Seating Depth

tws3b2

tws3b2

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Asheboro NC
New to reloading. Using Hodgdon data I 'm loading some 9mm, 147gr xtp bullets with no cannelure. Hodgdon gives 1.100 COL. When I set the bullet to the Col it just didn't look right to me. Looked like it should go deeper into the case. The bullet is 0.65 in length. When I set to COL only around 0.35 sets into the case. Just over half. Anyway, It just seemed a little weird to me. Seemed maybe 1.07 would be more like it should be.
It just got me wondering. How important is col. Would more or less make a lot of difference? 20231124_204355.jpg
 
The shorter OAL the higher the pressure within the case, smaller volume. Can’t stick it out too far either or it’ll increase pressure by running into the rifling. It also affects feeding from the magazine. OAL is very important. to find a working OAL, try the plunk test.
 
With the higher pressure (35kpsi) cartridges like 9mm, yes seating depth does make a big difference. As always when dealing with pressure, less volume for the expanding gases can raise pressure to dangerous levels. Notice the word “can.” That’s because it is followed by “dangerous.” Seating deeper will raise pressure - that’s not in question - but how much and for how long is an unknown.
The data compiled for a certain seating depth is observational, gathered using testing and data gathering equipment. Changing the seating depth - and by extension the amount of space between the base of the bullet and the bottom of the powder column - requires changing other parameters: powder charge, definitely and possibly the neck tension, case design and primer type.
I would suggest that changing anything in reloading for reasons of aesthetics is unwise. Down that path are many visits to the Emergency Room. Fit is King. Looks is the court jester. 😁
 
tws3b2 said:
That's what I was thinking. Maybe to 1.07. Like this.
Would 1.07 col be Bad?
Click to expand...
As mentioned, what OAL does your 147 Gr JHP data show?

Because yes, in a high pressure low volume case like the 9MM small changes in OAL make a big difference.

Hodgdon shows 1.100 with that bullet, so that’s what you need to try first. Will it chamber? Check. Will it feed? Check. Good to go.

If not, and you have to go shorter, you’ll absolutely have to adjust the max load down.

Looks don’t matter if it fits/feeds
 
Appearance has very little to do with "correct" loading...always start with the "book" spec. The only legitimate reason to deviate from that is the maximum allowed by your magazine or the minimum required by the chamber of your pistol.

I personally try to load as long as possible. 124gr RMR RN out to 1.150" and 124gr RMR Matchwinners at 1.114"

FWIW: the OAL you have pictured that you feel looks "right", is about what a 115gr would look like...a lot shorter bullet (less bullet shank inside the case)
 
I would suggest you load a dummy round and pull your barrel for the Plunk Test. This will tell you if it will fit your chamber or not. Then adj the length as needed so it past the plunk test. Once you determine your OAL then you can start load workup, low to high. Note if shorter than mfg suggest you need to adj the max load.
 
I have loaded that bullet in the 9mm... that's a lot of bullet in that tiny case. As others have said... load it to book specs and then test it to make sure it fits your pistol's barrel without issues. I would be very reluctant to shove any more of that bullet into that already crowded case.

tws3b2 said:
Would 1.07 col be Bad?
Click to expand...


OP, what powder are you using?
 
Welcome ! OAL is set by how your bullet fits into your barrel.... NOT the OAL listed in the loading manual.
► You did not tell us your gun, so no one here can suggest an OAL.
► The OAL in the manual is the OAL they used in their gun. Their "handgun" looks like this....

1EzSG7Gl.jpg


• Hornady and Hodgdon are REPORTING the OAL they used during their testing. They are not making a recommendation.
• You'll need to measure how that bullet interfaces with YOUR barrel and then make reasonable adjustments and plans based on your experience with the cartridge and pistol. Each bullet-to-barrel interplay is different/ unique/ individual.
• Understand that ALL auto pistol cartridges allow a RANGE of OAL to be used. There are PHYSICAL limits used by the shooting industry, and then typically further restricting those are the LOAD limits set by Your gun and Your load recipe.

The following cartoon shows/ explains this better....

BhLepH4l.jpg


► On the outside we have the SAAMI Physical limits for 9x19 Luger. Longer than ~1.169" won't fit inside the mag; shorter than 1.000" won't feed well.
► Typically, further restricting those are the additional limits of reality. You don't want to go shorter than the Reported OAL in the recipe, to prevent chamber pressure spikes. You do not want to go longer than what the barrel will accept, due to fears of creating a cartridge that has the physical ability to create an Out Of Battery accident. Every bullet is different; every barrel is different. No one here can advise you on this number... you have to measure it for yourself.

