How to check I have a safe level of neck tension

[SGK]

@jr600yd

Ha my head isn't going to explode. My original question was merely to do with safety. I was worried I had loaded ammo for testing with too light tension.

Other than that I'm trying to learn and understand best process ahead of further rifle purchases. Of course I understand that while my current rifles are superb sporters, they're not benchrest rifles. They are, however, easily sub-MOA (and likely sub 0.5 MOA). I like the idea of pushing these to their (and my) limit. So on the one hand I want to explore best practice reloading for target but also be able to load for game. (For big reds or fallow in New Zealand I use the 7mm Rem Mag when hunting open country. Even then I draw the limit at 350 yards. In the bush it's the 308.) Thanks for the guidance on hunting load neck tension.

I suspect benchrest competition isn't my bailiwick but some form of F-class or perhaps even PRS has potential interest. Until then the competition is me. I haven't purchased a dedicated target rifle as I'm undecided on what I would like built. I like most the idea of a highly accurate rifle I can shoot target with and also take into the field, but I recognise that requires compromise or pain lugging it around the hill. (My 7mm RM has a Hardy Rifle Engineering carbon fibre wrapped barrel and carbon fibre stock as a means of trying to thread that needle. Long, extremely stiff barrel yet light on the shoulder.)

 

[SGK]

This is not true at all with bushing(partial neck) sizing. Here, tension amounts only to an area of neck spring back (grip force) against seated bullet bearing. Seating forces created by sizing to excess interference fit, and/or excess friction, contributes nothing to tension.

Partial length size a neck down to produce ~1thou under cal after springback.
Partial length size a neck down to produce ~10thou under cal after springback.
Seat bullets in both, measure seated neck diameters, then pull those bullets, and measure your necks again. They both measure the same, which is ~1thou under loaded diameter.
Sizing down an excess (~10thou under) was negated when you then used a bullet as an expander mandrel(not good by the way). And you end up with ~1thou of springback gripping either bullet either way.

This was what I was trying to say above, but much more eloquently put. Grip force is a finite function governed by the elasticity of the brass in question. Necking down under cal too much doesn't get you anywhere and is in fact disadvantageous. The only question is what amount under cal achieves maximum grip for a given surface area of contact. Does one thou generally cover a lot of bases (range of brass conditions) or only good for newly annealed brass? (and if 1 thou doesn't, does 2 thou - Redding mention 1-2 thou under bullet diameter plus 2x neck wall thickness)

 

[SGK]

Measure the neck diameter before and after seating a bullet. After seating, has the neck expanded .002"

One thou. Metrics/measurements are mentioned above. 0.336 to 0.337". (bullet diameter .308, 2x neck wall approx 29 thou)

too much

Ok

 

[SGK]

I will never use less than 1 thou with jumping bullet.
In your case, what you might see is a mini shoulder on the neck if the bushing does not re-size the entire shoulder (which almost never does). It will help center the case in chamber neck and and gives you room for doughnut.

Ok so things to watch out for. I noticed the Redding bushing neck die wasn't resizing the full neck. I was concerned about this when sizing down ahead of using the neck turning expander mandrel. I didn't want to shave this higher brass overly thin with the turner. So I used a Lee collet neck die to do the resizing ahead of turning. Post turning, I just used the Redding bushing die with a .336" bushing.

 

[Bart B.]

Ok so things to watch out for. I noticed the Redding bushing neck die wasn't resizing the full neck.

Redding says the unsized part of the neck by the case shoulder helps center the case neck in the chamber neck. Even if it's smaller in diameter than the chamber neck.

I disagree, but that's another thread.

 

[jr600yd]

@jr600yd

Ha my head isn't going to explode. My original question was merely to do with safety. I was worried I had loaded ammo for testing with too light tension.

Other than that I'm trying to learn and understand best process ahead of further rifle purchases. Of course I understand that while my current rifles are superb sporters, they're not benchrest rifles. They are, however, easily sub-MOA (and likely sub 0.5 MOA). I like the idea of pushing these to their (and my) limit. So on the one hand I want to explore best practice reloading for target but also be able to load for game. (For big reds or fallow in New Zealand I use the 7mm Rem Mag when hunting open country. Even then I draw the limit at 350 yards. In the bush it's the 308.) Thanks for the guidance on hunting load neck tension.

