Forster micrometer vs brass

[steffen707]

I'm loading with winchester brass for my 7mm RM. i'm guessing the brass is pretty poor compared to lapua ect. So is my problem the brass, or technique/equipment?

After bumping shoulder back .002" then trimming, brush neck, inside chamfer, outside chamfer, brush neck again I use dry neck lube and run a .283mandrel through the neck. I prime, powder (not a compressed load, bullet not touching powder) and put my forster micromester bullet seating die into the press.

For simplicity sake, lets say I want a bullet to ogive length of 3.000", I initially guess the depth and seat a bullet to 3.005". I then turn the micrometer down 0.005", take the same cartridge with bullet already seated at 3.005", run it through the die, check the length and now I get 3.002".....

If I leave the micrometer alone, prime, powder another prepped case and seat another bullet, it'll be at 3.000"

But in order to get the FIRST CASE bullet ogive down to 3.000", I have to adjust the micrometer down another .002-.003" and run it through again. THEN adjust the micrometer back up the .002-.003" for the rest of the bullet seating.

Its almost like with 1 cycle of the bullet die, the die will seat the bullet where I expected it to, but if I have to adjust the bullet down after the initial cycle, somehow the neck is springing back or something.

 

[Rob5589]

Did you measure the bare bullets for consistency? I'd guess there is some variation within the batch.

 

[tdot]

I've found similar issues with certain brass and bullet combos, this is across several dies from Forster, Whidden and Redding. I've also found that the speed of seating the bullet can affect the final OAL. Personally I'll finish loading all of the rounds and the tweak the first few pieces. I also have some combinations that don't yield this result, using identical procedures.

Essentially I've put it off to the speed of seating the bullet and the momentum created can affect the depth of the bullet seating. It seems to be most prevalent with light neck pressure and lube present in the neck. These are just my observations and resulting assumptions. Happy to hear another reason.

 

[83cj-7]

Simply put, neck tension variations are causing the issues you describe. I fought this for years and fixed the whole thing by turning necks and using bushing dies to get less neck tension. I still have some issue when the bullet is touching the powder in the case, this can cause .001 to .002 variations in seating depth.
The other benefit to turning case necks is that my ES in most cases went down to single digits and sometimes better.
The link below is a long read but really Interesting. Since reading the article I try to find a load that shoots really good with the bullet .040 to .080 off the lands. This allows small variants in seating depth to be less sensitive to accuracy. This is summed up in the article below.

Bullet Jump: Is Less Always Better?

About 2 years ago, Mark Gordon shared some preliminary research he’d conducted with the Applied Bal...

precisionrifleblog.com

 

[TX_Diver]

Out of curiousity what bullet are you seating?

Read some reports of longer bullets like the VLDs or some of the Hornady ELD-Ms not working with standard seating stems. Sounds like the bullets nose will contact the top of the stem rather than the stem contacting the ogive. It also sounds like that's typically not a problem with the forster ultra micrometers though so it's probably not your issue... But was still curious.

 

[Dreeko]

I have noticed the same symptoms with my forster seating dies. I don't have the perfect fix but when adjusting down to my desired OAL, I will typically turn about 2-3 thousandths past my desired length and then comeback up to where I want it to be.

It seems to help with the variation between the first couple of rounds and the rest of the batch.

 

[steffen707]

It seems to be most prevalent with light neck pressure and lube present in the neck. These are just my observations and resulting assumptions. Happy to hear another reason.

I run them through the factory forster full length sizing die, then run a .283 mandrel through the neck. I've been thinking of buying a SAC mandrel set for .284 and playing with different neck tensions, maybe i'll give that a go.

Did you measure the bare bullets for consistency? I'd guess there is some variation within the batch.

I didn't. Should I measure from the end to the tip, end to the ogive?

Simply put, neck tension variations are causing the issues you describe

it certainly could be neck tension variations, i'm not annealing the winchester brass, though i'm only up to twice fired brass. Also I figured taking the expander ball out of the full length die and using the mandrel would give me consistent neck tension. I don't have a concentricity gauge to test for this however.

I also bought 50 rounds of new Norma 7mmRM brass that I was going to start trying. I wanted to try the Norma and Nosler because Lapua doesn't make 7mmRM.

Out of curiousity what bullet are you seating?

Read some reports of longer bullets like the VLDs or some of the Hornady ELD-Ms not working with standard seating stems. Sounds like the bullets nose will contact the top of the stem rather than the stem contacting the ogive. It also sounds like that's typically not a problem with the forster ultra micrometers though so it's probably not your issue... But was still curious.

I ran into this issue with both the 168gr Nosler ABLR and the 154gr Hornady SST, so i'm not convinced its a bullet style issue. Definately could be a bullet or brass consistency issue though.

