New Barrel Puzzling Developments???

[RonAKA]

I decided to dust off an old Browning Mauser Action chambered in 264WM. It belonged to my father and I inherited it from him. The original barrel was burned out, and he had a new barrel fitted just before he passed away, and it had never been fired. I have no idea where the barrel came from and who chambered it. Unfortunately it is a light weight 22", so not ideal for this big cartridge.

So I loaded up some Federal brass for it that had been sized down from 7mmRM. Have done that many times in the past and thought nothing of it. However when I tested it I got some strange results, including poor accuracy. I did 20 loads with H4831, and 107 grain Sierra bullets. It included 5 loads each of 64, 65, 66, & 67 grains. The starting load was extrapolated from the Hodgdon loading data, which gave 63.8 as a starting load and 68.7 as the max load.

So here is the most obvious bad effect. Three cases had major dents after firing:

The left two came from the lightest batch of 64 grains, while the right one was from the next lightest load of 65 grains. Could this be a secondary explosion effect with too little powder, that Sierra warns against? or??

Here is what the primers looked like. The left one is 64 grains, middle one 66 grains, and right one, the heaviest load of 67 grains.

To my eye, the middle one is showing the least pressure. It had 66 grains. The right one is getting up there for pressure at 67 grains. But strangely the lightest load 64 grains seems to be showing significant pressure too??

I measured case webs of the fired cases and got based on the average of 5 cases:

64 grains - 0.5081"
65 grains - 0.5079"
66 grains - 0.5073"
67 grains - 0.5080"

This suggests highest pressure in the lightest load and the one that had two dented cases. Similar to the primer story the 66 grains seems to be the lowest pressure.

Last I measured the fired case neck OD, and this may be part of the problem. I got a 5 case average of 0.2897". This seems to suggest a chamber neck of about 0.2907, and very tight for a sporting gun. The Norma cartridge drawing shows 0.298 to 0.299 for a loaded round neck. Since I used necked down 7mmRM brass, I suspect I had a very tight fit in the neck, but I don't remember the cases being that hard to chamber. Thoughts? Am I looking at neck turning these cases to make this gun safe?

Help!

 

[243jimb]

To me that looks like hydraulic denting, are you sure that the chamber is clean and free of oil or grease? If it has been in storage for a while there may be traces of thickened oil that may require careful cleaning and degreasing of the chamber (and barrel !)
Jim.

 

[Dgd6mm]

Looks like hydraulicing.

 

[jo191145]

What your seeing is blow by. For one or several reasons your brass is not sealing/obturating in the necks. Usually blamed on light loads it also can be caused by age/work hardened brass.
Any excess headspace does not help.
I'm not familar with the cartridge so won't comment on the charge weights.

Try to drop a bullet in your fired brass. Good chance it won't slide in on most cases. Check them all and maybe you'll find one that does (higher charges most likely)
If you find a case a bullet will drop into you can begin to compare measurements. If you find a sloppy one and you'll have a better idea of the chambers neck diameter.

If you don't its possible you have a tightneck and hardened brass.



If you do find some that expand more than others you can anneal or buy new.

 

[OKIE2]

if you like the rifle then scrap the barrel 22 inch is no good for 264 mag anyway. you can also send it to E. R. Shaw they will fit a 26 inch barrel on it for you about $200.00.
I have bought 3 barrels from them they are all good accurate shooters.
And buy some new brass.

 

[Laurie]

What your seeing is blow by. For one or several reasons your brass is not sealing/obturating in the necks. Usually blamed on light loads it also can be caused by age/work hardened brass. [Joe Hecht]

Joe is dead on - definitely failure of the case to to obturate, and often called 'gas dents'. For some reason, 6.5s are prone to it and I've seen it many times in 6.5X55mm despite that being a much smaller case and the only fireforming being a new case to the chamber. You can see powder fouling inside the dent on the middle case in the photo.

Portuguese FNM 140gn FMJBT 6.5X55mm factory cartridges were very prone to suffer this problem, but it would only appear at certain times in any particular rifle for no obvious reason. This ammo was very lightly loaded and used what looked an inappropriate powder too - a fast burning small diameter spherical type that only filled two thirds or so of the case.

