Does COAL matter if the round chambers in my rifle smoothly?

[BoiseKG]

So I have started to reload .308 and I am having issues getting an accurate measure of my chamber (using hornady gauge) in my Savage 10FP-SR. So I made some dummy rounds and if they chamber smoothly does the COAL matter. The dummy round is 2.905 and as far as I can tell no issue with chambering this round as in it feels as smooth as if there was no round in there at all. Like i said I'm new to reloading and if I need to put more info let me know but I appreciate any info on this.

Thanks!

 

[leadbullet]

Absolutely, smooth feeding is so much more important than accuracy. Who needs load development with a smoothy.

 

[WaltHer]

The short answer to your question is yes, COAL matters even if the round chambers in your rifle. The amount of jump that the bullet has before it engages the rifling can dramatically effect your precision. The trick is to find the sweet spot for your rifle/projectile/powder/primer/case etc. As you probably have begun to figure, there are a lot of variables to contend with. SAMMI spec for the .308 win is 2.800", and that is a fine place to start. Many shooters find improvements in precision by loading longer than spec. Some competition shooters will go so far to "jam" the bullet to a point where it is seated .001-0" from the lands as a way to get the most precision despite increasing wear on the throat of their barrel. For shooter utilizing a magazine fed semi-auto, this may not be possible.
For me, the longer answer goes something like this: First, stop thinking in terms of COAL, at least for conventional (non-solid/CNC turned projectiles.) Think in terms of case-base-to-ogive (CBTO). For an introduction to CBTO measurements start here http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-1/ and here
http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-2/ . This will help move you past inconsitencies in your projectiles leading to inconsistencies in your results.
For a good instructional video on precision reloading, and load development please let me recommend this video:
Reloading for Long Range Hunting It has been an invaluable tool in helping me refine my reloading technique. And lastly, if you want an even bigger glimpse into the factors you're up against, please consider either of Brian Litz's fine books or video.
Let us know more about your load development, and results.
Best Regards, Walt

 

[BoiseKG]

Thanks Walt for the info. To elaborate more I do plan on doing load development as this is a precision rifle I put together. As of right now Im learning a lot of the reloading stuff. I guess i was wondering if it was more or less safe to start with that COAL as it chambered in my rifle.

 

[Dogtown]

Start with the COAL spec for that cartridge and adjust the seating depth TO your chamber/barrel. That's the point he's trying to make. Just starting with an arbitrary COAL that still closes in your chamber is a bad idea.

 

[Layton]

Take some empty unprimed cases, put a bullet just barely in the mouth and close the bolt with it in the chamber. Measure the COAL. Do that a few times and take the average. That will give you you max COAL touching the lands and a starting point to back off from. If you dummies are withing a few thous you may want to back off a little to start.

L

 

[hlee]

To reach within 0.05" of the lands in my 270 with 130 grain Barnes bullets, the loaded oal is outside the max oal for the round. The cartridges load smoothly, fit within the mag, and the bullets are held firmly by the neck tension. So, in my experience, COAL does not matter.

 

[CH Luke]

I have a Savage 12 VLP in 308 with a stock 26" 1:10 barrel. When I started hand loading a few months back I discovered that Sierra's website had load recipes in PDF using the same action and barrel with a 2.800" COAL on 2.000-005" cartridge for their SMK 168 and 175gr BTHP's. So that's where I started.
Later when I bought a gauge I discovered the Sierra spec was right on the money providing .020" jump. Not sure if it's a characteristic of my rifle and bullet combo but I also discovered a noticeable improvement in my group size once I got closer to the max charge in the Sierra load data.



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[redneckbmxer24]

Do you have some rounds on the barrel to break in the throat and get rid of the burrs from machining? If not you should do that before attempting to find the lands. Does that round at 2.905 fit in the mag with at least .020 clearance? Fitting in the mag and reliable feeding is much more important to me than touching the lands.

If you have shot the rifle, and they fit color the bullet with sharpie and see if you have rifling marks. That's how I find the lands, I never could get the hornady tool to work for me. Don't worry if you can't touch or get close to the lands. Most bullets shoot just as good jumping and you don't have to worry about an imperfect bullet seating and the ogive is a bit further out and it jams. I like to load out as long as possible to get the case capacity but my first thought is always mag fit and feeding. It's never a bad thing to know exactly where the lands and are how far it's jumping though.