Consistancy of Bullet OAL & Round OAL

[charliemopic]

When reloading 9mm pistol rounds how consistent or inconsistent can I expect the OAL to be from round to round?
I sort my brass by headstamp hoping that will offer more consistency.

I dug up a box of factory loads, Remington green & white box 9mm Luger that I bought from Walmart in 2006. Its 115gr FMJ, not plated.
--The OAL is 1.094 up to 1.104.
I disassembled one of the rounds and it had 4.0 grain of unknown powder and the flat base projectile looked a ZERO 115gr FMJ.

--If I were to trim my brass to .754 could I expect the OAL to alot more consistent?
--What is Good OAL consistency of finished 9mm rounds?

Considering bullets-projectiles only.
I like and use 'ZERO' brand bullets from David Matthews at MPS in North Carolina and Precision Delta bullets.
--How consistent can we expect the OAL of these or any bullets to be?
--What is acceptable projectile OAL consistency?

The reason I am focused on finished round Over All Length is to begin with there isn't much vessel space in a 9mm Luger case. Changing the OAL could change the pressure and perhaps to an over-pressure condition.
I don't have a chronograph at this time.

Thanks For Your Time
charliemopic

 

[Rule3]

The length of the brass case does nothing for Cartridge OAL. Unless you are seating to a crimp line or cannelure.

 

[Gadawg88]

If I were to trim my brass to .754 could I expect the OAL to alot more consistent?

No. The brass length has nothing to do with the finished round oal. Variance in oal can be caused by a number of different factors and sometimes these variables can stack in the same direction to produce larger than desired differences in OAL. One cause is inconsistent bullets, particularly bullet shape. Typically, the bullet seater stem does not contact the tip of the bullet, rather it contacts the bullet between the tip and the ogive. Slight differences in bullet shape will result in differences in oal. Inconsistent operation of the press can cause oal differences. If you use a progressive, not having a round in each stage will create differences in oal. I believe that sorting your 9mm brass by headstamp could lead to more consistent oal, but I would also say it is not worth the effort. I would say a variance of .005 in oal for pistol ammo would be a reasonable target variance. Of course if you are using a hot load on the ragged edge of reasonable, a shortened oal could become an issue.

 

[X-Ring]

Short answer +/- 0.005 OAL and you will never have a problem.

 

[rsrocket1]

Just as a thought experiment, I ran your numbers through Quickload. Pretending the powder was 4.0g Titegroup, the difference between 1.104 and 1.094 COL with a 115g RN bullet, the difference in muzzle velocity goes from 1064 fps to 1072 fps through a 4" barrel. You'd never feel the difference or notice the difference in accuracy.

 

[lpsharp88]

I've never had more than +/- .005" variance in anything I load.

 

[LiveLife]

I sort my brass by headstamp hoping that will offer more consistency.

If I were to trim my brass to .754 could I expect the OAL to be alot more consistent?

No, as case length does not effect OAL/COL and sorting by head stamp either. What determines the OAL is the distance between the shell holder/plate and the point where seating die stem/plug pushes on the bullet. Factors that effect these will vary the OAL.

Most bullet seating die stems/plugs do not contact the bullet tip of FMJ/RN bullets but further down on the nose and consistency of where the stem/plug pushes on the bullet effects OAL.

When reloading 9mm pistol rounds how consistent or inconsistent can I expect the OAL to be from round to round?

I have used Montana Gold jacketed bullets for match loads and Winchester FMJ for my 9mm reference loads for decades along with various plated and lead bullets. Depending on the consistency of bullet nose shape/ogive, OAL could stay within a few thousandths or vary by .005"+.

If you are reloading on a progressive press and seeing large swings in OAL, try using resized cases to remove shell plate tilt/deflection effect on OAL. If OAL variation decreases when resized cases are used, check for loose shell plate. If tightening the shell plate does not resolve the OAL variation, you may need to resize your brass separately to decrease OAL variation.

Modifying the seating stem/plug end to match the shape of the bullet nose (custom order, machining, JB weld, etc.) will decrease the OAL variation.

I dug up a box of factory loads, Remington green & white box 9mm Luger that I bought from Walmart in 2006. Its 115gr FMJ, not plated. The OAL is 1.094 up to 1.104.

Even factory rounds will vary in OAL by several thousandths.

 

[Wreck-n-Crew]

My 2 cents....
No need to trim 9mm brass. Also as already mentioned it doesn't change OAL. Also as mentioned the slight variance in OAL you mentioned does nothing worth mentioning in velocities and will not change the accuracy either.

I've never had more than +/- .005" variance in anything I load.

Same here.

 

[Walkalong]

A .005 spread is pretty good. Some bullet/seating stem combinations will do better, some worse.

+/- .005 isn't all that good. I would look to improve on that.

 

[Metal God]

Have I been looking at the term +/- wrong all these years ? When I see +/- .005 . That to me say a total swing of .010 , +.005 OR -.005 of your intended measurement ??

 

[Wreck-n-Crew]

Have I been looking at the term +/- wrong all these years ? When I see +/- .005 . That to me say a total swing of .010 , +.005 OR -.005 of your intended measurement ??

No you saw it right and so did Walkalong. I missed that detail.

+/- .003 is more like it. I read it wrong too.

 

[wlkjr]

I've loaded my 9mm anywhere from 1.120 up to 1.135 with no appreciable notice in difference in performance. Find what OAL works for your pistol and resist the temptation to chase windmills, unless you are on the ragged edge with your loads.

 

[Walkalong]

A .005 spread isn't all that hard to get with 9MM. Seating stem fit is key, as well as consistency in everything you do.

