(Continued from Part 5. This concludes the article.)
The 6.5×55 Performance Standard
A modern heavy for caliber bullet that is soft in construction and has a very high ballistic coefficient is the smarter way to compensate for modest velocities. The 6.5x55mm Swedish Mauser cartridge is emblematic if not iconic for sedate velocities yet flat trajectories and spectacular accuracy at ranges that can exceed 1,400 yards. A high ballistic coefficient allows a bullet to retain its momentum and buck the wind far better than most higher powder cartridges and it does this at pressure suitable for most antique actions.
Beyond 100 yards the very high ballistic coefficient of heavy-for-caliber projectiles for the old Model 1896 6.5×55, namely the 140-grain bullets, will outperform 7.62 NATO at extended ranges in all regards. And this is the reason, its offspring with similar genetics and performance, the 6.5 Creedmore became widely and wildly popular. For us old and long-time admirers of the M96 Swedish rifle and 6.5×55 cartridge, we can gloat and say: “We told you so.” But it can only perform this feat with 24 to 29-inch barrels. We can greatly improve the trajectories of .308 projectiles using both very long 29 inch barrels and with very high ballistic coefficient of either light or heavy-for-caliber bullets. For .308 barrels, the 178 grain Hornady ELD-M or Speer 180grain BTSP is the best choice. For barrels that are less than 24 inches long, the Hornady 155 grain Amax is a better choice.
Long Barrels, Larger Cases and High B.C. Bullets
Even if it is possible to find top velocity at top working pressures that push the limits of the action, I ask why one should attempt to squeeze every last drop of velocity out of a cartridge? The 1891 Argentine Mauser in full dress shooting its original 7.65x53mm out of its 28.5-inch barrel is already on par with M80 ball. For reloaders, I would use a powder that produces the lowest pressure that produces the greatest velocity and accuracy.
This load would likely use a powder that has a medium to slow burn rate that can use a longer barrel to push heavier projectiles that have higher ballistic coefficients to the highest velocities possible without exceeding the pressure limit. Faster powders can not leverage the advantage of long barrels nearly as well. I would prefer IMR4895, IMR04064, IMR4320, H4895, Varget, for 125 to 165 grain projectiles and slower IMR4831, IMR4350, H4350 and Reloader 15 for heavier projectiles, yet medium burn rate powers work well with heavier projectiles well enough. As top choices with .308 to .312 projectiles, Varget for up to 168-grain bullets and Reloader 15 for heavier bullets in .308 Winchester provide excellent accuracy at top velocities for their respective bullet weights. Most reloading manuals used 24-inches barrels to develop their data rather than a 28.5-inch barrel. Data for 7.65x53mm is usually developed using a 28.5-inch barrel.
The best cartridge for the 1891 Mauser has a case of equal or greater in capacity to the original case that is 53mm in length. Some 1891 Mausers were re-barreled to .30-06 (7.62x63mm). That has a case length of 63mm. It can hold a much larger amount of slow burning powder that makes the most use of the longer barrels while producing top velocities at modest and lower pressure than cases with less capacity.
For example, according to the Hodgdon Reloading Center, a .30-06 case with a compressed load of 61.5 grains of H4831 can push a 175 grain projectile upwards of 2,791 fps from a 24-inch barrel with no more pressure than the 44,400 CUP that the 1891 Mauser action can tolerate. This performance is significantly higher than M118 7.62 NATO, about 100 fps faster at the same or less pressure, and it can be produced from an antique 1891 Mauser or later production action when attached to a 28 to 29 inch barrel. H380, Varget, H4895, and BL2 would also be suitable powders for an accuracy load and top velocities that do not exceed 44,500 CUP (49,000psi).
I would not be surprised that this has not already been done. If I can think of it, it has likely already been consicdered. I would ream out the chamber on a good original full length 7.65x53mm barrel and use a .311 bullet in a .30-06 case and call it the 7.65x63mm. Using a 175 grain projectile with 61.5 grains of H4831, I would expect the velocity out of a 28.5-inch barrel to be at least 100 fps faster, or upwards of 2900 fps. This load would compete with 6.5 Creedmore inside of 1,200 yards. The potential of an antique Mauser in a countersniper role is more than plausible. While cumbersome to handle, the long 28.5-inch barrel has its virtues.
Here is an excerpt from an article that is several years old that I authored that documents the benefits of using modern high ballistic coefficient projectiles at the modest pressures though a 28.5-inch inch barrels of antique Mauser rifles — Choosing a Practical Antique Rifle – Part 4:
A Comparative Analysis of Antique Versus Modern Rifle Trajectories
“Using the results from the well-respected JBM ballistics calculator, this is the expected trajectory of M118 out of this rare Chilean Mauser as compared to the trajectory out of the U.S. Army’s M21 rifle, both chamber in 7.62 NATO. The table indicates estimated trajectories for M118 ammunition, and are useful for only for comparative purposes. The data was generated assuming a 200 yard zero, and a full value cross wind, a 90-degree 10mph cross wind.”
