What happens when you don't remove case lube?

[Major Dave (retired)]

I loaded up 50 rounds of 7x57, after lubing the brass and full length resizing it. Since I am new to reloading, I developed a load, working up from listed starter loads to near max loads.

No matter how "weak" the loads were, all fired brass came out with flattened primers. I saw no other signs of excessive pressure, as described in the 3 different loading manuals I referred to.

After much thought about the flattened primers, I realized that I had never removed the case lube from any of the finished rounds.

Could this be the reason for the flattened primers?

Also, if I load another batch of near MAX rounds, then remove the lube before firing, can I expect higher pressures? Should I start over on load development, using "starter" powder charges?

[Scorch]

Leaving case lube on the outside of the case will increase case setback, but the 7X57 is so mild it generally does not have issues ike this. In once-fired and properly resized cases that should not be much of an issue, but it can be an issue if you set the shoulder back in resizing.

I have loaded 7X57 for 30+ years. What is your load? What is your case length? What is the OAL? What rifle are you shooting this in?

[jamaica]

When you fire a round the case expands to fill the chamber and it tightly grips the chamber walls and reduces the forces put on the bolt. If you do not remove the lube, the casing will not grip the chamber walls and it will slip back and put undue stresses on the bolt. This can be a dangerous situation.

[Major Dave (retired)]

Glad to find someone with 30+ yrs experience.

Load: 44.5 gr IMR 4320
Win cases trimmed to 2.225"
139 gr Hornady bullets, #2825 BTSP
COL 3.025
Primers: WLR

Rifle: DuBiel custom, bolt action, 1:9 twist, deep throat (approx 0.25" )

Chronographed velocity 2,950 fps, 15 feet from muzzle

Your learned opinion, please.

[Slamfire]

When you fire a round the case expands to fill the chamber and it tightly grips the chamber walls and reduces the forces put on the bolt. If you do not remove the lube, the casing will not grip the chamber walls and it will slip back and put undue stresses on the bolt. This can be a dangerous situation.

Actions and bolt lugs are sized ignoring case friction. There is no other way to design the system as you cannot predict "just how much" friction you are going to have.

So case lubrication is dangerous if:

1. Load is above SAAMI pressures. Frictional forces somewhat reduce the load on the bolt. Lubricating the case will give the bolt the full thrust. If the round is overpressure to start with, then the bolt thrust is increased.

The real solution to this: don't load overpressure ammo.

2. Excessive headspace leading to peening. This is bad regardless of whether the case is lubricated or not. Having a lot of distance between the case bottom and the bolt face will create peening. Lubricating the case means the case slides back faster than if the chamber was dry.

I have shot lubricated cases in my M1 Garands and M1a for over a decade. Shot out three barrels on one M1a. No ill effects to bolt or receiver. These rifles open up early and stretch cases. Many people report case head separations in this rifle after five reloads. Lubricating my cases have given me very long case lifetimes. (I took one set 22 reloads and never had a case head separation) My loads are not max, but they are "full power".

What I have noticed is that dry cases often show flat primers, while a lubricated case firing same load/bullet/gun, will show a rounded primer. Obviously combustion pressures are the same, so the dry case primer is backing out before the case expands to the bolt face. Whereas the lubricated case slides back to the bolt face before the primer backs out.

The Army conducted research into case lubrication to improve the function of automatic weapons systems. Early machine gun designs had oilers. The following section is of experiments in the 60's/70's. Case lubrication, while it improved certain things, was a bother, and the weapon systems of the time worked fine without it.

From Army Material Command Pamphlet AMCP 706-260 Engineering Design Handbook, Guns Series Automatic Weapons. Feb 1970


Chapter 8 Lubrication of Machine Guns

8-3 Case Lubricant


Although the gun designer is not directly involved with ammunition design, he is directly concerned with handling, loading, and extracting during firing. A smooth chamber is essential for extraction and a properly lubricated case is a decided asset. The lubricant should be a dry lubricant and should be applied at the factory. Considerable effort has been made to find suitable lubricants for this purpose. Some success has been achieved but continued search is still being advised, especially since two independent facilities are not in total agreement.

The Naval Research Laboratories conducted test of brass and steel cartridge cases coated with films of polytetrafluoroethylene (Teflon). Results were outstanding in meeting required protection and lubrication properties. Laboratory results, later confirmed by firing tests, showed low friction and consequently less wear in gun barrels. Other desirable features include freedom from cartridge malfunction, no chamber deposits, decreased ice adhesion, and less chance of thermal “cook-off”. Teflon can be applied to steel and brass ammunition by mass production methods. Its protective ability permits pre belting and packaging of ammunition since no further handling prior to use necessary. Its supply is abundant and its cost reasonable. Thus the use of Teflon in this capacity seems ideal.

