Feenix, you are correct. The long freebore does drop pressure. I have had three reamers from zero freebore to .030 Freebore. One reamer had a short neck(.050), the other two had normal-length necks. I took a print from PTG, and changed the freebore length on two reamers, and on one the neck length and freebore length with the other for use with Winchester brass..
My motivation in the project with the .050 shorter neck was to simply have a quantity of brass to use, and to increase the barrel life, which the short freebore did.
I had a quantity of PMC 257 Weatherby brass which is just incredible in strength, I kept the neck at normal length.
We have had custom barrels put on with these reamers in Mauser, Savage 110, Remington, and Browning A bolt. It is amazing to see a dirt cheap savage 110 with it's factory wood stock shoot 1/4"-3/8" groups, a barrel nut was not used. My cousin is still shooting that rifle today on deer and coyotes.
Most are concerned about the brass flow into the shoulder forming the dreaded doughnut. The double radius impedes that brass flow more than a standard case, Roy Weatherby was a genius in this design, if you had a case in your hand, you would see what I am talking about, an issue that is never spoken of. It has occurred to me more than once that the forming Winchester brass in the 7mm Weatherby, 270 Weatherby, and a 6.5-257 Weatherby may be worth the effort due to the double radius eliminating the doughnut at the shoulder neck junction, allowing much deeper seating, thereby increasing barrel life. A bullet will only jump so far before it starts getting crooked in the throat as it obturates in the barrel, this is NEVER spoken of.
Of course, we are hunters, not target shooters with these rifles, but the accuracy/speed is undeniable. Accuracy is always first with our family, Speed is the bonus. The way these fast bullets kill deer and hogs is just amazing.
We used Hart, Pac Nor, Krieger, Brux, and X Caliber barrels. Pac Nor has over 2000 reamers, and they do have a zero freebore reamer that can be throated to anything you want by providing dummy rounds with the bullet seated at the depth you like.
Feenix, to answer your question directly, we are running some pressure, but like normal rounds, we stop our load development when we find heavy bolt lift, case head swipes, etc. We are careful to discard cases that do not have tight primer pockets when we hand-seat the primers. Every 257 Weatherby we have had built, craters the heck out of primers in all actions used. We attributed this to over size firing pin holes in the bolt, we ignored that issue as no one has had primers pop burning a hole in the bolt face or firing pin.
We changed from 100g bullets at 3850fps to the Berger 115 and the Nosler Accubonds when they came out with the accuracy node being 3590 in a 25" barrel and a little over 3600 in another barrel, both 9 Twist X caliber barrels, accuracy is sub 3/8". We never had issues with the 100g killing in the field with various bullets, we were just bored and wanted to try something new. A Weatherby factory 257 W. may shoot an occasional small group, but NEVER to the level of accuracy, we are seeing with these shortened freebore chambers. Getting the bullet started straight in the throat is of major concern to achieve the level of accuracy we are seeing.
None of the actions used were trued, but PTG Recoil lugs were used on the Remingtons. My introduction to Savage 110 was with my cousins where he used a Hart #5 taper with a Shrewd muzzle break. Load development was 12 rounds including getting it on paper with sub 3/8" groups, we have shot the round so much we pretty much know what the load is with R#22, Fed 215's. It sure is a strange feeling seeing a clunky Savage in it's Wood stock shooting such tiny groups, over and over again.... makes you wonder.
Actions were bedded, barrels freefloated, triggers tuned before we ever pulled the trigger.
This short freebore in 257 Weatherby has been ongoing since 1989, it is nothing new to us. The first short neck 257 Weatherby on a Rem 700 was in 1995, and my first experience with the Short freebore was in shooting a Gunsmiths rifle from San Diego, those 85g at 4130 sure get the hair flying on the coyotes!
Short freebore pushes the brass pretty hard, another reason for the use of the Winchester 264WM and 7RM brass. If there is a way to get longer brass life with the Roy, it will be with AGD brass, make no mistake about it.
Reloaders do not like to turn necks or form cases. This kind of project of short neck and short freebore is for guys that have the time and where with all to tinker, and they are few and far between. There was a great gunsmith down in Dawson, Ga that Ackley Improved the 257 Weatherby making it a 6.5 also. I rode down to visit him during deer season to speak with him on the project and there were three other deer hunters there shooting his Wild cat, all shooting the 120g Match king at velocities between 3500-3600. There was a cult following on this 6.5-257 Weatherby AI, and it was amazing how they all got giddy talking about all the one-shot kills with a non-hunting bullet. Case life was 3 firings on the brass, no one cared, and performance trumped all! The gunsmith had a Cult following on this 6.5/257 Weatherby Wild cat is an understatement!
The double radius impeding the formation of the doughnuts is a major issue to remember, this allows deeper seating of the bullets, extending barrel life, plus promoting the bullet getting started into the lands straighter.
