Shoulder Bump

[Rath]

Hi Gents,

I read that it's best to aim for a .001-.002 shoulder bump when full length resizing. My question is should I let my cases grow until they need full length sizing or should I measure case stretch and "bump" .001-.002 after each firing?

Thanks in advance.

Rath

 

[Winchester69]

The idea is to maintain a minimum headspace, clearance between the case's shoulder and the gun's chamber. You can't do that if you shorten the case before it stretches far enough to contact the barrel.

 

[groupshooter22]

Full length size after every firing for best consistancy.

 

[1000yardstare]

Shooting F Class on an Army range with a .223 on a hot summer day can result in sticky case extraction if the cases have been fired a number of times and only neck sized. Rifle is an 8 twist MacLennon barrel on a trued 722 action, 75 AMax moly at 3000 fps.

For this reason I neck size first and then bump .001 with every reload. Result is smoother bolt closure and opening. Also have noticed fewer fliers when shooting off a 300 metre bench when bumped every reload.

 

[Rath]

Thanks for the replies.

Would it be worth using a couple of cases as gauges, that is allowing a few to grow until I know what the limit is, then setting the "bump" from that limit?

Would this method allow me to setup my die so that I resize after each firing and best ensure minimum headspace? Or should I setup dies to bump based on the case stretch from the most resent firing?

Thanks,
Rath

 

[NorCalMikie]

Find one of your fired cases that is starting to get tight on extraction or on closing the bolt.
Measure it. Write that measurement down. Set your die so it bumps the shoulder back about .001 to .002. Try one resized case in the chamber. If the bolt closes easy, you're set.
If a fired case goes back in the chamber easy with out being resized, neck size it and reload. You might get by with 3 or 4 firings before it starts getting tight and needs a shoulder bump or body size. YMMV.

 

[Gearheadpyro]

What die is used to bump the shoulder back on a case?

I have the .308 Redding body die and a .308 full length sizing die, both of which do substantially more than bump the shoulder when I run the case through it.

I've got the body die set up to push the shoulder back around .002", but it squeezes the rest of the case a good bit as well. The chamber is factory Remington 700 and I know it's loose. Is there any way to bump the shoulder only on these cases?

 

[Mikem]

Gearhead:
There is one die I know of, the "Forester neck bushing, shoulder bump die", that's what I use on all my BR cases, and I love it.
You can set the amount you wont to bump the shoulder back, every time you size the neck. I have mine set at .0015. And how much of the neck you wont to size, plus how tight you wont the neck with the bushings, and it also deprimes, if you wont. This one die, does it all, or only one thing, depending on how you use it.

If you use this die, or any neck only sizing die, at some point you will need to squeeze the body back in a bit. So I use a Redding body only die for this, about every 5th or 6th reload, and then just enough to fit snug in the chamber, with this body die you can move it in as much as you wont. And you already have this die.
You could use a F.L.die for this also, and just not push it all the way down, or your back to factory specks, and lose the advantage of using Fire Formed cases.

The Forester die is no more expensive than any other bushing type neck sizing die, and the Redding body sizing die, having no moving parts, is cheap by comparison.

So its a good way to go in my opinion, and it gives you all the options to keep your cases snug in the chamber, with out moving a lot of brass around. This method will extend the life of the brass allot, how much depends. Eventually you will start to get loose primer pockets.
Mike.

 

[Winchester69]

Would it be worth using a couple of cases as gauges, that is allowing a few to grow until I know what the limit is, then setting the "bump" from that limit?

You're not thinking about what you're doing. When cases get to a length where they won't chamber easily, size them down until they do. Then your die is adjusted for your chamber. Size all of the cases using that setting.

 

[scout1]

[/quote]
You're not thinking about what you're doing. When cases get to a length where they won't chamber easily, size them down until they do. Then your die is adjusted for your chamber. Size all of the cases using that setting.
[/quote]

Take the above suggestion, measure your case with this headspace guage then set you sizing die accordingly. http://www.larrywillis.com/

 

[Gearheadpyro]

Thanks Mikem, I've got the Forster bump die on order.

Any tips on selecting a bushing for it? I've heard you measure the outside neck diameter on a finished round and subtract .001-.003" for neck springiness, does that sound about right? All of my cases are annealed so I'm thinking my neck springiness will be minimal.

 

[Mikem]

Yes, that's about right, (I'm having a brain fart) and cant recall the numbers, and my gun room is out in another building, but I go down .003. Get several at .001 apart, and you cant go wrong.
Mike.

 

[Gearheadpyro]

I ordered the Forster Bump Die kit from Cabelas, they were the only place that had one in stock. Bushings 336-334-332 are included. I also got a 330 bushing. I figure that from those I'll be able to make something work. My finished rounds neck diameter is .333" so the 330 should be the one I wind up with.

 

[Mikem]

I didn't realise they were that hard to find, but that's the way all of this stuff is right now, there's a war on remember, and were under attack.
I wonder it this will get deleted?
M.