40 Major PF question

[jimbullet]

Just wanting to get some thoughts from other reloaders/ shooters of 40's.

I am fine tuning my IPSC load utilizing 180 gr projectiles, and during a chrono today, my recipe got me the following results:

first batch of 5 rounds, average fps was 986 - PF 177

Second batch of 5 rounds, average fps was 983 - PF 176

third batch of 5 rounds, average fps was 941 - PF 169

Since I need to pass standard division PF of 170, I couldnt help it but worry that I had one set of 5 rounds failing to reach major PF.

If you guys were in my shoes, would you try to bump up the load a little more (say another 0.1 grains of powder) or would you be comfortable of the results?

Note that all test rounds are all identical, except for brass where I have been using a mix of winchester and federal nickel brass and OAL appears to have a difference of +/- 0.001.

Apart from that, all, i.e. primers, projectiles, crimp, powder charge are all the same.

[RePete]

We need the load data you are using to effectively advise you what to do.

For a minimun PF of 170, I would recomend that you shoot for a PF of 180 - 183, and this make sure that you will pass chrono.

With my loads, for my required 165PF, I'm running 177.

[jimbullet]

The load is as follows:

180 gr CMJ projectile

5.6 grains win231

Fiocchi pistol primers

mix of winchester or federal nickel brass

OAL 1.159

crimp 0.421

Runs through an STI Edge

Lowest velocity recorded was 939 fps, highest velocity was 1021 fps.

[blaster113]

I would look to reach 177-178 pf so an increase of .1 or .2 grains of powder is in order.

[jimbullet]

It does appear to be reaching PF 177 based on the two lots of 5 rounds where PF was 177 and 176 respectively however a wrong combination where probably majority of the 5 rounds were on the lower band had resulted to an average velocity that had a PF of 169.

If I increase my load, the higher band is likely going to take it to PF180

Edited October 26, 2014 by jimbullet

[Hi-Power Jack]

Lowest velocity recorded was 939 fps

I usually fire at least 20 rounds and I bump powder up

until the slowest bullet makes major.

So, yes, I'd bump it up a bit and fire 20 more

shots ...

[jcc7x7]

Couple of ideas

See if your loads get lower SD with one kind of brass. that may be one answer

If you like me with the 45 bump up powder charge to get 180 PFso your lowest round will still make 170

that way you don't have to think about PF when you get to bigger matches, it is a pain to be thinling about that all day along with what you're going to be doing on each stage.

[bonglee0507]

Load 5.0gr VV n320. My chrono from that load is 173

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[jimbullet]

Should I be concerned of over pressure? Given the longer oal from saami specs, I don't real have anyway to compare. Then again I suppose it is fine to get the 40 shooting at 1,050 fps

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[jimbullet]

Bong, I don't want to be too near the 170 either. I have seen some chrono at the home range doing 174, when at a regional match, for some reason his went down to 169, then they got one or two rounds and that made him pass at 170pf.

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[Lifeislarge]

With the Edge you can load a lot longer OAL to reduce pressure if need be. I've gone out to 1.22 with Clay's so if you do bump your charge you can always adjust if you start seeing flat primers. I think most guys load their .40 major rounds to about 1.180 OAL for the STI 2011.

Edited October 26, 2014 by Lifeislarge

[JASracer]

I am surprised at the inconsistencies of the velocities that you posted. There is almost 100 fps difference in them. Almost everything I am using is different, but my velocities were only a difference of 35 fps when I checked my ammo with a chronograph. Are you getting consistent metering of your powder? I have played with a couple of different loads and powders, each time I tested any, I recorded the velocities for each round fired and fired a minimum of 25 rounds. The biggest difference I had was about 35 fps. I would double check the amount of powder you are getting in each casing. Sounds like the loads are not consistent.

[jimbullet]

I thought of that too whether there is inconsistent metering but I can think of why it would do that. I've used dillon SDB. Win 231 is supposed to meter well. Thoughts?

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[Maxximuss]

All my 2011 loads are at a 1.175 OAL. I use 4.9 grains of N320 for a 171 PF. There is no reason to punish yourself with extra recoil, give yourself a cushion so you don't go Minor and call it a day.

[jwhittin]

The most important value from your chrono is the STD. Use 8 rounds to measure and add 2 to 2.5 times the STD to the minimum velocity required to meet PF. This will give you 90 to 95% confidence in meeting PF as measured per the rule book.

Note that the values 2 and 2.5 assume 8 rnds are used to measure STD.

Let's see new data with the STD.

Edited November 6, 2014 by jwhittin

[ivan]

In the short term, if you're not comfortable with the results go a bit hotter (as stated .1 or .2 won't hurt anything). There are SO many variables between when you test for yourself and when you show up at a match that you need many, many chrono sessions to get a truly comfortable feeling on what your REAL velocities are. Brass type, lot-to-lot variations in powder, ambient temperature, barrel cleanliness, powder charge variation, bullet weight variation, chronograph inaccuracies (these can be WAY higher than most people suspect) all contribute to variations. After you get enough data that your loads are sufficiently hot, then maybe back the charge off a bit to fine tune it (ie: err on the high side then gradually back it down to optimal).

-ivan-

[motosapiens]

Was group 3 low because all the velocities were low? or did you have one really light load that threw off the rest of them?

First thing I would do if I were you is go fire another 5-10 rds.

[jimbullet]

The 3rd lot was low due to 1 round being really light so the average dropped for a 5 shot string. The 1st and 2nd lots were ok but that just got me worried.

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[motosapiens]

The 3rd lot was low due to 1 round being really light so the average dropped for a 5 shot string. The 1st and 2nd lots were ok but that just got me worried.

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if you only had 1 round that was really light, I wouldn't stress over it. At a real match chrono if you get unlucky and get 1 real light round, they will just shoot another 3 and take the best 3. At least that's how uspsa does it. No clue if ipsc chrono procedures are different.

I would probably keep an eye on it tho and see if I could figure out why that one round was light, and whether it's a recurring problem or just a random glitch.

[jimbullet]

I think ipsc requires 3 rounds and if you fail, they will get 1 more and average out the 4. If the 4th doesn't make it high enough, then it's going to be minor.

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[ivan]

For IPSC or USPSA, they will take 8 rounds. They will pull one apart and get the weight. They will fire 3 and determine the average velocity. If your velocity times weight makes the grade:you're done. If not, they'll fire 3 more and take the average of the fastest 3 of the 6. If you make it: you're done. If not, you have the choice of them firing the 8th round (in hopes it will now be faster than one of your fastest 3 rounds), or you can have them weight it (in hopes it will be heavier than the first one they weighed).

... simple enough?

-ivan-