Bullet Seating Depth??

[nosler06]

Just curious how others would go about running a seating depth test. I want to play with the seating depths to tighten up some of the groupings that I have with two of my rifles. What would be the best incriment to drop by from OAL to find each rifles sweet spot? What would be the best number of rounds to shoot at each depth incriment? I was thinking either groups of 3 or 4, but have no idea what length incriment to drop by. I also thought about trying a box of factory ammo to see how the groupings are and measure from there. I have never in 32 yrs shot factory ammo through my Win Mod 70 30-06.

 

[DrMike]

My method is dependent on general bullet construction. For cup and core bullets, whether bonded or not, I usually begin testing closer to the lands. For monolithic bullets, I will begin testing positioned further from the lands. When a load shows small standard deviation, I will begin testing for a node if necessary, in increments of ~0.040 inches. Once a node is found, more precise measurements can be tested.

 

[nosler06]

Right now and have been for 32yrs Nosler Partitions have been shot in both rifles.

 

[RiverRider]

When I have NO idea where the sweet spot is, I sometimes shoot groups of two using increments of 0.010" to see if I can get a general idea where the (or a) sweet spot is. Groups of two don't tell you much about what works, but they can sure tell you about what WON'T work.

 

[PJGunner]

Right now I'm working with three rifle, or will be when it cools down some. Not much fun when it's 100+ in the shade. The bullets I'm working with are the 100 gr. barnes TSX in a .257 Robt. and the 120 and 140 gr. TSX in the 7x57 and .280 Rem. I have them seated fairly close to the lands for the first shot and use a Lyman Tong tool to adjust the seating depth. I'll shoot three, adjust the seating stem down a half turn and shoot another three and so on. At 100 in the shade, it takes too darn long for the gun to cool off. I've come to a couple of conclusions. One is I think the 140 gr. bullets is a bit too heavy for the 7x57 and would be more suited to the .280 Rem. Two, that two rifles exactly alike do not necessarily like the same load. :shock: Until I taught my ex-son in law to load his own ammo, I got "stuck" with the job. Both his M70 FWT .257 Bob and mine like the exact same max load regarding pressure. His rifle is sub-MOA all the way. Best mine will do is is 1.25" on a good day. At first it was more like 1.50" but as I've been seating the bullets deeper, the groups are getting smaller so I'm thinking it's only a matter of time. I have Tong Tools for the "Bob" and 7x57 but not the .280. Would love to find a set. I'm thinking of making a spacer for the seating die for the 7x57 but the thickness of the case at the shoulder may be a problem. I can always make a set up for the Rockchucker to fix that problem.
Paul B.

 

[Richracer1]

I'll initially start with around .020 off the lands or what will function in the magazine. Find the powder charge that gives me the best group size, then start seating the bullets .005 deeper from the original depth and shoot three shots per depth.

For instance, my RUMs are maxed at 3.670" by the magazine, so I start there as they will cycle reliably. Once the charge weight is found, I'll start working back, 3.665, 3.660, 3.550 and so on. Ended up with 3.635 as the OAL and I've used that OAL to develop loads for the other RUMs I have. All of them ended up pretty close to that 3.635" OAL.

 

[Oldtrader3]

I start at factory COAL and go longer, about .015 each increment until I either hit lands or loose group size. Since I mostly shoot PT's, AB's and BT's and I have 50 years of loading history, I don't do a lot of COAL testing unless Nosler change a bullet or my groups open up. All of my rifles except the newest 9.3mm, shoot sub MOA groups. The 9.3 shoots just about MOA and I am working on loads for it, as we speak but it is a hammer and does not need to be sub-MOA!

I am most proud of my .257 Roberts. I took it with careful crafting, from 3 MOA to 1/2 MOA with 85 gr varmit loads.

 

[nosler06]

Thanks so much for the advice. I am going to have load up some more rounds and try to intermix some range with hunting season. I am not sitting too bad with either rifle as they are shooting 1.5" to 1.75" groups at 100yds. Will have no prob dropping an animal with either. Maybe I will play with them after the season ends.

 

[DrMike]

That is certainly MOE (minute of elk) out to, oh, say, 500 yards or so. Of course, all of us want the precision that allows us a greater degree of confidence. Good luck in your season.

 

[nosler06]

I was checking my .308 and right now it is the one that is 1.75" groups. My handload seat depth for this is 2.805" and I see that the Nosler load data shows 2.810" as maximum S.A.A.M.I. OACL. I am thinking that the groups will tighten more should it be seated deaper. I am running 44.0grs Varget with the 165 Nosler Part and CCI200 primers. I have done all the ladder testing and this was the best load that this 70' Browning BLR lever liked. I guess time will tell me once I start doing some seat depth rounds to find where the sweet spot is. I think that I will run 3 shot groups to be confident.

