Post by Bullshop on Aug 2, 2019 8:19:24 GMT -7
Yesterday while looking through our 375 caliber bullet inventory I found some bullets from a mold that I forgot I had and had never tried the bullets in any of my 375 caliber rifles. This was a custom design order I did for a customer quite some time back for a 375 caliber 220gn bullet we designed with enough meplate for lever actions but not so much that it looks like a SWC. I believe it was intended for the 375 Winchester cartridge and should be good for duplicating factory ballistics for that cartridge.
So yesterday I found an old stash of these bullets that were showing some oxidation from age so no longer as pretty as new ones. This seemed the perfect opportunity to test some lighter bullets in my 375 Whelen. My established loads for this caliber use three different bullets ranging in weight from about 320gn to about 375gn depending on the alloy used. I have always intended to try lighter bullet weights in the 375 Whelen but just never got to it until yesterday when the opportunity presented itself when not only finding the forgotten bullets but also finishing up with orders early enough in the day to still have enough time.
Now getting to the point of this key jabbing session where do you find load data for a 220gn bullet or any bullet for that matter for the 375 Whelen ? When Hawk Labs was in business they published some data for the 375 Hawk Scoville and I do have a copy of that data but most folks will not have access to it. The 375 HS might be compared to the 35 Brown Whelen in relationship to the standard 35 Whelen in that the Brown version has the shoulder moved forward resulting in a slight powder volume increase but also resulting in a shorter neck. The same relationship exists between the 375 Whelen and the 375 HS in addition to the HS version also having the Ackley improved type sharper and slightly larger diameter shoulder.
So with little available data for any version of 375 caliber on a 30-06 case I set to find something close to the same volume in the same caliber and what I came up with is the 376 Steyr. The steyr case is slightly larger in diameter at the head and shoulder by .030" but the 06 case makes up some of the difference in case volume in head to shoulder length.
Also listed powder volume is on par with all calibers on the old reliable 30-06 case at about 57 to 60gn of appropriate burn rate for caliber and bullet weight. In this case the 376 Steyr being the same caliber as the 375 Whelen and having nearly the same case volume though slightly greater for the Steyr the powder burn rate for bullet weight relationship is identical which between RE#7 on the fast side to 4895 on the slow side may seem fast but you must consider the relationship between case volume and expansion ratio of the fairly large caliber.
At any rate allowing for the slightly larger case volume of the Steyr case I decided to reduce a listed starting load for the Steyr with a 220gn bullet of 50.9gn of IMR 3031 down to 48.5gn a reduction of 2.4gn or about 5% . Actually I didn't have any 3031 on hand so I substituted with VV# 133 a powder I have found to be identical in burn rate in several other applications. With the charge of 48.5gn VV#133 and the 220gn bullet in the 375 Whelen I estimated a velocity in the 2400 fps range and is what the Steyr cartridge shows for the full load of 50.9gn of 3031.
Loads were tested in two different rifles one having a 21" barrel and one a 26.5" barrel and the velocity difference between the two is exactly what you would expect.
21" barrel --2372, 2361, 2369, 2400, 2414, 2421, average @ 2390 fps
26.5" barrel -- 2446, 2409, 2395, 2444, 2397, 2426, 2461, 2448, 2440, average @ 2430 fps
So it looks like starting data for the 376 Steyr with about a 5% reduction can be used as starting data for the 375 Whelen. My data source for the 376 Styer data was from the Hornady 7th edition load data book. I do not know if newer editions have data for the Steyr cartridge but I will assume they do since that cartridge though perhaps not in the USA is very popular with Euro hunters.
So this was a fun project to finish a work day with. Also I discovered a few things about these two rifles. These rifles proved exactly opposite of what I had expected with the carbine length barrel shooting about 15" higher with the lighter bullets than with its normal 300+gn bullet while the longer 26.5" barrel only rose about 2" above the POI with its normal 300+ gn bullets. Its hard to say why for sure because there are several things involved but easy to accept that with the longer barrel gun there is no need to re-zero with the full range of bullet weights and that is a major bonus!
So yesterday I found an old stash of these bullets that were showing some oxidation from age so no longer as pretty as new ones. This seemed the perfect opportunity to test some lighter bullets in my 375 Whelen. My established loads for this caliber use three different bullets ranging in weight from about 320gn to about 375gn depending on the alloy used. I have always intended to try lighter bullet weights in the 375 Whelen but just never got to it until yesterday when the opportunity presented itself when not only finding the forgotten bullets but also finishing up with orders early enough in the day to still have enough time.
Now getting to the point of this key jabbing session where do you find load data for a 220gn bullet or any bullet for that matter for the 375 Whelen ? When Hawk Labs was in business they published some data for the 375 Hawk Scoville and I do have a copy of that data but most folks will not have access to it. The 375 HS might be compared to the 35 Brown Whelen in relationship to the standard 35 Whelen in that the Brown version has the shoulder moved forward resulting in a slight powder volume increase but also resulting in a shorter neck. The same relationship exists between the 375 Whelen and the 375 HS in addition to the HS version also having the Ackley improved type sharper and slightly larger diameter shoulder.
So with little available data for any version of 375 caliber on a 30-06 case I set to find something close to the same volume in the same caliber and what I came up with is the 376 Steyr. The steyr case is slightly larger in diameter at the head and shoulder by .030" but the 06 case makes up some of the difference in case volume in head to shoulder length.
Also listed powder volume is on par with all calibers on the old reliable 30-06 case at about 57 to 60gn of appropriate burn rate for caliber and bullet weight. In this case the 376 Steyr being the same caliber as the 375 Whelen and having nearly the same case volume though slightly greater for the Steyr the powder burn rate for bullet weight relationship is identical which between RE#7 on the fast side to 4895 on the slow side may seem fast but you must consider the relationship between case volume and expansion ratio of the fairly large caliber.
At any rate allowing for the slightly larger case volume of the Steyr case I decided to reduce a listed starting load for the Steyr with a 220gn bullet of 50.9gn of IMR 3031 down to 48.5gn a reduction of 2.4gn or about 5% . Actually I didn't have any 3031 on hand so I substituted with VV# 133 a powder I have found to be identical in burn rate in several other applications. With the charge of 48.5gn VV#133 and the 220gn bullet in the 375 Whelen I estimated a velocity in the 2400 fps range and is what the Steyr cartridge shows for the full load of 50.9gn of 3031.
Loads were tested in two different rifles one having a 21" barrel and one a 26.5" barrel and the velocity difference between the two is exactly what you would expect.
21" barrel --2372, 2361, 2369, 2400, 2414, 2421, average @ 2390 fps
26.5" barrel -- 2446, 2409, 2395, 2444, 2397, 2426, 2461, 2448, 2440, average @ 2430 fps
So it looks like starting data for the 376 Steyr with about a 5% reduction can be used as starting data for the 375 Whelen. My data source for the 376 Styer data was from the Hornady 7th edition load data book. I do not know if newer editions have data for the Steyr cartridge but I will assume they do since that cartridge though perhaps not in the USA is very popular with Euro hunters.
So this was a fun project to finish a work day with. Also I discovered a few things about these two rifles. These rifles proved exactly opposite of what I had expected with the carbine length barrel shooting about 15" higher with the lighter bullets than with its normal 300+gn bullet while the longer 26.5" barrel only rose about 2" above the POI with its normal 300+ gn bullets. Its hard to say why for sure because there are several things involved but easy to accept that with the longer barrel gun there is no need to re-zero with the full range of bullet weights and that is a major bonus!
