Neck tension

Tack-243

Tack-243

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So I loaded up some Berger 108's yesterday with 31.2 grs of reloader 15 with neck tension of .269 in a .272 no turn chamber. I have 1.883 to the lands so I seated the bullet at 1.896 for a .013 jam....this was a load I used to produce a .093 group last December. I did a test load into the chamber and remeasured the seating depth and found it to be 1.880 so to me thats only a .003 jam into the lands....WTF. HOW the heck do people get this so called .015 jam etc, is .003 neck tension not enough to hold a bullet in the neck. CONFUSED :confused::confused::confused:
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Not bad grouping over all but still wonder why the 108s are being pushed deeper into the neck.

Cheers

Bucky
 
You have a long throat!

Anyway, one of the problems is the method you may be using to measure your lands. When you use tools such as the sinclair seating depth tool, they work on the base of a bullet resting against the lands.

If your throat is beginning to wear, the prominence of the lands begins to diminish, and as such, the point of first land contact can be very difficult to accurately determine. Even a slight amount of forward pressure seats the bullets significantly deeper because the lands are closer to parallel with the bullet ogive

Having said that, the 108 is NOT a seating depth sensitive bullet. If you are shooting at short range, I would find a powder node then work on seating depth by simply starting at an arbitrary distance and working forward. The best results with these bullets seem to be from jumping them.

Read Rishu_pepper's post. BERGER 105 VLD hunting match!
 
to establish the 'zero' or 'just touching' point:
-Remove firing pin. assy from bolt.
-Full length size a case that's been fired in your chamber. If you are using a bushing die, use a bushing that's .003-.004 under loaded round measures. You want a good amount of neck tension for this process.
-Seat the bullet 'way long.
-Polish the bullet with some 0000 steel wool.
-Make sure the chamber/barrel are clean and dry. Lube the locking lugs.
-Chamber your dummy round. It will close hard, as the long seated bullet meets the rifling.
-Open the bolt and remove the round. If the bullet stays in the bore, just tap it out with a cleaning rod or wooden dowel.
-Examine the bullet and you'll see the marks from the rifling. If the bullet stayed in the bore, just resize the case, reseat it and re-polish with 0000.
-Seat the bullet deeper by .010 and repeat. You'll see the marks starting to fade as you move the bullet further into the neck each time you change the seating depth. When the marks start to get noticeably lighter, change the seating depth change to .005, as you're getting closer to 'zero'.
-When the marks just disappear, you're at the 'zero' or 'just touching' point for that bullet.

Record the seating stem length or base-to-ogive dimension and record that. Repeat for each bullet you're going to use.


swiped from another forum, this is the process I use.
Trevor
 
I measure neck tension by first measuring the thickness of the neck. Say it is 12thou.

times 2 plus bullet diameter (243") and the loaded rd should be 267" with NO neck tension.

to get 3 thou of neck tension, you need to use a 4 thou bushing smaller then the NO neck tension diameter. In this example 267 - 4 = 263. you need to account for brass spring back which is usually 1 thou but may be more depending on the springiness of the alloy in the neck.

To measure spring back, just measure the interior diameter of the neck after sizing. 243 - interior case neck diameter yields neck tension in thou's of an inch.

If your necks are 13thou thick, you have essentially NO neck tension at 269.

At 12 thou, the bushing shouldn't even touch the brass.

At 14 thou, you have about 1 thou neck tension (remember 1 thou spring back) and VERY little clearance in the chamber.

15 thou, 3 thou which is high and that is pretty thick a neck for match ammo. Wouldn't chamber anyways

Personally, I have found 1.5 to 2 thou plenty for match shooting and even functions fine from a mag. 3 to 4 thou is pretty high and typical of standard FL sizers - great for inducing runout too.

The low neck tension explains why the bullet is being seated back into the case upon chambering.

although it works for many shooters, I don't tune using bullet seating depth and never jam because it adds another variable to my loading.

Remember that as you shoot that brass, the neck will work harden changing its elasticity and springback. Neck tension then changes

Hope this helps.

Jerry

PS I use jiffy marker around the bullet which will rub off when it contacts the lands. Very easy to see and you can get contact down to the last 1 or 2 lands
 
That is a HOT load.

Have fun buying brass every 2 reloads. ;)

AS far as finding your lands, buff up a loaded bullet with steel wool and chamber it, your marks for the lands should show up shiny in the light.

