more velocity with less powder?

[jbcricket]

Hey guys, i was wondering if anybody has ran into the issue i did yesterday when testing some loads. First of all let me start by saying i've worked up to these loads very carefully and slowly by 1/10th gr increments and examined all the brass individually as i went so please no comments on the nature of the loads. Having said that, i tested W296 and H110 with 125 gr Hornady SST's and the starting load of the day was 19.1 gr and the max load was 19.5 gr, i ran these over the chronograph and both powders of course gave the same basic results, the weird thing was the highest velocities came from 19.1 grs and went down from there. Which brings me to my question has anyone else ran into this diminishing velocity with more powder scenario?

(by the way, those loads are well over max in the hornady book so i think we all know the disclaimers, use at your own risk, work up slowly, what was safe in my gun might not be safe in yours, ect...)

[bangbangping]

Can you give actual data? Velocity, number of rounds, es, etc.

[jbcricket]

I can later tonight when i get home. I dont have my info in front of me at the moment. If i remember correctly at 19.1 gr it was averaging just under 2200 fps and at 19.5 gr it was just over 2100 fps and thats from a SS wilson 16" recon barrel.

[DoubleJ]

Velocity regression is a sign of high pressure. You should also see your ES numbers get larger. When I see it with my 5.7 loads, it means I'm way over and should have stopped a while ago.

[r.tenorio671]

...not unusual, encountered same with all the powders I've used so far (A5744, #9, H110, LilGun)... each barrels chamber has that "node" where your greatest efficiency is found, as well as the accuracy. Chasing the FPS numbers will be counter productive, find what gives the greatest consistency (which typically results in greater accuracy) for your gear....

BTW, I see this all the time for ALL the calibers, pistol & rifle that I reload...

[jbcricket]

thanks for the info guys, guess i'll just do the wise thing and back off a bit and work on some accuracy loads now...

[Dolomite_Supafly]

I have worked up loads and once they get to a certain point the velocity does not increase regardless of the amount of powder. That means that some of the powder is not burning in the barrel.

I suspect the powder is a lot more densely packed with more powder so rather than igniting a lot of the powder at the time of ignition you are only igniting small portion. And because you are igniting less that means it is taking longer to burn and that means some of it is burning outside of the barrel.

[oldpapps]

r.tenorio671 has got it right (my view), I call 'it' nulling out.

I have encountered it a number of times. (so far) Only with one powder-bullet combination in the 300, my cut down cast 130 grain lead/powder coated bullets with Lt'Gun, see spread sheet, they don't copy and past well

300 Lt cut 30 130 LtGun 17.4 *2142.5 DSA 5/23/2014 2.024 in Cast, sized .311, powder coated, sized
300 Lt cut 30 130 LtGun 17.5 *2151.66 DSA 5/23/2014 2.024 in Cast, sized .311, powder coated, sized
300 Lt cut 30 130 LtGun 17.6 *2093.16 DSA 7/14/2014 2.024 in Cast, sized .311, powder coated, sized
300 Lt cut 30 130 LtGun 17.7 2068 DSA 5/30/2014 2.024 in Cast, sized .311, powder coated, sized
300 Lt cut 30 130 LtGun 17.8 2048.3 DSA 5/28/2014 2.024 in Cast, sized .311, powder coated, sized

The loads with the velocity marked with a '*' are valid, over 15 samples, the others have not reached the sample mark of 15 and I don't see me testing them further.
With this bullet, I have standardized at 17.5 grains, just below the null.

With a different round/powder, this is what it looks like:

2400 'O' 29.7 2526.5
2400 'O' 29.9 2552
2400 'O' 30 2552
2400 'O' 30.5 2551.5

The above test with 2400 powder are NOT in a 300 BlackOut! Each if these are valid, 15 or more samples, results. As this series was fired in a 22 inch barrel, I think the energy had just reached it's limits with that bullet weight and chamber volume. The velocity changes are far less than the standard deviations. With a 6 tenths change in powder and no difference in velocity. That's nulling to me.

I isn't no scitest and don't know none of all dat fancy stuff, so be carful and don't take my results as more than the babbling of an old man.

Load with care,

OSOK

[steve franklin]

I loaded five different charges of 125 BT's and Lil'gun from 17-18 grains and got similar results compared to oldpapps. Slight pressure signs at the higher charges, little change in velocity.

[mrgein]

i am wondering if my thinking is correct so everyone please critique this comment.

i was thinking the fps would drop in higher powder charge because the ~19.1 you put in is probably all it took to get it out of the brass and down the barrel and even 19.1 was a little excessive but it was a small enough surplus that it burned up during dwell time. but with 19.5 there is too much excess and it all is not getting ignited and thus reducing the actual amount that is propelling the bullet. does that make sense?