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Bravo_Victor

Mixed brass and OAL variation

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So let me start by saying ive been loading 9 major with MG 124JHP with AA7 and strictly Hornady brass for some time. Ive been loading them to 1.140 and the only deviation ive been getting was 1.142 on the high end and 1.138 on the low end once in a blue but everything usually seems to stay around 1.139-1.141 for the most part. Never had any crazy oal issues. Now i moved to mixed brass and all of a sudden im getting crazy OAL issues. If im loading 1.140 i will get 1.147 the highest and 1.136 the lowest on average but ive noticed theres been a couple 1.125’s, 1.130’s, 1.132’s. Nothing has changed on my 650. Everything is cleaned and tight. Same batch of bullets as well. Theres no particular headstamp that is causing the issue except for Blazer usually being on the high end. The rest of the headstamps seem to be back and forth. 

 

Any idea?

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The mixed head stamp brass will definately give you a little more variance. I am loading 9mm for minor power factor to 1.14 oal. I give myself an allowance of +/- .005, so 1.135-1.145 goes to a match, anything outside of that within reason goes in practice ammo. On my 550 I get an occasional round outside of my allowance, but it’s not the norm. If you are getting a large quantity way outside of spec., I would be investigating further, otherwise I would chalk it up to the mixed brass.

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I totally agree with Steelslinger86

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21 minutes ago, Steelslinger86 said:

The mixed head stamp brass will definately give you a little more variance.

 

When loading mixed brass, I also give myself a variance of .005 +/-  

It's just the nature of the beast when loading mixed brass.  For USPSA competition, the variances are negligible for the distances shot. 

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This used to drive me nuts. But I finally just learned to live with it. Now when I change bullets or oal I do an average to my target oal. I’ll load a few then measure 10 and average. If I’m under or over I’ll adjust to get a little closer. I’ll set up, load a 100, measure 10 then average. My target right now is 1.120, I’ll get anywhere from 1.115, to 1.125. After I load a 100 I’ll pick 10 average, right now I’ve got an average of 1.119.

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I load major at 1.161" OAL in fully processed mixed HS brass.  It has been resized, deprimed, primer pocket swaged, push through or roll sized, cleaned, dried and lightly waxed.  My OAL variation with this brass is +/- .001" on a Hornady LnL using Hornady dies.  I've just started reusing cases I shot  at the practice range.  I checked a couple and they were right on.  Now that I hear there is a problem, I'll have to check more thoroughly.

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I've found WIN brass loads longer.  Or looked at another way, needs 1/8" turn down of the seating die to get the same OAL as Blazer and FC.

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9 hours ago, Bravo_Victor said:

Any idea?

No avoiding it unless you do like me and sort by headstamp. 

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What Sarge said.  Reloading 9 MM minor I load 100 reload primers and if changing head-stamps I recheck OAL, sometimes it is amazing how much changing brass can change OAL.

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Yeah. It drove me crazy on my 650 - I tried everything to tighten the OAL variance -  Widden clamping toolhead, different seating dies , etc etc etc. Only thing that really made a difference was sorting by headstamp.

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Different thickness of brass, different hardness of brass, difference as to when taper to bottom of case starts and probably more variation in length of case all contribute to more variation in mixed brass than in all one brand brass.

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Posted (edited)
3 hours ago, Steve RA said:

Different thickness of brass, different hardness of brass, difference as to when taper to bottom of case starts and probably more variation in length of case all contribute to more variation in mixed brass than in all one brand brass.

 

With a 124gr at that length he shouldn't be getting into the case taper on any brand of brass, and case length has no effect on OAL. That load is probably a compressed charge though, and different case capacity of various headstamps does affect the amount of compression, which has a direct affect on OAL. 

 

OP - you should see a lot less variation with a Minor load that is not compressed; the exception being if you use a long bullet that seats into the case taper on some brands, that'll cause OAL variation too.

Edited by Yondering

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14 minutes ago, Yondering said:

 

With a 124gr at that length he shouldn't be getting into the case taper on any brand of brass, and case length has no effect on OAL. That load is probably a compressed charge though, and different case capacity of various headstamps does affect the amount of compression, which has a direct affect on OAL. 

 

OP - you should see a lot less variation with a Minor load that is not compressed; the exception being if you use a long bullet that seats into the case taper on some brands, that'll cause OAL variation too.

You are correct. It’s slightly compressed. Minor i have no issues with. But i find it strange that i had barely any OAL issues with all Hornady brass but with same headstamp of other brands i have much more of a variation. It is what it is. I already have to load short bc my barrel isnt reamed so my worry is getting a long around that wont seat all the way. 

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Posted (edited)

Some brands definitely have more variation than others. With most of them though, you should still have less variation than with mixed brass. However, be aware that a few brands have put their headstamp on brass from different manufacturers or made significant changes in brass over the years, so you can end up with 2 or more "groups" of varying case capacity within the same headstamp. This is more noticeable with rifle brass, but can be significant (as you're discovering) with pistol brass when you're pushing the limits with max loads. 

 

If you decide to sort by headstamp, FC brass might give you the least variation; that has been my experience although I haven't used a large volume of Hornady 9mm to compare. 

Edited by Yondering

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1 hour ago, Yondering said:

Some brands definitely have more variation than others. With most of them though, you should still have less variation than with mixed brass. However, be aware that a few brands have put their headstamp on brass from different manufacturers or made significant changes in brass over the years, so you can end up with 2 or more "groups" of varying case capacity within the same headstamp. This is more noticeable with rifle brass, but can be significant (as you're discovering) with pistol brass when you're pushing the limits with max loads. 

