Guidance with OAL and Seating depth

[konertjm]

I am currently trying to develop a beginning load for Xtreme 124gr hollow point.
These are not like other hollow points, rather than defensive bullet, these are more like a target bullet.

Sierra and Lyman basically state an OAL of 1.075 for hollow points.
The Xtreme 124gr has a bullet length of .535, an OAL as stated would leave the bullet seated to a depth of .211.
I measured a factory Freedom with a 115 gr rn. (Not HP I know) with an OAL of 1.152, and a bullet length of .553, this calcs as a seating depth of .150.

So, with this 124 Gr HP, should I go with a shallower seating depth of .150, which would give me an OAL of 1.134, or stick with the seating depth of .211 and an OAL of 1.075?

BTW my maximum OAL length that will chamber measures 1.154, as described in this thread http://www.thehighroad.org/showthread.php?t=506678

Thanks for all your help.

 

[LiveLife]

After you determine the max OAL/COL, you should function test using your pistol/magazine and dummy round (no powder/no primer) and incrementally decrease the length to determine the working OAL that reliably feed/chamber from the magazine when you release the slide. Working OAL can be the same as max OAL but depending on the pistol brand/model, will often be shorter than max OAL.

Once you determine the working OAL, you should then calculate the seating depth and reference listed OAL in the published load data to see if your seating depth is deeper or not. For me, if my seating depth is deeper than listed, I may elect to adjust the start/max powder charges by .2-.3 gr depending on the burn rate of the powder (this is for semi-auto not for revolver). If you don't want to do the math calculations, you can do what rcmodel usually suggests and just use the published start charge and carefully conduct the powder work up.

 

[Artofgolf]

Succinct

 

[Walkalong]

I am loading them at 1.060. That is a bit short, but it works in my guns and is accurate. 3" EMP to 16" AR.

1.075 sounds like a good length to try.

 

[LeftyTSGC]

I load my 124gr Xtreme HP at 1.120. That provides the average seating depth that operates well for me in my STAR30M 9mm. ( my max OAL is 1.157)

case .754 + .535 = 1.289 now subtract your OAL of 1.154 = .135 so that is pretty light bullet seat. If you go with a OAL of 1.120 you would have a bullet seat of .169 half way between your two choices.

Also remember most 9mm cases are not set at .754, many are slightly shorter (some longer), mechanically if your case is shorter your bullet is seated longer which reduces the seating depth given the same OAL.

Either way you should always work up your loads to find what works for you.

 

[Sunray]

There's no arithmetic required when reloading. It's far from being that complicated. Seat the bullet to get the max OAL given in your manual and you'll be fine. Assuming this is a 9mm, max OAL with the bullet is 1.169". That will change a bit by bullet weight and shape. but the really important part is fitting the mag.

 

[LiveLife]

Seat the bullet to get the max OAL given in your manual and you'll be fine.

Really? I disagree.

Usually, listed OAL/COL in the load data is the minimum, not the maximum. And using the listed OAL in the manual will not be fine, especially with HP profile bullets as nose shape can vary quite a bit depending on the bullet manufacturer and the pistol brand/model used. Using listed OAL in the load data may not ensure reliable feeding/chambering in some pistols.

Assuming this is a 9mm, max OAL with the bullet is 1.169".

As LeftyTSGC posted, using mixed range brass will result in varied case lengths after resizing. If you load your rounds long, varied case lengths will result in different amount of bullet shoulder protruding above the case mouth. Since semi-auto cartridges like 9mm headspace on the case mouth, this may allow the shoulder of the HP (bearing surface) to hit the start of rifling when the round is chambered, not a good thing in my book.

Using the barrel to determine the max OAL and then function test to identify the shorter working OAL will address this reloading variable. Ammunition manufacturer may be able to use SAAMI max because they are using new brass with more consistent case lengths.

