When does more powder = less velocity??

[turbo54]

Did some chrono work yesterday with my Savage 308 and my CED M2. All loads were with Lapua brass, Varget, 175SMK and Fed 210M primers. All were 5 shot strings. It was hot as hell yesterday, and i let the ammo sit in the sun and bake for 30 minutes before shooting. Each string was shot in about 5 minutes, with 10-15 minutes between strings.

44.00: average - 2622, es - 34, sd - 11
44.25: average - 2605, es - 24, sd - 9
44.50: average - 2631, es - 21, sd - 7

I defintely did not make a mistake in my charge weights, or labeling which rounds were which. Ever see this phenomenon before? I see the trend that I'm not gaining much velocity for my powder increases.

I'd REALLY like to hit 2675(ish) if I can, to match my partners trajectory. Yes, he can back his down to match mine - but faster is better if accuracy is there. I am not seeing pressure at 44.5gr in Lapua brass, but DID find pressure at 44.5gr in NATO brass...average velocity was within 3fps between the two types of brass.

Should I bother chasing more velocity, or am I just wasting powder and putting extra wear on my barrel?

 

[Aimsmall55]

Re: When does more powder = less velocity??

Sounds like the heat probably had alot to do with it. Not only that it probably effected the accuracy of the chrony and threw off your exterior ballistics too. I shot myself yesterday and your right it was just too damn hot. The only thing I can say is what kind of groups were you getting? Velocity is not everything. Stability and Continuity are. Your standard deviation was superb. Just need to know what kind of groups you were getting

 

[MitchAlsup]

Re: When does more powder = less velocity??

There are situations where velocity plateaus out for a short range as the charge weight continues to rise. I suspect this is waht was going on in your groups. Becides, you should not expect a large MV variation with only 0.5 gr difference.

As to chasing velocity:: basically no, what you chase is accuracy, and take whatever MV gives you the accuracy. Then you construct the ballistics tables for that load in your DOPE book,......

But since you have not run into any pressure signs, you can drift towards heavier CWs until you find the accuracy (or MV) that you want.

 

[turbo54]

Re: When does more powder = less velocity??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">There are situations where velocity plateaus out for a short range as the charge weight continues to rise. I suspect this is waht was going on in your groups. Becides, you should not expect a large MV variation with only 0.5 gr difference.

As to chasing velocity:: basically no, what you chase is accuracy, and take whatever MV gives you the accuracy. Then you construct the ballistics tables for that load in your DOPE book,......

But since you have not run into any pressure signs, you can drift towards heavier CWs until you find the accuracy (or MV) that you want. </div></div>

Thanks for the input. The only ladder I chronoed with this rifle was the 155 scenar, which was showing 10-15fps/.25gr. Seemed strange I saw a 20fps LOSS with 1/4gr more powder with the 175 though.

In general, i totally agree with finding accuracy and dealing with whatever MV you get. However, Im trying to have identical trajectories for my partner and I, provided accuracy is adequate. This rifle can do 1/4 MOA with a 180smk. So far I havent seen that with the 175, but, I would forego 1/4-1/2" at 100 yards to have matching trajectories. Dont think ill have to though. This rifle seems to shoot any charge of Varget with 174smk 1/2 moa.

Im going to keep pushing onward and upward and see what i get. So far, we have a common "node", his rifle at 42.7 @ 2608av,25es,9sd...my rifle at 44.25 @ 2605av,24es,9sd... His rifle shoots 30 caliber hole ten shot groups here, and mine is 1/2 moa. He has another load that is 2676av,12es,3sd that also shoots better than bugholes. Me driving both rifles.

Wish me luck, my 24" tube definitely has to work harder than his 26" one.

 

[esorensen]

Re: When does more powder = less velocity??

I've run into the same thing plenty of times, in 7mm and 30 cal. It is usually at the higher end of charge weights towards max. Certainly counter-intuitive, but not unheard of. I can tell you that I have not chosen any of the charge weights that exhibited this as an accuracy load.

 

[turbo54]

Re: When does more powder = less velocity??

Alright...hit it with a bigger hammer and found:

45.5 - 2656av, 20es, 8sd, 1/2 moa (coulda been better, i was racing the shadows)
46.0 - 2666, 25es, 9sd, 1/2 moa
46.5 - 2678, 23es, 7sd, 1/2 moa

Didnt find max pressure, but chrony started to drop out due to shallow sun angle.

My partner has a GREAT load at 2657. I think my load at 2656 will bughole. My rushed group was a TIGHT cloverleaf of 3, and a double 1" away ...... at 200 yards. So 1/2 MOA with "fliers". This is all for tactical shooting anyway, so a
rushed 1/2 MOA is fine by me. No signs or pressure, either....again, I let the ammo sit in the sun before shooting.

 

[Clark]

Re: When does more powder = less velocity??

I know that in 357 mag with LIL'GUN and 158 gr, the recoil and noise keep going with higher charges, but the velocity goes down.

The fireball keeps getting bigger, and that is where the energy went, out the muzzle before it burned.

 

[turbo54]

Re: When does more powder = less velocity??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">I know that in 357 mag with LIL'GUN and 158 gr, the recoil and noise keep going with higher charges, but the velocity goes down.

The fireball keeps getting bigger, and that is where the energy went, out the muzzle before it burned. </div></div>

I know what you mean. Developing FAST loads for my 10mm, I learned that recoil and blast (12.5gr Blue Dot) does not necessarily mean high velocity (200gr at 1100). 10.5gr of 800X (200gr at 1350) had little blast and was not dramatic.

 

[Clark]

Re: When does more powder = less velocity??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"> Developing FAST loads for my 10mm, I learned that recoil and blast (12.5gr Blue Dot) does not necessarily mean high velocity (200gr at 1100). 10.5gr of 800X (200gr at 1350) had little blast and was not dramatic. </div></div>

In 10mm, 13.2 gr Blue Dot, 200 gr 1.3" Glock 20, is wimpy.
In 10mm, 14.2 gr 800X, 200 gr 1.3" Glock 20 kicks hard.
In 40sw, 15.5 gr 800X, 200 gr 1.175" Glock 22 kicks hardest.

Don't try these with stock Glock barrels or the case will blow out.
Don't let your girl friend shoot one of them, or the recoil will end your relationship.

 

[Jimlaw83]

Re: When does more powder = less velocity??

I had the exact same situation occur with same bullet, rifle, and powder. I think I posted the numbers on here, but it was a .5 gr increase that resulted in loss of velocity. To be honest I'm still trying to figure this out, because it occurred with all three of the loads I was testing. (ar comp, 2000 mr, and varget) only occurred at one load spot, and the rest had a fairly predictable velocity gain between loads. I thought I had accidentally reversed the load labels on my box or something!