But yea, if the spread is .010 and it shoots great, no reason to sweat it. The OCD in me couldn't accept worse than that though, and I am much happier with .005 or less.

 

[Metal God]

Since I started using a bullet comparator . I've been quite surprised how inconsistent the tips of bullets are . I just finished loading some Hornady 75gr match BTHP in 223 . This is for my NM service rifle so my max COAL is 2.260 . When finished I had one cartridge measure 2.2605 , another at 2.252 and everything in between . How ever when measured using the comparator I only had a difference +/- .0015 Which I was not all that happy with but it's still better then .008 swing . It nice to understand COAL differences is not that big a deal as long as you have the same jump to lands . Well unless you're pushing right up against your max mag length .

 

[sbwaters]

Setting up my Hornady seat/crimp die, with the ram up holding an empty case, I screw in the die until it meets the resistance of the case. Then a bullet is put in the expanded case and the seating adjuster is moved slightly down successively until the COL is what it should be.

Forgive me for using .45 ACP instead of 9MM, but that is what is in my head: If my cases are trimmed to .893 when the die is set up, what will happen to the over all length when a case measuring .890 is fed into the press. My intuition is that my 1.260 OAL that fits comfortably in my Springfield 1911 comes out of the press as a 1.262.

Is my mind experiment correct?

 

[LiveLife]

No.

If the same bullet is used with different length cases, OAL/COL will be the same but the seating depth will vary - longer cases will have deeper seating depth and shorter cases will have shallower seating depth.

BUT reality is not all the bullets are exactly same and depending on the manufacturing, nose profile/ogive will vary. So if bullets with different nose profile/ogive is used with same length cases, OAL will vary.

And if reloading on progressive presses, different amount of shell plate tilt/deflection will also contribute to OAL variation and using resized cases will reduce this variation.

 

[Reloadron]

Have I been looking at the term +/- wrong all these years ? When I see +/- .005 . That to me say a total swing of .010 , +.005 OR -.005 of your intended measurement ??

That would be how I see it and have seen it for decades. +/- .005" tells me an allowable tolerance from nominal is 0.005" in either direction so if the measurement nominal is 0.057" +/- 0.005" the allowable range or tolerance is 0.052" to 0.062". I don'y know of any other way to interpret it?

Ron

 

[sbwaters]

bds, I appreciate your point about the seating depth varying and agree. However if the ram tops out when it stops the .893 case at the bottom of the die, then when the ram tops out with the .890 case, it would be .003 below the die.

Wouldn’t the overall length of the round be .003 longer because the seating adjustment has not changed?

The .003 has to go somewhere and it would seem to me the 1.260 set it for using the .893 case would leave me, now using a .890 case with 1.263 OAL and a shallower seating for the bullet as you suggest.

 

[Reloadron]

bds, I appreciate your point about the seating depth varying and agree. However if the ram tops out when it stops the .893 case at the bottom of the die, then when the ram tops out with the .890 case, it would be .003 below the die.

Wouldn’t the overall length of the round be .003 longer because the seating adjustment has not changed?

The .003 has to go somewhere and it would seem to me the 1.260 set it for using the .893 case would leave me, now using a .890 case with 1.263 OAL and a shallower seating for the bullet as you suggest.

No, think about it again. I adjust my bullet seater plug down from the top. The actual plug in that die is going to be a fixed distance from the top of my ram stroke, imagine only a shell holder. When I add a case nothing changes. The distance from the seater plug to shell holder, including with a case inserted will always remain the same, whatever I set it for. Therefore the case length really does not figure into things. With a case 0.003" longer it just means there is more bullet in the case. Does that make sense?

Ron

 

[sbwaters]

Duh! It is the ram height that matters.

Ya know, it makes sense when it is explained so clearly. Thank you.

 

[Reloadron]

Duh! It is the ram height that matters.

Ya know, it makes sense when it is explained so clearly. Thank you.

Now you got it, ram shell plate to the die seater plug.

Ron

 

[sbwaters]

A similar question that won't affect OAL, then.

When using mixed trim length brass, should one set the seating/taper crimp die according to the longest or shortest trim length?

It would seem if you set it for the shortest, the longest would push harder against the die. Or, since you are talking at most .005-.007 difference in length it won’t really matter.

 

[Metal God]

Others will say different but the case length matters a lot IMO . So does case wall thickness . IMHO at minimum you have to segregate at least by trimming ever case or separate by case wall thickness .

 

[Reloadron]

A similar question that won't affect OAL, then.

When using mixed trim length brass, should one set the seating/taper crimp die according to the longest or shortest trim length?

It would seem if you set it for the shortest, the longest would push harder against the die. Or, since you are talking at most .005-.007 difference in length it won’t really matter.

While I try to avoid differing case lengths (I want them equal) where the unequal cases will show up is if you are loading bullets with a cannelure. Depending on case length the case neck may or may not be centered on the cannelure where it belongs. The COAL will be the same.

Case neck thickness will cause problems if they are not uniform in some cases. For example with bottle neck cases like .223 Remington or .308 Winchester I rely on neck tension to hold my bullets in the neck. There are work arounds for neck thickness. Some hand loaders favor the Lee FCD (Factory Crimp Die) but I won't go off on that tangent.

I sort my brass when I load and I trim to length. Good ammunition starts with uniformity in your components.

Ron

 

[wlkjr]

Others will say different but the case length matters a lot IMO . So does case wall thickness . IMHO at minimum you have to segregate at least by trimming ever case or separate by case wall thickness .

I don't have that much time left.