► ► Between those 4 Limits is a "zone" or range of OALs that is safe to use. This part is the Science of Reloading. Then, based on your past experience with your handgun (and the notes in your reloading notebook), within that range is an OAL that will allow your handgun to feed well and deliver the desired accuracy. This part is the Art of Reloading. Welcome to Reloading !

Hope this helps.
 
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there's some rule of thumb about seating depth to get a proper grip/hold of the projectile, I think it is minimum of the bullet has to be seated as the case is wide, but that is a minimum and I'm not sure if that is real rule or just something I heard. I think you are in that range so, I would not worry too much about it. first thing I do with new components, especially a semi auto - is make a half dozen dummy rounds with no powder or primer that I think should work, and measure them all OAL and take an average. Cycle them a bunch fo times and see if they jam or not. Measure them all again and see if the average is lower, you really want it to be the same, or you are getting setback, which is an issue to be aware of and watch out for.
 
Charlie98 said:
I have loaded that bullet in the 9mm... that's a lot of bullet in that tiny case. As others have said... load it to book specs and then test it to make sure it fits your pistol's barrel without issues. I would be very reluctant to shove any more of that bullet into that already crowded case.




OP, what powder are you using?
Click to expand...
I'm using w231 powder. Loading for multiple semi autos, 3" - 4 1/2 "barrel. Hodgdon's data shows 3.0min. - 3.4max. powder. I'm using 3.2.
 
rfwobbly said:
Ha !!

And on top of all that, for some eastern European barrels and specialty "target barrels" there are limits on using 147gr bullets.
When your head stops spinning... then we can talk !! o_O
Click to expand...
When my head stops spinning??? If it stopped right now I think I would be flung off the face of the earth.
And I was going to keep it simple. Silly me.
 
tws3b2 said:
When my head stops spinning??? If it stopped right now I think I would be flung off the face of the earth.
And I was going to keep it simple. Silly me.
Click to expand...
It's not exactly Rocket Science, but you do have to pay attention, because you can get hurt.

If your barrel tells you that you need to use a fairly short OAL, realize that 147gr bullets are physically longer than 115gr or 124gr bullets for the same caliber. But if you'll look (and measure) deep inside your case, you'll see that at some point the case wall starts to get thicker. So you can end up with a "Catch 22" situation where the barrel is telling you to seat deeper, but the case can't physically accept a bullet seated that deep !! You MAY have safely shot thousands of XTP bullets in 115gr and 124gr and this never occurred, but the longer 147gr bullet MAY be trouble in some barrels. See the cartoon below....

AqEIWkYl.jpg


And that my friend is the problem with a GENERAL reloading board like this. You may get great advice from someone who loads for a Brand A, but you may be shooting Brand Z. The guy loading for Brand A says "Not a problem", because it isn't and never has been.... on his Brand A. While the exact same OAL may be a BIG problem for you on Brand Z.

So advice from several responders can each be True, but may not be the truth for you and your needs. Just remember: All barrels are different.
 
Are you aware that not all 9mm cases are the same size, even by their manufacturer. You may want to check your case length and
if you have an assortment of different brands. The different lengths will surprise you.
 
Another reason to plunk the chambers of ALL the guns you will be shooting in-

Some guns are notoriously short. I have a CZ P-10S that doesn't like anything longer than 1.085, A P-01 that needs 1.95 and a Tisas 1911 that will feed and shoot anything.
 
I ran a bunch of loads with Quickload and entered the predicted MV and Pmax one Saturday morning many years ago when I was bored. This graph shows that the muzzle velocity increases linearly with increasing seating depth, but the pressure increases exponentially with seating depth.

With a massive case like a 44 Magnum, the seating depth makes little difference but with a case already nearly full like 9mm, a small decrease in volume leads to a big increase in pressure.


smFrYEiV_o.png


Early in my reloading days, I made some bullets out of hot melt glue and shot them with a primer only in my 357 gun in the garage. When seated normally, the bullets didn't exit the barrel. When I seated the bullets all the way into the case, they passed cleanly through one wall of a carboard box. I don't do that anymore because the primer smoke contains lead from the lead styphnate primer compound.
 
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