Figuring fps

[shootrj2003]

If I am shooting a reduced load, (60 percentof max.isok ) max load is 33.5 GR. H 4895 W/150 GR BULLET,reduced load can be 60 % of max.=(33.5÷100=..335 ×60=20.1)so according to my info,I can use /reduce my load of H4895 TO 20.1 GR.FOR A 150 GR. Hardcast,in this case a hunter supply .311 150 gr.HPGC 16 bhn, 10 rds without gc. 10 rds w/ a gas check.bullets were lubed also by mfg. Green waxxy lube ,Rifle is a Marlin 336(1966) exc.cond.bore was slugged using .311 bullet fairly tight micro groove .308 bore for it's years .
What is the est. Velocity of this load?I would like to have an idea before I actually load it,I would like 1500 to 1600 fps.knowing how to figure it would be good also ,my math skills are suspect at times!so please check my figures

[Tatume]

The guidance provided by Hodgdon on reduced loads specifically says to use H4895. If you use IMR 4895 you're on your own.

[Tatume]

Published load data (not reduced) show velocities for the 30-30 between 1351 and 1562 FPS using a cast 160 grain bullet and H4895. Since these published, pressure-tested data closely approximate your desired load, there appears to be no need to extrapolate.

http://www.hodgdonreloading.com/

[BigAlofPa.]

I run shotgun powders. For reduced rifle loads.

[popper]

use H4895 - no reduced data for IMR! I've gone to 20gr H4895 and 20 gr LeverE without problems but fps was less than desired (1200).
Try 9 gr unique - 1500 fps.

[shootrj2003]

10-4 on the H 4895,my mistake, I do have both,on shotgun and pistol powders ,and small loads in general at this point I would prefer to avoid them and use something with more bulk as well as something I have (and I do have H4227) and avoid the further problems of position sensivity and use of Dacron questions in a bottleneck case which I will tackle as I go,I do intend to delve into casting and stick with it so I do have time.shooting j- bullets had gotten a bit ho him,and this has peaked my interest plus there are things I want to figure out,questions I need to experiment with I have wondered about,,materials to be used yes,new strange,WONDERFUL THINGS....oh sorry,I get carried away heh !sometimes!
So anyway,how do I go about figuring the fps of a given load ,in a given powder ,I mean I can guess ,but there must be an accurate way,right? or is it as simple as say,deviding the Max fps 2390,by the the Max gr. 34.0 And call it 70.2 fps for every grain?I actually used this and it was very close,within 3 fps.

[sureYnot]

Quickload or similar software will get you a close guess. Only way to know for sure is to measure it yourself, I suppose.

Sent from my XT1710-02 using Tapatalk

[shootrj2003]

Thank you every one your help is invaluable to me,I am thinking 22 gr. H4895 for about 1500-1550 fps.

[Tatume]

Thank you every one your help is invaluable to me, I am thinking 22 gr. H4895 for about 1500-1550 fps.

Again: 160 GR. CAST LFN
Manufact Powder Diam. C.O.L. Grs. Vel. Pressure Grs. Vel. Pressure
Hodgdon H4895 0.308" 2.485" 17.5 1,351 15,200 CUP 21.0 1,562 3,100 CUP

www.hodgdonreloading.com/

[shootrj2003]

How do you get that info there?I get only two loads and no lead cast info .called Hogden tech support talked to Luke he agreed that 22.gr. of H 4895 should put me right n the 1500_1550 area with a 150 gr Lcb

[Tatume]

How do you get that info there?I get only two loads and no lead cast info .called Hogden tech support talked to Luke he agreed that 22.gr. of H 4895 should put me right n the 1500_1550 area with a 150 gr Lcb

PM Sent.

[indian joe]

10-4 on the H 4895,my mistake, I do have both,on shotgun and pistol powders ,and small loads in general at this point I would prefer to avoid them and use something with more bulk as well as something I have (and I do have H4227) and avoid the further problems of position sensivity and use of Dacron questions in a bottleneck case which I will tackle as I go,I do intend to delve into casting and stick with it so I do have time.shooting j- bullets had gotten a bit ho him,and this has peaked my interest plus there are things I want to figure out,questions I need to experiment with I have wondered about,,materials to be used yes,new strange,WONDERFUL THINGS....oh sorry,I get carried away heh !sometimes!
So anyway,how do I go about figuring the fps of a given load ,in a given powder ,I mean I can guess ,but there must be an accurate way,right? or is it as simple as say,deviding the Max fps 2390,by the the Max gr. 34.0 And call it 70.2 fps for every grain?I actually used this and it was very close,within 3 fps.

