C.O.L ??? Hollowpoint JHP vs RN FMJ

[RedDuc]

Hi reloaders.

I'm trying to find a manual or reference to the proper COAL numbers
and if there is a difference for a 180gr FMJ vs 180gr JHP projectile.

The bullet dimensions are different (i.e. The JHP is longer) and so if I keep the COAL the same the bullet will obviously sit a bit deeper in the case. This will change the the pressure within the cartridge right?

All things remaining the same and I load the powder for the same bullet weight.

Do I need to concern myself on the COAL?

ie the Hogdon's guide says:

for an 180gr HDY XTP the COAL should be 1.125"

which is typical for .40 S&W.


Suggestions???


Thx

 

[tjhaile]

Don't worry about chasing a number from the manual. Make a dummy round with the bullet seated a bit long and use the barrel from your pistol as a gauge. Gradually decrease OAL until the dummy round drops freely all the way into the chamber. Save the dummy round to aid in resetting your seating die when you load different bullets. You may end up with different OALs for the two bullets depending on shape.

Once you have determined the correct OAL, it is time to work up a load from the starting charge. I would expect that the powder charge you choose for the JHP will result in lower pressures if you substitute the shorter FMJ bullet, but test both before loading large quantities.

 

[Wrathchild]

Just making a dummy to the lands may end up too long. Make sure it loads and feeds nice from the mag. I don't think too long is an issue, too short is.

 

[curtmg]

Fits the magazine? Feeds reliably? Over the Minimum OAL?

If yes to all three, you're ready to start working up your load. You probably should work up the load, but you're unlikely to have much trouble with just using the same load, so long as lengths are reasonably close and you're not too close to the max.

 

[RedDuc]

@tjhaile

I 've been doing more searches and see you've posted this type of method in other posts.
Thanks for placing it here again.

I did exactly what you said and managed to get a bullet dropping all the way @ 1.146" COAL
which by my calculation puts these JHP bullets sitting 0.014" deeper into the case than FMJs of the same weight.

They seem to fit and feed properly.

I'll start loading up based on the starting powder amounts... but I should be good to test fire rounds, yes?

I have a chrony so I assume should be expecting somewhere around the low end of the velocity rating correct?

I think I'm just overthinking the possibility of creating too much case pressure by pushing these bullets in deeper than I was expecting.

Thanks again all for the advice..

 

[rdgietz]

What powder are you using? There are charts from various powder manufacturers that will give you a good range of powder charges to try OR YOU SHOULD BUY A RELOADING MANUAL!!!. Keep in mind that a longer OAL will reduce your velocities from the charts supplied using a standard OAL..

The longer OAL will give you some cushion so you dont have to worry too much about exceeding recommended loads and pressures.

I would load up 5 rounds of each powder weight and then chrony them to verify the velocity... If you are loading for a powder factor this will dictate your final load..

RDG