Shoulder bump consistency

[jlorenzo]

How consistent is your shoulder bump piece to piece? I am getting what seems to be more variation than I thought I would. Was trying to bump .002", some are that others are around .0035-.004". Just lake city brass, Hornady custom FL die. What is an acceptable spread and how would I gain more consistency?

I am also looking at the Mighty Armory sizing die. Not sure how it works exactly, can you change out the mandrels in that die to the size you want? It isn't clear to me.

 

[WSnyder]

If your case lube and sizing procedure is working I’d say you shouldn’t be more than +-.0005” and probably less. Most variation in my experience is due to your case lube procedure. Dial that in and your variation will plummet and be a non issue.

 

[OmegaRed]

What caliber are you sizing? Bolt or gas gun?

General accepted variation is .001. Things to thing about in no specific order:

• How well the die matches your chamber
• How many reloads?
• Lubing consistently?
• Is your die clean?
• Are all rounds on the same number of reloads?
• Is your process consistent (bottom out die on shellholder, let dwell for a few seconds)?

Try to bottom out your die on the shellholder during your stroke, then turn your brass a quarter to half turn and run the die down again. Sometimes that helps. I've found that most of the gizmo's that people use to help or measure with consistency like concentricity gauges, measuring bump, etc. are often fixed by a good fitting die set up correctly. I use Harrell's on BR guns and Wilson on hunting guns almost exclusively.

 

[L.Sherm]

If you mix up brass thats fired more times than others it will not bump the same.

 

[Ruger15151]

The amount of variance you tolerate is a function of how accurate you need your ammo to be.

I assume since you said your goal was a .002 shoulder bump than you are loading for a bolt gun. .004 shoulder bump will still go boom but is way to much for precision reloading in a bolt gun.

I shoot long range competition so precision and consistency is very important. I get .0005 variance at most when sizing. These helped my sizing constency.

- Use quality brass
- anneal brass every firing if possible
- develop a method to get same amount of lube on every case. More lube will push the shoulder back further
- clean dies regularly because they will get lube buildup in them.
- don't over lube
- use the same pressure at the top of the stroke with every case. More pressure will increase bump.
- use a good set of calipers. Cheap calipers will give you false readings

Has the brass all been fired in your rifle? If not and it's range pickup or once fired, the brass has been fired out of several rifles with different chamber dimensions. As a result, you are going to have different "shoulder to base" measurements before you size. Cases with longer 'shoulder to base" measurements are going to have the shoulder pushed back more and will then have more spring back. Cases that are shorter will not spring back as much.

Separate out 5 cases that all have the same base to shoulder measurement. Then size and see if you get the same variation from case to case.

Once you have fired them in your rifle, they should all size more consistently if your sizing process is good.

 

[Murray Brook]

As others have posted the # of times a case has been fired and whether or not annealing is done has a direct effect on shoulder bump. Keeping a constant procedure ( press stroke etc) is also important. JMO

 

[LCazador]

I'll echo what others have said previously. I'll add if you're backing your die off to achieve your .002" shoulder bump you will not get a consistent and accurate bump. Use a competition shell holder set instead.

 

[BoydAllen]

Years back, a friend had a problem with shoulder bump consistency. We determined that the cases had not been annealed to a uniform state at their respective factories. We did not want to make the necks too soft for magnum use, hunting, heavy bullet, from a magazine. We were able to anneal the cases so that they met our specifications with very good shoulder bump consistency, and necks that were not too soft. This was with a two torch annealer with excellent annealing time control. Certainly the whole point of the Redding competition shell holder sets is to improve bump consistency, because they allow setting up a FL die so that the press toggles at a variety of die settings. That toggling makes the linkage stretch/compression factor more uniform. Other factors are the amount of lube, and how long the case is at the top of the ram stroke in the die. I do not think that anything can overcome differences in brass hardness except annealing. I always shoot batches of brass in rotation so that within that set the effects of work hardening on uniformity will be minimized. Even with that, there will be differences.

 

[Bill Norris]

As others have posted the # of times a case has been fired and whether or not annealing is done has a direct effect on shoulder bump. Keeping a constant procedure ( press stroke etc) is also important. JMO

I have found that if there is adequate amount of dwell time at the top of the press stroke with good quality brass ( I allow @ 5 seconds when F/L re-sizing ) with the Rock Chucker press the variations in shoulder bump is almost zero. I believe there is truth in the fact that brass will continue to "settle in" while any force is applied to it. Just my .02.

 

[Straightshooter1]

How consistent is your shoulder bump piece to piece? I am getting what seems to be more variation than I thought I would. Was trying to bump .002", some are that others are around .0035-.004". Just lake city brass, Hornady custom FL die. What is an acceptable spread and how would I gain more consistency?

I am also looking at the Mighty Armory sizing die. Not sure how it works exactly, can you change out the mandrels in that die to the size you want? It isn't clear to me.