The usual causes are wrong powder and/or too light load and/or primer that the load doesn't like. I would start by increasing bullet weight above the very light 107 that you're using, or if you're going to stay with that bulletr weight, switch to something a bit faster burning like 4350 for a fireforming load. Running your 107 / H4831 loads through QuickLOAD, they look OK pressure-wise although the starting load of 64gn is a bit on the low side for an over bore capacity magnum at only 48,500 psi pressure.

I don't know how much fireforming is involved in 7mm Rem Mag to .264 Win Mag, but ruined cases caused by such dents are not unknown in other fairly drastic operations such as 6BR to 6 Dasher.

Have a look at the various threads on this forum on forming the 6 Dasher for tips. To save barrel life, many people use no bullet methods with small charges of fast burning pistol powders such as Bullseye or Unique and a COW or other breakfast cereal filler, or a case-neck plug alone made of candle wax softened by melting with some olive oil. With the .264's short barrel life, this may be a good option.

Laurie,
York, England

 

[Tozguy]

Just curious as to why the dents can not be 'fireformed' back out using the appropriate load. Reason I ask is that I have some 300WSM FC brass with small dimples in the shoulder from too much lub in the sizing die and was hoping they could be salvaged.

 

[Laurie]

Just curious as to why the dents can not be 'fireformed' back out using the appropriate load. Reason I ask is that I have some 300WSM FC brass with small dimples in the shoulder from too much lub in the sizing die and was hoping they could be salvaged.

That never seems to work, nor even for relatively small shoulder dents or folds - don't ask me why! There's certainly no chance with the sort of dent on the cases in the photo. The inward facing folds alone will stop it happening.

 

[Tozguy]

Thanks for saving me some trouble Laurie.

 

[RonAKA]

Thanks for all the really good comments.

I don't think there was any kind of special preservative in the chamber, but that is a good point, and I will clean the chamber just to be sure.

I agree that the basic problem seems to be insufficient pressure to expand the neck and seal it. The gases blow by and collapse the case. This would suggest at some point the pressure outside must be higher than inside, and it would be after the bullet has left the neck. I don't know how that fits with the possible secondary explosion effect, or if that is occurring. I measured all the necks and found the largest one measured 0.2992. This was one of the light loads, but not a dented case. This case fits back in the chamber with no noticeable interference, so the chamber neck must be at least 0.300 or so. In this case I could force a 0.2638 Sierra bullet in (same 107 ones I tested with), and a Speer that measures 0.2632 easily drops in. In other cases Sierra does not fit, and the Speer sometimes can be forced.

So I don't think I have a neck size problem, and will put the neck turning idea on the back burner until after I have tested some heavier loads, to see what my chamber neck really is.

The brass was brand new, so it shouldn't be too hard. I've sized down cases before from 7mm to 6.5mm and gotten 20 loads out of them before the neck splits -- no annealing. Possibly this is a hard batch of brass. So, I think I will anneal them all after resizing just to be sure they are stress free.

There really is no fireforming required for converting 7mmRM to 264WM. The cases are identical except for the neck diameter. 264WM on left and 7mmRM on right.

Thanks again for the comments. I will probably do more testing starting at 67 grains and working up. I think I will contact Hodgdon and tell them of my experience, and question whether the starting loads are correct for H4831. I know when you look at their loads for 140 and 160 grains that something must be wrong. Either 140 is way underloaded or the 160 is overloaded. I've used 62 grains of 4831 for years behind 140 grains. That is way over their max load. And based on this recent experience, I would not consider their starting load of 51.7 grains. Seems way way too low.

 

[Kenny474]

Ron, My manual states 65.5gr of H4831 as a starting load, and 71gr as max load for 100gr bullet. It also states 56gr start and 61 max for 140. 52.5 and 57 for 160.

From what my manual says, your 67 grain load will probably be a good starting point.

