another 9mm question...

[texasgunhand]

After looking through my books and looking through your suggestions on the win231,,,124gr FMJRN
I have a question about OAL,from what my books say and your oal it ranges from 1.13 to 1.15.

My question is knowing that the more you compress a 9mm load the more pressure it builds.
Would there be a huge or small leap if i were loading say 4.3gr of win231 at 1.15 then droped it to 1.13 or is the pressure difference not that big a deal at that small of an incremental drop?
Or would it speed it up a lot if i went from 1.15 to 1.12 or not really?

Iam trying to get a grasp of how much OAL efects pressure and speed. My glock 19 seemed to shoot. Blazer brass 124 gr fmj really well,i had saved one to measure OAL of it but now i cant find it.
I measured some factory 115 gr fmj i had but they were around 1.15 or so. Sorry about the noob question.lol

[williejc]

Google this: 9mm setback question to read a good discussion of the topic in the The High Road forum.

The 9mm case has a low volume but is loaded to high pressure. Increasing bullet seating depth reduces case volume(and air space between powder and bullet). The result is higher pressure. How much higher depends on the powder's burning rate. Pressure jump will be more pronounced with fast burning powders like Alliant's Bullseye or Winchester's 231. Maximum loads will show a giant pressure hike.

Your question asked the effect of changing seating depth by .02 inch. The answer must consider all the variables mentioned. My advice is select a manufacturer's suggested over all length. Next, use techniques that will prevent bullet setback. NO setback=No problem.

Seating a 9mm bullet .02 past the recommended o.a.l. is a poor idea--especially if fast burning powder has been used to produce a maximum load. I repeat. Work up a safe load using proven methods to prevent bullet setback. Remember that pressure increase does not necessarily produce a corresponding velocity increase.

[texasgunhand]

So if the book calls for 1.13, and i make them 1.14 or 1.15 it isnt gona change much?

[williejc]

Correct. Overall length can vary this much between rounds of the same batch. Slack or 'slop' in the press or not moving the handle all the way down every time until the ram stops its upward movement are two factors determining o.a.l. In the case of cast bullets, lube accumulation on the seating stem will affect o.a.l.

[texasgunhand]

So factory115gr 9mm fmj pretty much seems to be 1.15.. FromThe speer and hornady books say they want it at(Speer1.135)....(hornady 1.100)..and for the 124gr fmj..(speer1.135) and (hornady 1.150)..

I dont have any factory 124gr fmj to measure. What iam getting at here is what if i load the speer data for the 124 gr fmj but instead of making it 1.135 i made it 1.150 what would i be loseing?

Could some one measure a factory 124 fmj rn and see if its 1.150 like the federaland blazer 115gr i have,just to see if they are just making both the 115 and 124 at 1.150 OAL.

Thanks for the help iam just trying to figure out coal and everythings different.after i get this down i think i got it.

Also iam using the lee FCD at half a turn for a light crimp, is this about right??Its in there good, but you can also go a full turn for more crimp of course.

[masan]

CO AL for factory 9 mm will vary a LOT From brand to brand. You will lose nothing by loading your 124's at 1.150, so long as they fit in your mags.

Set your crimp die up only enough to straighten the case mouth (only remove the bell of the case mouth). 9mm head spaces off of the case mouth, over crimping can lead to your cases moving past the chamber and getting stuck in the rifling. The crimp on 9mm is not to hold the bullet in, the case already does that just fine.

[Onyx Z]

Yep, the crimp is only to straighten out the case mouth belling. I would not use a FCD on a semi-auto pistol round since they headspace off the case mouth.

[LoboTBL]

Actually, the factory crimp die is EXACTLY what you want to use on semi-auto pistol ammo. The Lee FCD squeezes a larger area of the case mouth evenly around the bullet as opposed to a roll crimp which is designed to just bend (roll over) the very edge of the case mouth into a cannelure. A roll crimp can allow the round to go past the point where it should be because it substantially reduces the diameter at the case mouth and does not leave a defined edge at the case mouth. An FCD only reduces the diameter a negligible amount and the round will still properly headspace in the chamber.

A half turn is a light crimp, a full turn is a heavy crimp. As long as you don't go past one full turn on the adjustment after first making contact with the case mouth, you'll be fine. I set my FCD somewhere between 3/4 turn and full turn, it depends on the brass. It sounds like you have the Lee carbide FCD/post sizing die which is an excellent crimp die.

Correct OAL for 115g FMJ is 1.10, for 124g FMJ it is 1.15

[texasgunhand]

Yes , the Lee carbide FCD for 9mm taper crimp.
I have bought a fcd for everything i load exept 6mm, they dont make one. I do need a neck sizing die for the 6mm rem. still i have the F/L set,now i just need to buy a neck die for it,i will only be firing it outa the same bolt action.
Hard to find factory ammo for it anymore ive been looking for some brass for it not readly available anymore.

[bigedp51]

You can make your overall length longer or shorter than what the manual states (within reason) as long as you start at the suggested starting load and work up. And if you notice bullets of the same weight can vary in COL between manuals. The real trick is to set up your pistol and bullet for the proper OAL. (see below)

Below is a very good read for setting up "ANY" pistol and its OAL and not just the CZ pistol. Read the posings by Wobbly it contains some great info.

How to determine Max OAL for a CZ Pistol
http://www.czfirearms.us/index.php?topic=34225.0

[texasgunhand]

A good read thanks for posting,as it says if your oal is longer you reduce pressure.
But iam i loseing speed to?. Say the difference. In 1.12 and 1.15 or is it not really enough to care about? I know the 1.15 will work becouse the ammo ive been using measures 1.15..

[bigedp51]

A good read thanks for posting,as it says if your oal is longer you reduce pressure.
But iam i loseing speed to?. Say the difference. In 1.12 and 1.15 or is it not really enough to care about? I know the 1.15 will work becouse the ammo ive been using measures 1.15..

The answer to your question is only answered by a chronograph or possibly a Quickload guesstimate. But even Quickload needs to be calibrated with a chronograph by changing the burn rate in Quickload until the two velocities match.

With a rifle when fire forming cases I will jam the bullet into the rifling to hold the base of the case against the bolt face to prevent stretching. And the load must be reduced to prevent over pressure.

Bottom line, seating too low can increase pressure and seating too long can increase pressure and normally the manuals are somewhere in the middle.

[masan]

Yes you will lose speed if you seat to a longer oal WITHOUT increasing charge weight. It will not be a lot of velocity drop, if you end up getting yourself a chronological you can measure results for your gun.