10FP 308 case length and my lands measurements

[fastex500]

I've been working up some loads for long range and have gotten my bullet, powder, primer and cases all worked out, so I'm on to the OAL settings.

Well..... I have measured the length of a case with 178 gr Hornady A-Max in my stock 10fp heavy barrel and the bullet doesn't hit the lands until a COAL of 2.901". I know the A-Max is a long skinny bullet, so the ogive is further back.... But that seems like a long throat. Should I even mess with pushing the length into the 2.890" area, or just use the 2.835" that seems to hold a good consistent group from previous loading?

[Aircraftmech76]

My customized Savage 12FV has a jam length COAL of 2.825" with the 178. Your 10FP sounds like it's got quite the long throat. Is this a centerfeed action? If you've got a throat that long, you might consider trying some 208 AMAX's. They perform superbly at long range (especially when pushed with RL17), and if you've got the throat and action length to run them, you might look at that option. For reference, I use the Stoney Point OAL (BTO-Base To Ogive) gauge (now Hornady LNL), and my BTO measurements for both the 178 and 208 AMAX are 2.197 and 2.222, respectively. This gives the 178 a jam length COAL of 2.825", and the 208 a jam length of 2.947". My rifle doesn't seem to care what COAL the 178's are at; they run 1/2" or better with everything from .005" to .030" off the lands. Good luck with your loads!

Kevin

[fastex500]

Thanks for the info Aircraftmech. My rifle is a pre-accutrigger stagger feed. My measurements were using a slotted brass casing and one of the 178 A-Max bullets. I measured it 5 times with 2 different bullets and got a COAL of 2.900-2.901 every time. I have no idea how many rounds are thru the rifle... I've put 400 thru it over the past 6 months, and not sure how many before I owned it. She still holds great groups (I was shooting 4" clays at 830 yards), so I guess there is no reason to mess with a good thing, I was just surprised at the throat depth as well.

[Aircraftmech76]

No worries bud. My 12FVSS is a staggerfeed as well. If 2.835" shoots that well for you, I'd say stick with it since it is a compatible length for your magazine. What kind of powder and charge are you running with your 178's?

Kevin

[fastex500]

Best so far is a 44.2 gr load of RL15 with Federal GMM primers in mil brass at the 2.835 length getting me 2630 fps.

[mil-dot]

178's A-Max measure 2.218" using a Hornady comparator and measuring to the ogive. 2.218" is pushing it all the way to the lands.

Jesse

[fastex500]

Jesse, That sounds about right. My COAL to lands of 2.901" puts it at around 2.270" camparator measurement to the ogive with the 178 AMax..... so I guess I'm only around 50/1000th off from others. My 2.835" gives .06 jump, relatively lower pressures than 2.800 and seems to be happy. Sometimes reloading voodoo gets me thinking too much.

As Todd Hodnett says "the bullet's the truth"