Excessive Pressure in Factory Ammo

[Still Shooting]

I have just acquired a (new, unfired) Savage Model 11 chambered for 7mm WSM. I took it out to the range for a sight-in and barrel break-in yesterday and today. Yesterday, the 4th round fired bound up the bolt. I brought the rifle home, and last night took the barreled action off of the stock, examined everything, and was able to open the bolt. I found that the case head had flowed slightly into the extractor groove, and the primer was cratered (didn't leak) and somehat flattened.

I was shooting Federal Premium ammo, 140gr. Nosler Ballistic Tip (the same bullets I have bought to reload with in the near future).

My initial thought was that since I was running a lightly oiled patch down the bore after every shot, I might have left some oil in the chamber. So today I was extra careful to make sure the chamber was clean, and changed to patching the bore every 3 rounds. I had a half-dozen more over-pressure rounds in the remaining 16 Federals.

Has anyone else seen this kind of irregular charging/overloading in Federal factory ammo? Is there anything else that might have caused the symptoms?

 

[oerllikon]

ive noticed that S&B 7.62x54r had primers crater, and it kicks pretty hard. My only thought is that its loaded hot for hunting, or sloppy QC. I noticed cratered primers on the federal 9 luger brass i picked up at the range.(Im frugal) Its a little freaky

 

[M1key]

Have a smith check headspace.




M

 

[snake284]

I don't think I would run an oiled patch down the bore of any rifle while shooting it. The bore, if anything, should be very very lightly oiled. Not drenched i it. Oil is liquid and doesn't compress. Always have your bore clean and dry before shooting. What is your purpose of lubing it between shots? I would never do this. If you are trying to break in the barrel like this, that's not the proper method. All that will do is ruin a barrel. Get some good copper solvent. I use Deaton's Deep Clean. It is sold at Carl Deaton's web site right now as he is trying to go big time with his juice. You can order it at:
www.deatonsguncare.com it comes in 2 and 4 ounce bottles. It is ammonia based but has lubricants in it to keep the ammonia from damaging the barrel. Carl says you don't have to follow it with anything, but I do as a precaution. I always, after using any copper cleaner that contains ammonia, clean the bore good with it, then swab it dry with clean patches. Then I soak a clean patch in RemOil or BreakFree or something with Teflon, to coat the barrel in and out of the grooves. Then I swab this out well and swab it again with the same lubricant and clean it out again until the patches come out white. Anyway, for barrel breaking, if you're trying the shoot-clean shoot-clean shoot-clean method, use your favorite copper cleaner and clean it as mentioned here after each shot. But don't leave a thick coating of lub in the barrel. I do about five resolutions of the shoot once, clean once. Then after that, I go to shooting 3 rounds and cleaning. I do that about 5 revolutions of the three shots. Then I move on to five. As I increase the shots I observe how many times I have to run patches in before they come out clean. My last rifle build I broke in like this, after five rounds of shooting once ad cleaning, I moved to shooting 3 and cleaning. My bore began to clean up after only five cycles of this and then I moved to shooting it five revolutions, then cleaning as described. After five revolutions of five shots, I quit because the barrel was barely collecting any copper. But I was using Deaton's Deep Clean and I think it was getting all the copper out and therefore, the barrel where the rough spots were collecting copper, smoothed out and copper stopped collecting there way less. I called it broken in after that. Now that barrel is so accurate I can't believe myself. Now, I clean it once per range trip and it cleans up fast. Remember, Oil will not remove copper.

 

[Still Shooting]

I had used a copper cleaner both days, but on advice of a smith, done as follows: First, a patch with M-Pro 7 copper remover. Then clean patches until white, another with a drop of gun oil, and clean patch again. Yesterday, I dispensed with the oil entirely. No difference. Still had more over-pressure.

There are no signs on the casing of excessive headspace - no brightening of the case wall ahead of the case head at all, indicating stretching, just the flow and the primer. The rounds that did not bind showed neither of those things.

I also noted that the non-binding rounds were grouping at about 0.6", and those that bound up were "fliers," about 2" out of the group and high left or high right. Some of that could have been me, of course, getting used to the Accu-trigger

 

[Art Eatman]

I'm one of those who figures that "break in" is a waste of time. I enjoyed decades of sub-moa groups from quite a few rifles before I ever heard of breaking in a barrel, in 1999. Darned near 50 years of happy ignorance!

The nearest to dry that a chamber and bore can be and still not be in danger of rust is about all the oil I ever want.

As far as the performance and over-pressure, I'd check the headspace. Maybe mike the ammo's case length and overall length and check against publicized dimensions.

 

[243winxb]

Wet or oily chambers will make more bolt thrust. Same as a very smooth polished chamber. Buy a different brand of ammo. Shoot in a clean, dry rifle. If the problem goes away, you know its ammo related.

