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Topic: longer coal and effect on case pressure? (Read 1052 times) previous topic - next topic

longer coal and effect on case pressure?

question that i’m hoping someone with quickload might be able to answer.

i’m currently running 43.8 grains of rl-16 with hornady 147’s seated at 2.81 coal (mag length). my lands are way out at 2.924 meaning i’ve got an enormous jump going on. now if i loaded same load to 2.91 say, maybe accuracy gets better/worse, TBD. but what is the expected effect of case pressure/velocity? is a 1/100th change enough to make a difference at all?

mostly just curious if someone with quickload has the time to run two scenarios changing only the COAL from 2.81 to 2.91

thanks
-d

Re: longer coal and effect on case pressure?

Reply #1
Just checked and I don't have the 147 in the bullet library in QL.

Re: longer coal and effect on case pressure?

Reply #2
Just checked and I don't have the 147 in the bullet library in QL.

appreciate you looking - i guess the question still stands for anything in the 140-143 class. the 147 is a bit longer but i’m just trying to understand if adjusting the COAL .01 will have significant effect or not.

Re: longer coal and effect on case pressure?

Reply #3
appreciate you looking - i guess the question still stands for anything in the 140-143 class. the 147 is a bit longer but i’m just trying to understand if adjusting the COAL .01 will have significant effect or not.

That I can do....gimme a minute :)

Re: longer coal and effect on case pressure?

Reply #4
Assuming Hornady cases with approx H2O cap. of 53.5gr./ 26" barrel/ ELD-X 143gr / Rl-16 at 43.8gr

COAL 2.81, 105% compressed load, 66,988 PSI, 2930 fps

          2.91, 102% compressed load, 62,931 PSI, 2895 fps

Re: longer coal and effect on case pressure?

Reply #5
QL does not know where your lands is located along a continuum of increasing COAL.  I t will continue to predict decreasing pressure. Once the ogive kisses the lands and especially when it gets jammed, the pressure will radically increase rather than decrease as the software predicts.

Re: longer coal and effect on case pressure?

Reply #6
Jerry brings up an important point to consider.  Even though you have a predicted 0.014" jump to the lands at 2.910" COAL.....don't count on it.  Your loads are at/near max for the shorter COAL and if your longer cartridges are actually very close or touching the lands the pressure spike could put pressures exceeding 70K which can cause damage.  If you try the longer seating depth I suggest backing off a half grain and firing a cartridge or two and check for pressure signs as you work up to 43.8gr.  You only need one or two loaded at each charge to check pressures.

Re: longer coal and effect on case pressure?

Reply #7
You should see pressures drop until you start engaging the lands at loaded length. The best thing to do is redo your load workup at 0.010" - 0.020" and fine tune from there. Anything less than 0.005" jump to the lands should not give a noticeable increase in peak pressure. As long as you give the ogive a running start at the lands, the engraving pressuse stays withing safe operating conditions, assuming you are using a safe powder charge.

Edit: I'll also respectfully disagree with Robin, as much as I hate to, but I watch for pressure signs on high end loads every time I start shooting them, and consider one case with "signs" of pressure in 10 rounds one to many. Again, this is just my opinion, and Robin is a master handloader, so my disagreement with his low round count is purely that, my personal opinion not based on anything other than my opinion. Sorry to be negative @rardoin
Silence is golden. Duct tape is silver.
I have a lot of guns... There, I said it.

Re: longer coal and effect on case pressure?

Reply #8
Edit: I'll also respectfully disagree with Robin, as much as I hate to, but I watch for pressure signs on high end loads every time I start shooting them, and consider one case with "signs" of pressure in 10 rounds one to many. Again, this is just my opinion, and Robin is a master handloader, so my disagreement with his low round count is purely that, my personal opinion not based on anything other than my opinion. Sorry to be negative @rardoin

I think we are on the same page DJ.  I suggested loading a single case at say, 43.4gr, 43.6, and 43.8gr to look for pressure signs before assuming the original 43.8gr load is safe.  I am in total agreement that 1/20 overpressure cases means I have a problem to solve and the load is not to be considered safe until I can diagnose the issue.

As far as Master Handloader???  Who me???  One of my fishing buddies did dub me a Master Baiter and I had no objection ;D

Re: longer coal and effect on case pressure?

Reply #9
thanks for all the replies guys. i actually have played with single loads loaded to touch the lands before and the difference between just off and touching is pretty amazing in terms of chrono’d velocity and (i assume) pressure spike.

that’s why i was curious about how much less pressure moving coal longer but not actually to the lands gets me since everything lists 2.81 as coal for max charges.

it looks like it’s not all that much different actually from 2.81 to 2.91 3000psi, less than i might have guessed. i’m pretty happy with my load/velocity at 2.81 but if i could generate same velocity with less pressure by loading longer and then bumping charge maybe .1 that’s interesting too. might load 10 up at longer length .002 off the lands but same charge and see if the group any better/worse than current load just to play around a bit before i invest in any accurate mags


Re: longer coal and effect on case pressure?

Reply #10
unless you’re really jamming them i don’t see a lot of guys advocating kissing the lands so i’ll probably stay a ways off them to avoid the pressure spike issues we’re talking about above

Re: longer coal and effect on case pressure?

Reply #11
As far as Master Handloader???  Who me???  One of my fishing buddies did dub me a Master Baiter and I had no objection ;D

I don't fish that much, but I have been married for 15 years now, so, the title fits me as well.
Silence is golden. Duct tape is silver.
I have a lot of guns... There, I said it.

Re: longer coal and effect on case pressure?

Reply #12
I don't fish that much, but I have been married for 15 years now, so, the title fits me as well.

Sometimes a man's gotta take his love life into his own hands. ;)

Re: longer coal and effect on case pressure?

Reply #13
unless you’re really jamming them i don’t see a lot of guys advocating kissing the lands so i’ll probably stay a ways off them to avoid the pressure spike issues we’re talking about above

I feel the same way.  I was working with a bullet and sticking with a 0.006" seat depth and it was working pretty darn good.  But, I would get unexpected vertical that dropped me out of the ten ring at least once per 20 shot string.  That dog would not hunt with the level of competition I am shooting with.  When I finally ignored the bullet makers recommended jump and experimented I found Nirvanna at 0.016" and + or - a thousandth was still in the money.  I feel that when the ogive is near touching, or touching and not jammed, any minor variation with ogive shape can cause my perceived distance from the lands to be inaccurate and pressures will vary a bit from shot to shot.  Further off the lands makes those small variations inconsequential.  

Re: longer coal and effect on case pressure?

Reply #14
Only time I jam is when I'm fireforming Dasher blue box brass. My match load for said same is .018 off the lands. Consistent laser with Berger 105 Hybrids.
RIP Chris Cornell