FPS Increase Per Grain Increase?

Wildalaska · July 15, 2007, 08:11 PM

Anyone got some highs and lows here....approx how many fps to you gain with an increase of one grain of powder.....in a medium rifle case?

WildwillgivemorespecioficsinabitAlaska

mc223 · July 15, 2007, 10:19 PM

As you say approximate, maybe 30 to 100. Too many variables to say that these are even semi-realistic.

Archie · July 15, 2007, 11:31 PM

Please note, this information is from load development and may not be suitable for your rifle.

From a .308 Winchester rifle, using Federal cases, WLR primers, military 174 grain boat tail spitzers and the following powders, I got these average chronograph readings:

IMR 4895

39.0 - 2366
40.0 - 2469
41.0 - 2550

VV N550

43.0 - 2438
44.0 - 2535
45.0 - 2576
46.0 - 2625

I don't have any information for light bullet loads. However, this may give you some data to ponder.

Please note, these are not recomended loads. Check your loading manual and proceed with caution.

cdoc42 · July 16, 2007, 09:41 AM

If I understand your question correctly, you're looking for how many feet per second increase you might get per grain of powder charge.

I fooled around with all these calculations in the past, usingdata in the various reloading books, and concluded you simply cannot make any predictions.

First, as stated in these threads, there are too many variables. But let's assume you use the same powder, same bullet, primers, seating depth, rifle. Look at the data presented here with 4895 and VV550.

4895: 39gr gives 60.67 fps per grain of powder
40gr gives 61.73 fps, so you've gained 1.06fps per grain added
41gr gives 0.49fps so there seems to be no advantage to 41 gr.

But that particular load MIGHT just be more accurate. You need to test the loads.

Moving to VV550: 43gr gives 56.7 fps per grain
44gr gives an additional 0.91 fps
45gr -you lose 0.37 fps and 46 gr you lose 0.24fps

I've read somewhere when you see a drop in fps with additional powder you have likely exceeded the pressure curve for that load.

I've not extracted anything usefdul playing with these figures over the years.

Wildalaska · July 16, 2007, 12:53 PM

Hi thnks that is the info above I was looking for, I will post deatrils later

WA

July 15, 2007, 08:11 PM	#1
Wildalaska Junior member Join Date: November 25, 2002 Location: In my own little weird world in Anchorage, Alaska Posts: 14,172	FPS Increase Per Grain Increase? Anyone got some highs and lows here....approx how many fps to you gain with an increase of one grain of powder.....in a medium rifle case? WildwillgivemorespecioficsinabitAlaska

July 15, 2007, 11:31 PM	#3
Archie Senior Member Join Date: May 26, 2000 Location: Hastings, Nebrasksa - the Hear Posts: 2,209	According to my records... Please note, this information is from load development and may not be suitable for your rifle. From a .308 Winchester rifle, using Federal cases, WLR primers, military 174 grain boat tail spitzers and the following powders, I got these average chronograph readings: IMR 4895 39.0 - 2366 40.0 - 2469 41.0 - 2550 VV N550 43.0 - 2438 44.0 - 2535 45.0 - 2576 46.0 - 2625 I don't have any information for light bullet loads. However, this may give you some data to ponder. Please note, these are not recomended loads. Check your loading manual and proceed with caution. __________________ There ain't no free lunch, except Jesus. Archie Check out updated journal at http://oldmanmontgomery.wordpress.com/

July 15, 2007, 10:19 PM	#2
mc223 Senior Member Join Date: January 20, 2007 Location: n/w Wisconsin Posts: 365	As you say approximate, maybe 30 to 100. Too many variables to say that these are even semi-realistic.

July 16, 2007, 09:41 AM	#4
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	If I understand your question correctly, you're looking for how many feet per second increase you might get per grain of powder charge. I fooled around with all these calculations in the past, usingdata in the various reloading books, and concluded you simply cannot make any predictions. First, as stated in these threads, there are too many variables. But let's assume you use the same powder, same bullet, primers, seating depth, rifle. Look at the data presented here with 4895 and VV550. 4895: 39gr gives 60.67 fps per grain of powder 40gr gives 61.73 fps, so you've gained 1.06fps per grain added 41gr gives 0.49fps so there seems to be no advantage to 41 gr. But that particular load MIGHT just be more accurate. You need to test the loads. Moving to VV550: 43gr gives 56.7 fps per grain 44gr gives an additional 0.91 fps 45gr -you lose 0.37 fps and 46 gr you lose 0.24fps I've read somewhere when you see a drop in fps with additional powder you have likely exceeded the pressure curve for that load. I've not extracted anything usefdul playing with these figures over the years.

July 16, 2007, 12:53 PM	#5
Wildalaska Junior member Join Date: November 25, 2002 Location: In my own little weird world in Anchorage, Alaska Posts: 14,172	Hi thnks that is the info above I was looking for, I will post deatrils later WA