I suspect benchrest competition isn't my bailiwick but some form of F-class or perhaps even PRS has potential interest. Until then the competition is me. I haven't purchased a dedicated target rifle as I'm undecided on what I would like built. I like most the idea of a highly accurate rifle I can shoot target with and also take into the field, but I recognise that requires compromise or pain lugging it around the hill. (My 7mm RM has a Hardy Rifle Engineering carbon fibre wrapped barrel and carbon fibre stock as a means of trying to thread that needle. Long, extremely stiff barrel yet light on the shoulder.)

Most of today’s factory rifles are capable of .5 to 1 inch groups. This can be improved with reloading or some type of rifle modification like a new stock or bedding. Sounds like your rifles are ready to go. Now for neck tension. Yes if you have .001 tension they are safe to shoot. This is good and bad. Good from an accuracy stand point. Bad depending on how long you loaded the bullet. As stated above you don’t want to chamber a round then unchamber it and leave a bullet in the throat and powder all over the action. Bad JuJu! Next is recoil. You don’t want the bullet seating deeper in the case due to recoil. So if it were me I’d add some neck tension.

 

[dcali]

If the bullets fall out, your tension is too loose. If the bullets shave going in, the tension is too tight.

This is really the only answer you need. If the bullets get knocked around so that they move at all within the case, you need more. I would amend the above to say that shaving is usually a matter of a poor chamfer on the brass rather than too little neck tension, but a tight fit certainly makes it worse. Don't overthink it. .001-.002 of neck tension is usually plenty, depending on application.

 

[Bart B.]

Ha my head isn't going to explode. My original question was merely to do with safety. I was worried I had loaded ammo for testing with too light tension.

I've pushed bullets into sized 30 caliber case necks with only a few ounces of seating force. About the same force to pull them out. Both by gripping them between thumb and index finger. Excellent accuracy, too.

 

[SGK]

Thanks for all the responses and help. You guys are great. I'll carry on.

(At the same time I will keep thinking about my next rifle. Probably 6.5 Creedmoor or 6BR rather than my previous inclination to 6.5x55 Swede which seems uncommon here. I'm still at the proverbial fork in the road looking between F class style stocks, e.g. McMillan, and a good single shot action like a Barnard versus a magazine capable Defiance Deviant Tactical or Surgeon action with a Manner's Tactical or Masterpiece Arms stock. Don't say just get both. I still like the Hardy RE carbon wrapped barrels but that's probably just because I'm a Kiwi. Their moderators are the best I have used. Jewell Trigger. But most of all a good gunsmith who can guide me through all the details and put it all together. Too much to choose from here!)

 

[fguffey]

Neck tension or hold is all about an interference fit. The smaller the hole, the more interference there is, the tighter the fit, the more pressure it will take to get the bullet moving.

Release the bullet: I never wonder how long it takes the neck to expand when releasing the bullet, it is important the neck has enough room to expand. Someone should wonder about the difference in time it tales the neck to expand. It was not that long ago when members did not believe gas passed the bullet before the bullet hit the lands.

F. Guffey

 

[Bart B.]

Someone should wonder about the difference in time it tales the neck to expand. It was not that long ago when members did not believe gas passed the bullet before the bullet hit the lands.

F. Guffey,

When a 30 caliber bullet is held by the case neck such that it takes 10 pounds of force on its base to start pushing it out of the neck, and the bullet is .005" back from the lands:

• What's the psi amount inside the case needed to start moving the bullet?

• Will the case neck fully expand off the bullet before the bullet moves .005" to touch the lands?

 

[mikecr]

Does one thou generally cover a lot of bases (range of brass conditions) or only good for newly annealed brass?

Necks won't spring back more than this, and you should see this yourself with the test I mentioned, so it's all the grip you can get (interference-wise). Any more interference is excess.

 

[rebel]

Release the bullet: I never wonder how long it takes the neck to expand when releasing the bullet, it is important the neck has enough room to expand. Someone should wonder about the difference in time it tales the neck to expand. It was not that long ago when members did not believe gas passed the bullet before the bullet hit the lands.

F. Guffey

Non answer to the OPs question. There is not a tool you have that can measure a thing you are talking about.
One must play with tension, grip or hold - whatever the hell you want to call it - when she tightens up, you are good.

 

[CaptainMal]

Now don't laugh but you can test how much pressure it takes to move that bullet.

Load a case with NO POWDER or even a primer. Prepare the case as you see fit then seat a bullet. Now you are going to ruin that bullet but get a feel for how much it takes to move that bullet. Push it down on a bathroom scale and watch as the pounds go up. When it moves you now have an idea of how hard it it sot move that bullet.

