Seating depth and neck tension question

[Centurian22]

I was just loading some .308 for a work up (Federal cases once fired from my rifle, neck sized, CCI LRprimers, IMR4895, 168gr BTHP Sierra matchkings), first time loading out closer to the lands on my rifle (first workup I did all at 2.80"), and I noticed something. First my lands are at an overall length of 2.845" with 168gr SMK's and this length luckily fits in and chambers from my mag. Seating to 2.835 (which to the ojive is 2.174) trying to stay 0.010 off the lands, only gives me 0.208" of "seat" into the case not counting the boat tail. To explain better: I measure the length when I set the bullet on the case by hand, then measure after its seated and the difference is only 0.208. I know the standard is seating one caliber length into the case which would be .308. Neck tension is good as I am unable to force the bullet any deeper by pushing it against a wooden bench with significant strength. Are there any other concerns with not having more bullet in the case or is this common with loading long out to the lands (as I imagine it would have to be)? Thanks!

 

[918v]

You imagine correctly.

I found that chasing the lands is a waste of time unless you have a short freebore. Then you can chase the lands all you want and soft seat the bullets even. But that requires a custom chamber.

 

[Centurian22]

I'm trying a method learned from I think gamestalker on another thread. Starting load dev at the longest COAL I plan to use (2.835 in this case), find my 'node', then try seating deeper just to see if it improves anything. I need more trigger time anyways so I don't mind playing with some factors while I'm practicing. Plus I'm obsessive with details so it will give me peace of mind to know I explored all options possible to give my loads the best chance. Then from there I can see about eliminating steps to see where the point of deminishing returns is.

First thing I plan to check is how much my Lee Perfect Powder Measure varies with IMR4895 and if there is a noticeable accuracy difference between perfectly weighed/trickled charges or just the drops as they fall. I could save SOOO much time if I could just trust (and spot check) the drops like I do with my 9mm and titegroup.

 

[spitballer]

Good question centurian, I've got some 40 grainers that will be .030" over in my sporting .223 chamber if they're not seated too deeply into the case neck, and I'd like to hear from anyone else who has done this sort of thing.

 

[Andrew Leigh]

Seating depth affects tension, if you are not using the entire length of the neck that is. Your given example would mean that you are running at a third less tension than you could have had, having said which clearly you have sufficient tension so you should be OK. What is more important for me is that whatever neck tension you have is equal across all loaded rounds.

Seating depth can also affect run out.

I am wrestling with distance to the lands myself. I hear of people quoting that once the node has been reached then to seat a little deeper. Other speak of groups miraculously closing up. People chasing as small a jump as possible. Just today I loaded up and went to the range with my 6.5mm I was at 2 705 fps and seating deeper by 0.012" results in a 4fps change in velocity so seating from 0.040" out to 0.086" saw just 16fps change in velocity.

With my .375 I cannot get closer than .25" from the lands yet have achieved .28MOA?
Factory ammo has no respect for any chamber and comes out at SAAMI specs and shoots sub MOA.
My 6.5mm shoots 0.5MOA whether 0.100" or 0.024" off the lands. As long as the speed remains the same the accuracy is there.
It is not the distance to the lands that counts but the resulting speed change which comes from the pressure change. I believe that we confuse distance to the lands with the speed.

 

[Centurian22]

All great info. I love learning as much as I can online but also must learn some from personal experience and I think this is just one of those things. I'll see when I get to the range. All this fine detail stuff may be lost on my 'entry level sporting rifle' (Savage Axis) or I may put holes in paper to shut up the nay-sayers. We shall see. I have figured out that I'm happy with the neck tension and no longer concerned. COAL measured off the Ogive with a Sinclair hex but comparator was VERY consistent too. 2.174 for 38/40 one 2.175 one 2.173. Amazing compared to the +/- .009 when measured at the tips (2.834-2.843).

 

[gamestalker]

I seated .010" off, with 110 gr. TNT's in a bare bones 700 SPS using a stout charge of RL22, worked up of course. My point being, the groups I was getting at almost 3700 fps were 1/2 and better up close to the lands, even with a light super high velocity load like this. I didn't find another accuracy node that was as tight at further off the lands either.

It's worked this way for me for better than 30 yrs. with nearly every stock rifle I've loaded for. Granted, I've been fortunate that most of the rifles I load for have relatively short throats, so I never struggle with soft seated bullets concerning me or causing problems. Now, there are some rifles, bullets, and powders that just don't fare well in this respect, but for the most part, I find one of the most accurate nodes to be up close.

