.38 Trajectory

[KiwiKev]

I am shooting a 38/357 Rossi 24 inch octagonal. At the range yesterday I was shooting out to 50 meters the following loads: All off the bench

4 gr of Trail Boss 158 gr LSWC
4.2 gr of Trail Boss 158 gr LSWC
4.2 gr of Tail Boss 158gr LRN

The first combo shot a group of about 3 inches dead centre.
The LRN formed a tighter group, about 2 inches, at 2 o'clock mainly in the 7 ring.

Have others noticed much of a difference in trajectory between LSWC and LRN?
The 4.2 gr load I would expect to shoot higher.

Cheers.

[Arminius]

different bullets will have different angle at departure of barrel ... only THEN sets Trajectory in ....

[AJMD429]

different bullets will have different angle at departure of barrel ... only THEN sets Trajectory in ....

Sorry if this is a dumb question, but why would two different bullets not be able to have the same angle at departure...???

I could see that even with the same weights, your loads COULD have different velocities, even if powder charges the same (different friction in barrel, or different crimps), and that could affect things (and even therefore recoil differently). More obviously, of course their ballistic coefficients would be different, though you'd have to put them into a ballistic software program to see just how much a ballistic coefficient change would actually affect down-range velocity. My guess is that between those shapes it wouldn't be all that much, but I could well be wrong about that!

It would be very interesting to see the chronograph results between the loads, if you have access to one.

COSteve has done lots of long-range shooting with the 38/357 out of long-barrel leverguns, so may chime in with just the information you're after.

[pokey]

The 4.2 gr load I would expect to shoot higher.

a projectile traveling faster means less time in the barrel under recoil, thus
"usually" impacting lower on the target.

[FatJackDurham]

A cronograph is needed here. The Ballistic Coefficient between LRN and LSWC for a Hornady is .159 to .127, but that only translates to a .1" difference at 50 yards, for a trajectory zeroed at 100 yards.

I think more likely to be affecting you here, is the the speed of the bullet as it leaves the gun. Did you change the seating deapth to account for the longer tip on the LRN bullet? If your COL was the same for both, the base of the LRN might be slightly deaper in the case, giving you a higher pressure at ignition and possibly changing the speed of the bullet.

Also, also, in flight, the bullet may not be travelling precisely on a line around the center of the bullet. If the bullet is slightly heavier on one side, or if it tips a little as it leaves the blast envelope, it can wobble around a kind of corkscrew on its way to the target. So, if one bullet is in a different part of the corkscrew , it will hit off center from the other.

Plus, the 38 spl. is a pretty slow round, around 770 fps, even at 50 yards, that is a long time to target, relatively speaking.

[KiwiKev]

I think the LRN is seated a limitless bit deeper. Also I am wondering about my crimp. I crimp just below the final band on the Lee TL358-158-2R.
I noticed the LSWC has a ballistic coefficient of .117 and the LRN has one of .207
As a newbie to reloading I know my loads will be a bit rough.
Also these LRN came prelubed and sized with plenty of alox on them. Does that make a difference?

I have loaded some 4gr trail boss LRN, I will see how they fly.

Cheers guys.

[FatJackDurham]

As someone who has only be reloading a year, I'll let the others judge, but, in my experience, the bullet shape and BC were the least affecting characteristics of my loads. Consistent powder weight, proper case trim, good cleaning and primer pocket care, consistent crimp, these were all greater factors for me.

I especially learned a lot from using a chronograph, which aren't that expensive, to help find the best loads. If you are shooting in a levergun and a revolver, too, I'd stay away from the LRN, and just go with a LSWC, and develop a consistent load for that. Also, you might be surprised at the difference .2 grains of powder makes. I would have a fun time loading up ten bullets at the minimum powder, hand weighed, and increment two grains on up to the max listed in the book. Then, down to the range with the Chrony, and test them. Sure enough, I would have a couple of loads that shot 1 1/2 " at 50 yards within 2 grains of each other, then the next higher or next lower load would shoot 5 inches, 10 inches.

So, take copious notes, measure your COL for each load, and once you have a sweet load, try to duplicate it, and duplicate the results. Then stick with it.

I have bought the 140 grain Hornady Cowboy bullet and it worked great for target practice and CAS shooting. There is also a place near me that makes 1000 bullets for $55, and if I need a 125 grain or a 158 grain, I go there.

If the bullets come prelubed, i'd leave it alone.

[retmech]

I shoot out to 200 yds with my Rossi 92's and reloads running 1100 fps to keep them subsonic just like std velocity .22's. The Lee 158 swc tumble lube bullet is very accurate in my guns but has a BC of .117. The Lee RN 158 grn tumble lube bullet has a BC of .207 so I thought it might help wind drift a bit and hopefully shoot as well as it's flat nosed cousin. Well it's just as accurate but impacts at the same point as the swc at 200 yds at the same velocity. That shouldn't happen! With a higher BC it should retain more velocity and hit higher on the target but in the real world it doesn't. I don't know why but with the same load, same muzzle velocity and same sight setting the SWC's and RN's hit the same point at 200 yds. Both bullets are identical except for point shape and BC. According to ballistics calculators there should be about 5" difference at 200 but there isn't. Go figure.