

 

[drjjl]

Jam is the point where the bullet will not go into the lands any further. Lets call it 3.200"
Jam - .020 = 3.180"

I somehow missed it when I was reading. And yes I did assume that the - was a "minus" sign, but somewhere along the line I read a post that seemed to indicate they were jamming further than that.

Anyway, thanks for helping and answering my question even though Erik already answered it.

 

[drjjl]

I used a Hornady tool to find the lands at 1.800 and loaded at 1.815 when you say change seating depth would you work to like 1.815, 1.812, 1.809, 1.806, 1.803 1.800 1.797, 1.794?

I'm shooting 105 Berger match VLD

That's correct.

This was the post that had me confused, but all clarified now. Thanks a lot guys! Can't wait to try this method. Seems very straight forward.

 

[jsthntn247]

7-08
168 classic hunter
H-4350
44.4, 44.8, 45.2, 45.6, 46, 46.3. Top left to bottom right

 

[/VH]

"That is correct. In this context the "-" indicates subtract .020" from the cartridge length. I.e. increase bullet jump."

As stated by JohnMill; Erik did provide a very concise explanation of establishing jam length.

brians356,

Please consider the possibility of jam length, as established by Erik's method, where the bullet may be jammed more than. 020" into the lands: Seating the bullet .020" deeper into the case will decrease jam but will not increase jump.......on account of it will still be jammed.

 

[Erik Cortina]

There are three points of reference. Jump, in the lands, and jam. The bullet will go in the lands a certain distance before finding jam. You can not jam the bullet any distance, if you can, you haven't found jam yet. When you hear/read "jammed .020 thou", what they mean is they are .020" in the lands.

What I do is find jam and back off .020" and start working up a load.

 

[/VH]

I stand corrected by the technical definition of jammed, which I agree with. What I should have stated is:
Please consider the possibility of jam length, as established by Erik's method, where the bullet may be more than. 020" into the lands: Seating the bullet .020" deeper into the case will decrease the amount the bullet is into the lands but will not increase jump.......on account of it will still be into the lands, no jump involved.

 

[spclark]

There are three points of reference. Jump, in the lands, and jam.

Yep, and what frequently gets left out is how neck tension affects all three.

"Soft-seat" (low NT) and the effects from 'on' or 'into' the lands in minimal as the bullet likely gets pushed deeper into the case anyway.

As NT increases the pressure curve changes as the bullet moves forward; just to what degree will vary dependent on how much NT you decide is optimal.

 

[jweb308]

Below is a test I ran today with Berger 155.5 FB. This is my first time firing a 155 class bullet.

Stiller Tac30 w/ 30 inch Hart 12 twist.
LC LR Brass/Wolf LR Primer/IMR 8208 XBR.
Test was from 42.8g - 44.2g in .2g steps.

Weather Info
45 Degrees F/70.4% RH/30.74 BP/-600' DA

There were no signs of pressure during the test. I felt the recoil pulse become slightly sharper at the 43.6g mark. Based on the attached photo I am inclined to continue the test several more steps up the charge scale, but I would like to see what the thread has say.

Note: I did not chronograph today as I use a Magneto and prefer to see the grouping first before I begin to worry about velocity.

Stay safe,
WEB

 

[Erik Cortina]

Below is a test I ran today with Berger 155.5 FB. This is my first time firing a 155 class bullet.

Stiller Tac30 w/ 30 inch Hart 12 twist.
LC LR Brass/Wolf LR Primer/IMR 8208 XBR.
Test was from 42.8g - 44.2g in .2g steps.

Weather Info
45 Degrees F/70.4% RH/30.74 BP/-600' DA

There were no signs of pressure during the test. I felt the recoil pulse become slightly sharper at the 43.6g mark. Based on the attached photo I am inclined to continue the test several more steps up the charge scale, but I would like to see what the thread has say.

Note: I did not chronograph today as I use a Magneto and prefer to see the grouping first before I begin to worry about velocity.

Stay safe,
WEB

Looks like a wide node from 43.2 to 43.8