Works 100% of the time 99/100. :D
 
I have a long neck sounds like something different to me......anyway what is the length of your bullets to the lands if you don;t mind me asking Ian.

THANKS FOR ALL THE INFO,and help.

I have not measured the case neck multiple times throughout the process so as for Jerry's comments on spring back etc that is probably the answer. May need smaller bushings or do some annealing.

Good comments on the 3025 fps of my 108s, I only had a 1/2 lb on Reloader 15 in the closet so I loaded up 10 rounds for testing, I will switch to Varget and produce a slower load in the future.

Cheers

BuckyR:d:
 
Annealing is an area I am trying to figure out. I think it is really important to keep neck ductility constant through the life of the brass especially since match brass can be fired so many times.

I would suspect a smaller bushing is what you need. Nothing too radical like maybe 2 thou smaller (measure your brass). we don't need huge amounts of neck tension for match shooting.

With pressures like you are running, tuning can be a royal pain and you are well into proof pressure loading which is very hard on your action.

Most are running their 105/108's in the 2800 to 2900fps range. Reliable, predictable and ACCURATE. Still an elevated pressure load but nothing modern stuff can't handle.

when you EXCEED a 243 with 2/3's the powder, you gotta wonder how hot you are running the ammo?

Jerry
 
Hi Bucky,

My barrels are all slightly different, but they range from 1.690 to 1.720 to the lands with Berger 105's. I will measure with a 108 later today to see how it compares, but yeah, your throat sounds long. How many rounds down the pipe? I also agree with Jerry... throttle back. You are going too fast. Try getting down to 2875-2925.

I am a devoted fan of annealing, and I have perfected a technique using two propane torches and I approach the neck from 4 and 8 o'clock. I hand hold the torches and simply apply heat until the case looks exactly like a new 6BR case. (I have a glass-topped patio table and just set them up on the table and heat the necks.) I have gotten to the point where I can recognize the optimal amount of color change on the neck, but it has taken a bit of practice. I have also discovered it takes ALOT to over heat the neck, so I am less worried, having done lots of experimentation.

The results are friggen amazing, and I have been able to restore hundreds of work-hardened cases that I had quite using. I anneal before each reload now.
 
Obtunded said:
Hi Bucky,

My barrels are all slightly different, but they range from 1.690 to 1.720 to the lands with Berger 105's. I will measure with a 108 later today to see how it compares, but yeah, your throat sounds long. How many rounds down the pipe? I also agree with Jerry... throttle back. You are going too fast. Try getting down to 2875-2925.

I am a devoted fan of annealing, and I have perfected a technique using two propane torches and I approach the neck from 4 and 8 o'clock. I hand hold the torches and simply apply heat until the case looks exactly like a new 6BR case. (I have a glass-topped patio table and just set them up on the table and heat the necks.) I have gotten to the point where I can recognize the optimal amount of color change on the neck, but it has taken a bit of practice. I have also discovered it takes ALOT to over heat the neck, so I am less worried, having done lots of experimentation.

The results are friggen amazing, and I have been able to restore hundreds of work-hardened cases that I had quite using. I anneal before each reload now.
Click to expand...



Ian I'm guessing around 800 rounds through the gun at the moment and am using the bullet inside the dremmel cut neck procedure to measure were my lands are, seems to be quite tight and need to pull the bullet out with pliers after I'm finished.(maybe too tight)
I have done extensive annealing with my 243 brass and it seems to be successful so when I've finished shooting the 196 rounds I have just loaded I will anneal the 6br brass as well.

CHEERS
Bucky
 
Hi Bucky,

If the bullet is tight in the dummy case, it will seat the bullet too tight in the lands and give you an artifically long measurement. The throat should be in good shape, but those loads you've been shooting ARE hot. You should be good for at least another 1000 rounds before setting back.

I use a fired cae and simply squeeze the neck slightly out of round and chamber the bulle that way. If the bullet requires force, or you need tools to remove it, it is way too tight and will give a false measurement.
 
Obtunded said:
Hi Bucky,

If the bullet is tight in the dummy case, it will seat the bullet too tight in the lands and give you an artificially long measurement. The throat should be in good shape, but those loads you've been shooting ARE hot. You should be good for at least another 1000 rounds before setting back.

I use a fired cae and simply squeeze the neck slightly out of round and chamber the bulle that way. If the bullet requires force, or you need tools to remove it, it is way too tight and will give a false measurement.
Click to expand...

