308 mesaurments w/Hornandy Comparator

[HermanH]

My first time reloading 308 (I've loaded .223 in the past)

I'm using my Hornandy OAL gauge in my Remington 700 VSF.

Bullet being measured: Sierra Matchking 155 gr. BTHP

I took 10 measurements, threw out highest ( 2.354 ) and lowest ( 2.346 ).
Average of the remaining 8 was 2.347 (base to ogive).

Looking at this, it appears to me, only 3mm of the neck holds the bullet.

I removed the comparator die and measured the COAL based on the 2.347 ogive measurement and it sizes to 2.918.

According to the Hornandy guide, I should back-off from the lands, 0.020 - .040. This would put the COAL at 2.898" - 2.878"

As for the rest of the actual components: CC#200, Varget, Hornandy and Nosler match brass, once fired, trimmed to 2.005".

My question: should I measure all of my loaded cartridges on the ogive measurements, minus the back-off (I'm going to go with 0.025 ), or on COAL? My gut tells me to leave the Comparator die in place and go for 2.893" ( 2.347 - 0.25 ). The reason behind using .025 is if I'm off by +/-0.005, I'm still ok.

TIA

[FLIGHT762]

I shoot a lot of 155's in my four 308 rifles. I load them all to a COL of 2.775" to let the bullet seat properly in the case neck. These bullets are short. Even with a lot of jump, these bullets will shoot .5 MOA or a little under. In my GAP 10, I'm getting .4 -.5 MOA pretty consistently with the 155's @ 2.775".

I want my bullets to have at least one caliber (.308") of seating depth in the case neck, giving good neck tension.

Have you actually shot any of these bullets loaded to 2.800" or so?.

Remington factory rifles have a very long throat and seating any bullet just short of the lands are going to give you lengths that will not feed from the magazine.

I don't shoot matches or shoot for money, but the 155's @ 2.775" are plenty accurate for me and feed 100% from the magazine.

[HermanH]

That's what worries me; the amount of actual surface around the bullet doesn't seem to have a lot of neck tension with the measurements I took.

I even compared this to the boxed Hornandy Match ammo I didn't shoot yet. They appear to be seated well but COAL is 2.797 on average, however, those are 168 gr. So based on the boxed ammo and my measurements, I'm 0.081" further. Based on your load data, I'm a full 0.103" off, which is significant but it sounds closer to the Hornandy Match loads.

I guess I can try using your data, then matching the boxed ammo COAL, then what I measured and see how all 3 do.

I'm definitely going to need to chrono these things. Thanks for your reply.

[baih777]

I just measured my rem 5r last week. I am also using the hornaday gauges.
my chamber measured 2.34 with 168gr and 2.32 with 175gr.

as far as the neck feeling loose. resize the case again. BUT... remove the decapping pin and collar. it will be tighter. try the first bullet in your rifle to make sure it chambers.

I am actually working on loads for my savage right now. chamber measurements are .010 less than the Remington. I am seating my bullets .010 less than the measured length.

as far as the calipers. I use the Harbor Freight Digital calipers. works better.

[BLR81]

The 155 gr SMK's are only 1.150" long give or take a few thousands with the varying tip. But, they are also a BT, which doesn't touch the neck so can't be included as part of the neck tension.

The length of the bullet minus the BT is approx. 0.980, so considering your case length of 2.005, your 2.893 target length leaves only 0.055" of bullet touching the neck. If you're single feeding your bullets for a slow fire match, you might be able to get away with that although I like to go with at least 0.125. But, if your loading a magazine or your shooting a semi-auto, that isn't a good idea.

The SAAMI max length for a Win 308 is 2.810 and even that only gives you 0.175" of bullet touching the neck. But, if you use the old adage that you need the calibers length seated in the bullet and you don't discount the BT then 2.810 could be enough.

My Lee 2nd Edition recommends 2.775 for the 155 and Varget. If you're shooting a bolt gun, you could start with the 2.810 and experiment going longer and shorter but not much longer. Also, remember that if you go longer then you're reducing overall pressure and muzzle velosity unless you're actually into the lands.

For semi-autos, stay with the recommended COAL, and live with the jump. You may find that the bigger Jump gives you better accuracy then being .025" off the lands.

[HermanH]

My Remington 700 VSF is a bolt with 4 round capacity. It's just a target rifle (sorry if I wasn't clear.)

I forgot to mention I do have a Redding resizing die with individual neck collars - I had measured all 4 mfg. ammo before firing them, and based on Reddings instructions, I obtained .334 and .335 collars for the necks, to hopefully put the proper tension when I seat the bullets.

Thanks again for the advice. There is of course, one way to do this and that's with the Hornandy Reloading manual with the recommended COAL of 2.800 of a similar BT round but it's not a hollow point ( 155gr. A-Max ). Max. recommended is 2.810 as mentioned earlier.

Then there's Hodgdon with a COAL of 2.775 as FLIGHT762 has recommended.

I'll research other sites for more info. In the very worst case, I could go with 2.800 of the A-Max bullet and see what 10 of those will do.

[Khromo]

I've got a 700 VSF, Herman, and while I don't recall the exact measurements, my experience with trying to get a tight seating depth mirrors yours. I couldn't even get close to the 0.020-0.040" off the lands I was attempting to get!

The gun shoots at or under 1/2" anyway, like clockwork, so I try not to think about it! A buddy has a 700 that he got the barrel set back on, to minimize the throat length, and the gun really didn't shoot any better after the barrel work.

I've taken to seating at maximum magazine length or about 0.250" of surface contact, whichever is shorter. If the manual specifies a length with less surface contact, I will use that. The target doesn't lie!

[HermanH]

Khromo: thanks. Just so everyone else knows what I'm up against, I took a fine point Sharpie to mark where the neck ends on the 155 Gr. Sierra Matchking and as 'best' as I could, measured it to where the boattail begins for both the comparator measurement and at 2.800. The difference is significant:





At .073", it's well under my estimated 3mm (which would be 0.118"). But at 0.167" (again, very approx. as best as I could), it looks much better.

[J-cat]

Tangent Ogjive bullets like Sierra and Nosler jump very well. You can get excellent accuracy by loading them to magazine OAL. That is the best place to start. Once you are familiar with the rifle you can experiment with different OALs.

FWIW, my TRG22 shoots .25" groups with an OAL of 2.800" with 175SMK.

[HermanH]

Yes, I think it's time to stop asking questions and load up a few... Thanks again everyone. I'm sure I looked like I was being a bit overly cautious but as I always tell my kids, the only stupid questions are the ones you never ask.