Aberdeen Proving Ground is more reserved in its appraisal of Teflon coating. Whether or not the techniques of applying the coatings were similar, those used at APG were not free of coating defects; a high cull rate existed. When tested with cartridges coated with microcrystalline wax, ceresin wax, and uncoated ammunition; the Teflon-coated wax showed many advantages but was also found wanting in some respects. Teflon and micro-wax had better extraction properties and Teflon left a much cleaner chamber than the others; micro-wax was second best. About 50 percent of the Teflon-coated cases had slight bulges after extraction; other types also were similarly damaged but with no apparent significance attached to a definite choice. For dusted ammunition, the Teflon and micro-wax were far superior to the other two types with Teflon having a slight advantage, although when fired in a comparatively rough chamber, Teflon was outperformed by all. Reiterating, the gun designer, aside from providing smooth sliding surfaces, is almost totally dependent on the physical properties of the lubricant to make his gun perform satisfactorily under all assigned conditions.

The last sentence is a summary of the chapter; not a comment on case lubrication alone. A copy of AMCP 706-260 and other out of print AMCP pamphlets can be ordered from NTIS at 703-605-6000.

[Scorch]

Load: 44.5 gr IMR 4320
Win cases trimmed to 2.225"
139 gr Hornady bullets, #2825 BTSP
COL 3.025
Primers: WLR

Well, the first thing that comes to mind is 44.5 gr of IMR 4320 is a pretty stout load. The highest charge of IMR 4320 I ever loaded with the 139 gr Hornady was 45.0 gr, and that was a pretty hot load in my rifle (Ruger 77R), but 44.5 gr may be OK in your rifle since you have such a long throat and you are seating the bullets out. Just realize that you are approaching max loads, so the flattened primers are not lying to you.

You are getting very good velocity, probably due again to that long throat (freebore). Things I would try to do:
* neck size only to eliminate case stretch,
* clean the bore really well and use a bore conditioner (I like Tetra, but Militech works good) on the bore to reduce friction
* you might try to seat the bullets out a bit further to 3.050", but make sure you have enough bullet in the case neck with that boattail.

IMR4320 was my favorite with the 139 gr Hornady and the 140 gr Nosler Partition for many years. Very accurate, and dropped them right where they stood. I have since switched to WW760 with good results.

[HAMMER1DOWN]

AHH!! more 7X57 mauser shooters than i first thought. I love that round, as a matter of fact i am taking it with me on a bear hunt this weekend.
I shoot a.....
160 grain Nosler Accu tip bullet
36.5 grains of IMR 4895
PMC brass
C.O.A.L. 2.975"
I shoot this combo out of a Ruger M77 Mark II, recently just worked the load and love it. At 150 yards I get very nice sub-MOA groups.

[bfoosh006]

AND.... since most case lubes are water-based.... your chamber can rust ! One of my friends had it happen, the chamber got so badly pitted (Ruger No. 1) that we had to knock out the case with a cleaning rod. Almost ruined his hunt.

[Major Dave (retired)]

HAMMER1DOWN, what velocity are you getting with your 160 gr load?

[Xwrench3]

if you do not remove the case lube (i was using the rcbs lube at the time) and store the ammo for a long period of time, the cases will corrode much more. i did this with some 30-30 shells that i reloaded back in the late 80's, and looked at them this past fall. they were UGLY! the factory ammo in the box next to it was not pristene, but was in way better shape that the stuff i loaded. i no longer use the rcbs case lube (to be fair, i quit using it before i found this out), nor do i leave any lube on the brass now.

[Alleykat]

Any hydraulic in the chamber at the time of firing will, of course, increase chamber pressure. Isn't that really what this thread is about?

[a7mmnut]

As I told in an earlier post, I found from random chrono results years ago to do away with "grease" type case lubes. There's practically no possible way to get it all out if overlubed, and this will build up in the die, crinkling the case shoulder. I got very inconsistent velocities (resulting in poor accuracy) in various calibers while using the standard RCBS lube found in most reloading kits. Since then, I have always used powdered graphite as a dip when neck sizing rifle brass. Powdered mica will interchange just fine, and there's no way you can "overlube" with either if your cases are clean and dry in the first place. Don't forget that you must always tear down your resizing die and clean the plunger rod and inside walls as well when using any liquid case lube to prevent buildup and corrosion.


-7-

[HAMMER1DOWN]

On my 160 grains I am normally getting 2,750 fps. I haven't chronoed it, yet but that is where the book says it should be at. I don't know though for the 7X57 it bucks kinda hard.