 

[Okcafe86]

It's already been touched on but the farther you seat the bullet into the case, the less powder you want to use. That's why you start low and work your way up. It's best to use a chronograph to see where your at velocity/ pressure wise. I don't have a chrony but I use quickload to help determine a good load. This is all within published load data of course.

On another note. I've been loading 9mm recently my self. I've found loading lrn has caused me to seat pretty deep. (1.065) The only reason I'm seating this deep is it failed the plunk test in my pf9 with anything greater. Take the barrel of your pistol out and drop a dummy round in. Make sure it head spaces right. My cases are also on the short side. (.744) these are once fired military brass. Another factor is with the alloy I'm using the bullets are dropping 7 gr heavier than published. All these factors entered into quickload have brought my max charge to the midway point in published load data. Now I really don't think if I went to the max published data I would blow my gun up or even have pressure signs. I AM confident I would be in the ++p range though. Not something you want to batter your gun with on a regular basis. My point is, start low and work up. As far as load data, I'd go with data for a VERY similar weight lead bullet. Determing your OAL... Longest length that will properly headspace and fit in your magazine.

 

[wlkjr]

I've been loading that same bullet at 1.120-1.130 using Titegroup, which doesn't nearly fill the case. I suppose it might depend on what powder you use too, so as not to compress it. I shoot them in all three 9mm Glock models.
We've shot several thousand of these at those depths and had no problems whatsoever.

 

[konertjm]

You guys are great. You have given me quite a bit of info.
WLKJR thanks for the info on the same bullet.
Based on your experience I think I will go with the 1.120 oal. This gives seating depth of .165, a good compromise between .150 and .211, which I felt was too deep.
I'll be using CSB1 to work up a load. The starting load is 10% less than max for 125 grn bullet. I think the oal and seating depth will work great.

Jim

 

[JamieC]

Don't forget, the OAL has to work in YOUR gun. There are a couple that have 'short throats', do a 'plunk' test, make sure the bullet isn't into the rifling.

 

[konertjm]

Thanks JaimieC (and everyone else as well), for all the great info and insight.

I always do the plunk test, so far, for the few months I have been reloading pistol, every single round.

 

[LiveLife]

I always do the plunk test, so far, for the few months I have been reloading pistol, every single round.

You shouldn't have to check every single round.

Using the barrel/plunk test to determine the max OAL/COL allows you to identify the maximum cartridge length your barrel will allow (for that particular brass case anyway ). But, there are other variables that affect reliable functioning of the pistol, so we need to determine the "working OAL" next.

Most of us use mixed range brass with unknown reload history and after resizing, the case length will vary. Since semi-auto rounds headspace on the case mouth, different case lengths will result in different amount of bullet's bearing surface protruding above the case mouth. So to avoid bullet's bearing surface hitting the start of rifling when the round is chambered, we "compensate" this variance into our working OAL.


To simplify the example, let's say a hypothetical pistol allows the max OAL to be the working OAL of 1.165". And let's say case lengths vary by .005". So I would subtract .005" from 1.165" and use 1.160" as my "compensated working OAL"


In my Herco 40S&W thread, to help 1KPerDay identify an accurate load with 180 gr TCFP bullet, I wanted to use the longest OAL that minimized high pressure gas leakage. Most reloaders would start with SAAMI max of 1.135" for 40S&W for their max OAL determination. Well, some barrels support OAL beyond SAAMI max due to longer leade/free bore and more gradual start of rifling.

So when the max OAL was 1.149" for Glock/Lone Wolf barrels, I used 1.143" as my max "working OAL" that reliably fed/chambered from the magazine and also factored in variance of case lengths. As indicated by the shot groups (and verified by 1KPerDay), longer than SAAMI max length rounds produced greater accuracy for our particular pistols/barrels - http://www.thehighroad.org/showthread.php?p=9362819#post9362819

 

[konertjm]

Thanks BDS, good advice.
I use 'once fired' brass from a good source, or that I fired myself. I also sort my used brass by head stamp, so that I have somewhat consistent brass in size, weight, and case length when I load a batch of ammo.

