6,5-06, pressure problems.

S

Stefan Karlsson

Guest
A good friend of mine have a 6,5-06 built around a Tikka action and a Walther SS barrel 1-9". The rifle is built with the Swedish F-Class clone and longrange BR in mind. The rifle shot really well in the beginning with 123 gr. Scenars and everything was just fine. After a few hundred rounds strange high pressure starts to shows randomly even with moderate loads. A load of 50 gr N-160 behind a 123 Scenar works great but every now and then there´s pressures that makes the primer fall out of the case and heavy marking on the case from ejector etc:eek:

We have tried to find the cause of this behaviour but we can´t really se whats wrong!? It seemes like it´s a bit better when the barrel is really clean but the problems comes so quick that I really doubth that fouling build up is the problem. I checked the barrel tonight with my borescope and I can´t se anything out of order.

Any ideas?
 
Perhaps ***

Some of the case necks are getting too thick for the neck in the chamber. If you can not finger seat a bullet in a fired case that may be the problem. If so neck turning should cure the problem. Good luck
 
If that dont work

Check to make sure that you are not oversizing the cases too much. I only have experience with the PPC but I ran into that when I was shooting the upper load window and bumping the sholders back too far.
 
The necks have been turned to rule out that but with the same results as with unturned necks...... I´ll check with my friend about the shoulder bumping!

Thx.

Stefan
 
Necks are turned so there should be no problems with the outside dia beeing to close to the neck dia of the chamber. The length is also checked and rechecked.........

The shoulder is set back 0,001" while resizing, ecsess headspace isn´t the problem......
 
Stefan

Try seating a bullet in a resized case, no powder or primer. Then measure the diameter of the neck where the pressure ring of the bullet stops in the neck. Compare that measurement to the neck diameter thats stamped on the barrel.
I like 1.5 to 2 thousands clearance a little more wont hurt. You might also try removing the fireing pin and "feel" how that same case chambers in the rifle ( if it is indeed the thick neck or cases too long, you can feel it when lightly closing the bolt). If your sure thats not the problem then take several measurements on one of the cases that show pressure and then resize that case and compare measurements. That may reveal the problem.
Good luck
 
If you haven't explicitly verified the neck and shoulder of those cases that have problems against those that do, you could be making assumptions that, on measuring, could be incorrect.

I had a similar issue with some PPC cases. Turned out to be two things:
1. On some cases, I made errors turning the necks. It was my first attempt and I plain goofed it.
2. On some cases, the shoulders would not set back. I assume, but do not know that this was caused by old, work-hardened cases getting mixed in with my good cases.

I cured both by throwing away the whole lot and starting over with new cases. I also now measure, measure, measure.
 
Going along with what SG said

Does your friend have the proper measuring tools to determine sholder bump and neck thickness.? First he must know the neck diameter of the chamber and the overall length. If its not stamped on the barrel he needs to contact his gunsmith and get the diminisions of the reamer. A pair of good calipers will tell you if your neck is too thick, (a 1" mic is better) or if the case is too long. A good tool to measure sholder bump is the stoney point device. Keep in mind that is not the true datum only a reference point. To measure push the primer out without resizing the case and take a measurement. Next resize the case and re measure. I'm sure that Im being too basic but other than an overcharge (faulty powder scale or drop) I cant think of anything else that would cause his problem. Most of us have been guilty of not measuring correctly. Please dont continue to shoot it till you find the problem
 
Is the top of the boat tail in the neck or is it seating below the neck shoulder junction. If the bearing surface of the bullet is seating below the neck, you could be seating into a doughnut caused from neck turning. Try new cases and see if your problem goes away.
 
Isn't about time we considered checking whether the clase length is within tolerances? One here & there that's grown enough to jam into the throat could cause these signs.
 
John Kielly said:
Isn't about time we considered checking whether the clase length is within tolerances? One here & there that's grown enough to jam into the throat could cause these signs.
Click to expand...

That would probably be one of the first things to check especially with the shoulder angle that an '06 case has as they would be prone to grow in case length.
 
Good possibility

John Kielly said:
Isn't about time we considered checking whether the clase length is within tolerances? One here & there that's grown enough to jam into the throat could cause these signs.
Click to expand...
I've seen that also But SG and myself mentioned that as one of the contributing factors in our previous post
 
The bullets was indeed seated quite far down the neck and close to the neck/shoulder are but NOT past the end of the neck. We decided to throat the barrel about 3 mm and give it a try. We fired 10 shots today with bullets clear away from the end of the neck/shoulder area without any signs of high pressure:confused:

The fact that we used fresh cases and the bullets wasn´t seated past the neck into the "doughnut-area" convinsed me about the deep seated bullets wouldn´t be a problem....... The fact that we formed 30-06 cases mabye result in a "long doughnut" that will result in a jam in the chamber that sends the pressure thru the roof in some cases?

We had -14 C toady and that calmed us down a bit regarding staying around at the range:cool: We will go on and do more tests and make sure the pressure problems is gone when the temeratures rices a bit:D
 
Hello: I had the same problem with my 6.5 Gibbs on the third firing of 50 cases. Even when I fireformed new cases I would end up with ejector marks and loose primer pockets. I kept lowering my powder charge but the pressure problem was still there. Checking out the barrel with my borescope didn't seem to show anything in the throat area. I happened to mention this to a very experienced shooter and he said there is a possible carbon buildup or a slight roughness in the throat of the barrel. I closely looked at the throat with my borescope again and didn't see much if any carbon build up but there was that roughness from the start of throat erosion. Anyway, he recommended that I use Iosso paste and clean up the throat. Well I did and it fixed the problem. I used a nylon brush with the Iosso on it. I assume it cleaned up some of the carbon and a little of the roughness. Iosso is not very abrasive so it couldn't have done much. The throat sure was nice and shinny thou. I imagine you could use any of the bore pastes to do this with. This might not be the same thing you have wrong with your rifle but it is another idea to try.
 
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