The advantage goes to the Chilean Mauser as it has a 29-inch barrel that is assumed will generate an additional 100 fps of velocity over that of 24 inch barrel of the M21 rifle. The M118 cartridge creates the same amount of pressure in both rifles (46,000CUP or less). Typically, as barrel length is reduced, there can be on average as much as 25fps (clarification: 25 to 50 fps) loss per each inch it is reduced. There are exceptions, and other contributing factors, so this can only be a rough estimate. In any analysis, the Chilean Mauser would generate no less velocity, and would be equal to, and likely greater in velocity from 50 to 125 fps greater. It is safe to say that the trajectory would be at the least be about the same, if not flatter shot out of the Chilean Mauser.
(An interjection: It is now popular to have a rifle with 22-inch barrels or less.)
Projectiles
It is better to improve a cartridge with an appropriate bullet choice and use a powder that produces the highest velocity with the least amount of pressure and harness the advantage of very long barrels of antiques if a flatter trajectory is needed. Hornady’s line of Extreme Low Drag bullets or Speer’s line of BTSP that have comparable ballistic coefficients are good and affordable options to that of expensive Berger projectiles for maximizing an antique in a counter-sniper role.
For flatter trajectories inside of 600 yards use Hornady’s 155-grain Amax that has a B.C. nearer that of most 165 grain .308 bullets. The Amax bullet is not a practical hunting bullet at normal hunting ranges, but it is a good choice at ranges under 500 yards on targets and would produce the flattest trajectories possible in rifle chambered in .308 cartridges and the best accuracy within that limited range. It is a good bullet for antique actions that need all the advantages possible to be on par with military cartridges.
The combination of conservative pressures with light for caliber bullets with very high ballistic coefficient is synergistic and will produce better and safer results than simply applying a greater force, or a ‘bigger hammer’ in terms of powder that may produce excessive pressures that over time shortens the service life of the action and unnecessarily exposes the shooter to injury. Simply adding more powder is kind of like using hammer for all of your tool needs. The odds of eventually striking your thumb increases, over time.
Commercial Ammunition for Antique Rifles
The .300 Savage can be made to meet or exceed 7.62×51 NATO performance levels in modern rifles that can handle 60,000 psi. Hornady’s Superformance 150 grain SST ammunition attains 7.62 NATO performance, yet I would not recommend it for 1891 Mausers or any small ring Mauser actions rechambered in 300 Savage as the pressure could be on the ragged edge it’s maximum working pressure.
This Hornady line of ammunition is known to be on the hot side and that should be no surprise as the ammunition advertises the highest velocities for their exceptional Superformance ammunition available in many cartridges that is designed to exceed the performance of competitors and yet not exceed 46,000CUP. For a lightly used 1891 Mauser, 44,500 CUP would be on the ragged edge of too much pressure and might stretch the action over repeated firing and create an unsafe amount of headspace within the chamber. Not good.
I would not in general use commercial ammunition in any 1891 actions unless it is its original configuration and uses 7.65x53mm. It should be obvious at this point that even 7.62 NATO ammunition that by its category has a pressure limit of 51,000psi (46,000CUP) is too hot in my opinion for the 1891 Argentine Mauser.
Rifles with M93, M95, and M96 actions are likely, but not guaranteed to handle all commercially-loaded ammunition. Most of these actions are stronger than M1891, yet there can be for example softer M95 actions made in-country and not in Germany, or there can be 7×57 Mauser ammunition for example that is loaded a tad too hot. That Is intended to be sold to modern rifles chambered in 7×57 Mauser.
Unfortunately, the only indication on the box would be the advertised velocity if it is indeed made available. If it is not, do not buy this ammunition. If the velocity stated is higher than those typically stated in reloading manuals that indicate a pressure less than 46,000CUP and a velocity for a given bullet weight that lower, then odds are that this commercial ammunition is too hot for those actions that generally speaking have a limit of 46,000 CUP. When purchasing commercial ammunition for these actions. In my opinion it is best to stick with the PPU or S&B ammunition brands. When in doubt consult the manufacturer, or a gunsmith, or both.
Conclusion
As reloaders, young and old, we can play a significant role and use our knowledge and skills to solve logistic problems in the future. During the Great Depression and into WW2 commercial ammunition became very difficult to find for sale, if it was affordable at all. These conditions greatly inspired much experimentation and innovation. Vintage reloading manuals in the 1940s and 1950s passed along what was learned during those difficult years when rifles were needed to feed families.
The following is a list of free manuals. Having both these early and later publications will greatly expand our knowledge, and at no charge. The skill and knowledge to reload firearm cartridges is being lost with the last of boomer generator in large part. I am doing what I can to pass along some of what I know. In the future bad times ahead, the ability to make ammunition from various and seemingly unrelated components will be a very important ability.
Some Free to Download Reloading Manuals:
(Note: You will need to do web searches to find most of these.)
ADI Powders 9th Edition (2016) (PDF)
ABC’s of Reloading (Lee Precision) 7th Edition (PDF)
Accurate Powder’s website
Accurate Powder Load Manual (2003) (PDF)
Accurate Powders (Edition 3.5) (PDF)
Alliant Powder Reloading Manual 1996 (PDF)
Alliant Powder’s 2019 Reloader’s Guide (PDF)
Vihtavuori Reloading Manual 2019 (PDF)
Western Powders (Accurate and Ramshot Powders) 5th Edition (PDF)
Western Powders (Accurate and Ramshot Powders) 6th Edition (PDF)
Winchester Reloader’s Manual, 15th Edition (1997) (PDF)