Thanks Ian I will go back to the drawing board and do some checking, as far as the hot loads I have only put 20 rounds through the gun so I hope that is not the problem.
Cheers
Bucky

GREAT INPUT FOLKS THANKS AGAIN.
 
Bucky, you do not necessarily need to switch to Varget for slower laods, back down your RL15 load to 2950 or 2850fps. 3025 is pretty damned fast for the BR.

BTW I am using a .267 bushing with (turned) .013 neck thickness brass for a .269 loaded round.
 
CyaN1de said:
Bucky, you do not necessarily need to switch to Varget for slower laods, back down your REL load to 2950 or 2850fps. 3025 is pretty damned fast for the BR.

BTW I am using a .267 bushing with (turned) .013 neck thickness brass for a .269 loaded round.
Click to expand...

I would agree there Richard, however I only have 1/2 LB OF Rel oared 15 and 14 lbs of Varget so thats the only reason I will be switching.
I'm going to check my setup again and figure out what the heck is going on, I will be sad if I WAISTED 800 rounds because I was jamming my bullets too much but even being close to 58 I'm still learning so theres hope for me yet.

Cheers
Bucky
 
As a general rule (not a hard and set rule) BT's like to be jumped and VLD's like to be jammed.

That being said, I used to jam my 107 BT's in my Smith barrel and they shot really well, that is until the throat eroded and the bullets started to jump, then it started shooting even better. (I was not aware that you had to chase that lands at this point in time.)
 
CyaN1de said:
As a general rule (not a hard and set rule) BT's like to be jumped and VLD's like to be jammed.

That being said, I used to jam my 107 BT's in my Smith barrel and they shot really well, that is until the throat eroded and the bullets started to jump, then it started shooting even better. (I was not aware that you had to chase that lands at this point in time.)
Click to expand...

So here is what I found.

Well #### head here found on a new lapua 6br case if you cut two slots in the neck and stuff a bullet in that it was quite tight down were the case turns from neck to shoulder so needless to say I was getting a false reading at 1.880. I took a drill bit and reamed out the neck so the bullet would slide in and out with very little preasure........well now I find my length to the lands to be 1.740 as close as I can see. I will test some loads on the lands, .010 off the lands and .030 off the lands and see what happens. I'm surprised that I actually had a .093 inch group with the 108's the first time I tried them.
Off we go again.
Bucky
 
Tack-243 said:
So here is what I found.

Well #### head here found on a new lapua 6br case if you cut two slots in the neck and stuff a bullet in that it was quite tight down were the case turns from neck to shoulder so needless to say I was getting a false reading at 1.880. I took a drill bit and reamed out the neck so the bullet would slide in and out with very little preasure........well now I find my length to the lands to be 1.740 as close as I can see. I will test some loads on the lands, .010 off the lands and .030 off the lands and see what happens. I'm surprised that I actually had a .093 inch group with the 108's the first time I tried them.
Off we go again.
Bucky
Click to expand...

Wrong yet again I think...

Took some loads out yesterday starting at what I thought was on the lands 1.740 to be exact. Set up 5 at 1.740 ,,,5 at 1.730 and 5 at 1.720,

the first group where around 2860 fps the second where around 2790 fps and the last where about 854 mph...my crony switched to mph.
They all grouped around an amazing 1.6 inches at 100yds :(:(:(:confused:

So back to the bench and did the cleaning rod down the barrel calibration method.
I'm now at 1.838 to the lands closer to my original seating depth ( go figure)
so I will test some more and see wtf is going on. Stupid is what stupid dose.

Cheers
Bucky
 
Bucky,
Take a regular case (not cut neck) and seat a bullet @ 1.850. Polish the bullet with a piece of fine steel wool or a fine scotchbrite pad and chamber it. If you see land marks on the bullet turn the seater stem in re-seat, re-polish and chamber. Keep doing this until you see that it leaves the tiniest of marks on the bullet. You will now have a dummy round at your "at the lands" measurement.
 
CyaN1de said:
Bucky,
Take a regular case (not cut neck) and seat a bullet @ 1.850. Polish the bullet with a piece of fine steel wool or a fine scotchbrite pad and chamber it. If you see land marks on the bullet turn the seater stem in re-seat, re-polish and chamber. Keep doing this until you see that it leaves the tiniest of marks on the bullet. You will now have a dummy round at your "at the lands" measurement.
Click to expand...

Thanks for the help Richard, must be blined ...can't see any marks for the life of me.
Cheers
BuckyR:d:
 
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