How much difference does O.A.L make?

C

Chainsaw.

New member
Heres the situation. Been loading my 9s with 4.8 grains of titegroup. CCI 500 primers. Everglades 115gn concave base jacketed bullets. Mixed range brass.
O.A.L of 1.24

The recipe calls for a O.A.L of 1.1X + 115 + 4.8 gn = 1158fps

Ive always had decent luck in my glock but my buddy did have a couple of FTFs with it though.

Runs the gun fine, so I went with it, I finally got a chance to use a buddies chronograph, to my suprise my velocity was only about 950-1000 fps. Crap.
I need to make power factor for idpa.

So the question is will .1X shorter O.A.L really make 158 fps difference? Not sure when Ill be able to use the chronograph again and dont want to damage my firearms or myself. I figure Ill work down to a shorter O.A.L and just see how it feels as I go. Am I going about this correctly?
 
.1 is a lot. 158fps seems much for .1 though, if you said 75fps or maybe 100fps I wouldn't be surprised. I would suggest you not use mixed brass either, you will get variation from that too. If your struggling to make major you will want to give yourself the confidence you know will hit major.
 
Looks reasonable to me.
I got 70 fps higher velocity by seating 9mm .034" deeper.
I have reduced the powder charge 9.5% to get back where I was.
 
I'm not an expert by any means but 4.8gr is max load for that bullet weight . I would not just seat them deeper . If I were going to seat a 9mm bullet deeper when using titegroup . I'd reduce the charge a few tenths and work back up with the new seating depth . I've heard Titegroup can get temperamental at peak pressures so caution might be in order . It's a light for caliber bullet so you may not have an issue but if this was a 147gr bullet I'd say reducing the load would be a must if you plan to seat the bullet that much deeper .
 
How far away was the crono? My 124s run 1,000ish fps, but with bullseye and 231.

total guess, I don't compete but I bet you need a bigger bullet :)

Good luck
 
Have you "plunk" tested that load? Seriously? I load my 9mm to 1.15 (124 gr prn) because that is the max length that will plunk test ok. Hmm.

Shortening to 1.15 would not freak me out, but you probably want to do a "plunk" test. Set your OAL to what passes. Then redevelop your load, which probably needs a bigger bullet to meet some power factor as i would expect the oal change will be lucky if it gives you 25 fps.
 
You work up to the max load or just pick it?
.1" is 1/10". That much can give you no end of grief. Not feeding. Not chambering. Not fitting in the mags. Etc. Etc.
Max OAL for a jacketed 115 is supposed to be 1.100", according to Hodgdon. However, Max OAL for 9mm is 1.169". You have a bit of wiggle room, but your OAL is too long for any 9mm. Kind of surprised a near 1.250" 9mm feeds or fits in a mag.
 
Chainsaw,

1.24" is well over the 1.169" SAAMI max. Are you sure you didn't drop a digit and mean 1.124"?

Hodgdon has a recipe for a 115 grain Speer Gold Dot that uses 4.8 grains of Tightgroup to get 1158 fps from a 4" barrel, but the COL they use is 1.125", not 1.100". Also, the Gold Dot is a heavy plated bullet and not a jacketed bullet. A Speer tech warned me that some of the Gold Dot loads are too hot with jacketed bullets, so I am not sure reducing COL is the best thing to do. It also may or may not make the difference you are looking for. In some loads pressure goes up a lot with seating depth, while in others the primer unseats the bullet before the powder really gets burning and actually drops pressure, so this can fool you.

I think, in your shoes, I'd be working up a load of Power Pistol or HS-6 for which the claimed velocities for maximum loads are about as much faster than minimum power factor with that bullet weight as your Tightgroup load proved too slow. It may be your barrel and chamber dimensions, but no point in stressing out over it when you can buy a safe solution.

When chronographing I often take two units, and Oehler and a CED. I like to double-check one with the other to be sure the light isn't throwing one of them off. I've been present for chronograph errors of up to 10% due to lighting conditions while comparing one unit it another.

It may be time to get your own unit. An expense, but there it is. If you get the same kind they measure for power factor with at the match and use it the same way, that's a good strategy for getting a matching reading.
 
4.8 grains of titegroup. CCI 500 primers. Everglades 115gn concave base jacketed bullets. Mixed range brass.
O.A.L of 1.24

The recipe calls for a O.A.L of 1.1X + 115 + 4.8 gn = 1158fps
Click to expand...

Who's recipe???

So the question is will .1X shorter O.A.L really make 158 fps difference? Not sure when Ill be able to use the chronograph again and dont want to damage my firearms or myself. I figure Ill work down to a shorter O.A.L and just see how it feels as I go. Am I going about this correctly?
Click to expand...

I don't know, to the first and I don't think so to the second.
First off, I don't use the powder or bullet you have, and so will not make a specific recommendation. However, while deeper seating does, in general, increase pressure by decreasing powder space, and the effect seems consistent because it does happen, the AMOUNT of change is not the same will all powder, and is not, as far as I can find out, linear. Meaning, .xx" deeper does not equal a given amount of increase, every time.

The change will be specific to the powder, bullet, seating depth and other factors. A concave base bullet would, I expect give different results than a flat base bullet, for one thing. What I am trying to say is that I know of no way to accurately predict how much change you will get for every .x or even .0x" change in depth.

Uncle Nick beat me to it, your listed COAL is over SAAMI specs for the 9mm Luger. HOWEVER, that is not automatically a bad thing, IF your gun handles it (feeds from mag flawlessly, bullet not jammed in the rifling).

As to the second question, I think you are going about things wrong, (incorrectly) because you are looking for a load that makes major power factor with a 9mm, without having your own chronograph, or one you can use at want, not need.

Think of it as trying to frame a house but you only get to use your friend's tape measure once in a while. You got lumber, hammer, nails and saw, but no way to check your measurements. And to play in the game, you have to meet "code" with your building.

Get a chronograph (they're relatively inexpensive) so you can do your own testing. And be prepared to try different powders if need be.
 
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