9mm OAL

[obiwankabaldi]

How does OAL affect ballistics. My commercial ammo 9mm FMJ 115gr different brands all are about 1.150" I am using Bullseye powder and the guide give 1.125" OAL. This seems rather extreme. I have built some up at 1.140" and they seem to shoot great. Any feedback since I am trying to understand the effects of OAL on bullets in general and why the big differences.

[CocoBolo]

How does OAL affect ballistics. My commercial ammo 9mm FMJ 115gr different brands all are about 1.150" I am using Bullseye powder and the guide give 1.125" OAL. This seems rather extreme. I have built some up at 1.140" and they seem to shoot great. Any feedback since I am trying to understand the effects of OAL on bullets in general and why the big differences.

Any true understanding will come from the Crono. It may feel good but then is it really good only the crono will tell the tale.

[Poppa Bear]

I bit more complex way of looking at OAL is to measure the bullets themselves. Compare this against the over all length of the cartridge. Deduct the bullet length from the cartridge length and you have how much bullet is inside the case. Take the new bullet of similar weight that you want to load and measure it. ADD the length of the new bullet to the interior case dimension and you get a OAL that uses the same interior space as the known cartridge.

This is especially important if you are changing from a round nose to a flat point or even to a semi wad cutter. All three have a different length for the bullet themselves but using the correct math gives you an over all length that leaves the same internal dimensions for all three cartridges.

[Hi-Power Jack]

How does OAL affect ballistics. My commercial ammo 9mm FMJ 115gr different brands all are about 1.150" I am using Bullseye powder and the guide give 1.125" OAL. This seems rather extreme. I have built some up at 1.140" and they seem to shoot great. Any feedback since I am trying to understand the effects of OAL on bullets in general and why the big differences.

Your gun/mag can handle up to some maximum OAL - beyond

which you will experience malfunctions.

Each gun also shoots each type of bullet more or less

accurately at different OAL's. E.g. my BHP shoots

147 gr bullets at 1.12" very accurately, but is not

reliable. At 1.13", it is reliable, but I have lost

a little accuracy - so I shoot it at 1.13")

Jack

[Red Ryder]

OAL is given for a particular bullet recipe to maintain the exact conditions that the powder company tested their loads for a particular powder. You should also note the barrel length used by that powder maker to collect the data. All of this information is provided so you (the amazing reloader) can replicate a safe load within their "guidelines". If you change one factor (the OAL, barrel length etc) it has an affect on the outcome (your reloaded ammo). Sticking to the subject of OAL, when you increase the OAL, generally you reduce FPS and pressure, but not by much. It is generally safe to increase the OAL.

DANGER!!! It is NOT generally safe to reduce OAL. The result could be a compressed load which increases pressure and FPS and may result in a damaged gun and possible injury to the shooter. Different OALs can affect feeding reliabilty. It is up to you, the reloader, to test your loads by trial and error and arrive at the most accurate load with the desired power factor and feeding reliabilty using the guidelines (recipe info) provided by the powder maker. A chronograph is a necessity. It is the tool you use to test the velocity of your load to ensure the proper power factor.

Edited June 11, 2011 by Red Ryder

[superdude]

cartridge overall length varies for many reasons, several of which have been mentioned. in many cases the bullet nose shape and length can be the determining factor. for practical advise on overall length see:

http://www.38super.net/Pages/Bullet%20Design%20and%20Feeding%20Reliability.html

http://www.38super.net/Pages/Overall%20Length.html

Edited June 12, 2011 by superdude

[obiwankabaldi]

Superdude, thanks that is exactly what I was looking for. Learned a lot.

[Bob DuBois]

Seems I've been shooting more minor nine the last few years. When working up loads you'll need to spend time with the chronograph and shooting what I call Dots. I'll stick them to a test target and shoot groups once I'm satisfied with the power factor. Minor nine is not a sensitive as some of the other loads but load a few shorter then medium length then long. Shoot some groups to see which your pistol likes.

I've settled on 1.140 using 147 and 135gn cast bullets.

That length worked well with a Frontier plated bullet also. For me load as long as can that rounds will run in the magazine.

Your gun, the powder your using, spring weights, bullet shapes and weights all come into play. Spend some time tuning it will improve your shooting.

[superdude]

Sorry to keep bringing this up but I am looking to understand what I am doing.

I am using Bullseye powder and the manuals say 1.125" for OAL but all of my commercial ammo is measuring closer to 1.160" I have loaded a bunch at 1.140" and they shot great, though a little dirty. My question is should I go with the manual? if you're using the same brand bullet as in the manual, sure. it's a good place to start. the most critical feature is to make sure it fits in your chamber at that length because some chamber dimensions vary.

Will that longer length affect the amount of residue? not hugely unless the powder charge is on the low side, as some powder burn less efficiently then.

