N320 And Temerature Changes In Velocity

[firematt100]

I am loading N320 4.7gr. under 200gr. Zeros loaded to 1.22. Last crono was 50* outside and very low humidity. PF was 174.

Does anyone know what a change in temp will do up or down?

Thanks for the help.

[kevin c]

Look here for some of what you want to know:

http://www.brianenos.com/forums/index.php?...ure+sensitivity

The short version is that N320 is temp sensitive, but it seems to matter more what temp the powder gets to in the hot chamber of the gun than what temp it is in the magazine. IOW, your first round may be at lower temp being shot out of a cold chamber on a cold day, but the subsequent rounds will warm up and shoot hotter. A warmer day will warm up the first round some so that it might shoot a bit faster, and later rounds a bit faster than that. The difference for me was 20 to 40 fps, enough to make some difference at the chrono for the first round, but you do get several more to shoot to make major.

Every load is different, so how much your load will change can only be known by testing it, and remembering that a different chrono and different conditions will make the numbers vary even more.

Kevin C.

Edited April 27, 2006 by kevin c

[ErikW]

The warmer the ambient temp, the higher the velocity. I think I gained 10 PF with N320 a couple years ago in Oregon with 105+ F temps. Humidity diminishes the velocity.

[Zerwas]

While this isn't a VV response, I'd like to share with you something that happened over the last weekend with me at the WI sectional... These are notes removed from my "pistol shooting histories"

4-22-06 MAPSA match; 89rds Zero 180gr JHP with 4.8gr Titegroup, OAL 1.185”. 0 malfunctions. They chronographed 3 rounds today using a Kustom Pro Chronograph(sky screens, out in the open--shade conditions). They came in at 956, 929, 969 for an average of 951fps. It was sunny and 64 degrees

4-23-06 Holman gun club (WI): Wisconsin sectional match, 200rds Zero 180gr JHP with 4.8gr Titegroup, OAL 1.185”. 0 malfunctions. They chronographed my loads today with a chronograph box. It was sunny and 51degrees outside. They came in at 925, 890, 928fps for an average of 914. They chronographed 3 more rounds at 908m 913m 902 for an average of 908fps. They chronographed a last round at 902fps, They then took the highest three which was 925, 913, 928 for an average of 922fps which had a power factor of 166.2.

The loads I used on both days were made at the same time, about a week before the match.

I could NOT believe the difference in velocity, and the fact I BARELY made major.

Anyone else have a similar experience with titegroup?

Now, I'll be paranoid when I step up to the chrono box (unless its 60+ degrees outside).

[HSMITH]

Steven, EXACTLY the same thing happened to me.

In my gun on on 4-9-06 with a friend, 20 rounds with 180 Zero JHP at 1.185" over 4.7 grains of Tite-Group averaged 998 fps. Temp was around 55, bright sun, infared screens. Ammo cooled in the car overnight was about 50*, it averaged 998 just like the ammo from my house that was about 65*, ammo heated in my pocket to around 90* dropped to about 980. Gun barrel had not been cleaned for 1500 rounds.

On 4-18-06 temp was about 60*, ammo was about 60*, same recipe EXACTLY. Overcast conditions, not sure about the type of screen but it was attached to a Pact MKIV. Average velocity of about 20 rounds was 990 FPS. Chamber had been cleaned, barrel had not been touched.

Get to Holmen, round one was 919, round two was 914, round three was 924. Average 919 and a power factof of 165.1!!!!!! Barrel and chamber had not been touched and about 150 rounds were shot on 4-18.

I think Tite-Group DROPS speed with temp. My gun was hot coming off the steel stage, and I think the ammo heated in the chamber between chrono shots. I don't have ANYTHING to back this theory up, it is just the only thing I can come up with to offer any explanation.

The ONLY one I talked to all day on Sunday that did not chrono lower than normal was Perry. He told me and a couple others that his steel calibration load was within one power factor of where it always shoots. A few people went minor even. I went from 180 to 165.1, nearly vapor-locked when I saw the three shots and thought I went minor..

[ChuckS]

TG guys,

It sound like it is time to build a temporary box and go chrono your loads in the open and in the box and see if there is a difference. A large cardboard box and a couple of incandescent work lights should do the trick.

