OAL vs increased powder charge

[vluc]

Which is the best way to go to increase velocity (and power factor) - decreasing the OAL or increasing the charge?

I have a load of 9mms that test out like this:

9mm, 124 grain Montana Gold, 4.2 grains Titegroup at 1.16 oal

chronographed indoors with a shooting chrony and chrony indoor light fixtures. Each pistol had two strings of 10 shots fired. Shoot, set down pistol, record score, shoot...

Glock 34 1113 fps PF 138

Sig 226 1028 fps, PF 127

SIG 225 1022 fps, PF 126

I shoot both USPSA and IDPA. The Glock does not concern me as I have room to spare above that 125 PF. But I use the SIG's in IDPA and that's a touch too tight.

I like loading long...it is very reliable in its feeding and the loads shoot excellent...very little deviation in the strings.

So...do I wait and chrono outdoors to see what the difference is or begin to adjust the loads? If I adjust the loads, do I go to the maximum charge Hodgdon lists (4.4 at 1.09)? Their data indicates I can get 1126 out of a 4" barrel, but with the OAL set at 1.09, not the 1.16 I really like.

So, as the topic states...do I address the OAL or the charge?

Any and all help is appreciated.

[Flexmoney]

vluc,

This is out of my area of (very limited) knowledge.  My take is that you use the OAL to adjust for maximum feeding realiablility.  Adjust the powder level for changes in velocity.

You certainly have lots of room to work with though.  Why not load a few dozen up each way and see how they test out?

You appear to be in a win/win situation.  TG is cheap enough that a few tenths won't break the bank.  You are under the max load.  And, you can afford to bring back the OAL.

Hopefully someone who knows a heck of a lot more than me will post.

Please report your results.  

BTW, what shape bullet and what primer?  (I may copy your load)  

[vluc]

flexmoney, I'm using Winchester primers and 124 grain FMJ, round nose Montana Golds.  Cases are a mixed lot - Winchester, Federal, PMC, PMP...

I really like this load and the bullets.  Nice shooting and quite accurate...nothing like confidence in the load you make!

[BSeevers]

I would watch out using mixed cases, max load,  shortest OAL.

Its common sense but you could get a marginal piece of the smallest volume brass. That would also have a poor crimp because it is worn,, Going up the ramp its OAL changes a couple tenths shorter and boom.

9mm approaches 35,000 cups. That's high pressure and its not like your .45. I used to load .45 til it cracked. I would not do that with 9mm

My Shooting Chrono is very consistant but  25 fps slow, I used to factor that in, but now use a pact which is right on with Greg "chronoman" Lent(parallel chronos) or any of the majors I have been. I think your load sounds good just would consider what you would happen if you max it  out. Also the Sig speeds would mean more if you listed the deviation. I load very close to PF but my match loads vary 5 fps.

[vluc]

Thanks bseevers.  I will get the SD info and post it from my record sheets.  Interesting to hear that the shooting chrony appears 25 fps slower.  If that is the case, then the load does not need changed at all as it would bump up to a PF of 130.

I really do not want to go too much to the max (conservative though it may be) as I did do a few loads awhile back and did not like the sharpness of the recoil at 4.4 as compared to the 4.2.

As for the brass.  While I use several brands, I'm anal in that I do sort it and load them seperate so i have a run of one, a run of another, and document that on my boxes.

(Edited by vluc at 5:39 pm on April 22, 2002)

[Patrick Sweeney]

Load the oal for reliable feeding, and adjust your powder weight for velocity.  As for a particular chronograph being 25fps (or some other amount) different than the "standard," that may not hold for all examples of a particular brand or model.

If the screen spacing is two feet, and the difference is 25 fps in a 1000fps load, then the screens may be off by only half an inch. (one foot spaciong, a quarter-inch.)  Seems like a lot, but consider the distance of the bullet above the screen, the angle the slit is at vs. the direction of the bullet, etc.

That is one reason we load a comfortable margin above the PF threshold.

[vluc]

bseevers, here is some additional data.

Glock 34

         string 1 - spread 34 fps, Standard deviation 10.14

         string 2 - spread 18, SD 6.32

SIG 226 string 1 - ES 31, SD 9.75

             string 2 - ES 27, SD 9.38

SIG 225 string 1 - ES 45, SD 16.4

             string 2 - ES 18, SD 6.55

[BSeevers]

vluc

The Glock/226 looks great. The 225 on 1st string seems to be too extreme. Could cost you a match as not making minor means you don't shoot for score. Course you probably won't use it in an IPSC match. The difference between strings is puzzling but could be explained by mixed lots/brands of brass. They would all have different internal volumes. I don't load 9mm, how far is your OAL above min? Reason I ask is a full case usually will improve consistancy(ES and SD) but caution must be exercised

[Carlos]

Adjust powder, not AOL.  Pressure increases from decreased AOL can be exponential - and unpredictable.  At least loading data should tell you the effects of increased powder charge - decreased OAL will increase pressure/vel by unknown amounts.

[vluc]

wow...great replies...keep 'em coming!

A follow-up.  I plan to test all of them again outside, as my first test was indoors.  i needed to know what they were doing and access to an outdoor range is limited and I did not want to wait.

What's been the experience on differences for those that have done both indoor and outdoor chrono of loads?  I have this little voice telling me that outdoors is going to be higher than the indoors due to temerature differences and that I should/may be fine with that current load.

Some discrepancies may have arisen as I do find that the dillon will dump a slightly larger charge into the next case if there is a pause or lull in my reloading routine.

Each lot of rounds had the same cases.  When I say I mix, it's not that they are all in a bag and I just pull randomly.  I load all Win, or all fc or all whatever, so these three pistols were all using the same brand of cases, all made in the same run on the same date.

(Edited by vluc at 7:54 am on April 23, 2002)