And how critical is OAL within the range lets say 1.125" to 1.160"? with respect to pressure? pretty significant. with respect to reliability? uncertain as it will depend on your pistol. if the bullet fits the chamber and your magazine and runs reliably, that's the criteria. but the pressure is the important thing to consider. rule of thumb is to load on the long side to keep pressure low, as this tends to also enhance reliable feeding - if it fits in the magazine and chamber (though this is more of a guideline and isn't absolute). the pressure issue becomes more important whenever you load near the maximum recommended charge weight. you have less leeway for error then. it also depends on the powder you're using. bullseye is a fast powder and fast powders tends to be more sensitive to pressure concerns than others, but if you keep a close eye on it you'll be fine.

Lastly what is the advantage to longer or shorter OAL. again, the usual issues are pressure and reliability. it's usually a balance between the two. but if your current load runs and shoots fine with no signs of excess pressure (examples of classic pressure signs in primers can be seen at http://www.38super.net/Pages/Factory2.html), that's about as good as it gets. you might not need to worry about changing it - if it's not broken, don't fit it, and all that.

I see that most guys are suggesting trying to get to the longest OAL that a specific pistol will allow. sometimes they're trying to achieve a specific goal - load long for reliability etc. if you're loading for Major Power Factor then loading long is good because it helps to keep pressure down and that's important for 9mm because there is so little case volume in the first place and to make Major in the 9mm the pressures get really wildly high, especially with light bullets (115-125). oh, and for Major you want medium to slow burning powders. Bullseye would likely cause a gun to spontaneously disassemble.

I have been reloading for a while and always went by the book. Thanks.. books are a great reference and it's good that you're paying attention to detail. that's what keeps you safe. there is some leeway when considering overall length, the concerns mentioned are pressure and fit (magazine/chamber). if those are okay, then load-em up and blast away.

[obiwankabaldi]

Wow great info. Thanks to everyone for the tutorial. Just what I needed........

[himurax13]

Well Bullseye is a fantastic powder but it is very easy to double or even triple charge the case without noticing a difference and I find it a little on the dirty side.

[noylj]

Cartridge Overall Length (COL) has several variables:

the bullet ogive

the magazine (the COL it will accept and when the lips release the round to be fed)

the feed ramp geometry

the barrel chamber, particularly the chamber throat.

Per Ramshot Load Guide v4.1:

SPECIAL NOTICE ON CARTRIDGE OVERALL LENGTH "COL"

It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.

The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.

This parameter is determined by various dimensions such as

1) magazine length (space),

2) freebore-lead dimensions of the barrel,

3) ogive or profile of the projectile and

4) position of cannelure or crimp groove.

As such, there is for each bullet and gun a range of COL that will feed properly. In general, best accuracy is with the longest COL that feeds and chambers 100%. In general, for a given charge weight in a straight-wall pistol case, the pressure will go up slightly as COL goes down.

As per Ramshot, the COL in a manual is a COL that is only of real interest to the industry, and is NOT a recommendation for the reloader. All it can be taken as is the minimum COL that the max load relates to. It is usually a COL that is shorter than most reloaders would use (if they didn't think that the COL was a recommendation).

Some guns have very short throats and some have very long throats. Thus, some guns use longer COL and some shorter COL.

One of the most important safety tips for all reloaders is to have some means to inspect the charged case before the bullet is seated. This can be by eye or by a Lock-Out die. Using a progressive press properly with auto-indexing will eliminate most causes of double charging, but actual inspection is the best method.

One should determine the functioning COL before starting to load (using two or three inert dummy cartridges—inserting them in the magazine and cycling the gun) and then verifying at the range with 20 or so rounds.

Thankfully, most guns will most feed most reasonable COLs just fine.

Edited January 30, 2015 by noylj

[texasref]

As to your original question: OAL affects ballistics due to internal pressure. The shorter the OAL the higher the pressure.

1.125" is the min for 9mm. I load mine to 1.65. You want to load longer than the manual states to be on the safe side.

If your rounds at 1.14" shoot well, keep on shooting them.

[Steve RA]

1.65 is pretty long, did you have to have your chamber reamed very much ???

[Hi-Power Jack]

1. The shorter the OAL the higher the pressure.

2. 1.125" is the min for 9mm.

1. True, theoretically, but as someone else mentioned, if the case is half empty,

shortening the OAL may produce NO increase in pressure/velocity.

2. Not sure this is universally true - depends on the individual bullet. I've heard

of some EAA shooters loading well below 1.125" with heavier bullets.

[texasref]

My appologies Steve, 1.165" is the overall length I load. Thank you for bringing that to mine and others attention. Mis-information the bane of others existance.

Once again you prove to be an excellent checker of statements with facts