I did multiple tests with 30-30 ammo a number of years ago. Different annealing procedures, neck wall thickness and neck tension. 30 - 60 lbs was the range of pressure I had to push on to get a bullet movement. Flat messed up my hand pushing that hard. Still, it is an idea.

 

[Webster]

Hi

I'm doing my first lot of reloading. I turned the necks of my fire-formed .308 brass rather conservatively with a good amount of "low-side" untrimmed brass visible. I got the turner set to achieve about 0.0146" versus an initial target of 0.0145". My target was calculated from a sample of 50 neck wall thickness measurements so as to shave about 75% of the samples. While I could have shaved more off I decided to stop there. A bushing size of 0.336 was selected/purchased based on my target thickness (0.308 + 2x0.0145 - 0.001 = 0.336).

I was planning to follow Berger's recommendation for getting into the very rough zone for seating depth - loading 6 rounds for each of 90, 50 and 10 off the lands with a conservative powder load (6% below max listed in my Hornady loading manual for Varget and 168gr ELD-M). I just loaded the first six, at the deepest seating.

With a good deal of low side showing I'm now a bit nervous that I won't have enough neck tension. With these first 6 rounds there's obviously a large amount of bearing surface seated and the bullets certainly aren't falling out. But I thought it good sense to check with your experience before I go any further.

Thanks in advance for the guidance

Steve

Take a dummy round with a bullet in the case and push it against the edge of a work bench, then you will know if the bullet has some grip. Need a bullet puller to get the bullet out.

 

[Homerange]

Thanks for all the responses and help. You guys are great. I'll carry on.

(At the same time I will keep thinking about my next rifle. Probably 6.5 Creedmoor or 6BR rather than my previous inclination to 6.5x55 Swede which seems uncommon here. I'm still at the proverbial fork in the road looking between F class style stocks, e.g. McMillan, and a good single shot action like a Barnard versus a magazine capable Defiance Deviant Tactical or Surgeon action with a Manner's Tactical or Masterpiece Arms stock. Don't say just get both. I still like the Hardy RE carbon wrapped barrels but that's probably just because I'm a Kiwi. Their moderators are the best I have used. Jewell Trigger. But most of all a good gunsmith who can guide me through all the details and put it all together. Too much to choose from here!)

The Swede will outperform the 'new' 6.5's all day long if you handload them. They're not popular here as factory loads are low pressure to be safe in the old' 94 Swede actions.
I looked hard at 6.5's too and came to the conclusion as a handloader the Swede would be the way to go for something with some 'reach'.

BTW, SGK are you anywhere close to me in West Auckland ?

About neck tension, a .308 Lee Target model handload set we had years back reamed inside necks so you could press projectiles in by hand. I'm guessing 20-30lbs is all it took and we never had any shift in all the years that they may have bumped around in our gear up on the hills. Uniform tension is all that matters and for hunting purposes not all that much.

 

[fguffey]

Now don't laugh but you can test how much pressure it takes to move that bullet.

Load a case with NO POWDER or even a primer. Prepare the case as you see fit then seat a bullet. Now you are going to ruin that bullet but get a feel for how much it takes to move that bullet. Push it down on a bathroom scale and watch as the pounds go up. When it moves you now have an idea of how hard it it sot move that bullet.

"Don't laugh?" You are dealing with a bunch of compulsive laughers. With the same scales you can determine the amount of effort necessary to seat a bullet. If you cut the case head off you can measure the amount of effort necessary to pull the bullet by pushing the bullet out from the case head end.

Problem: Bathroom scales do not measure in tensions; again it always comes back to pounds and bullet hold.

F. Guffey

 

[711rollerdog]

 

[fguffey]

I was worried I had loaded ammo for testing with too light tension.

Bullet hold: I want all the bullet hold I can get, I like the ideal if getting the powder up to speed before the neck releases the bullet and then there is that short time between igniting the powder and maximum pressure. If pressure escapes between the neck and bullet the neck must expand.

There was a time necks were staked to hold the bullet. And there was this company that made reloading tools etc that claimed crimping was a bad habit. I agreed.

F. Guffey

 

[fguffey]

shtnrise, and that gage does not come with a conversion from pounds to tensions. I have dampened gages, I am not convinced the damper is necessary on the slow, low pressure gage used on the bullet seater you listed.

F. Guffey