Let us know how it works out,

Chuck

PS: Perhaps there was some stray cheese slowing things down at Holmen

[XRe]

I talked about my experiences w/ N320 and temperature variations over on this thread. At the DoubleTap Championship, I made 166PF with 4.7gr (and a Precision 185gr) - it was cold, maybe 40-ish degrees when we chrono'ed? In the dead of summer, 4.2-4.3 is more than plenty to make 170PF. So....

It wouldn't suprise me if Titegroup were somewhat similar in this respect...

[Zerwas]

I went from 180 to 165.1, nearly vapor-locked when I saw the three shots and thought I went minor..

Laugh out loud funny!!!

I did the same thing after not making major with the first 6 rounds. I thought, OH MY!

I had some others say their rounds chronographed like they always do as well. I can't believe the variance in the chrono reports. HMMM. I forgot to add these recipe I use is the same recipe I have used for the last 1-1/2 years and had NO problems making major at the Limited Nationals last year or the MN section, all of which had the covered box type chrono. The only thing I can figure is the temps were hotter (especially in IL) and that probably made the 40fps difference.

[pskys2]

I've run into Titegroup velocity loss with a Revolver as it gets colder. Plus, it always seems to heat up the pistol quicker. Up to scorching your hand from 30 rounds. Area 3 last year the first round was 708 with a 230 Ranier, the next 2 then went 745 and 761. But it's better than WST which loses velocity as the Temperature goes UP!

I've also noticed pretty wide differences in Lots of Titegroup. At one point I had 1 can/lot that I would use for match ammo only. Everything else I bought would chrono out 20-30 f/s lower. I finally gave up on Titegroup.

Did you happen to notice what light source they used in the box. You can't use any flourescent lighting. The flickering causes wierd velocities. If it was powered by a Generator and flickering it might cause the same type of problem. Sounds kind of like their set up wasn't quite right. Usually a "Box" gives higher velocities than what I get at home under the Wide Blue Skys.

There's a reason why the Chrono Stage is always the most feared!

Edited April 28, 2006 by pskys2

[HSMITH]

The heat generation with Tite Group is the number one reason I am working on a new load. TG has my gun so hot I can't touch it in short order.

I don't know what powder I will end up with......

[SRT Driver]

Back to N320 and temp...

I've found that N320 is very predicable with temp change. Most of my testing has been in 9x19, 9x23, and 38 Super. Each degree equals right around 2 fps +or - depending on the direction of the temp change.

For example:

58 degrees = 1045fps avg

65 degrees = 1051fps avg

75 degrees = 1074fps avg

87 degrees = 1101fps avg

Hope this helps.

[Zerwas]

That looks similar to Titegroup. The other powder I was looking to go to was the VVN320.

HHMMMM thanks for the info SRT driver.

[Tom Mainus]

I know this is a thread hijacking but here it goes. I went minor at the WI sectional shooting VV 310 out of my revolver. My load at home were right at 750 FPS with a 230 grn bullet ginving me a PF of 172. My first shot at the chrono was 686.WTF. My best I could muster out of my gun, with me tipping it back before the 8th shot was 713. I heard alot of guys say that they were suprised at how low they were at the match. I was shocked at how low I was. I know that they will have the exact same chronos at area 5 so I guess I have to load special area 5 ammo next time. Great match had a blast.

Now back to your regularly scheduled thread.

Tom

[BigDave]

Am I the only one that thinks that the match chrono may be the culprit here? I realize that the match chrono is the one that matters on game day, but isn't it odd that a whole group of people with a variety of loads an a variety of guns are experiencing the similar results over the same chrono?

Not looking to flame, just asking a question.

[38superman]

Temperature will make a difference but....

Chronos are not consistent.

It is a fact of life.

I have seen matches (especially Nationals) that had two chronos side by side and two sets of screens so that each shot is read by both machines.

The two chronos will often vary when reading the same shot.

The RO's deal with this by taking the higher of the two readings or an average.

I have a 200 gr. VV340 load that I have used for two years in my 40 cal.

It chronos around 172 Pf on my machine.

I've had this load checked at a dozen major matches and it has read as high as 178 pf

At two matches it barely made major.

It was (165.3) pf at last years nationals and dead on 165 at Fla Open. (warm weather matches)

165 to 178 is quite a varience in the same load.

Leave yourself a little margin for error or you may find yourself needing all "A"s.

Tls

Edited April 28, 2006 by tlshores

[HSMITH]

TLS, the match in question DID have two chrono's and two sets of screens in the box. Both were reading, and the higher of the two readings were used. At least that was the case when my gun was shot.