9mm too Hot?

[chances R]

124 gr. Montana Gold HP - 5.0gr. WSF - COL 1.130 - Fed Match SPP

Gun S&W M&P Pro 5" bbl. (powder measurement verified with bal.beam and digital scale)

My Winchester book notes 4.7 to 5.3 velocity 1015 - 1115,

6 shot string Avg.1240, spread 5.83, SD 2.0

1237, 1241, 1239, 1238, 1239,1243

No abnormal cartridge signs. Do I hold what I have or should I lighten up a little bit. Recoil does not seem heavy and accuracy is better than factory RN.

Thanks

[leroy]

Ya got a good barrel. Keep shootin.

leroy

[Guest Lester Weevils]

Hi Chances R

Wish I'd written it down because now I can't remember. A few months back went web crawling and found info claiming that in a 9mm barrel a 1" increase in barrel length is good for either in the ballpark of 100 fps increase. Or maybe it was in the ballpark of 50 fps increase. I think it was nearer 100 fps per inch but wish I'd written it down.

Does your winchester manual note the length of their test barrel? The ramshot data I've been using uses a 4" barrel for 9mm. They specify different length barrels for some other calibers. I think I read that most factories will publish velocity of their 9mm ammo using a 4" barrel as well, but dunno if that is true.

If Winchester was using a 4" barrel, and if an extra inch of barrel is good for "about" 100 fps, then you are only a little on the high side?

Standard deviation is not real statistically reliable unless you have a pretty big N. I've been doing 10 shot strings but even an N of 10 is nowhere near good enough to have much confidence in the standard deviation value, but I keep record of the numbers anyway. I figger if I keep shooting at the chrony enough, then eventually I'll manage to hit it.

It doesn't matter enough to look up but if you happened to be crazy obsessive-compulsive, you can find tables or calculations that will tell you the error bars for your standard deviation, based on your N.

Apologies drifting with trivia. Just sayin, that is an WONDERFULLY low SD. I don't think I've ever got an SD that low so you are doing something right.

There is another thing you can do with Standard deviation so they can be compared between different-velocity batches. It is based on Z scores as best my bad memory recollects of statistics. It has different names and maybe my name isn't right but I call it Normalized Standard Deviation Percent, because that makes it easy to remember what the number means. Simple to calculate-- (SD / MeanVelocity) * 100 percent

So if you happened to have a batch at 1200 fps with a NormSDPct of 1%, and then you have another batch at 1000 fps with a NormSDPct of 2%, then you know which batch is "tighter". The one batch has a standard deviation of 1 percent of the mean velocity and the other batch has a standard deviation of 2 percent of its mean velocity.

My standard deviations are quite a bit larger than yours, in the 0.7 to 1.2 percent range, and my standard deviations are substantially lower than most factory ammo I've tested. So you are doing great with a NormSDPct of 0.16%. Dang that is low!

Edited June 15, 2012 by Lester Weevils

[Guest pfries]

First of all good read Lester I like how you track it and am going to borrow some of it if'n ya don't mind.

Second I'd say 100 FPS is a bit on the high side I would guess more in the 40 to 50 fps range. There are many factors that can have an effect, such things as the barrel/cylinder gap, etc. and sometimes something as simple as a slightly different crimp applied can alter speeds considerably.

Edited for tYpos and I still can’t get it right today TGIF

Edited June 15, 2012 by pfries

[chances R]

thanks for the replies....I am still learning about this pistol reloading (guess that never stops). The Winchester book did not give barrel length or COL. But since I was in the middle of their data thought I was being plenty safe....the velocities just threw me and made me wonder. Of course the temp was in the mid 80's as well which has a bearing. I was amazed at the SD as well......so I quit early .

