40 Major load

[sauza45]

Iam shooting a Brazos SC Limited. My load has chroned at 171 several times. Shot the Florida Open in Feb. and my load chroned at 165.0 to close for me.

My Load is

Win brass

5.0 N320

WSR primers

MG 180 jhp

1.220

My question is should I bump the charge up to 5.1 or lower the Oal down to 1.200 With 5.0gr at 1.200 the pf is at 175, and With 5.1gr at 1.220 its at 173

The gun will feed both oal fine.

[yoshidaex]

load up a few of those test rounds and shoot them thru a chrono.

I'm not sure how well N320 meters but getting a consistent 5.1 grains each and every time don't sound possible out of any powder measure (unless you're weighing each charge).

I use a +/- of 0.1 grains for any ammo I load. My target charge for hs6 in open is 9.1 grains. With a +/- of 0.1 any of my rounds could fall between 9.0 and 9.2 grains.

[Flexmoney]

How did you decide on the OAL that you are running now?

My thinking is that you should alway run the OAL that gives the best feeding in the gun. (you say you are fine there, either way)

Another aspect to OAL...do you get better accuracy with one vs. the other?

Yet another aspect of running with a longer OAL is reducing peak pressure in the case.

I wonder why you have chrono's at 171pf at major matches before, but now hit right at 165.0pf? Has anything changed? Ammo or powder lots? Bullet weight?

If not, maybe your barrel is getting worn down?

Maybe your scale is out of calibration?

[Bigpops]

What about the chrono's...are they the same? (yours and at a match)

I will tell on myself here, I was doing almost what you are. I was nailing 169-170PF at home and then getting 174-176PF at two major matches. Both places used CED chrono's...I do too.

I had a little problem with mine and sent it back to CED to be fixed. I also sent a letter explaining my load numbers and how it varied on numerous occasions. Long story short I was doing it all wrong. The "chrono man" at CED set me straight and explained things in detail.

Bottom line....balanced light is your friend!

[Classic_jon]

I ran into something similar when I was doing some testing on some of my loads.

What was the temperature of the range when it was at 171 vs 165?

The reason I am asking is that N320 is reverse temp sensitive and when it is colder it will burn hotter/faster. I gained about 50fps at ~40F in my loads with N320.

As an example:

At ~80F my loads average around 147 PF (950fps and a 155gr JHP)

At ~40F my loads average around 155 PF (1000FPS and a 155gr JHP)

[sauza45]

The load was from Brazos it has work on my chrono. The accuracy is the same on both loads. As for making major at other matches, this was my first major match. Nothing has changed in the load, the temp was about 68*

my chrono data temp was 72* Both loads function 100% in the gun, I was just wondering which way to go. Eather up the charge to 5.1gr or shorten the oal to 1.200

[Joe4d]

How much room does 320 take in the case ? is it a low volume powder like tight group, or high volume like WST ? OAL is generally a function of feeding reliability. If your gun feeds shorter rounds why load em so long ? shorter rounds with less powder kick less, granted an extremely tiny bit less, but less it is, They also use less powder which costs a little less. I use Tight group under a 180 but generally only load to 1.180 in a STI, Para, and homemade single stack.

[sauza45]

N320 fills the case about 1\2 way. I was searching diffrent loads and it seems that not to many people load that long. Most load in the 1.180 to 1.200 range. That is what got me thinking

about setting the oal to 1.200 instead of going up to 5.1gr

[Classic_jon]

The load was from Brazos it has work on my chrono. The accuracy is the same on both loads. As for making major at other matches, this was my first major match. Nothing has changed in the load, the temp was about 68*

my chrono data temp was 72* Both loads function 100% in the gun, I was just wondering which way to go. Eather up the charge to 5.1gr or shorten the oal to 1.200

Personally I would do two things.

1) Shoot the current load in a different gun and see if the chrony results are the same

2) After testing it in another gun, go up .1 or .2 and see what happens. Be very aware though that my Sierra manual says that 5.2 is the max load for a 180gr JHP with N320 so be careful. According to the book 5.2 gr should put you at 1000FPS with a 180Gr JHP and about a 180PF

[sauza45]

Thank you for the help. I will chrono the rounds again and see what happens.

[earlbob]

There's a post here somewhere in these forums that gives some clarity to the issue of SD. It will likely help you to understand what is perhaps going on with your PF deviations.

If I run across it I will edit and insert the URL here. ( http://www.brianenos.com/forums/index.php?showtopic=92433)

earl

Edited March 6, 2010 by earlbob

[sidnal]

I shot with 5.0 of N320 for a couple of years and finally bumped to 5.1 ensure that I was major at any temperature. It's a great powder but its too bad meters so badly through a dillon powder measure.

[A63111]

I recently ran some rounds over the chrono. VV320 at several different charge weights and OALs, close to or the same bullets in weight. 1 load had a SD of 4, others varied to about 10. Seemed as though the higher case fill volume worked best. The lowest SD was with Zero 180gr JHPs and 4.6 or 4.8 of VV320 @1.135. As I lengthened the OAL the SD increased and FPS dropped.

Here is 1 example, all were fired on the same afternoon, same weather and same gun 5" STI with a Barsto barrell.

4.8 VV320 180 Zero JHP 1.180 OAL 915 FPS AVG SD9 164.7PF

4.8 VV320 180 Zero JHP 1.135 OAL 944 FPS AVG SD4 169.9PF

[sauza45]

I checked and my SD is 14. Good link to the SD, I will load some more test rounds with 5.0gr at 1.200 and 5.1gr at 1.200 and 1.220 and see what that does and if the SD is lower.

If I go lower on the OAL say around 1.180 can that affect accuracy? I will also load up some at 1.190 and 1.180 and see.

[Flyin40]

The load was from Brazos it has work on my chrono. The accuracy is the same on both loads. As for making major at other matches, this was my first major match. Nothing has changed in the load, the temp was about 68*

my chrono data temp was 72* Both loads function 100% in the gun, I was just wondering which way to go. Eather up the charge to 5.1gr or shorten the oal to 1.200

What chrono did you use originally to chrono the load?? Seeing that it was your first major maybe its just the different chrono's. Most major matches use Ced chrono's. I found out my chrono is about 15fps higher than a Ced. When I go to a major I always chrono lower than what my chrono say. Also are you using your chrono in the sun?? There are alot more factors involved before even working on your load.

Flyin