elkaholic
Well-Known Member
There has been a lot of discussion around comaparing the 6.5's and I have personally had a lot of pm's asking questions about the 6.5 Sherman so I thought this might be a good time to try to cover it all on one thread. What I would like to do is try to explain the differences, and similarities, of some of the 6.5's in question. Some of the differences that I can easily explain are based on actual measurements, so can be taken as fact, and some of my comments may be my own beliefs and interpretations.
Let me start by saying that I shot a 6.5 A.I. for many years and believe it to be a fine cartridge, and was in fact the reason for the development of the 6.5 Sherman. When it was time to re barrel my last A.I., I decided that since I was wildcatting anyway, why not try to improve on what I thought to be an already good thing. My intent was to keep the '06 sized bolt, increase velocity while maintaining accuracy, barrel and case life, as well as brass cost and availability, and ease of forming.
To back up for a minute, my first thought was to build a Gibbs, which is also a proven performer. I went so far as to order some brass from Quality Brass, but when I looked it over, I really didn't like the extremely short neck on the Gibbs, so on to the Sherman.
The Gibbs was limited at its inception, because it was based on the '06 case which is .046" shorter than a .270 or .280 case. In order to gain the case capacity, the sacrifice was made in the neck. The A.I has a good neck, but lacks the case capacity of the Gibbs. I WANTED BOTH!
I started by taking the exact case specs of each, and then easily decided on the .270 as a parent case to gain the extra length needed. I spoke with some knowledgeable people as to what minimum body taper would be and what I thought a good neck length should be for the caliber. I chose the 40 degree shoulder for two reasons. First of all, it gives maximum case capacity and more importantly IMO, in conjunction with the neck length, it keeps the flame point more confined inside the neck rather than directly into the throat. It is my belief that this is why the A.I. and Sherman barrels last longer than many 6.5/.284 barrels that hold approx. 11% less powder than the Sherman. The body taper I decided on was less than the A.I., and far less than the Gibbs, which left me with a .460" diameter at the shoulder. The shoulder was moved forward farther than the A.I. but still maintains a .300" neck length which is plenty for a 6.5; Less than the A.I. and far more than the Gibbs, resulting in more capacity.
The end result was a case with the same capacity as the Gibbs with the good qualities of the A.I. Field tests so far have proven the value of each. I can reach 3200"+ with 140's in a 26" barrel. Accuracy is great, and case and barrel life have proven to be very good. (You could add approx. 40'/sec/inch of barrel length) i.e. 30" barrel = 3360'.
The case performs very well with a large variety of powders from 4350 to retumbo, all giving good accuracy and velocity. I currently have fired around 1300 rounds with no apparent loss of accuracy.
This cartridge will exceed any other '06 sized bolt face and in fact, will equal the 6.5 WSM, which is also a great cartridge, although I doubt the barrel will last as long as the Sherman. The Gibbs will equal the Sherman velocity as well, but, IMO, is an inferior design for the above reasons. I have had very good feed back on another build, and look forward to seeing some more out there!
I have had comments that "it is nothing more than a Gibbs or an A.I. by another name", but if that is the case , we only have about a half dozen cartridges in existence! The truth is, the only dimension the Gibbs shares is the case head and the A.I., the case head and shoulder angle.
I hope this clears up some of the questions, and myths. Feel free to pm me if there is something that can't be handled on the open forum.......thanks.......Rich
Let me start by saying that I shot a 6.5 A.I. for many years and believe it to be a fine cartridge, and was in fact the reason for the development of the 6.5 Sherman. When it was time to re barrel my last A.I., I decided that since I was wildcatting anyway, why not try to improve on what I thought to be an already good thing. My intent was to keep the '06 sized bolt, increase velocity while maintaining accuracy, barrel and case life, as well as brass cost and availability, and ease of forming.
To back up for a minute, my first thought was to build a Gibbs, which is also a proven performer. I went so far as to order some brass from Quality Brass, but when I looked it over, I really didn't like the extremely short neck on the Gibbs, so on to the Sherman.
The Gibbs was limited at its inception, because it was based on the '06 case which is .046" shorter than a .270 or .280 case. In order to gain the case capacity, the sacrifice was made in the neck. The A.I has a good neck, but lacks the case capacity of the Gibbs. I WANTED BOTH!
I started by taking the exact case specs of each, and then easily decided on the .270 as a parent case to gain the extra length needed. I spoke with some knowledgeable people as to what minimum body taper would be and what I thought a good neck length should be for the caliber. I chose the 40 degree shoulder for two reasons. First of all, it gives maximum case capacity and more importantly IMO, in conjunction with the neck length, it keeps the flame point more confined inside the neck rather than directly into the throat. It is my belief that this is why the A.I. and Sherman barrels last longer than many 6.5/.284 barrels that hold approx. 11% less powder than the Sherman. The body taper I decided on was less than the A.I., and far less than the Gibbs, which left me with a .460" diameter at the shoulder. The shoulder was moved forward farther than the A.I. but still maintains a .300" neck length which is plenty for a 6.5; Less than the A.I. and far more than the Gibbs, resulting in more capacity.
The end result was a case with the same capacity as the Gibbs with the good qualities of the A.I. Field tests so far have proven the value of each. I can reach 3200"+ with 140's in a 26" barrel. Accuracy is great, and case and barrel life have proven to be very good. (You could add approx. 40'/sec/inch of barrel length) i.e. 30" barrel = 3360'.
The case performs very well with a large variety of powders from 4350 to retumbo, all giving good accuracy and velocity. I currently have fired around 1300 rounds with no apparent loss of accuracy.
This cartridge will exceed any other '06 sized bolt face and in fact, will equal the 6.5 WSM, which is also a great cartridge, although I doubt the barrel will last as long as the Sherman. The Gibbs will equal the Sherman velocity as well, but, IMO, is an inferior design for the above reasons. I have had very good feed back on another build, and look forward to seeing some more out there!
I have had comments that "it is nothing more than a Gibbs or an A.I. by another name", but if that is the case , we only have about a half dozen cartridges in existence! The truth is, the only dimension the Gibbs shares is the case head and the A.I., the case head and shoulder angle.
I hope this clears up some of the questions, and myths. Feel free to pm me if there is something that can't be handled on the open forum.......thanks.......Rich
. The best brass to use is probably the 6.5x65 RWS which is really strong and is a natural to form with the really long brass to start with. I have two versions (you simply run the reamer in farther and use the correct go gauge). One holds approx. 1 gr. more powder than the other. My hunting load is a 140 at 3150'. I've shot some 3" groups at 880 yards with this load. If you want an unbiased opinion, contact "cmantha" on the forum. He built one last year and loves his! pm me if you like and i'll give you my phone #....Rich
