zero 147 JHP lenght.

[sigsauerfan]

hi all. i don't post a lot since there's so many much more experienced shooters/reloaders than me here,i'm quite shy to say anything lolol...but i'm always over here looking at the mine of infos BEF realy is ....

on top of that, all infos needed is always available with the search function ....however, i couldn't find a clear answer to my ??,so here i am looking for a precise answer.

ok. since awhile, i elected my stock G17 as my main production gun, we mix well together.

my ususal load for that gun is 3.8grs of VV340 under a cam-pro 147Grs fmj-rn at 1.130 coal wich gives a 920-950 fps.

i've got a batch of zero 147jhp to try, so i've mesured those bullets to discover that the bullet lenght is 0.670 compared to 0.639 for the cam-pro FMJ-RN bullets i'm using normaly.

i wonder IF the narrower shape of the 147JHP tip means that i can load longer in my stock glock, or should i keep the same coal ,then reducing the load ?? .

given the longer bullet lenght, if i keep the same coal(1.130) , the space used inside the case by the bullet base will increase because the 0.030 differential in lenght of the JHP(0.670) and the FMJ-RN(0.639), wich mean higher pressure right??

i'd like to keep the coal that work well in my G17, but i've heard that JHP's can be loaded longer for any given barrel because of the tip shape of the JHP bullet allowing a trouble free feeding (HP).....is that true??

Edited April 22, 2011 by sigsauerfan

[CocoBolo]

When I'm fitting a new bullet to my gun I start by sizing a case bell it then insert a bullet and keep sizing it down till it just fits the mag any longer it would not fit the mag. I take the bell off the case with the crimp die. With the barrel out of the gun I push the dummy round into the barrel all the way with my thumb or press the barrel on the reloading bench. Now we know the absolute longest OAL that is possible to fit in the gun.

Next step is to measure it and say it comes out at 1.175, you know that your loader will vary slightly so you knock .01 off the length and start out with 1.165. Load up a few dummies in a mag and cycle them thru the gun very slowly feeling for how they feed, if its ok then try it fast. Please note that no where in these instructions does it say to put a primer or powder in these dummie rounds.

IMHO this is how I start out with a new gun or bullet. Common sense wth the load data and adjust the load depending on OAL and always start low and work up looking for pressure signs. Crono.

Shorter rounds more pressure but more velocity as well, so at the same velocity in a reasonable length the pressure should be about the same. A slower powder will reduce pressure some but may not create the effect that you hoped for.

[sigsauerfan]

hi cocobolo. i hope you're going fine .

i realy appreciate the great advices you're providing . the infos shared with me have always proved to be very usefull in my reloading endeavors. thanks !!

looking at it deeper,i realize that my concerns are only related to my fail at determining some sort of '''first glance reflexes ''' of calculation when trying to figure out quick the ''' coal reduction % VS load reduction % ''' conversion in a precise unfailable manner....i suspect that i hate '''working up''' my way through the usual technique (load incrementations) as i should do lolol. i'm guilty of trying to nail the recipe inside 2-3 increments.

thing i've noticed is that the tip of a JHP goes deeper in the chamber before touching the riffling.....

from then on, i asked myself IF i should put the extra bullet lenght( 0.030) in the chamber, or inside the case , this allowing me to keep the exact same powder charge!!!??!!!

Edited April 22, 2011 by sigsauerfan

[kevin c]

I think I see a few issues related to the OAL and different bullet lengths that you need to consider.

First is what will fit in the magazine. My understanding is that small frame Glock magazines limit the OAL to 1.155". Longer supposedly will cause jams as the round binds in the front and rear.

Next is what chambers in the barrel proper. Too long/too short, either one may not "break over" correctly, and cause feeding jams. Most factory chambers, from what I know, will take most bullet profiles if loaded to standard SAAMI specifications. Match chambered aftermarket barrels may not be so forgiving, and only testing with the aftermarket bbl in the gun with rounds loaded to the OAL and using the bullet in question will tell.

Extra long rounds may also bind in the rifling, as CocoBolo pointed out. This applies especially to aftermarket barrels.

The next issue is internal case volume and the change in pressure. A longer bullet loaded to the same OAL as a shorter bullet will take up more of the internal case volume. With the same powder charge you will have higher pressure. Loading the longer bullet out to an OAL longer by the difference in length of the bullets will get you close to the same pressure (but not exactly the same, since, in your case, the JHP is a flat based slug and the FMJ is likely got a dished base because of the crimped over jacket).

All together, it seems to me that you should load longer, dropping your powder charge and working up again. You should test some longer dummy rounds for cycling function, as Coco Bolo suggested.

Edited April 22, 2011 by kevin c

[Hi-Power Jack]

i suspect that i hate '''working up''' my way through the usual technique (load incrementations) as i should do lolol. i'm guilty of trying to nail the recipe inside 2-3 increments.

IF i should put the extra bullet lenght( 0.030) in the chamber, or inside the case , this allowing me to keep the exact same powder charge!!!??!!!

Sig, as you said, it will take time and experimentation to

work up your load properly.

But, it is worth the effort ...

You really should "start all over again" and start slowly

and lowly (lower powder charge) - and work up slowly.

Your OAL may affect accuracy as well - my gun is more

accurate at 1.12", but more reliable at 1.13", so I lost

some slight accuracy but gained reliability.

There really isn't any "magic formula" for YOUR gun -

pull the chrono out, and try some accuracy shooting -

and you will be rewarded with "the perfect" ammo for

YOUR gun.

Good luck.

Jack

[sigsauerfan]

a little update about my quest for a good recipe involving the longer bullet (0.670 of the zero 147JHP VS 0.640 for the cam-pro 147 FMJ-RN ) that is the zero 147 JHP.

after a quick re-check of my G17 chamber,obviously i may load as long as 1.155 AOL without touching the riffling with the JHP , but after a mag test and some dummies i doubt it would be reliable in match conditions.

i could even use the vihtauori chart wich (funnily) stipulate 1.142 AOL (for every 9mm loads), 0.012 longer than the usual 1.130 AOL wich work flawlessly in my gun...

sooo, i've decided to keep the AOL at @ 1.130 wich means ¸+ 0.030 IN the case.

so according to the viht chart i've reduced the charge to 3.5/3.6grs of VV320 @1.130 aol , instead of the 3.8grs@1.130 charge used with the shorter RN bullet .

i'll go through my pro-chrono digital monday to see how it goes.

since viht stipulate the 147HP/xtp in combo with vv320 start at minimum load :

(3.1grs at 1.142aol good for 784fps)

TO

( maximum load :3.9grs at 1.142 aol good for 978 fps)

i've figured out that my 3.5grs @ 1.130 should roll around 930-950fps (perhaps a lill more) wich is good for minor.

Edited April 23, 2011 by sigsauerfan