 

If you decide to sort by headstamp, FC brass might give you the least variation; that has been my experience although I haven't used a large volume of Hornady 9mm to compare. 

I might start sorting a little bit. I have 5k brass ready to load. So far ive noticed blazer brass being on the higher end of the spectrum but RP being kinda wonky. 

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Since seating is only based on contact between the seater stem and the bullet and the case head to the shell plate, where would case length come into the equation—assuming seating and crimp are separate..

Next, for almost any pistol shooting, normal COL variance of +/- 0.010" makes no difference to POI out to 50 yds and you'll never notice any pressure variance..

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49 minutes ago, noylj said:

Since seating is only based on contact between the seater stem and the bullet and the case head to the shell plate, where would case length come into the equation—assuming seating and crimp are separate..

Next, for almost any pistol shooting, normal COL variance of +/- 0.010" makes no difference to POI out to 50 yds and you'll never notice any pressure variance..

I know it doesn’t jive. The distance from shellplate and stem doesn’t change, it’s fixed so how does the oal change? I’ve been told that there are so many variables that you cannot control is the reason why. Not stoking the ram same way, bullet crooked on case, loose shell plate, different brass thickness, the list goes on and on. So just accept the fact that in 9mm your going to have +or - .005, so adjust your max oal to allow for this so that your rounds do not touch barrel rifling, or use same headstamp.

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6 hours ago, rooster said:

I know it doesn’t jive. The distance from shellplate and stem doesn’t change, it’s fixed so how does the oal change? I’ve been told that there are so many variables that you cannot control is the reason why. Not stoking the ram same way, bullet crooked on case, loose shell plate, different brass thickness, the list goes on and on. So just accept the fact that in 9mm your going to have +or - .005, so adjust your max oal to allow for this so that your rounds do not touch barrel rifling, or use same headstamp.

Same here. I gave up caring how or why. BUT headstamp definitely affects oal.

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Posted (edited)
9 hours ago, noylj said:

Since seating is only based on contact between the seater stem and the bullet and the case head to the shell plate, where would case length come into the equation—assuming seating and crimp are separate..

Next, for almost any pistol shooting, normal COL variance of +/- 0.010" makes no difference to POI out to 50 yds and you'll never notice any pressure variance..

 

Case length has nothing to do with OAL. Zip. 

 

I'm different than Sarge though; I prefer to understand what causes variations so I can minimize or eliminate them. As the saying goes, "knowing is half the battle."

The idea that there are so many variables we can't control is not true either. We can control almost all of the variables if we take time to understand them. I often get the impression that a lot of this stuff is black magic to some reloaders, but all of it is within our capability to understand. 

Edited by Yondering

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54 minutes ago, Yondering said:

 

Case length has nothing to do with OAL. Zip. 

 

I'm different than Sarge though; I prefer to understand what causes variations so I can minimize or eliminate them. As the saying goes, "knowing is half the battle."

The idea that there are so many variables we can't control is not true either. We can control almost all of the variables if we take time to understand them. I often get the impression that a lot of this stuff is black magic to some reloaders, but all of it is within our capability to understand. 

I agree, if i wasnt super anal about certain things this post wouldnt exist. Most importantly this post is reassurance that its the brass and not my press, althought ive read the same thing about mixed brass 100 times. I figured maybe there was something i didnt realize and i can fix it. Either way i chronod the real short ones today and they barely made a difference and there were no overpressure signs. Now my only concern is the longer ones with them chambering. Worst case scenario if i dont wanna sort brass is find the longer ones in the bunch and cycle them back after adjusting the die. Luckily i have the redding comp die lol

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You figure out the max oal for the that bullet in that barrel then you subtract .015 to .020 that should allow for any oal variance. You have to do this for every different bullet profile that you use in that particular barrel.

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Agree with Noylj and yondering--shouldn't make a difference unless you're shooting bullseye with a minimum headspace, tight  chamber and short throated barrel -- fire your loads over a chrono for velocity variance between the longest and shortest rounds. I would be interested to see your results. Keep in mind the +/- manufacturers acceptable chronograph error .

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18 hours ago, Yondering said:

 

Case length has nothing to do with OAL. Zip. 

 

I'm different than Sarge though; I prefer to understand what causes variations so I can minimize or eliminate them. As the saying goes, "knowing is half the battle."

The idea that there are so many variables we can't control is not true either. We can control almost all of the variables if we take time to understand them. I often get the impression that a lot of this stuff is black magic to some reloaders, but all of it is within our capability to understand. 

It seems some of the more rational conclusions center around case wall thickness. Bullets require more or less force and hence oal can vary. When I tried to figure it out I came to the same conclusion that depth should not be affected at all by length of case so it had to be some other parameter. 

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It may not make a difference if you are using two seperate dies to seat and crimp, but it will make a lot of difference if you are using one die to do both.  

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Posted (edited)

I see OAL being at least somewhat of a function of the effort it takes to resize.

 

I sort headstamps and if I an loading Blazer Brass which sizes relatively easily I will get on average a slightly shorter OAL than if I'm loading CBC which is one of the headstamps which provides the most resistance to sizing.

 

Whether that resistance is due to different metallurgy or different case wall thickness I have not investigated.

 

Edit to add: So to finish my thought that I apparently got sidetracked from...the resistance to sizing a case is indicative of the its resistance to seating a bullet into that case and therefore the longer OAL.

Edited by ddc

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