Waves or indentations on 06 brass?

[Dr Killdeer]

This is one pretty strange, so I better give you guys the load specs first.

30.06 Browning BAR
180 grain Nosler Accubond
55 grains of H-4350
200 CCI LR primer
Remington brass; 7th time reloaded.
3.280 OAL
Average speed for a 10 shot string is 2609 fps.

The load is not hot by book specs and the spent brass confirms that there are no telltale signs of excessive pressure. It cycles perfectly and I get very tight groups at 100 yards from a cold barrel.

Here’s the problem; Yesterday I shot three groups of three shots each from the lead sled, allowing for barrel cool down time. (long day for only nine shots) In two of the three groups there was a flyer. I thought it was me, but I realized when I got home that two pieces of brass had waves or indentions on the shoulder.

Those two pieces look like they were put in a shotgun crimp starting die, except the waves were not as sharply pronounced and they were on the shoulder. Nor was there any symmetry to them. One piece had opposite waves at say, 6 and 12 o’clock, while on the other piece they were all together, like in a row.

They’re not dents, just small waves, right on the shoulder, from the beginning of the taper to the bottom of the neck. They’re visible, but you can hardly feel them.

I inspected the chamber and there’s no foreign matter or debris that would have caused it. With the pressure in there, you would think it would be impossible for brass to have any kind of concave indentations after firing, especially on the shoulder, Right? It appears to defy the laws of physics.

And why only two rounds out of nine? Why not all of them? Why two waves on one piece and three waves on the other? I’ve never even heard of such a condition before. What the hell could be causing that? I’m at a complete loss for answers here!

[RaySendero]

Doc,

Any chance you could post a pic of these cases?

[oneoldsap]

I've no idea what those dents might be , without pictures . What I do know however is that IMR-4350 is a poor powder choice for a gas operated semi-automatic and will damage the recoil buffers in your Browning , with repeated use . Use a powder with a faster burn rate , such as 4064 or 4895 . You didn't say if you were cleaning between strings or not . If you are and are leaving a touch of solvent or oil in the chamber that might account for your flyers and wrinkles !

[PA-Joe]

Are these bulges from using too much lube? Did you check some of your other reloads for this same twist/bulge?

[steve4102]

What I do know however is that IMR-4350 is a poor powder choice for a gas operated semi-automatic and will damage the recoil buffers in your Browning ,

This has been debated before, so I'll be brief. The BAR is not a Remington or a Garand and it will not be harmed from a powder such as 4350.

Winchester Supreme ammo is loaded with Win Supreme 780 Powder, it's close to R-22 in the burn chart. I contacted both Winchester and Browning awhile back and asked if it was safe to shoot Supreme ammo in my BAR. I was told, Yes it is safe and it will not damage the BAR. So, if Supreme 780 will not damage the BAR a faster powder like 4350 certainly will not.

As for your dents/waves, pictures would help.

[dawico]

A basic question here, but are the cases trimmed to proper length? If they are too long or not square at the mouth that could cause some funny business with pressure in the chamber.

[F. Guffey]

I do not have a clue, but, if it happened to me I would think the case is coming apart near the head of the case leaving the rear of the case to slide to rear and the front of the case to slide forward, the case body sliding forward cause the case to wad up, crease or fold.



Because I check head space first then form instead of fire to form, I do not believe this is an event I have to worry about, fired 8 times in a bolt gun? NO, in a Bar,, then there is that thing about full length sizing and then full length firing, I try to cut down on all that case travel, for me full length sizing 8 times for a Bar chamber would be a few too many firing cycles, and the problem did not appear in the first 7 firings?



F. Guffey

[Unclenick]

As suggested before, the dents have to be occurring hydraulically during firing or being applied during ejection, or the pressure would have ironed them out. A flattened wrinkle would be one thing, but a smooth concavity will not survive firing pressure unless it is being hydraulically impressed during firing. Oil, grease, or even water could conceivably do it. Grease is likely to survive and be present in the dent. Oil and water can evaporate in the heat.

For dents on ejection, look for scrape or scratch marks inside the dent or for a rounded object they could strike during ejection. Look for brass rubbed onto such a location on the gun. They can happen. I once watched a fellow firing a German light machinegun that put a rounded shoulder dent into every single case. The cases were struck in the gun before getting clear, but not on a sharp edge of any kind.

In your case, dents caused during ejection that don't normally appear could be a symptom of a round that fired with different pressure, so, in that event, the cause of the problem is not what made the dent, but rather is something that resulted in operating the gas system such that a dent occurred. It could be a bad charge, bad primer, an untrimmed case that jammed in the throat as Dawico suggested (which raises pressure, dangerously), or a case that has just passed its life expectancy and is stretching too easily at the pressure ring. Inspect your cases carefully, feel for the pressure ring with a paperclip probe.

If the gun got the dents hydraulically, that can raise start pressure a little, but more likely interferes with the 50% or so of powder that normally starts out chasing the bullet down the bore. That raises pressure a little further. A chronograph would help the diagnosis because you would expect to see the velocity of the errant rounds to be significantly different from the others.

As the guys said, a picture really would help.

As to using 4350, I suspect both sides of the argument are correct. I say this because Browning's own history of gun on their site says the whole gas system was redesigned for the Mark II that was introduced in 1993. The purpose was to improve reliability, which likely covered everything from feeding well to tolerating any kind of commercial ammo. So, if you have one of the two pre-'93 models, then slower powders are probably to be avoided, but if you have a post-'93, you should be good to go with any of them.

[woods]

Do the dents look like this

[Unclenick]

To my eye, that looks typical of a case striking something on the way out the door. A simple verification test is to see if it will drop back into the chamber to the same depth as a fired case without that dent does? Don't close the bolt, as that may force it. Just go by finger. If the dent was formed inside the chamber (hydraulic) it should still fit as well as any other fired case. If formed by a strike it will typically be raised a little around the perimeter and not fit smoothly in.

[Uncle Buck]

Is it possible the brass has thinned enough around the shoulders and is filling or flowing from the pressure

(UncleNick, Is this the right terminology?)

If it is not hydraulic, that is the only thing I could think of. I would probably not use the brass again.

[Dr Killdeer]

My trim length is 2.484 and I keep it consistent. I regret not using the Chrony for those nine shots.

I tried to take some pictures of the brass, but it doesn’t show the waves. No, Woods, yours is a real dent. Mine are small waves, but I think you guys put the hound on the scent.

I’m going to check to see the fired cases with “waves” will chamber the same as the other fired cases. That might tell the tale. Then, I’m going to completely break the rifle down to check the chamber and the whole gas system for any oil, solvent or water. Next, I’m going to swab the resizing die with Q-tips to see what turns up there.

Those rounds were on spec and pristine after I loaded them, but I can’t discount the possibility that maybe there was case lube on the neck from handling them after resizing. I didn’t think of that.

I’m also going to break out the Dremel and cut a case in half lengthwise. Then I’ll borrow a friend’s high resolution camera and post pics of both the inside and outside of the cases.

Tomorrow I’m going to call Browning and pose the powder question to them, using my gun’s exact serial number.

I know BAR’s are tough on brass, but I don’t want to alter anything until I know exactly what’s causing this problem. It could be something simple, buy with my luck, I doubt it. In any event, it’s not beyond the capabilities of the pooled knowledge on this forum.

Thanks again guys for the scoop. To be continued: