Pull Weight

[Andrew]

Or do you at all? This is a subject that interests me greatly and would be interested in all opinions or methods.~Andrew

[Alycidon]

Or do you at all? This is a subject that interests me greatly and would be interested in all opinions or methods.~Andrew

 

 

Are you talking about trigger pull weights or the energy needed to pull a bullet from a live case?

 

A

[Andrew]

The latter, sorry. Never thought about triggers.~Andrew

[jon]

Seem to remember seeing a ad from someone making a bullet seater with a force/strain gauge on it for use with an arbor type press..... ?

Perhaps this is a question for the benchrest shooters?

But as a thought ... if the bullet it seated at or in the lands the engraving force would be far greater than the hold of the case?

[Alycidon]

Generally the amount of force needed to seat a bullet depends on the case neck spring back after resize. I use a stepped gauge to measure this with one (20BR)of my cases and then if needed resize again with a smaller bush. If the bullet is into the lands it could well stay there if you try and unload a live round filling the action with unburnt powder.

 

I cant see why the actual force is that important as long as it is consistant. A fired case from my .270 chamber neck I will usually resize with a .2670 bush, my 12.7thou neck walls plus a .2430 bullet gives a .2684 loaded neck diameter so 1.6 thou of clearance in total.

 

Having rezized with the.2670 bush the neck id is .2416, when I stick a .2430 bullet into it I have 1.4 thou of grip if I have worked the maths out right !!

 

Clearances on my 20BR are a lot tighter than that, to the point where I am still a bit uncomfortable with them. But the rifle certainly shoots well.

 

Dont know if that helps you or not !, probably not!

 

A

[jon]

That seems to make more sense ..

there is a short paragraph in Harold Vaughn's book 'Rifle Accuracy Facts' p.228 on case neck tension where he measures the seating force needed ... and compares the outcomes. ... he could see no difference between high and low seating forces. As Alycidon says it might be about keeping things as consistent as possible??

[Andrew]

I think there might be too many variables in seating force, even from round to round. A slight misalignment of the case/bullet or a difference in chamfer? To me, the amount of pressure required to free the case from the bullet seems more accurate? Maybe I'm seeing the glass half empty?? ~Andrew

[Cornishman]

I think there might be too many variables in seating force, even from round to round. A slight misalignment of the case/bullet or a difference in chamfer? To me, the amount of pressure required to free the case from the bullet seems more accurate? Maybe I'm seeing the glass half empty?? ~Andrew

 

Andrew, yup I think you're just getting too worried about this. I did some tests a while ago after noticing that some bullets needed noticeably greater force to seat than others. There was no difference in the grouping between the different rounds but having put the worry in my head I had to do something. Now I polish the inside of the necks with a power drill and an old bronze brush with a twist of very fine wire wool. This also cleans up any burrs remaining from case trimming and the result is that all bullets seat with silky smoothness. All this does mean an extra wet clean of the cases to remove any tiny, tiny bits of wire wool and means I have to suffer the taunts of friends who marvel at my ability to find still more ways to extend the loading process. Still, it's a hobby.

 

Oh, while I'm thinking about it, if the pull force varies enough to be a problem wouldn't that show up over a chrono? Personally I'd be more worried about any deformation of the bullet, or scoring of the jacket, whilst seating. There, that's something else to worry about......

[Laurie]

This is a short, apparently simple question whose answer is anything but!

 

To manage it involves good brass (well annealed in the neck area and consistent dimensions-wise), careful sizing including both adequate and consistent lubrication of the inside neck walls if a die fitted with an expander ball is used - better still to have turned or very consistent cases that can be sized with a bushing alone.

 

There are factors that you can't manage with a factory rifle - the size of the chamber around the neck, hence case case expansion on firing and the amount of sizing down subsequently required. I once worked out that with a typical factory chamber and set of standard off the shelf dies, the case-neck was being expanded, sized and re-expanded by 30-40 thou' in each firing / reloading cycle. Compare that with the benchrest shooter with small-diameter 'fitted' neck set up and bushing sizing only where the total brass movement is 5 thou' or less.

 

Many factory dies size the neck down far far more than needed, then have to expand it back up a lot to get the right amount of bullet grip. The more you change the neck diameter in firing + reloading, the more variations in bullet pull you get in the results, and the faster the brass in the neck work hardens. Answer? You can reduce the sizing and expanding amounts by getting a bushing die or a custom die with the neck area reamed out so it sizes the brass down a minimum amount. Forster Precision will do the custom die work on its sizers, but this option only works if you restrict yourself to one make of brass or neck-turn all cases to the same thickness.

 

You can often tell what's happening through press-handle 'feel' in the bullet seating seating stroke. When my Southern Gun SSR-15 was still chambered for .223 Rem (6.8mm Rem SPC as of a few weeks ago), Winchester cases had really noticeable variations in press effort on seating from around the 7 or 8 loadings mark, so presumably 'pull' was equally variable. The odd neck split would also appear at that point, so the brass was at the end of its useful life - for longer range shooting at any rate. (The odd thing was that it would still give excellent 100yd groups. However, MV spreads would increase, so elevation spreads would have appeared at ranges over 300 yards.)

 

In some rifles, seating the bullet to be a 'jam fit' in the rifling is one way around bullet-pull variations, as the effort needed to get a jammed bullet moving is much greater than just moving it out of the neck. BR shooters sometimes use a very light grip and bullet seated out, so the bullet is pushed back into the case on chambering leaving every cartridge virtually identical on firing in this respect. But the neck brass has to be thin, consistent and lightly sized for this to work really well.

 

Case lubrication is often overlooked in the sizing process - the type of lube and amount applied can have a big effect on both effort and the dimensions of the sized case. I didn't realise this until I read an article in Precision Shooting years back by a guy shooting a .308W M1A semi-auto service rifle in US NRA Hi-power. Headspace is critical in this rifle design - too much and accuracy and case-life are poor; too little and you blow the rifle up as the M14 / M1A will fire with the bolt half-locked. Simple - set the sizer to take fired case shoulders back a couple of thou is what 'everybody' says. What this guy found was that he was getting huge variations in shoulder position, and when he looked into the causes found that lube was a major factor. So, if it affects shoulder position a lot, you can be pretty sure it affects neck tension too!

 

There's probably a few more issues at play too, but I think that's enough to start on. To sum up, use the best (Lapua, RWS, Norma) brass you can afford, lube the neck well inside and out, size it as little as possible, and keep an eye on handle pressure in the sizing stroke. Or ........... if you're getting nice groups you're happy with, just forget all this malarkey, as life's too short and has too many other things to worry about!

 

Laurie

[Alycidon]

Excellent reply Laurie, spot on.

 

A

[Andrew]

Laurie: Excellent answer that covered all bases.

Cornishman: I don't worry about it much and have my own ways of handling the situation -much like your own and the ones Laurie described. I was curious as to how other folks handled the situation and I see that we all pretty much think alike. I think that the four of us would be surprised as to how many people are oblivious to the need for uniform neck tension... no matter what method is used to get it.~Andrew