Custom 30-378 problems...

[1Bullethead]

Hello everyone,

I am new to this forum, it appears there are quite a few knowledgable folks, so I am looking for some advice. Several years ago my uncle, a friend, and I had three identical guns made. Winchester stainless .375s rebarrelled to Wby 30-378. A reputable gunsmith did his magic on the fit, barrell, bolt, and magazine work. My Uncle's and mine have "seizing/jammed" bolt problems, the 3rd does not. We only shoot factory loads (until we get this figured out).

After my first three shots the action could not be cycled by hand. A rubber mallet was used to coax the bolt up. The primers were blown so I knew it was a pressure problem. I made inquiries to Wby and the traced my box of ammo to a lot that was one of their first produced and admittedly made too hot. The box was replaced by Wby. Since then, about every 5 shots I experience the same stiff action problem, but not nearly as severe. I can work the action by hand, but very difficult and would be a bad deal if it happened in the field.

The gunsmith has looked over the rifles two separate times, no improvement. I have since moved away from him, so I am trying to solve this with new resources. There are consistent score marks that are about 3/8" wide, start 1/2" from the shoulder and disappear at the belt. They are more pronounced on shells that "jam" after firing.

I am thinking I need to put some ultra fine paper on a dowel, in a drill and polish the chamber. I am a little nervous about this, so I am looking for advice. Could my problem be caused from something else?

In general the gun is great. It has a 27" barrel with 1 3/4" of porting. It is very accurate and amazingly reasonable to shoot, less the noise. A picture of a shell with the score marks is below, a little blurry. Any help is greatly appreciated.

[1SHOT_1KILL]

Judging by the looks of the marks on the case it looks like it could be either; An egg shaped chamber, a rough spot or a scored area caused by a chip or shaving under a flute of the reamer, in the chamber or it could be that the marks were made on feeding into or extracting from the chamber by hitting the mouth of the chamber, magazine lip, and/or feed ramp.

As for the sticky bolt, it could be that the headspace is just a thousandths or two off or it could be that the bolt has been set back a couple thousandths. Either way I would have the headspace rechecked first. Then, check the locking lugs to see if they have not been set back or burred. If the headspace is off, it is a fairly simple matter of resetting the headspace, and while your are at it have the lugs lapped in. At most you'll should only lose about 1/16" of an inch or .062", of barrel.

I forgot to say that you should NOT run anything like dowel with sand paper or emery cloth, or anything else in the chamber. The only thing that will is ruin the chamber, no matter how careful you are.

[UncleNorby]

I'm no expert either. The only thing I would suggest is having your chamber worked by another smith. I would not try any sort of sandpaper.

You could do some testing with "light" handloads. Start at the low end of the recommended loads and see if you have the problem. Work up until you begin to have trouble, then back it off. Maybe you'll have a load that works for you. If not, I guess you need to have it re-worked.

[pharaoh2]

1bullet, are you noticing any blow-back? gasses leaving "burn" marks on the case or by the exhaust ports on the side of the reciever?

[Briman]

Winchester stainless .375s rebarrelled to Wby 30-378. A reputable gunsmith did his magic on the fit, barrell, bolt, and magazine work. My Uncle's and mine have "seizing/jammed" bolt problems, the 3rd does not. We only shoot factory loads (until we get this figured out).

Was there sufficient freebore cut into the chamber?
Weatherby gets away with hypervelocity chamberings by making the freebore very long to keep pressures down. Fairly common problem with nonweatherby rifles rechambered for weatherby cartridges if the gunsmith doesn't know exactly what he is doing.

The scratches or irregularities are the brass being swaged into imperfections in the chamber under very high pressure, you probably won't see these if the loads are shooting within sane pressure limits.

[1Bullethead]

I knew this would be the right place to go...

1Shot_1Kill - You were correct in that the score marks I am seeing are coming from feeding. I cycled some nice new shells and yup they were there. Appears to be hitting the mouth of the chamber. Now that I am paying attention to it, I can feel some slight resistance on the bolt as I chamber a round. I miked some spent casings against the new ones/spec, nothing appears to be deformed. Other than the shoulder radius is blown out a bit. I am assuming this wouldn't be a problem even when reloading these cases... correct? Thanks for the other advice, the original gunsmith re-checked headspace and lapped the lugs, plus more. I am still going to take it to someone else for a second opinion. Finally, I will NOT try and polish the chamber, thanks for the heads up.

Pharaoh2 - I have no visible blow back on the case or gun. I did from the 3 shells from my first box which Wby told me they were "hot". None since.

Briman - The light bulb went off when I read your post. I remember the conversation with the gunsmith (now over 3 years ago) about what weight bullets I would be shooting, so that he could set the rifling lands. At the time I responded with "180's only". My plan was/is to only work with that weight, to get it as accurate as possible. The thing that burns me is that I knew then, that Wby free bores their rifles. Like an idiot I did not think to question the consequences. Additionally, I do see very small "striations" running the length of a spent case, consistent around the whole thing. They are small but many. I believe you are correct that I am experiencing high pressure problems due to not having free bore.
*** For sanity I inspected some spent cases from my other calibers. No marks on them like I am seeing on the Wby.

I will again ask for advice on options. I am figuring I can have free bore cut -or- hand load with less powder. I have heard there are negative impacts on accuracy with free bore, but I have no direct experience with this. Currently, I am very pleased with the accuracy.

The gun was kind of a "why not"/fun project for my uncle and I. We have been life long hunting companions, so these rifles hold some sentimental value. For me the gun is only used for Elk and one particular deer hunt in PA we do every year. For the deer hunt we go in by canoe and hunt a secluded river bottom that typically affords long shots across tributaries.

Again, thanks everyone.

[handloader1]

1bullethead:

I have a Weatherby Mark V Sporter chambered in .340 Wby. Mag., and the free bore has not affected my accuracy. If I do my part, I obtain .408" at 100 yds. three shot group with a 250 gr. Barnes XFB. Good luck.