Home Forums Reloading Big Game Rifles A new one --Bullets slightly too large OD.

I have some 150gr Partitions loaded to 3.340OAL for a factory chambered Ruger #1 in 270WBY.
After much messing around I have found the bullets are just slightly too large on the OD. They don't want to chamber and a couple that do are a tight fit. Upon removal of loaded round you can see where the bullet fit snugly into the freebore.

Anybody else ever see this? I don't think it appear except on a chamber unless it has WBY type freebore.

Dave

You`re saying the bullet is making contact with the free bore in the rifles throat, not the rifleing?

Yes. I don't have a micrometer and with a dial caliper it's too close to measure. It would only take a couple ten thousands if the freebore is cut minimum diameter.

Double check you didn't stuff 7mm -.284" bullets in there instead of .277".

What are you refering to as the freebore?

You need to check the dia. of the bullets. As DesertSandman says, you might have loaded some 7 MM bullets.

First thing I did was check bullet diameter. Being a ex-machinist it was the first thing. I don't have a micrometer at home, just a dial caliper. Not really accurate enough to measure to the 4 digit.

1234567 - WBY chambers have an larger than normal area in front of the neck without rifle. Somewhere between .200" and .350". You can get by with about .150 most of the time and still use WBY factory ammo.

Dave

The parallel throat on the reamer used on my 270 WBY measured .2775. So there was only about .0005 clearance between the bullet and the parallel throat. Throw in a little bullet runout, some carbon residue and it contacts with to much COL. Try pulling back COL to 3.300. See if it works there. It should with a stock SAAMI 270 WBY chamber.

Also make sure you do not have a big nasty carbon ring forming in the parallel throat.

Above all, do not light one off until you've got this one figured out. Especially with a Weatherby class charge. 1Minute

NRA Handloading, copyright 1981, lists the max. overall length as 3.250". The reproduced chamber dimensions in the back of the book show the freebore as .377". The diameter of the freebore is listed as .2774". The drawings and tables do not indicate what the tolerances are for the lengths and diameters. I don't think it is safe to assume that the Ruger #1 has any freebore, unless you do a chamber cast to verify it. 1Minute is right. You don't want the rifling touching the bullet when you trigger it off.

And then there was PO trying to blow up a rifle (Arisaka, also?) by chambering it for larger bullets without benefit of a larger bore... Believe he had trouble doing that!

Sitka Deer:

I remember something about that, but very little. Do you have any details on PO's test. It seems like I remember that a larger than normal bullet diameter did not appear to increase pressures greatly.

I also remember reading about someone who used a drill bit to re-chamber a 6.5 Jap to 30-06. He drilled out the throat to take the .30 caliber bullet. Other than a lot of recoil, IIRC, there wasn't any problem.

I have a Mk V in 240 Weatherby and mine was doing the same as yours. It would sometimes pull the bullet if I tried to remove a loaded round. Weatherby told me that I was hanging the bullets too far out. So I went back to the overall length that the Hornady manual reccommended and everything worked fine after that.

P.O. did increase the throat diameter to match the larger caliber bullet diameter and then shot them through the smaller bore. It worked surprisingly well. Must have had some exciting times in that Utah shop! Bear

"First thing I did was check bullet diameter. Being a ex-machinist it was the first thing. I don't have a micrometer at home, just a dial caliper. Not really accurate enough to measure to the 4 digit."

What did they measure to the third digit?

You never have explained exactly how you determined the bullets were oversized, only that they contact the throat. A 'long throat', or a throat longer than normal is a free bore.

The question 'how did you determine the bullets were oversized' is not meant to be sarcastic. I asked because it is an exact measurement that you need to know, because if they arn't oversized, then there is buildup in the throat or something else is wrong. If the bullets are actually oversized, .2780, 2782, etc, then problem solved.

I have 7 M/M Weatherby, and have owned Wbys in different calibers, and I have never had a bullet contact the throat. Either in a Weatherby or any other rifle.

Rifling origin? Yes, many times, when the bullet was seated out too far, but you state that the bullet contacts the throat, which is supposed to be groove diameter.

Ok, I'm back.

Some bullets in this batch measure .2777. Most are .2772 and some inbetween. The freebore in this chamber must be right at minimum of .2774. If I load the .2772 or less bullets than no problem. .2775 or more and they won't go.

Called Nosler and I am sending all that I have in that lot.

A older 150 Partition along with some a Bal Tip and Accubond all measure ~.2765-.2768.

No carbon or other contaminant.

If there ever could be a weird deal happen it'll happen to me. Always did in the engine business.

Dave

Thanks for the reply. I have never seen something like this, and as you said, it is weird.

The reason for all the questions was that I was curious to know what was causing this. You learn something new every day.