Diff powder, same velocity

[Handley]

Loading for a Miroku 45-70 with 250g Shockhammers. My most accurate load was IMR4198 at 2500fps. I haven't seen 4198 for months, so ordered RL7. I ran a few charge weights to see where I would max, then backed off, and I'm right at 2500fps with this powder as well. So all that said, should I expect it to shoot as well as my original load? Seems like if the powders are launching the same bullets at the same velocity, I should expect similar results. I've heard the two powders are similar, but the RL7 charge is about 1.5g less than the 4198 to achieve same velocity, fwiw. I'll hopefully test it this week, just wondering....v/r, c

 

[Taylorbok]

maybe yes, maybe no. Gotta try it and see.

 

[RegionRat]

Just food for thought.
We already have an unequal charge weight, but that gets converted to gas at a pressure and temp so we open the door for a difference in total performance even if the muzzle velocity is identical.
Sometimes, we get a higher pressure but shorter peak, sometimes we get a lower pressure but longer peak. Could those cause acceleration differences even when the muzzle velocity comes out identical?
As @Taylorbok said... maybe yes, maybe no... We are going to find out.

 

[Handley]

Yes thanks, that's exactly what I was wondering. 1.5g is just over 2.5% less powder, maybe not enough to matter, idk. Or maybe RL7 burns more completely than 4198. I guess all kinds of things can factor in. I'll post back when I can shoot.

 

[gunsandgunsmithing]

Same velocity really has very little to do with how the pressure builds along the way and the in-bore time of the bullet, even at the same speed at the muzzle. It won't be far off though and my limited experience with that cartridge is that they tune pretty easily...if you're not a wuss like me to shooting the damn mule! Ultimately, a few tenths one way or the other and I bet it'll shoot but ya really don't know until ya just do it. I just wouldn't try to equate velocity of the two to one another, as the pressure curve will be somewhat different.

 

[Straightshooter1]

Just food for thought.
We already have an unequal charge weight, but that gets converted to gas at a pressure and temp so we open the door for a difference in total performance even if the muzzle velocity is identical.
Sometimes, we get a higher pressure but shorter peak, sometimes we get a lower pressure but longer peak. Could those cause acceleration differences even when the muzzle velocity comes out identical?
As @Taylorbok said... maybe yes, maybe no... We are going to find out.

Just my quick thought . . .

Seems to me with different powder having the same muzzle velocity doesn't mean they'll have the same barrel time. How that powder burns internally up to that point effects the harmonic timing where the same velocity may not produce the same results on paper.

 

[gunsandgunsmithing]

Just my quick though . . .

Seems to with different powder having the same muzzle velocity doesn't mean they'll have the same barrel time. How that powder burns internally up to that point effects the harmonic timing where the same velocity may not produce the same results on paper.

Yes...THIS^^^
If it was just velocity at the muzzle that mattered, why tune anything? Just load for a given speed and that's it. It doesn't work like that, for the reasons you just mentioned.

 

[bozo699]

Yes thanks, that's exactly what I was wondering. 1.5g is just over 2.5% less powder, maybe not enough to matter, idk. Or maybe RL7 burns more completely than 4198. I guess all kinds of things can factor in. I'll post back when I can shoot.

Handley,
Not trying to hijack your thread but I’ve been looking at a 1886 in 45/70 for a couple weeks in my lgs , it’s new unfired on consignment the price is a little steep and it’s not the pistol grip I really want but I’m leaning hard towards buying it but it’s not a original Browning or Winchester it’s the Miroku 26” take down, is that what you have?… and how well does it shoot? Any issues or concerns?… thanks in advance for any input
Wayne

 

[piie]

With a big bore your barrel harmonics would likely play a smaller role ito accuracy. Your biggest concern should be over pressure. Perhaps someone could run your load through Quickload to verify this if you can supply the required inputs.

 

[Handley]

Handley,
Not trying to hijack your thread but I’ve been looking at a 1886 in 45/70 for a couple weeks in my lgs , it’s new unfired on consignment the price is a little steep and it’s not the pistol grip I really want but I’m leaning hard towards buying it but it’s not a original Browning or Winchester it’s the Miroku 26” take down, is that what you have?… and how well does it shoot? Any issues or concerns?… thanks in advance for any input
Wayne

No prob, mine is a Miroku 24" "deluxe," and I really love it. Killed my elk last year with it, even though it's a boat anchor to pack. It's become my main whitetail rifle the past two years just for the fun of hunting with it. I added a rear peep from Providence Tool Co. I initially shot 405g lead FN, but unhappy with terminal performance, felt like there were better options. It was my first experience with lead, and I loaded them too hot initially, which tends to spray lead everywhere lol. Some fellas over at cast boolits set me straight, and they shot very well at appropriate velocity. Switched to copper jacketed bullets to get better terminal performance. Hammer recommended their 250g, and I can hold 2-2.5" at 100. It also shoots the Barnes 300g TSX as well, and the Hornady 300g FN. However, I did replace the front sight with a taller one due to the increase in velocity. The factory front is good for lead slugs going slow, but its also a bead and I shoot square more accurately. I have a milling machine, so it was just another project to make one, but Skinner Sights makes them. Miroku built as nice a factory rifle as I've owned, just really nice fit and finish, beautiful stock work, but if you want to shoot past 100yd, and really if you want to shoot well at all, you need better sights. Hope it helps...