 

[Elkman]

Like already mentioned I start at magazine length and drop .10 at a time. I use 2or 3 shot groups. I am at 2.785 with my .308 right now and its stacking the 168gr. Nosler CC, and the Seirra and the 168 gr. Matchking, on top of each other.

 

[nosler06]

Like already mentioned I start at magazine length and drop .10 at a time. I use 2or 3 shot groups. I am at 2.785 with my .308 right now and its stacking the 168gr. Nosler CC, and the Seirra and the 168 gr. Matchking, on top of each other.

I just checked my 30-06 and the OAL is at 3.380" right now. I look at Nosler's load data test length is at 3.310" for the 180gr Partition spitzer. SAAMI for the 30-06 is 3.340". Wow that is giving a fair bit of range of depth seating. I am just checking do you start at your max length and then go down by 0.10" or 0.010"? It is very interesting that my OAL is only 0.005" short from max on my .308. I think I have a little bit of fine tuning to do still. Both of these rifles have shot under 1/2" groups at 100yds. That is until a whole bunch of powder testing with the .308 and a powder change and part protect pt to spitzer change on my 30-06. I am confident I can get it dialed back in. I hope.

 

[nosler06]

That is certainly MOE (minute of elk) out to, oh, say, 500 yards or so. Of course, all of us want the precision that allows us a greater degree of confidence. Good luck in your season.

Thanks Mike, and how did the moose hunting go this year? I hope you are getting out more this season. I am hoping this weather change we are having will get the elk bugling. I hate hunting in 30 degree weather. Animal is half cooked by the time it gets to hanging.

 

[DrMike]

I'll go look for a moose this morning. The bulls I've seen are all nocturnal, so far.

 

[Elkman]

Like already mentioned I start at magazine length and drop .10 at a time

My typo .010, to late for me I guess.

 

[SJB358]

I start .020" off the rifling or max mag length. Find the most consistent powder charge then start shortening .030/.040" at a time. Usually see what I'm looking for in that range. Then I will split the most accurate to see if it will continue getting smaller. I load 4 rounds per as I wanna have the extra round to assist if I shank one of them.

 

[rick smith]

Several things to consider, has to fit the mag box, has to feed from the mag box into the chamber without a hitch and must not be jammed into the lands. I measure the bullet to be a light touch with the lands, make a dummy round at that length. Check mag box fit and function from same. Then start 0.010-0.015 off the lands. Test 3 round groups with varying the powder charge. Pick the best group and then vary the seating by 0.005 deeper into the case and test some more. Usually find a load fairly quickly. If the dummy round doesn't fit the mag box, I seat the bullet until it will and start testing from there.Rick.

 

[nosler06]

Like already mentioned I start at magazine length and drop .10 at a time. I use 2or 3 shot groups. I am at 2.785 with my .308 right now and its stacking the 168gr. Nosler CC, and the Seirra and the 168 gr. Matchking, on top of each other.

I just checked my 30-06 and the OAL is at 3.380" right now. I look at Nosler's load data test length is at 3.310" for the 180gr Partition spitzer. SAAMI for the 30-06 is 3.340". Wow that is giving a fair bit of range of depth seating. I am just checking do you start at your max length and then go down by 0.10" or 0.010"? It is very interesting that my OAL is only 0.005" short from max on my .308. I think I have a little bit of fine tuning to do still. Both of these rifles have shot under 1/2" groups at 100yds. That is until a whole bunch of powder testing with the .308 and a powder change and part protect pt to spitzer change on my 30-06. I am confident I can get it dialed back in. I hope.

Sorry I think I might have to double check my measurement because I think 3.380" is 0.040" over what the max SAAMI length is. Dummy me. I think that the measurement should have been 3.338", but double checking my work is not something that I do not already do with all my reloading. Safety first is what I always say.

 

[Richracer1]

FWIW, The loads for my '06, a Vanguard Sporter, have an OAL of 3.39" and works very well through the magazine.

 

[nosler06]

Well just did a double check and the first measurement is correct 3.377" to 3.380" on 40 rounds. I am trying to figure out what the heck I was doing. I had taken an looser un-primed case and barely seated the bullet. I then placed it into the chamber and closed the bolt and removed the un-primed round. I then measured it and placed it into the RCBS dies and adjusted the seating ram to match the length. I then turned slightly each time until the bullet was seated 0.010" deeper than the bolt closed round. Tried the round back in the rifle and bolt closed smoothly and the round fit fine into the magazine.
I wounder if I should try three rounds at the SAAMI max length of 3.340" and see what they shoot like for a group. And then adjust from there. Does any one know if this extreme length past SAAMI max is alright? Does my method of finding the length that is just off the lands makes sense?