What is considered too hot?

[cst]

I have a 19" Lilja barrel shooting 123 scenar reloads. This weekend it hit about 90 deg...real hot. I had to shorten my reloads from my usual 2.275" to 2.265COAL to fit in my new Elander mags.

I have always chronoed between 2520 to 2540fps depending on temp. This weekend I was getting 2585 average SD 7. I am using LVR as a powder. Ive been shooting this load for 2 years now before shorteing the COAL. I dont know if the shortened length increased pressure to increase the velocity because Im pretty sure I was right on the lands at 2.275.

I kicker is..over 60 rounds....I have no pressure signs. I shot it suppressed and unsuppressed with no remarkable signs of pressure. Slight cratering of the primers but thats it. I am using a SLR sentry gas block however.

People are constantly saying that running the round too hot will shear a lug...Before the velocity increase Ive shot atleast over 1000 rounds with this bolt.

I guess Im going to have to redo my loads with the new COAL but my groups were all sub 1/2moa.

Im using a Magnetospeed V3 BTW if that makes a difference.

I know LVR tends to be temp sensitive but not much more than my RL15 on my 308s. What do you guys think? maybe my chrono is on the fritz? or I am indeed way high on the pressure and I should back off the powder a .5 to 1 grain.

[JASmith]

Have you plotted your velocities versus temperature to see what your experience with temperature sensitivity is?

Alao was you higher than expected velocity with the suppressor installed?

Last, backing off by a few tenths of a grain will reduce your pressures and may be prudent since 90F is not particularly warm. For example, im in N. CA and we are expecting 103F today.

[Bwild97]

What is your charge weight of lvr? Have you changed anything about the load other than COAL; primer(lot#) powder(lot#)?

[Allen]

As long as your brass doesn't show any more pressure signs than it did, you are fine.

[cst]

I'm using 31gr. of LVR....it always chronoed around 2520-2540. I don't have in front of me but I measured 2480 at 50-60 deg, 2520 at 75-80, 2540 around 85.

Unless my magnetospeed is unreliable, shortening the COAL must have increased the pressure...But...no noticeable pressure indicators in the brass...just some catering on the primers...didn't even notice any ejector swipes....

It's all the same lot of brass,powder, primer,bullets etc...the only thing different is this time I shortened the COAL from 2.275 down to 2.265

[PrecisionFirearms]

At 31 grains you are using a compressed load. I would suggest backing off .2 grains to be safe..

[LRRPF52]

Shorter COL won't spike the pressure. Longer COL will. Based on your velocity numbers, I would attribute this to the temperature.

Shorter COL will give you more jump, which allows more time to transpire for the initial burn. The primer blows the projectile into the lands as the powder ignites.

Again, I think this is a temp sensitivity issue more than COL in your case. The reduced COL probably made things milder for you than they would have been with 2.275" COL.

[cst]

I have to take it tjis weekend and retest at 75deg. And see if i get my original velocity of 2530. If thats the case then LVR is almost double the sensivity to temp of RL15. I always used 1.1fps/deg.. i may have to up it to 2.2fps/deg...

[sneaky one]

Can you try a different powder, say, cfe 223? as for a comparison?

It's a full bulky case filler- yet with great results.
RL 15 is used here too, yet in moderation. So is RL7 for the pills 95 gr & less..

H335 is a stellar powder too.

[LRRPF52]

I have to take it tjis weekend and retest at 75deg. And see if i get my original velocity of 2530. If thats the case then LVR is almost double the sensivity to temp of RL15. I always used 1.1fps/deg.. i may have to up it to 2.2fps/deg...

I looked in Volume 2 for comparison data, and there is 18" data with LVR under the 123gr AMAX. 31.0gr produced 2510fps using Fed205M primers. It's on page 88.

See what you get with the 2.265" COL tomorrow, and compare that to your previous 2.275" COL data in the same temp.

[Klem]

My experience is slightly different.