 

[bozo699]

No prob, mine is a Miroku 24" "deluxe," and I really love it. Killed my elk last year with it, even though it's a boat anchor to pack. It's become my main whitetail rifle the past two years just for the fun of hunting with it. I added a rear peep from Providence Tool Co. I initially shot 405g lead FN, but unhappy with terminal performance, felt like there were better options. It was my first experience with lead, and I loaded them too hot initially, which tends to spray lead everywhere lol. Some fellas over at cast boolits set me straight, and they shot very well at appropriate velocity. Switched to copper jacketed bullets to get better terminal performance. Hammer recommended their 250g, and I can hold 2-2.5" at 100. It also shoots the Barnes 300g TSX as well, and the Hornady 300g FN. However, I did replace the front sight with a taller one due to the increase in velocity. The factory front is good for lead slugs going slow, but its also a bead and I shoot square more accurately. I have a milling machine, so it was just another project to make one, but Skinner Sights makes them. Miroku built as nice a factory rifle as I've owned, just really nice fit and finish, beautiful stock work, but if you want to shoot past 100yd, and really if you want to shoot well at all, you need better sights. Hope it helps...

Thank you sir and yes that does help. Yes this ones fit and Finnish is as nice as they come. It’s new old stock never fired I think I’ll buy it.
Wayne

 

[Handley]

With a big bore your barrel harmonics would likely play a smaller role ito accuracy. Your biggest concern should be over pressure. Perhaps someone could run your load through Quickload to verify this if you can supply the required inputs.

Oh boy...I have QL, it has been helpful, but different than for bottleneck cartridges. Barnes does have published load data that exceeds this performance, fwiw (42000psi max for Marlin/1886 actions). I used a combine of the two for the Hammer bullet, but some powders have shown pressure signs (in my rifle) when QL indicates they are well under. I make no claim to be an expert at QL, but I understand the need for accurate inputs and tuning inputs. Before trying RL7, I tried n120 because it showed similar performance without being compressed and lower pressure than the estimate for 4198. In reality, I got pressure signs at much lower velocity. I wrote the QL developer, he had me tweak one of the propellant inputs for that powder I normally don't touch, but that doesnt help for any other powder. Anyway, results for RL7 are showing slightly lower psi for the same velocity as my 4198 load, but I really only feel confident so long as I don't have any case head marks or sticky lever. I've heard psi can be difficult to gage with lever guns and straight walled cases, but these are what I can observe. The sticky lever results from the case expanding just above the rim, which I have measured with calipers. This is reset on resizing. I assume this would lead to separation eventually, so I backed off.

 

[Doug Casner]

Good question. I ve wondered about this also. Guess thats why my 6.5 creedmoor shoots H4350 better than IMR 4350 with same bullet same velocity . Thanks engineers. I wasnt smart enough to figure it out. Doug

 

[gunsandgunsmithing]

Good question. I ve wondered about this also. Guess thats why my 6.5 creedmoor shoots H4350 better than IMR 4350 with same bullet same velocity . Thanks engineers. I wasnt smart enough to figure it out. Doug

I'm not an engineer but a simple way to look at it is a faster powder does the same amount of "work" in less time than a slower powder. So, the pressure curve and exit timing is different, even at the same speed at the end of the barrel. A bit over simplified but not much and that should give you the idea.

 

[Handley]

Thanks all. I went out and shot 4 rounds, looks promising. POI is a little high, but discounting the first shot, that's my best ever group, though it needs 2 more in there. I'll shoot more later, I forgot to grab a jacket or something for recoil, that was all my shoulder was good for lol. Velocity was only 25fps ES, which I've also not achieved before with other powders. Again, small sample size, will need to shoot more. Thanks for your thoughts.

 

[Larryh128]

I've played 4198 and RL-7 in a couple calibers, 4198 always won in terms of accuracy. What I'm going to now is Vit N130. It would be worth a try.

 

[bozo699]

Thanks all. I went out and shot 4 rounds, looks promising. POI is a little high, but discounting the first shot, that's my best ever group, though it needs 2 more in there. I'll shoot more later, I forgot to grab a jacket or something for recoil, that was all my shoulder was good for lol. Velocity was only 25fps ES, which I've also not achieved before with other powders. Again, small sample size, will need to shoot more. Thanks for your thoughts.

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Damn!…. That’s good shooting for open sights and heavy recoil even with the 1st shot!
Wayne

 

[bozo699]

Handley,
When you added the rear peep did you have to remove the ridiculous safety they put in the receiver?
Wayne

 

[Handley]

Handley,
When you added the rear peep did you have to remove the ridiculous safety they put in the receiver?
Wayne

I did not remove the safety. Not yet anyway. I went through a lot of internet time researching it, but so far have put it off. That will be a Turnbull job if I ever win the lottery.