Max powder load doesn't get me close to predicted velocity with 9.0 barrel..

[John Gault]

So if I'm at maximum powder load per manufacturing specs but significantly slower than predicted velocity (assuming due to 9 inch barrel vs 16 inch barrel)..... are the predicted max pressures still being seen?

Can I go beyond max charge to try to find the max velocity?

Loading 300 BKO with H110 and 110grain Zmax bullets.

My last outing showed 20.0 grains of H110 yielding 2100fps.

Also trying Vit N110 powder which so far has grouped better at 15.5 gr # 1880fps but doesn't meter as nicely and $ more..

I'm actually pretty happy with grouping of N110 but not sure if this round would do it' job real well at that slow velocity considering 2400 is the high side and 1880 isn't even in the book.

Previous uses of N110 at higher powder charts get me to 2000ish but they are slightly compressed loads..

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[American123]

you can go over max load data, just keep an eye on pressure signs and do it incrementally. Be very careful with any changes to seat depth or compressed loads.

Apples and oranges though comparing a 9inch barrel and a 16. A faster burning powder might even be necessary because of the large difference in barrel length.

 

[Member 5605]

While the powder may be burned up that doesn't mean the gas is completely expanded...

Max is listed due to powder burn rate and how fast the pressure spikes.

My guess is you will find pressure signs before you reach the velocity you want.

 

[IronMonster]

I suspect chamber pressure is a function of the chamber and detonation so by exceeding the max load you are increasing chamber pressure. There simply is not enough length in the barrel to allow for all the gas to interact with the projectile

 

[v0lcom13sn0w]

Give Accurate 1680 a try.


you can probably up the charge of h110 carefully if you just watch for high pressure signs.

next time i take my 300 out i'll run some loads thru the chrono and report back

 

[Argonaut]

My older manuals frequently show considerably hotter loads than new information. I am sure it is the lawyer effect. High velocity is generally obtained with slower burning powders, you might experiment with some faster burning stuff for the short barrel.

 

[jordanka16]

So if I'm at maximum powder load per manufacturing specs but significantly slower than predicted velocity (assuming due to 9 inch barrel vs 16 inch barrel)..... are the predicted max pressures still being seen?

Can I go beyond max charge to try to find the max velocity?

Loading 300 BKO with H110 and 110grain Zmax bullets.

My last outing showed 20.0 grains of H110 yielding 2100fps.

Also trying Vit N110 powder which so far has grouped better at 15.5 gr # 1880fps but doesn't meter as nicely and $ more..

I'm actually pretty happy with grouping of N110 but not sure if this round would do it' job real well at that slow velocity considering 2400 is the high side and 1880 isn't even in the book.

Previous uses of N110 at higher powder charts get me to 2000ish but they are slightly compressed loads..

You can go over the max load as long as you are careful to watch for pressure signs, it is harder in a semi auto than a bolt so be very careful. Generally I don't push semis too much, especially with a 300 blk as it's a short range round anyway, I would probably stop there and call it good. Comparing a 16" to a 9" barrel the longer barrel will always give more velocity, even with a fast burning powder like h110.

Hodgdon predicts 2,286 with 19.4 grains out of a 16", considering that, I'd say you are doing pretty well with 2100 fps.

4227 and CFE black both predict more velocity, so you might try those if you want more speed.

 

[Member 5605]

You can go over the max load as long as you are careful to watch for pressure signs, it is harder in a semi auto than a bolt so be very careful. Generally I don't push semis too much, especially with a 300 blk as it's a short range round anyway, I would probably stop there and call it good. Comparing a 16" to a 9" barrel the longer barrel will always give more velocity, even with a fast burning powder like h110.

Hodgdon predicts 2,286 with 19.4 grains out of a 16", considering that, I'd say you are doing pretty well with 2100 fps.

4227 and CFE black both predict more velocity, so you might try those if you want more speed.

4227 with a 150gr pill on a 16.125" barrel gave me 2100fps.

 

[John Gault]

The journey continues..
Some subs that i think are close to being good enough.. 1 more try using 11.0 and 11.2 gr. of 1680 and a retry of 8.4 grains N110 all on 208 grain Hornady HPBT

Supersonic
N110 - 15.5 gr shot well. Will chrono again
H110 - Retrying with loads from 17.0 to 20.4
All on Hornady 110gr Zombie Max

Thanks for all the input..!!

 

[AMProducts]

So if I'm at maximum powder load per manufacturing specs but significantly slower than predicted velocity (assuming due to 9 inch barrel vs 16 inch barrel)..... are the predicted max pressures still being seen?

Can I go beyond max charge to try to find the max velocity?

Loading 300 BKO with H110 and 110grain Zmax bullets.

My last outing showed 20.0 grains of H110 yielding 2100fps.

Also trying Vit N110 powder which so far has grouped better at 15.5 gr # 1880fps but doesn't meter as nicely and $ more..

I'm actually pretty happy with grouping of N110 but not sure if this round would do it' job real well at that slow velocity considering 2400 is the high side and 1880 isn't even in the book.

Previous uses of N110 at higher powder charts get me to 2000ish but they are slightly compressed loads..

You loose on average 50-100fps per inch of barrel, so going from a 16 to a 9, that's 7" of difference, Conservatively this should be a 300FPS difference, to a 700FPS difference.

PMAX usually happens between .5 and 2" of barrel length. It will happen at shorter distances, and give higher peak pressures the more powder you put in. I would not recommend boosting your charge with these powders at all.

 

[Jamie6.5]

The thing to remember about making max velocity, is to think about what the pressure curve looks like on a graph, charting pressure over time.
Max pressure for a very short duration won't make max velocity, when often more moderate pressures over an extended period of time will.
And unfortunately, short barrels don't allow for a lot of time for the pressure to work on accelerating the projectile.
This is what's known as "The area under the curve" meaning the pressure curve.
Short barrels mean short pressure curves. You can't make up all of the difference in the square inches of area under the curve by increasing the pressure by small or even moderate percentages if you don't have time on your side.

One of the easiest ways to visualize this is the longbow vs the crossbow.
While the crossbow may have a 150lb pull, and the longbow only 75lb, the arrow/bolt of the crossbow is only about 16" long with about 12-14" of pull, whereas the longbow may shoot an arrow 30" long, utilizing 27" or so of pull, and even though the arrow has greater mass than the bolt, is usually leaving the bow faster than the bolt leaves the crossbow. With almost twice the time/distance for the string to transfer the force of the bow's limbs, the result is more speed.
As a result, the longbow produces greater velocity and considerably more range.