175 Grain Bullet in Normal No Alterations 275 Rigby HS

[Bob Nelson 35Whelen]

Every rifle barrel off the lathe is different. (dull reamers sharpened undersize, fresh reamers, over/under throated that day, etc.)

What you need is a Hornady OAL gauge: https://www.hornady.com/modified-cases#!/

And you need a Hornady 7x57 brass OAL cartridge for it: https://www.midsouthshooterssupply.com/item/00005a7x57/lock-n-load-a-7x57-mauser-modified-case

That will let you place your desired bullet into the gauge, push it into the chamber, thrust the bullet forward in the case until it hits the lands, and then withdraw the fake cartridge. You'd then measure it to figure out the true OAL of the potential ammunition if it were loaded to touch the lands. You want at least .020" off the lands to prevent a pressure spike, or more if it gets more accurate shorter, or more if it is still longer than the maximum COAL of 3.045", or shorter if it won't feed from your internal magazine.

With the measured facts, you'll know if you can use a 175gr bullet of a given type, and if so just how deep in the case it would require. (which would inform you if you're accidentally creating compressed loads)

@rookhawk
I'm not that rich to own all that fancy gear.
I do it one of 2 ways.
1) using two people I drop a cleaning rod down the barrel to the bolt face and make the cleaning rod at the muzzle.
Then remove bolt and place desired projectile in the chamber.
Person 2 GENTLY holds said bullet in place with a length of small dowel.
Reinsert cleaning rod in barrel and Mark again.
This gives coal to the lands.

2) Partially neck size a case and partially seat a projectile. Blacken projectile with sharpie or candle smoke.
Chamber round, projectiles will be pushed back in the case and any land marks will show up.
This will give you max coal.

Once max coal is established desired seating depth can be worked out.

If all else fails just use book recommendations.
Has worked for me for a lot of years.
Bob

 

[Bob Nelson 35Whelen]

@franzfmdavis
To me personally that pretty piss poor manufacture service.
When ever I have had a rifle built my gunsmith ALWAYS asked me what the biggest bullet I planned on using and set the throat/ leade to suit that. Shorter bullets DONT SUFFER, they may need a longer jump but by being able to seat lighter bullets out further you can put more coal on the fire for higher velocity and do it safely.
Weatherby have been doing this for years.
To me personally a manufacturer should produce a rifle to handle the longest available projectiles to suit the calibre. Dang even the little 308 will chamber a 220gn factory loads.
For the price of a Rigby you would think they would get it right and not expect the customer to pay to have it modified to suit. Should be done at the point of manufacturing in my book.
You don't see a SAKO or tikka or other European brand that won't chamber a factory 175 gn load in the 7x57.
I don't suppose you would have to send a 30-06 back to have the throat fixed for a 220-240 round nose
Bob

That’s good to know for future reference!

When I was looking into it, I spoke with a tech at Rigby and with JJ Peredeau, both of whom recommended that I lengthen the throat. Rigby also mentioned that they offer throat lengthening as a customization on new rifles. None of them offered the other option you described above.

I did ask whether there would be any negative impact on using smaller bullets, such as the 140, after the throat was lengthened and they said no.

In retrospect, I am still happy that I lengthen it because I subsequently had the flexibility to develop a load using the 175 grain Northfork bullet that will hit the same point of impact at 100y as the 140g Hornady bullet at 100y, allowing me to use my scope and irons for either bullet.

I can imagine that if I was restricted in fps due to reduced case capacity, that may have become more difficult or not possible?