I woulda thought it dont work like that ---ie not straight line math ? maybe wrong but that just seems too easy to be true???

[slam45]

for velocity information to be relevant for your rifle to calculate trajectories and power you need to crono the loads in your rifle... anything else is just guessing, might be close but it may not be... if you want to know, test it...

[Texas by God]

for velocity information to be relevant for your rifle to calculate trajectories and power you need to crono the loads in your rifle... anything else is just guessing, might be close but it may not be... if you want to know, test it...

+1 above. It is not uncommon for two seemingly identical rifles to have 100+ fps difference with the exact same load.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[Tatume]

I woulda thought it dont work like that ---ie not straight line math ? maybe wrong but that just seems too easy to be true???

Actually, non-linear behavior can be modeled very accurately with linear extrapolation if the intervals are small. Think of a curve approximated by short line segments. Each of the line segments will be very close to the actual curve. The smaller you make the line segments, the closer they will be to the curve.

Suppose you fire your 30-30 rifle over a chronograph using a 160 gr cast bullet and two loads, 18.0 and 21.0 gr H4895. If your average velocities at each level are 1350 and 1550 fps, and you then try 19.5 gr of H4895, your average MV will probably be very close to 1450 fps.

[indian joe]

Actually, non-linear behavior can be modeled very accurately with linear extrapolation if the intervals are small. Think of a curve approximated by short line segments. Each of the line segments will be very close to the actual curve. The smaller you make the line segments, the closer they will be to the curve.

Suppose you fire your 30-30 rifle over a chronograph using a 160 gr cast bullet and two loads, 18.0 and 21.0 gr H4895. If your average velocities at each level are 1350 and 1550 fps, and you then try 19.5 gr of H4895, your average MV will probably be very close to 1450 fps.

He was talking seriously reduced loads with NO chrono baseline to start from ??? WAG I reckon !!!

[Tatume]

I know. Linear approximation is still the place to start. My example illustrates the process.

[missionary5155]

If we want to slow down a slug we go to Unique. Has never given us any issue for 40+ years. Cat sneeze to BP velocity is a happy routine in any hunk of brass up to 50-100. We do not have any 20mm to play with....

[GhostHawk]

Fast powders to go slow, slow powders to go fast.

Hard to beat 4.6 to 6 grains of Red Dot in everything I've tried it in.

[KWK]

So anyway,how do I go about figuring the fps of a given load ,in a given powder ,I mean I can guess ,but there must be an accurate way,right? or is it as simple as say,deviding the Max fps 2390,by the the Max gr. 34.0 And call it 70.2 fps for every grain?I actually used this and it was very close,within 3 fps.

There are some rules of thumb for single base powders. Lee's 1st edition contained some. They are not always accurate.

You've located the Hodgdon load of 2390 fps from 34.0 gr H4895 in a 24" barrel. When they reduced the charge 10.3% they got 2138 fps, a 10.5% loss in fps. This is not uncommon with single base powders, a roughly like % drop, as diagrammed in early Hornady load books, as well as the old Powley computer equations. So, a 40% drop in charge might drop velocity about 40% as well, call it 1430 fps.

QuickLoad is not usually accurate at these pressures. When I put in the 34.0 gr load, it reckoned 2394 fps, which is surprisingly close. Dropping 40% to 20.4 gr gives 1410 fps.

I don't know what is your barrel length (although you did say the fps was about right). If it's 20" QuickLoad figures 1340 fps with the 40% reduced load.

That should get you in the ball park.

Another rule of thumb for single base powders is that a 10% drop in charge will drop pressure 20% on the CUP scale (which isn't a linear pressure measurement). In Hodgdon's data, the 10.3% drop in charge made for a 24% drop in pressure, not 20.6%. As I said, rules of thumb are only rough estimates.