DarylS
(.700 member)
07/02/16 04:43 AM
Re: marlin ou 12ga



Ctg. - .45/60 or .45 1.9"
35" bl.GM 18" twist
Large diameter black-powder firing pin
405gr. Remington FN
48.0gr. Hodgdon's Benchmark
Federal 210 primer
Overall Ctg. Length: 2.580" - I use a modified Lee Factory Crimp Die
Velocity Av. at 15feet, 1,850fps.
Low pressure indicated.

11 shots off the bench 100 Meters .875" for 10 of those in the group. I pulled one - flinched for some reason and threw that one 1" from the group - the 9th shot. I then fired 2 more to make a 10 shot group, with the last 2 gong back onto the hole, which was quite round. The sights were a Soule Tang sight and Sharps Globe aperture front sight.

Data came from Hodgdon's Annual Manual in the .45/70 data. I suggest you check your copy of this Manual and follow along as I explain myself.

Note: We can assume similar pressures with similar overall ctg. lengths and loads due to Hodgdon using a standard 24" bl. for all their testing, and lot listing OAL. It appears the same weapon or test barrel was used. We also know for the Lever action data to be valid, they must have loaded to a maximum loaded length of 2.55", 2.60" at the longest as that length is needed for feeding in a lever gun. Also, crimp grooves are necessarily used in lever guns to prevent tube spring pressure and recoil from seating bullets deeper into the case, tying up the action, or worse.

In the Trapdoor section they list pressures up to 28,00CUP. Hodgdon shows, for instance, a weak co-relationship between a couple loads listed as max. for the Trapdoor and being starting loads in the Lever Action section.

Trapdoor max of 50.0gr. of Varget with 405gr. Cast bullet = 1,718fps @ 20,900CUP, which the same 50.0gr. Varget load in a Lever action being a starting load with a 400gr. jacketed bullet as producing only 1,655fps, but slightly lower pressure of 18,600CUP. This shows to me, the jacketed bullets seemingly was producing less pressure per grain of powder than the cast bullet, which was strange, but worth pursuing through testing, if careful loading practices were followed.

Thus, I started development at 45.0gr. Benchmark, the primer flow and slide lockup being my main concern/pressure indicator in this action. Due to the angle and size of the pin, this action shows pressures long before any other indicator arises or shows.

With Benchmark, the Trapdoor data shows 47.0gr. with 405gr. Cast bullet at 1,564fps @ 17,100CUP and 50.0gr. Benchmark at 1,695fps @ 22,600CUP.

I worked from there up to 48.0gr. Benchmark with the 405gr. Remington bullet, which produced 1,850fps in my rifle and the excellent accuracy shown. I have read other work on this bullet and it was suggested that 1,850fps was about the maximum speed one should load this bullet to, as it has a pure lead core and thin jacket. Also noted it is a wonderful bullet for moose and elk and bear. The article also noted it will make a huge hole in a whitetail, yet the bullet expands like bubble-gum, and does not break up at this muzzle velocity.

In this rifle, I also worked up to 50.0gr. Varget, which was close to a case full at an OAL of 2.580". The accuracy was not as good as with Benchmark, opening up to 2", however pressure indicated for that load in the Lever action data shows 18,600CUP at 1,655fps. I did not chronograph these, may some day as I still have some loaded, but they were totally safe in my BP firing pin 1868 Repro: Sharps action.

I expect they may produce approx. 1,900fps in my 35" barrel, thus they slightly exceed the suggested allowable speed for THIS bullet.

Thus, due to the comparisons between known data and the differences of Jacketed and cast using Varget, along with my extrapolations that the Benchmark load may produce 22,000 though not over 23,000CUP - a very soft load for most rifles, yet producing excellent ballistics- especially in the longer barrels. I firmly believe Benchmark to be a MOST excellent powder for the .45/70, with either case or jacketed bullets. It certainly is a very accuracy powder - in my rifle.

Hodgdon's data also shows that at 55.0gr. Benchmark, the 24" bl. will push a 400gr. Jacketed bullet at 1,856fps @ 29,600CUP, but Varget gets almost that speed using 55.0gr. @ only 24,000CUP - also within the realm of the double rifles by Baikal, having ceilings of 31,000CUP or PSI, as noted.

We have been told, that through pressure testing at the lower pressures, below 35,000CUP, that CUP and PSI numbers appear to be the same in the .45/70 ctg. I can tell from my own testing, the above information on this ctg. (and my own .45 1.9") is safe for lower pressure guns.



Contact Us NitroExpress.com

Powered by UBB.threads™ 6.5.5


Home | Ezine | Forums | Links | Contact


Copyright 2003 to 2011 - all rights reserved