 

[Slamfire]

My initial thought was that since I was running a lightly oiled patch down the bore after every shot, I might have left some oil in the chamber. So today I was extra careful to make sure the chamber was clean, and changed to patching the bore every 3 rounds. I had a half-dozen more over-pressure rounds in the remaining 16 Federals.

Oil in the chamber will not cause combustion pressures inside the case to increase. It will increase bolt thrust marginally, but whatever reduction case lubrication may cause, it is discounted in calculating the bolt load. Bolt lugs and receiver recesses are sized without any derating to case friction.

I really doubt that a lightly oil patch in the barrel would do much unless you filled the grooves with oil. Because of past fear mongering, I used to pass a clean patch down the barrels of my match rifles to clean out any oil left in the bore. I stopped that as I found that first shot down the barrel clears everything out and I have never experienced any pressure issues. First shot down a clean or lightly oiled barrel usually has no relationship to where the rest of the group will go. This is particularly true the further you go out.

A bore obstruction is a different matter. Grease, patches, etc, all must be removed from the bore.

As you found, oil in the chamber or not, those factory rounds are overpressure for your rifle.

Call Federal and Savage and tell them your experience. It may lead to a recall.

 

[Still Shooting]

More Info on Federal Ammo

After "clearing the decks" this morning, I did some research. Called an old friend who is a serious gun guy, and between us we got to looking up loads for the 140gr. bullet in 7mmWSM. Federal advertises a muzzle velocity for their round at 3310fps. While Nosler shows a max load velocity of 3295fps with MagPro, Hornady and Sierra are more around 3200-3250 for a max load with all powders. Makes me feel more than ever that the Federal ammo is a little too "hot" for the rifle. I will check headspace, even though no evidence on the cases of stretch.

The other thing that occurred to me is, there's a minor chance the barrel could be a little underbored. Anyhow, I've got about 60 rds. of brass I can load and I plan to load a "ladder" from the bottom up. We'll see what happens with the lighter loads.

 

[M1key]

My suggestion was your headspacing may be a bit "short". If so, you would not experience stretching of the case.

Did you notice any pressure blow-by or "spitting" back through the bolt?


M

 

[Still Shooting]

No blow-by, nor any other signals besides the tight bolt, a bright wedge-shaped area of about 30 degrees where the case head was scraped after flowing into the extractor slot, and some cratering around the firing pin dent. No signs of blown primer, just a little flattening, and no powder residue on the case neck or elsewhere. I just put those cases thru a full-length resize, and they sized pretty easily. The chamber is pretty close to the die size. I'm wondering if whoever loaded those rounds for Federal used the Nosler max load without thinking about the fact that Federal brass is usually thicker than most any other, with less resultant case capacity...hmmm...

 

[GJgo]

When I first bought my 300 WSM I had the same thing happen with the factory ammo I bought to "break it in". I think it was RemChester, I don't remember exactly. Point being I think the WSMs are a bit touchy, so if you don't handload I'd find a factory load it likes & stick with it. I'm sure your 7WSM will be great when you get it dialed in.

 

[x_wrench]

just my opinion, but first, i do not run an oily patch down the bore while between rounds. oil in the bore will raise the pressure. if you want to clean between every round, i would use solvent, and dry the bore after. second, if i had 2 rounds in a box of ammo that was over pressure, i would be calling the manufactere. most likely, they would tell you to STOP SHOOTING them, send you a new box of ammo, and a call tag for the remainder of the box (boxes if they were all the same lot). it is so much cheaper to do that, than have a product liability and / or personal injury lawsuit, it isn't even funny. if you have a box of ammo that you think is over pressure, you should never keep shooting it. it can ruin the gun at best, and put you in the ground at worse. i do not care how much the ammo costs, it isn't worth dieing for. if nothing else, think about how far $50.00 would go in a hospital enviroment. you would probably be lucky to get two tylenol and a glass of water for that!

 

[Fullboar1]

When you fire your rifle and have oil in your chamber when the case expands the walls of the chamber are to slippery for the case to stick to it (all happens in a 100th or 1000th of a second) and the case slams back against your bolt/firing pin and the case sometimes stretches as well as showing other signs of overpressure . I have had it happen a few times as well and oil in the chamber was usually to blame. If you are breaking in a barrel instead of running a patch with oil on it try running a patch with a good quality Window Cleaner after every shot, then after every ten shots run some copper solvent through it until clean. A number of barrel and rifle makers recommend using Window Cleaner for breaking in a barrel, try it and I think this will help you.

 

[M1key]

^^^
Because window cleaner has ammonia, the active ingredient in a lot of copper solvents/bore cleaners. Personally, I don't like to use such aggressive cleaners, at least very often, and I would advise against leaving them in the bore too long...like more than 30 minutes.

M