GS

 

[spitballer]

Obviously, one of the nice quirks about bolt action rifles is that one can use fire-formed cases and seat into the lands and not have to worry about the bolt closing completely and consistently every time. Lately I've been loading .030" over for all my rounds and use the lands to seat with. It seems to be a good system, but I'm probably sacrificing velocity; I doubt I could penetrate a steel pot even at 300 yards!

 

[gamestalker]

Velocity issues really? I punch 1/2" steel with .270 win. 130 gr. PSP 3100 fps load using IMR-4350. Same thing with 7 mag and 120 gr. PSP, 130 gr. and 140 gr. with RL22. I always seat at to the lands or just off. I tried with a 110 gr. TNT, but it just barely failed to punch all the way through, probably not enough projectile even at 3600-3700 fps..

GS

 

[Centurian22]

Why would seating to the lands sacrifice velocity? Unless due to running a workup at a shorter COAL then seating further out, in turn increasing internal capacity and decreasing pressure? Even then I would think the change to be minimal. Also running a powder workup from your desired coal should allow you full access / range of velocity shouldn't it?

 

[W.E.G.]

I try to seat bullets to a depth that roughly equals the diameter of the bullet. I feel that the bullet is well contained in the case when I follow this practice. Deeper or shorter may work for you.

If you are trying to seat bullets to some specific relationship to the lands, you are probably shooting a custom gun in a benchrest competition, or you are attempting to imitate some "nugget of wisdom" that gets passed around in shooting circles, but when tested usually shows itself to be of little or no importance.

 

[spitballer]

Well I haven't used the chrony yet on this new load but I pretty much finished with my dial-in this morning and I'm looking at 21.8 grains of IMR 3031 with 55 grain bullets. Seated off the lands I would be using more powder and probably getting higher velocity. I think.

 

[Andrew Leigh]

I try to seat bullets to a depth that roughly equals the diameter of the bullet. I feel that the bullet is well contained in the case when I follow this practice. Deeper or shorter may work for you.

If you are trying to seat bullets to some specific relationship to the lands, you are probably shooting a custom gun in a benchrest competition, or you are attempting to imitate some "nugget of wisdom" that gets passed around in shooting circles, but when tested usually shows itself to be of little or no importance.

I echo your sentiments. As a hunter I believe we take too many things from the bench boys which at my hunting distances (max 300m) cannot be resolved. I know of hunters who neck turn with poor results as they have larger chambers than the bench boys. Some chase the lands and then cannot get the rounds into the magazine causing a rethink.

The greatest improvement I have had in accuracy as a hand loader has been through practice and not employing nth degree reloading nuances.

 

[W.E.G.]

Well I haven't used the chrony yet on this new load but I pretty much finished with my dial-in this morning and I'm looking at 21.8 grains of IMR 3031 with 55 grain bullets. Seated off the lands I would be using more powder and probably getting higher velocity. I think.

I'm not sure where you are trying to go with your load.

Use whatever works for you I guess.

Even using .223 data instead of 5.56 data, it looks like your load is really under-powered, running much slower than the "normal" velocity for a 55-grain bullet.

 

[Centurian22]

For those following this ill post here but will also be starting a new thread with results:

I'll start with Gamestalker I *Bleeping* LOVE YOU!!!

Had an awesome day at the range! Found my winner in the upper right. Best group I have ever shot in my life. 4 rounds, 3/8" center to center @ 100yards in variable winds from calm to 12kts. .308 once fired fed cases, CCI LR primers, 41.2gr IMR4895, with 168SMK seated at 2.835". One slightly elongated ragged hole! I was stoked! And before someone tries to call me out, I was shooting round robin back and forth working my way down. When I shot this group I skipped the last three (40.8, 40.4 40.0) as there was no way they could compare. 43.2 wasn't bad either at 3/4-7/8". Oh by the way this was shot with a SAVAGE AXIS and Walmart Centerpoint scope! So all the haters and nay-sayers that dog on these 'entry level' rifles can..... potentially reconsider their opinions! LOL




Hey W.E.G. Any chance you're willing to punch in my load to quick load and shoot me the data. Just would like a rough idea of my velocity for building some tables. 22" 1:10" twist barrel, neck sized cases trimmed to 2.010, not sure what more info you need.

Thanks in advance!