Gunsmithing Thoughts?

[erikc641]

So I had a 22-6mm Remington built on an old M77 (tang safety) action with a Krieger barrel (8 twist). All the work was done by a smith who I had yet to have any reason not to trust the work. After the work was done, I shot the 80 grain ELD Match (48.0 grains of H1000, all same lot, set at .010" off the lands), using Hdy 6mm rem brass, for a little while. It was working great too. When I neck the brass down, the shoulders aren't touched and I use headspace gauges to set my dies. Anyways, on the 3rd firing of the brass, one of the pieces split about 1" from the base all the way around. It was a very precise, laser like cut. After, the gun is failing to hold 3" at 50 yards and bulges the cases about .016" about .25" from the base. I have a lot of ideas as to what had happened but maybe someone here can help narrow it down for me. All charges are weighed on a balance beam scale, calibrated before and after loading.

If there is any other information someone needs, please let me know. I keep very good records.

 

[erikc641]

I had to back the loads way down, to at or just below, listed starting. The gun is still bulging cases and showing pressure, which it didn't do before. The cases were growing .009-.017" per firing after the incident. Before they were still growing, but around .005-.007". With the lack of any real shoulder angle on the case, perhaps this is unavoidable but .017 is ridiculous.

 

[EXTREMEPREJUDICE]

Since you have headspace gauges check your rifle. Do you have a field gauge? If it's in tolerance I would be guessing you are oversizing your fired brass. A case mic or comparator is a much better tool to use to set your dies, rather than headspace gauges..........my opinion of course.

 

[erikc641]

The comparator is what I am referring to when I say "headspace gauges". It is the set, by Hornady, #HK66.

 

[erikc641]

I do have a go and no go gauge on the way, but no field gauge.

 

[ptm121]

So brand-new brass grows 0.017" using the hornady comparator?

You say you're not touching the shoulder when re-sizing. What kind of die are you using?

How far are you bumping the shoulder back when re-sizing? It shouldn't be able to grow any more than you bump it back...

It sounds like the shoulder isn't expanding properly on the first firing. Are you leaving a false shoulder so that the bolt closes with a little pressure after necking down to .22?

 

[Mordamer]

If you are "bulging" cases just above the head you need to stop firing the gun immediately. Take it back to the gunsmith and give him a chance to look it over. Take a bunch of the fired cases and virgin cases with you if you can. If this was a barrel I chambered I would certainly want to examine it myself to determine the problem. It sounds like something has stretched or changed as far as chamber dimensions. If this is the case, then the gun is unsafe to shoot until a competent gunsmith has examined it and given it his blessing.

 

[erikc641]

It is back with him now

 

[erikc641]

The shoulder is bumped .001-.002 when resizing. This is only done when they no longer chamber from neck sizing.

 

[erikc641]

It was working fine and then after the case ruptured, it isn't anymore.

 

[Mordamer]

It was working fine and then after the case ruptured, it isn't anymore.

Describe what happened when that case ruptured. Did it damage the firearm? Did you simply open a normal feeling bolt and eject half a case or was there a lot more to the incident than that?

 

[erikc641]

It didn't damage the firearm in a way that I could notice. The bolt opened normally, other than the feeling of not pulling a normal case out of the chamber. The rest of the case fell out by tapping the butt of the stock lightly. No damage to the bolt.

 

[erikc641]

The chamber was pretty black but a casting was done and was given the all clear by the smith. No damage was noted to the chamber. Then the bulging of cases started showing up. The case goes from about .463 at the base to about .475 about .250 up the case. Neck tension on my cases is between .001 and .002. Dies are clean polished and undamaged.

It's all very weird. The smith is taking care of me on it, but I want an explanation and so does he. There is a reason for all of this. We both have ideas and are just narrowing it down via process of elimination.

 

[erikc641]

Sad thing is that this is on a Krieger 7.7 twist barrel

 

[erikc641]

Threads cracked

 

[Mordamer]

Threads cracked

Barrel tennon threads cracked? If so you are lucky you didn't have a kaboom. Pics?

 

[erikc641]

On the receiver

 

[erikc641]

 

[Mordamer]

Wow. Interested to hear a potential cause.

 

[Mordamer]

So the headspace changed because the receiver cracked and stretched?

 

[erikc641]

Yes, the barrel unscrewed by hand. As far as the cause, I have heard a few things, many amount to this is why some gunsmiths will not work on this model of gun in particular (something with the way the receivers were made and not very strong, especially for a round like this). Regardless, it a paperweight now and some of the parts are now for sale.

 

[fdkay]

Wow. Interested to hear a potential cause.

The cause is likely the fact that it is a crappy, investment cast receiver.
There is a reason no one builds on M77's.
They are shit.

 

[whatsupdoc]

Seems weird, it looks like the threads failed.
Need the barrel spinners to chime in on this as there are a ton of these out there.
Are they that weak?

 

[erikc641]

I had second near miss with this "gunsmith" where a barrel wasn't properly put on after having it threaded. The barrel unscrewed by hand and luckily I caught it. Thinking is maybe what happened with this rifle too (maybe not that loose but loose enough to become dangerous over time ie backing out). The gun was a 22-6mm before I rebarreled it.

 

[WeiserBucks]

OP needs a new smith and someone with knowledge of the investment cast Rugers should chime in .

 

[erikc641]

I don't have him any more

 

[erikc641]

Having the second incident made me realize it may not be the receivers fault

 

[erikc641]

we will never know

 

[whatsupdoc]

OP do you still have the Ruger receiver? Looking at the picture with the hole in the threads, is that due to the front action screw being too long and maybe punching through the receiver.

 

[DAVETOOLEY]

From a barrel spinner who has done some builds on M77's.

Looking at your pic I don't see anything that alarms me. No crack on the face of the receiver. If I had it here in the shop I might have a different opinion.

 

[flatland1]

I don't know many guys who regularly work on the Ruger M77s, but always thought it was mostly due to prejudice based on a lot of BS being floated around about investment cast receivers. This sort of thing kind of makes me wonder though...

 

[fdkay]

I don't know many guys who regularly work on the Ruger M77s, but always thought it was mostly due to prejudice based on a lot of BS being floated around about investment cast receivers. This sort of thing kind of makes me wonder though...

Likely more due to the special jig it would require, can't remove the trigger hanger,