Load to ogive or COAL???

[SOcalsurferx]

So which is more important for producing accurate ammo. I did a search and couldn't fins a straight answer. I bought a Sinclair Comparator that measures the length of a loaded cartridgh from the base to the ogive. Is this dimension more critical than OAL. I realize variations in OAL will cause variances in case pressure and therefore velocity inconsistencies, but variations in the base to ogive dimension would cause pressure differences as well as that would effect the jump / jam length?

Wisdon appreciated!!

 

[groupshooter22]

Re: Load to meplat or COAL???

I think you mean ogive, where the bullet goes from fuul diameter and starts tapering to the tip. The tip of the bullet is the meplat where the jacket is formed over the core. Yes it will cause pressures to be different. Measuring to the tip is only for magazine fed guns. On a single feed you can put the bullet out to where your gun likes them. Usually a little into the rifling or just a little jump.

 

[janderson0]

Re: Load to meplat or COAL???

I only measure base to ogive, unless its ammo for my AR which is loaded to mag lenght.

Jim

 

[SOcalsurferx]

Re: Load to meplat or COAL???

yep, sorry meant ogive, edited the OP.

I think you mean ogive, where the bullet goes from fuul diameter and starts tapering to the tip. The tip of the bullet is the meplat where the jacket is formed over the core. Yes it will cause pressures to be different. Measuring to the tip is only for magazine fed guns. On a single feed you can put the bullet out to where your gun likes them. Usually a little into the rifling or just a little jump.

 

[bheadboy]

Agree, OAL is only for mag feed situations, the real important data is based on the bolt face to the point at which the tapering bullet contacts the taper into the rifling lands, all chambers are chambered with a throat, and the taper that gradually allows the bullet to enter the rifling. Thus you have two tapers working one on the bullet and one in the transtition from throat to full rifling contact.

The most accurat loads tend to be with these two tapers in close proximity, either slight gap (.015-.005) to slight contact (.005-.010")- as all bullets brands, styles, and even lots are not the same the ability to measure the case base to bullet taper (ogive beginning) is very important- also as throats open up with repeated firing this length will increase so should be checked often

Bob

 

[SOcalsurferx]

So, when you guys are reloading precision ammo, do you even check the COAL? If you know you want a .005 jump and have a comparator or tool to measure the distance from the ogive to the bullet base, is the COAL even an issue? I am shooting a bolt gun of course, so mag length isnt really much of an issue. As far as load development goes, where about is a good place to start? --> .01 jump? Less? More? I know you can play around with this after you determine a goodload recipe. I am shooting 175 SMK's out of a Krieger tube.

Thanks

 

[SOcalsurferx]

Thanks for clearing that up, I have learned sooooooo much in the last few weeks, finally feel like I am getting a good grasp on all of this. I'm due to test out my second batch of 308 handloads with 175 SMK's. the last batch of 3 different powder weights were all sub half moa, a little tweaking here and there and now my brass is fireformed to my chamber, so hopefully I will have a winner or be one step closer!!!

thanks again

 

[bheadboy]

additional input, when jumping you can usually use a slightly higher charge, when in the contact position on rifling, you will build presure, increase burning acceleration and velocity, and may need to reduce charge slightly,
however you need to balance this with what gives a good SD/ES and what shoots, the target is the judge as to jump or touch, the powder load varied to give close ES?SD readings,

I try jump .010, to touch .010 and watch the crono results/presure signs, when ES?SD are good and the case shows no presure signs and i have a reasonable velocity,i go to the range
using this technique i have a number of Rem 700 hunting and pd guns that shoot well under 1/2, my 40x dog guns under .2
Bob