Question on Bushings for .308

[venatic]

I have a .308 that I bought slightly used that has a Shilen barrel that is marked .340 neck. It came with 150 or so pieces of Lapua neck turned brass some loaded some fired.
It also came with a redding neck bushing die and Forster Comp seater. The bushing die has a .333 bushing in it and when I run fired brass thru it the brass comes out .332-.333 by my calipers. Now when I load a bullet they measure .337 and my question is that sure seems like too much neck tension. I have never used a bushing before but from a little reading it seems you really only want the bushing to take the fired brass (.339)down .003 or so and that my bushing should only be .001 smaller than my loaded round which would put me at .336 NOT .333 or am I missing something.

 

[savageshooter86]

335 and maybe a 336 bushing would work. The previous owner must have like more neck tension

 

[ShootDots]

No, you're not missing anything... We all have preferences for our cartridges. I shoot F-Open and AFTER I turn my necks I want a bushing that is 1.5-2.0K UNDER what a loaded round is. I have found that 1K neck tension is good for accuracy, however, you will pull bullets out of the case upon opening the bolt, IF you have a "jammed" round. I have found little to no difference in accuracy with my standard 1.5-2.0K neck tension and as of yet, I have not pulled a bullet out of the case! Remember, bushings come in 1K increments, so the only way I get the 1.5K neck tension comes strictly from how much brass I turn off the necks. I hope this little bit helps.. Oh I forgot to mention, a person using his .308 for hunting, MAY want upwards of 4K (you would be better off with 3K) neck tension.

 

[savageshooter86]

You have to account for spring back of the cases too. How much spring back is typical on fired cases? 1k?

So is that why to chose a bushing 2k under loaded round for 1k neck tension?

 

[ShootDots]

Andrew, the "spring-back" on your cases is more dependent on the elasticity of your cases.. "Virgin" or freshly annealed cases will expand and contract easily compared to a case that is so hard from lack of proper care, that it is almost impossible to extract a case over a carbide sizer-ball... Keep your cases in great shape, get a bushing 1.5 to 2.0 under a loaded round and don't look back... Go enjoy shooting..

 

[Shynloco]

Personally, if I had a measurement of .337 with a loaded bullet, I'd be using a .335 bushing on my Lapua brass.

Alex

 

[280nosler]

It all depends on the brass. federal GMM brass requires .334 for me, lake city match '06 needs 338, Lapua needs 336, and Winchester needs 337. Measure your loaded round, then back off .002 and you should be golden. Some people back off .003 if they are not annealing due to spring back, but that is it.

 

[venatic]

I got my new .335 bushing and it seems to be giving me the neck tension I am looking for. Now for the BUT part.

I had already sized all my Lapua brass with the .333 bushing and primed them all. This was after annealing and polishing. Yesterday I loaded 30 rounds so I could shoot them and check out the new bushing and see how the results would be. Out of the 30 rounds I loaded a dozen would not chamber and I have discovered the necks are to thick to chamber as they mic .340-341and my tight neck is .340. Now remember in my OP I said this brass came with the gun and all had been fired thru the gun more than once supposedly. Is it possible for the necks to gain enough thickness from one FL sizing to now need turning again??? The reason I ask is just being curious about the difference in accuracy I FL sized a portion of the brass to compare to the neck-sized a while back. They are all mixed together now so I was wondering if those are the ones that are too tight now. There may be something else going on here but I am not sure what it is.
Thanks in advance.
david

 

[savageshooter86]

I just do not see how, if they were 337 necks prior and all you did was change bushings to a 335, they are now reading 340-341" ???

they mic .340-341

Are you referring to the fired case neck sizes here or the necks of the loaded rounds that would not chamber?

I got my new .335 bushing and it seems to be giving me the neck tension I am looking for

How is this possible if they are reading 340-341?

I am confused here

 

[savageshooter86]

Maybe if you explain your reloading procedure to us we can try to point you in the right direction.

How many firings on brass?
How are you annealing? How often?
What load you are using?
How did you set up your bushing die?
What do the Lapua brass neck thickness measure?

 

[mike06]

Did you check your head space? Just a thought.

 

[venatic]

I just do not see how, if they were 337 necks prior and all you did was change bushings to a 335, they are now reading 340-341" ???

they mic .340-341

Are you referring to the fired case neck sizes here or the necks of the loaded rounds that would not chamber?

I got my new .335 bushing and it seems to be giving me the neck tension I am looking for

How is this possible if they are reading 340-341?

I am confused here

Ok let me try to explain better..

Brass was used when I got two firings I was told. Some were loaded some were fired. I have loaded all once using either a .333 bushing OR FL RCBS die some of them then shot all with no issues.

Now I Annealed for first time on one of these.

http://www.bench-source.com/id81.html

Polished after annealing with SS media then used a .333 bushing die to neck size all. When I seat a bullet MOST measure .337 outside diameter BUT some are measuring .339-.401 for some reason. The only reason the .335 bushing was brought into the picture was it seemed to me that neck tension seemed awful tight so after reading up I made this post and most agreed as I thought the .335 would be good. And it is ....as all the rounds I fired yesterday and neck sized today when reseated bullets felt good.

It maybe as simple as the guy did a sloppy neck turning job but I am too confused. I do not have a micrometer just a caliper. I can turn the necks again I guess. I may just give all the rounds that won't fit my tight neck to a friend who has a factory neck.