When you decrease the case volume (all other things being equal) you increase the muzzle velocity. Quickload also displays this. That is unless the bullet is loaded long to touch lands and then there will be a velocity spike. This is possible in an AR even out of a magazine that's shorter than the measured jump to lands.

In semi-auto's cycling the action is like a kinetic hammer. If you have low bullet grip at the neck (low static coefficient of friction) then when the rounds are slammed into the chamber the bullet will jump forward and maybe even far enough to stop at the lands. If the bullets all jump forward the same distance each time but do not touch the lands then all well and good. But if some of them do and some don't then there will be a vertical bias to your groups. There is also a difference in kinetic shock between when you first charge the handle to load a round and the more violent auto cycling. If the first round does not touch lands but the auto cycled do this leads to one round low and the rest all high...This has happened to me. I now pay particular attention to neck tension and am currently experimenting with a taper crimp die.

I do not have LVR on my Quickload however using other powders an OAL change of 2.75" to 2.65" shows only a 5 fps increase in the computer simulation.

Ambient temperature increases muzzle velocity, especially if the rounds were sitting in the sun prior to being loaded. Or sitting in the scorching hot chamber for enough time to heat up before being fired. This is more of an issue in AR's due to the auto cycling loading the next round sometimes before you would prefer. Or in direct sunlight through the window of a car. The outside might be 90degrees but inside will be higher.

[JASmith]

...When you decrease the case volume (all other things being equal) you increase the muzzle velocity. Quickload also displays this. That is unless the bullet is loaded long to touch lands and then there will be a velocity spike. This is possible in an AR even out of a magazine that's shorter than the measured jump to lands....

Unless the longest COAL is touching or jammed into the lands. Then QL and actual tests show a substantial increase in pressure. A jump of 5000 psi is easily possible.

Hence anything that causes the bullet to be in contact with the lands before the trigger is pulled will cause a jump in pressure.

[sneaky one]

Right, Joe.

Tweak- minimize the diameter of the expander ball on your die- to maximize Neck tensions. More is best-- in moderations.

Hone it down thru 2000 grit sandpaper-wet. Find a way.

That may help the bullet from moving forward on it's own- being in a jamm lands situation.

A few of us are in this same spot right now - maybe- with these new W3 pills.

I'm going back to crimping all Grrr pills.

[lrgrendel]

My experience is slightly different.

When you decrease the case volume (all other things being equal) you increase the muzzle velocity. Quickload also displays this. That is unless the bullet is loaded long to touch lands and then there will be a velocity spike. This is possible in an AR even out of a magazine that's shorter than the measured jump to lands.

In semi-auto's cycling the action is like a kinetic hammer. If you have low bullet grip at the neck (low static coefficient of friction) then when the rounds are slammed into the chamber the bullet will jump forward and maybe even far enough to stop at the lands. If the bullets all jump forward the same distance each time but do not touch the lands then all well and good. But if some of them do and some don't then there will be a vertical bias to your groups. There is also a difference in kinetic shock between when you first charge the handle to load a round and the more violent auto cycling. If the first round does not touch lands but the auto cycled do this leads to one round low and the rest all high...This has happened to me. I now pay particular attention to neck tension and am currently experimenting with a taper crimp die.

I do not have LVR on my Quickload however using other powders an OAL change of 2.75" to 2.65" shows only a 5 fps increase in the computer simulation.

Ambient temperature increases muzzle velocity, especially if the rounds were sitting in the sun prior to being loaded. Or sitting in the scorching hot chamber for enough time to heat up before being fired. This is more of an issue in AR's due to the auto cycling loading the next round sometimes before you would prefer. Or in direct sunlight through the window of a car. The outside might be 90degrees but inside will be higher.

Good info. Thanks

[cst]

So...even if I get su per high velocities not normal for this round/barrel length...am I over the max safe limits for the round even though there is no pressure signs (except for mild ejector wipes) on the brass?

I guess I'm trying to figure out can u have max pressure even though there is no signs?