Edited June 15, 2012 by chances R

[BigK]

good stuff guys, I gotta get a chrony

[RichardS]

For comparison, I use WSF and here are two recent data points out of a 4.5" barrel Springfield XDm, both using CCI 500 primers:

Remington 124g Golden Saber BJHP, 5.9g WSF, 1.125 OAL, 1190 avg, SD 2.9

Berry's Plated 125g HP, 5.5g WSF, 1166avg, SD 2.3

Seems quite a bit slower than your data given you are using a lot less powder. Possibly my beam scale is off and/or my barrell/bullet fit is not as good as yours. But my data does seem to be closer to the book, not sure what conclusions to draw here but wanted to offer up the data.

[Dave Shooter]

124 gr. Montana Gold HP - 5.0gr. WSF - COL 1.130 - Fed Match SPP

Gun S&W M&P Pro 5" bbl. (powder measurement verified with bal.beam and digital scale)

My Winchester book notes 4.7 to 5.3 velocity 1015 - 1115,

6 shot string Avg.1240, spread 5.83, SD 2.0

1237, 1241, 1239, 1238, 1239,1243

No abnormal cartridge signs. Do I hold what I have or should I lighten up a little bit. Recoil does not seem heavy and accuracy is better than factory RN.

Thanks

I run almost the exact same load, same bullet, powder and primer, EXCEPT loaded longer. 4.8 gave 1040 fps in a Pro and 5.0 ~1100, both chrono'd. Seating depth has huge effect on pressure and velocity in 9mm.

Good luck, load safe!

[Guest Lester Weevils]

Yes it is a little faster than I'm getting with 124gn bullets. But dunno if it is "too fast" or whatever. It would be nice to have an extra $1000 or so to buy a test barrel and strain gage rig and be able to "quasi-accurately" estimate pressure. Just to satisfy basic curiosity. But that would be an expensive answer to satisfy basic curiosity.

Jan 2012 chrono, (approx) 30 degree temp. Beretta 92FS 4.9" barrel

Rainier RN 124gn, 5.5gn Ramshot Silhouette, 1.160 OAL

Mean=1151 fps, SD= 13 fps, NormSDPct = 1.128%

XTP HP 124gn, 5.5gn Ramshot Silhouette. 1.060 OAL

Mean = 1193 fps, SD = 8.5 fps, NormSDPct = 0.71%

As best can tell, the Rainier RN velocity doesn't vary widely from the Ramshot published data of 988 to 1119 fps (4" barrel) for 5.0 gn to 5.8 gn powder. Some pistol load data seems to indicate not much velocity increase over the last few tenths grain powder, though the pressure gets on up there for the last few extra tenths grain powder. I was guessing that one might expect 5.5gn powder to be closer to the max velocity than the min velocity, but just a dumb guess.

The XTP load was a little faster than expected and I need to re-test in hot weather. Silhouette powder is sposed to be a little hotter in cold weather than hot, but dunno if its enough to matter. Only reason of interest on the XTP is that it seats so deep in the case at factory spec OAL. I don't know enough to know what to worry about, but probably wouldn't worry much about 1193 FPS with a shallower-seating bullet.

I had chrony'd a 5.4gn XTP load last summer that was "almost but not quite" as fast as factory XTP ammo, same gun, same day. So figgered adding 0.1 gn would get it real close. But didn't think to carry XTP factory ammo out for test last winter.

Web-searching, I found different allegations, but supposedly NATO spec 124 gn is "in the ballpark" of 1200 fps (5" barrel) as far as I could find out. Due to the short OAL of the XTP loads mine may be "on the borderline" one way or t'other of +P, but dunno anything about it. Federal small pistol primers pancake real easy even on normal loads so I'm not smart enough to read the primers. They don't look like they are about to blow out, but are dang flat. But even light practice loads can make a pretty flat federal primer.

They don't seem unsafe, but was aiming for something on the high-side of a normal load, not a +P load. Need to direct compare against XTP factory ammo again.

Edited June 18, 2012 by Lester Weevils

[Dolomite_supafly]

good stuff guys, I gotta get a chrony

Yes you do.

That is what I use to load. I start low then I work up to the desired FPS. And hopefully it works out to be accurate as well. If not I adjust by a few .1 until it does shoot well.

Dolomite