It just dawned on me that one reason I probably noticed the bullets seating harder using the .333 bushing was the fact that after scrubbing with SS media all the carbon is cleaned out of the necks so I could really FEEL the friction. Going to the .335 bushing really has nothing to do with my current problem at all.
Bottom line is 1/3 of my brass is now too big in the neck to go into my chamber for some reason. Brass that has been shot in this gun at least 4 times.

 

[savageshooter86]

sounds like you got brass that was not neck turned properly to fit the chamber. I would NOT give the Lapua brass away. I would get someone to turn the necks and get them GTG for your chamber. I would also get a micrometer to more accurately measure the necks of fired brass and loaded rounds.

Check out DJs brass here on the forum to possibly do your necks and get them so they are all uniform and fit the chamber. Or see if anyone here will do it for you or a friend.

**I turned my Lapua necks and now my loaded rounds measure 3365". All the necks are very consistent so neck tension is more consistent. My necks are turned to 0.0142ish.

 

[venatic]

I have a K&M neck turner so I guess that it what I will do. I do need to get a micrometer if I am going to do this right. I have really only skimmed the necks on my 17 calibers and one of my 6mm's as this .308 is my only tight-neck chamber.

Thanks for your input.

 

[savageshooter86]

http://www.midwayusa.com/product/544254/rcbs-vernier-ball-micrometer-1
This is what you will need to check neck wall thickness for neck turning

I also would get a std vernier mic if you can swing it to have to get more accurate measurements of stuff. I thought I wouldn't need it but have used it a lot on the loading bench lately
http://www.midwayusa.com/product/897310/rcbs-digital-micrometer-1

**If you live where there is a Harbor Freight store, that is where I would get the std mic at. It is like $22 IIRC**

I would turn the necks down to at least 0.0145" thickness. That should put you at a 337 loaded round giving you 3 thous clearance in the chamber with a round loaded


Don't be like the one guy at that got a custom gun with a tight neck chamber and brought his reloads to shoot and had not measured neck thickness. He told us he just turned some and did so until they would chamber. Didn't know what they measured on necks either just was going by what he thought. Seemed to us like a great way to have something happen to the gun/shooter

 

[jsthntn247]

I have a K&M neck turner so I guess that it what I will do. I do need to get a micrometer if I am going to do this right. I have really only skimmed the necks on my 17 calibers and one of my 6mm's as this .308 is my only tight-neck chamber.

Thanks for your input.

Take some of your brass that has the smaller necks and set the k&m up to just touch the neck, not cut it. Then turn the larger necked brass down to that diameter. If the necks that you say measure larger don't turn down any, then you have something else going to. I tend to believe that the shoulders arn't bumped back enough on those peices of brass and you have a headspace issue going on and not necks that are too thick.

 

[venatic]

I have a K&M neck turner so I guess that it what I will do. I do need to get a micrometer if I am going to do this right. I have really only skimmed the necks on my 17 calibers and one of my 6mm's as this .308 is my only tight-neck chamber.

Thanks for your input.

Take some of your brass that has the smaller necks and set the k&m up to just touch the neck, not cut it. Then turn the larger necked brass down to that diameter. If the necks that you say measure larger don't turn down any, then you have something else going to. I tend to believe that the shoulders arn't bumped back enough on those peices of brass and you have a headspace issue going on and not necks that are too thick.

I suspected the same so yesterday I ran each and every piece of unloaded brass into the chamber with no issues. I miked the outside diameter of a few at .332-.333 and just picked one that was .332 put powder and a bullet and NO GO. It would not chamber. I miked the neck again and its is .339 on my calipers so too tight for a .340 neck.
The puzzling thing to me is how I managed to shoot these before?

 

[savageshooter86]

I am lost. My Lapua necks without a bullet seated measure 0.3335" using a mic(these are neck turned down to 0.0142") and a loaded round with a bullet measures 0.3364". So I don't see how your case necks are too big

Take 5 or so cases and seat a bullet without powder or primer and measure the necks on them and see what reading you get?

**Are you using 30 cal bullets? I know it sounds stupid but just making sure :-[**

 

[venatic]

Savageshooter86 .....Thanks for all your replies. Your last post made me sit down and carefully review everything I was doing. I did take a piece of brass (all of it is primed) checked the outside diameter (.332)and then seated a bullet with no powder. Remeasured and got .337 so it should have chambered. It would not and in fact it was hard to get out I had to bang on the bolt a couple of times. I remeasured the neck and right at the edge or end of the neck at the bullet it measured .340. My first thought..cases are too long but wait I just chambered each and every one and they went in fine BUT I measured OAL of cases anyway 2.005 right where they are supposed to be. I trimmed about .002 off THAT case and chamfered in side and outside and YEP seated that same bullet and slid right in like butter. None of these cases had ever needed trimming so I had never thought after all that polishing/annealing the necks needing to be re-chamfered as well. So now I have done about a dozen cases with only chamfering inside and out with a VLD tool mounted on my RBCS case prep machine and danged problem solved. 8)
I am still unclear what is EXACTLY happening. My guess is that when I seat these bullets on some of the cases with squared mouths from being dinged around in the SS polisher they flare the un-chamfered edge of the mouth just enough to bump into the edge of the tight throat and thus not going into battery and if I try to force it I get it wedged in there. Does that make sense?

Anyway I once again say Thanks to all who replied.

 

[savageshooter86]

I'm assuming you mean case length measured 2.005"? Not 2.05!!

I hope more experienced reloaders will see this and chime in. I still don't see how not chamferring/deburr the case would be causing the reloaded cases to come out .003" larger when trying to chamber ???