Though a slightly faster powder, such as H450, may build pressure a bit faster and help the blow by issue by expanding the case faster. Though that is just a thought, as I have never loaded for a .264. The barrel length may also be playing a part, as it is awful short for such a large case with slow powder. Again, merely a thought.

I hope you get this thing figured out so you can enjoy it.

 

[RonAKA]

If you look at the Hodgdon Data Center on line they show the following for H4831:

140 grain - 51.7 start, 55.0 Max
160 grain - 58.1 start, 61.8 Max

http://data.hodgdon.com/main_menu.asp

I'm quite sure they have reversed the loads for these bullet. Serious error I believe.

 

[Kenny474]

I think you are right about Hodgdon's mix up. No way is the start load higher for a heavier bullet than max for a lighter.

The info I gave you is from Modern Reloading second edition.

 

[RonAKA]

I did some measurements on the seating depth of this 107 grain SMK relative to the lands in the barrel. There is little doubt that with the long boat tail, and low drag ogive profile, the front of the boat tail is exiting the cartridge neck before the bullet contacts the lands. Is this likely to contribute to the blow back and denting issue? I would think there would not be a significant pressure spike to expand the neck until the bullet contacts the lands.

 

[zullo74]

Just curious as to why the dents can not be 'fireformed' back out using the appropriate load. Reason I ask is that I have some 300WSM FC brass with small dimples in the shoulder from too much lube in the sizing die and was hoping they could be salvaged.

With an appropriate load, the dents WILL be fireformed out. I have seen it happen EVERY time I've had case lube dents in the past 30 some odd years of reloading.

 

[RonAKA]

Just curious as to why the dents can not be 'fireformed' back out using the appropriate load. Reason I ask is that I have some 300WSM FC brass with small dimples in the shoulder from too much lube in the sizing die and was hoping they could be salvaged.

With an appropriate load, the dents WILL be fireformed out. I have seen it happen EVERY time I've had case lube dents in the past 30 some odd years of reloading.

I will find out. I sacrificed the worst dented one to make a throat depth sizing tool, but I will save the other two for what I determine to be the safe max load, to see if that will round the case back out again. I fully annealed the dent area so if they are going to form, they should have the best chance.

 

[Adam Morris]

Ron, the picture of the dented brass seemed to indicate that the cases were dented in a very similar fashion and at the same location on the cases. Did you note if the cases were dented at the same rotational position relative to the chamber? If so, then that would possibly indicate that there might be an abnormal chamber shape contributing to the issue. The pictures of the three primers appear to show a normal progression of pressure, with the right hand side starting to show what I would consider a normal amount of pressure. I would carefully check the chamber, as previously suggested, before further firing of the rifle. I have never had dented cases like yours, but my experience has been that even deep lube dents have always blown back out(like the kind you can get from case forming).

 

[Ackman]

I have a real hard time believing those dents are from blowby. And if there were something rigid in the chamber causing it, those cases would never extract. Looks like maybe they banged into something during extraction. To really tell what's what, I think you'd have to see the actual gun and watch brass extract from it.

 

[RonAKA]

I didn't notice the dents until I got home, so no idea what the position was. There is no marking at the dents to indicate that it happened from some kind of mechanical damage, like dropping them, or foreign object in the chamber.

I shot 20 rounds total in increasing charge. There were five cases in each charge level from 64 grains up to 67 grains. So two of the first five at 64 grains dented, and 1 out of the second batch of 65 grains. All the rest of the cartridges look perfect.

 

[Kenny474]

Ron, I think you may have been onto something when you said the bullet was leaving the case before engaging the lands.

Maybe try crimping a few rounds to try and boost shot start pressure, or use a longer bullet that will hit rifling before leaving the case. I would be willing to bet the second option would give better results, and the first may help as well. I doubt either will hurt, and it may even help to solve the problem.

As far as being damaged on ejection, you would have to tear the bolt open with authority to eject cases fast enough to be getting dents like that. When my Remington 740 starts getting dirty it will cause neck dents and also smaller dents similar to yours, but it's a semi auto and operates a lot faster than most people cycle a bolt gun. Not to say it's impossible, it just doesn't seem likely to me. Unless maybe the ejector is ejecting too early.