Miscalculates seating depth

gitrdun

gitrdun

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I've been a bit embarassed to ask as I miscalculated my seating depth but here goes anyways. The rifle is my Tikka M695 in .338 WM. The bullets are 225gr. Accubonds. I calculated my seating depth by using a rod through the bore and up against the bolt face. I subtracted the lenght of engagment of this same rod agains the bullet end in the bore. From this measurement, I then subtracte by desired distance from the lands, in this case 0.025". The problem as I later realized was the the bolt was engaged uncocked, in other words the firing pin was protuding past the bolt face. My overall bullet length is obviously short by whatever the pin protudes past the bolt face. In spite of this error, my groupings is unbelievable - 3/8" or better. Probably, most of you will reply - so what's your problem? I do like the grouping, but does it make sense? Is it worth my while extending the bullets so that they sit where I wanted them in the first place, try it out. Am I sacrificing potential velocity be seating so far back? :redface:
 
I bet you gained a bit of velocity. Shorter seating usually equates to slightly higher pressures.

How many rounds did you load? You could always make some longer and try them out. Hell, if you are showing no pressure signs, you may want to try a few even shorter.

Experiment. Explore all the variables. That's what handloading is all about.

Worst case scenario: you fall back on on your original recipe.:)
 
If you are getting sub-moa accuracy with a sporting rifle why would you want to change anything??

The "keep the bullet close to the lands" thing is vastly overrated. It is one of these platitudes that keeps being repeated so often that some people start to consider it to be gospel.

In truth it is designed to compensate for any non-concentrate rifle chamber and/or the loaded ammo placed in it. If care and good components are used in loading your ammo, and your rifle is not terribly out-of-spec, accuracy even with a long jump to the land can be very good. Also loading with a bit of jump can sometimes help a re-loader avoid the sudden pressure spikes encountered when approaching maximum loads.
 
I bet you gained a bit of velocity. Shorter seating usually equates to slightly higher pressures
Click to expand...

Having chronographed many loads,I have found the opposite to be true.The closer the bullet is seated to the lands,the higher the pressure.Short seating provides the same effect as a longer freebore wich reduces pressure.
 
First off I agree with Stubblejumper.
Secondly, touching the lands or having the bullet seated out near touching the lands does not always mean more accurate. This is where you have to experiment after you find the load that works best. Every rifle is different some like no bullet jump some may shoot better .060" off the lands. Your miscalculation just happened to put you in the sweet spot, don't mess with it.
 
I think that there is far too much attention paid to tight groups from sporting rifles. Considering what a .338 is generally used for, I would be more concerned with dependable functioning rather than sub MOA groups. If the ammo works through the magazine without hanging up and you get tiny groups that's great, but if you are shooting big game out to a quarter mile, 2 MOA will kill em just as dead - if you can shoot up to your rifle.
 
I can attest to the fact that as the deeper the bullet is seated, the more velocity is lost as I've played with seating depth in my other cals. I did seem to hit a "sweet spot" per say, a little luck here and there is always welcome. Very informative guys, thanks. As suggested though, I think that I will use this load as my "baseline" and experiment with seating a few rounds further in and out just for curiosity's sake. It'll have to wait until hunting season is over though, I don't expect to do anything with it till after the new year.
Boo: I fell victim to that same gospel which you refer too, time to adjust my thinking as demonstrated with the "erroneous" load.

Thanks again. :)
 
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