The three things that really helped me for the consistency is:

Annealing after every firing
Proper amount of lube
Plenty of "dwell time" (keeping the case fully in the sizing die for 5-6 seconds before extracting)

 

[wkdickinson]

I used to have the same issue (243 Win & 6.5 CM, Peterson and Lapua brass, Whidden Dies). I annealed every other reloading. I did a number of things trying to fix the problem and found two things that helped the most:

1. I changed the way I lube - I have always used Imperial Sizing Wax, but I used to lube the entire case. Now I use Imperial Neck Lube (one dunk, before lubing the body), then a small amount of sizing wax on my fingers and I only lube the body of the case, being very careful to not get any on the shoulder.
2. I now also leave the case fully stroked into the sizing die for a count of 5 (dwell time) - which I think makes the biggest difference.

My shoulder bump is now consistently within .0005 or less.

 

[jamesk]

Sunday I bought 500 pieces of once fired .308 LC brass shoulders are all over the place, I'm leaving my locking ring loose but snugging up my die in my press and adjusting as needed from piece to piece.
Able to get 0.005-0.003 but is painstaking glad I only have to do it once, after fired just normal sizing routine required I hope. So far pretty satisfied with the brass bought it for a gas gun.

 

[skeeljc]

Annealing would be my first thing to consider. The other thing is your press/die setup. If you are depending on the press stop (or going over center) to control the bump that could be an issue. Allowing the shell holder to make hard contact with the FL die is the best situation but then you need shell holders with different depths to set the amount of shoulder bump. I use Redding shell holders (set of ten) and my MEC press is set to provide firm contact between the shell holder and the die. My shoulder bumps are within 0.0005" total variation. I anneal every five firings.

 

[jlorenzo]

This is twice fired LC and also Lapua. I am backing my die off a touch to bump .002 so I may need to look at shell holders.
I put my brass is a plastic pale and spray it down with Hornady one shot. This is for a Bartlien barrelled Tikka, range fun, some PRS and some 600y High power. I use the LC for banging steel and PRS, the Lapua for the high power.

I have been annealing with a powered screw driver, appropriate size socket and a torch.

I do pay close attention to the consistency and feel of each stroke.

I may need to look at some better calipers soon but I don't think they have a huge amount of variance.

 

[marchx]

How consistent is your shoulder bump piece to piece? I am getting what seems to be more variation than I thought I would. Was trying to bump .002", some are that others are around .0035-.004". Just lake city brass, Hornady custom FL die. What is an acceptable spread and how would I gain more consistency?

I am also looking at the Mighty Armory sizing die. Not sure how it works exactly, can you change out the mandrels in that die to the size you want? It isn't clear to me.

It depends on nuances- amount of lube (e.g. imperial wax), whether FL die was clean or dirty and first of all on the brass itself (quality, number of firings, annealing). I am not referring to quality of your press and dies, I am assuming they are perfect for the job.

 

[JFrank]

I’m told guys don’t shake the ‘one shot’ can Thoroughly, they end up spraying uneven amounts of lube on the cases.

 

[LCazador]

This is twice fired LC and also Lapua. I am backing my die off a touch to bump .002 so I may need to look at shell holders.
I put my brass is a plastic pale and spray it down with Hornady one shot. This is for a Bartlien barrelled Tikka, range fun, some PRS and some 600y High power. I use the LC for banging steel and PRS, the Lapua for the high power.

I have been annealing with a powered screw driver, appropriate size socket and a torch.

I do pay close attention to the consistency and feel of each stroke.

I may need to look at some better calipers soon but I don't think they have a huge amount of variance.

I don't think the Hornady spray lube is helping much in trying to achieve consistency. I'd opt for Imperial sizing die wax Also sounds like a competition shell holder set may help. By the way if the head diameter on the twice fired brass is larger than the head diameter of your chamber that may be causing your shoulder set back inconsistency. Your sizing die does not size this part of your brass and it may not be allowing the brass to completely enter the die the same way each time. So you'll get some pieces that enter properly and others that won't. Do you have the same issue with the Lapua brass?

 

[wkdickinson]

Sunday I bought 500 pieces of once fired .308 LC brass shoulders are all over the place, I'm leaving my locking ring loose but snugging up my die in my press and adjusting as needed from piece to piece.
Able to get 0.005-0.003 but is painstaking glad I only have to do it once, after fired just normal sizing routine required I hope. So far pretty satisfied with the brass bought it for a gas gun.

Why not just set your sizing die up to bump the shoulders back to "commercial" length? Then after you fire them in your rifle, they should be reasonably consistent.

 

[jamesk]

I did try that, they were still to inconsistent I didn't mention in my earlier post but I did anneal them first.

 

[JEFFPPC]

The horse is dead , give him a break.