I realize that the plunk test is not necessary for each round, as a fairly new (approx. 1000 rounds in 2 calibers) reloader in auto pistol, it gives me a little more confidence.

Bases on another thread in the tremendous forum, I have determined the exact measurement of the chamber, and use that as a basis for OAL comps.

Thanks again for all the knowledgeable help.
Jim

 

[Potatohead]

I did all that adding and subtracting a time or two, then I figured out it's not really necessary. As long as you start low and work up, and have "plunked" your chosen COL, you'll be fine IMO. I've ran that same bullet at 1.10 to 1.12 and many points in between, with no problems. PH

 

[LiveLife]

I use 'once fired' brass from a good source, or that I fired myself. I also sort my used brass by head stamp, so that I have somewhat consistent brass in size, weight, and case length when I load a batch of ammo.

I did all that when I started reloading as my reloading mentor was a bullseye match shooter. He had me sort Montana Gold jacketed bullets by exact weight, shave lead from FMJ base, etc. (memories ... )

But if you are loading lighter "target" loads with "plated" bullets, your extra work may not produce significant enough increase in accuracy to matter on target. I think more consistent powder charge, sufficient neck tension, minimum/no bullet setback for more consistent seating depth when the powder is ignited, will probably result in greater accuracy.

My QC check for neck tension and bullet setback is allowing the slide to slam the dummy round on the feed ramp of the barrel to chamber (similar to rough treatment the finished rounds will experience during live fire).

Go ahead and do a test.

- Make a dummy round (no powder/no primer) and measure the OAL/COL
- Load the dummy round in the magazine and lock the slide back
- Insert the magazine and release the slide without riding it
- Measure the OAL/COL
- Now repeat with several dummy rounds
- Ideally, your finished rounds should not experience bullet setback but depending on the bullet, condition of the brass, OAL/COL used and the reloading practice, you may experience some bullet setback
- If you experience OAL/COL reduction greater than a few thousandths, you may have neck tension issue that needs to be addressed

If your dummy rounds produce different amounts of bullet setback, this will significantly affect chamber pressures and inconsistent chamber pressures will significantly affect muzzle velocities and resulting accuracy, especially if your powder charges are not consistent and these reloading variables will "stack" on top of each other to produce even less accurate loads.

For me, accuracy is everything and holes on target speak volumes as they are the cumulative sum of all reloading variables. What matters more to me is the consistency of the "chambered" rounds' dimensions/bullet seating depths before they are fired and the shot groups they produce on target. Finished rounds passing the barrel/plunk test will only tell you whether they will fully chamber or not and tell only a part of the story.

Now days, I reserve known verified once-fired brass for near max/max loads for practice defensive loads using premium JHP projectiles like Speer Gold Dot and Remington Golden Saber.

In my 40S&W Herco thread, I actually tested once-fired vs worst looking-mixed range brass-reloaded multiple times using working OAL/COL that compensated for case length variation that still reliably fed/chambered from the magazine and the accuracy results were not significant - http://www.thehighroad.org/showthread.php?p=9362819#post9362819

Moving forward, I may only use worst looking mixed range brass for accuracy testing because that will tell me the "minimum" threshold/baseline for accuracy.

 

[lauderdale]

WOW thank you for the insight BDS and the other fellas as well! KUDO'S

 

[LiveLife]

I started to post and probably due to 104F+ heat the past 4 months baking my brain, I started to get off topic.

So I started a new thread instead to not hijack this thread - http://www.thehighroad.org/showthread.php?p=9605663#post9605663

 

[lauderdale]

Yes I live in WEST TN. and the 80* air just hit! I have the W231 filled and the RNFP 100 grainers in the pan on my blue bird! Oh and that 1000rnds of 380 STARLINE! its been awhile!