I have noticed the same symptoms with my forster seating dies. I don't have the perfect fix but when adjusting down to my desired OAL, I will typically turn about 2-3 thousandths past my desired length and then comeback up to where I want it to be.

It seems to help with the variation between the first couple of rounds and the rest of the batch.

That's something I can try. I'll turn down 5-6 thousandths and come back 2-3 on my next round of testing.

I didn't get any notifications of your posts (gotta check my settings), but thank you all very much for the replys and ideas. I'll give each of them a look. I certainly could have 2-3 things contributing to it. Its just weird because once I keep the seating die alone, I could crank out 20 rounds and they would all have the same length to ogive.

That's why i'm thinking its not the brass prep, or initial neck tension.
It could be the die adjustment like @Dreeko mentioned. Or not enough neck tension, or the speed at which i'm seating.

I'll start with those 3 first. I'm not into competetive shooting, and really just building a 7mmRM for deer, antelope, someday elk, but I like to tinker and want to get the best accuracy I can out of the gun/cartridge, that way I can enjoy learning to shoot longer ranges and know its on ME, not the gun/load.

 

[Dreeko]

Good luck!

I have found that after I find the happy spot for seating depth, I can usually finish loading the rest of my brass (400 pieces) without needing to adjust it. I usually spot check every 10-15 rounds just to be safe but I see very little variation once its set.

 

[TX_Diver]

I’d be curious what you determine. Have a Forster die on the way (eventually once they ship lol)

cheers

 

[steffen707]

well i'm loading 15 or so more rounds tomorrow, i'll post back on Sunday.

 

[Wrench]

Can you skip the mandrel and see what happens? If you are approaching case capacity, you may be crushing powder... or your neck tension simply sucks.

You can aneal in a pot of water with a torch in a pinch.

 

[steffen707]

Can you skip the mandrel and see what happens? If you are approaching case capacity, you may be crushing powder... or your neck tension simply sucks.

You can aneal in a pot of water with a torch in a pinch.

yeah i can try that. Its not at case capacity yet, can still hear the powder shake inside the round.

 

[Wrench]

Good...then I would aneal, size and not run the mandrel.

 

[steffen707]

Okay I ran a test with 6 separate pieces of winchester brass twice fired (not annealed, don't own one, i know theres some water method), all run through FL Forster die, trimmed to length if needed, inside/outside neck chamfer then cleaned with rotary tmbler and dried.

I then ran tests with just the FL Die, .282 Mandrel and .283 mandrel. Half with dry neck lube, and half with the dry neck lube brushed with 5 brush strokes after the mandrel was used. I also brushed the FL Die even though no dry neck lube was present (no mandrel use).

6 new bullets 154gr Hornady SST were used. I set the Forster micrometer to setting 20 for initial bullet seating and dialed it lower 5 settings for bullet 2, and then 5 more settings for bullet 3, then back up to setting 20 for next bullet.

I'm quite surprised by the results, but it does confirm what several of you have said.

brushing the neck gave more consistent results across the board. The .283 (lower neck tension mandrel) had the most inconsistent results with lube (how i've been seating for all my testing thus far, DOH!). The FL Die alone wasn't as consistent as the .282 Mandrel.

I'm guessing if I had it honed (thus creating less neck tension) it would be more consistent (closer to neck tension of .282 mandrel). Or if I used a bushing die, or bushing die with mandrel, or honed FL Die with mandrel. LOL. For now though the .282 will be used. Once I nail down powder/seating depth I may tinker with different mandrels which will probably throw off the optimal powder charge and i can do it all over again!

Thanks again for your help everybody.

 

[wapitibob]

I had the same problem as you. Neck tension was the culprit and I found that setting up my seater body to hit the shell holder made a big difference as did annealing after every firing. I still "walk it in" like you do but the final reading on the seater is usually within .001.
A propane torch will anneal your brass just fine.

 

[Wrench]

I love lee collet dies for this situation. Bushings depend on uniform neck thickness for results....or an expander. Expanders rely on the spring tension of the brass but work harden and can scratch brass.

Collet dies simply squeeze to the standard. If the standard needs to be more or less tension, a simple diameter change can be made. The part about the collet system that is hard to beat is that neck thickness can vary and the hole is still in the center of the datum.

 

[steffen707]

I had the same problem as you. Neck tension was the culprit and I found that setting up my seater body to hit the shell holder made a big difference as did annealing after every firing. I still "walk it in" like you do but the final reading on the seater is usually within .001.
A propane torch will anneal your brass just fine.

I'm only walking it because i'm working out the best seating depth, once i find that depth the seater will stay there for a while, till i play with new bullets. i'll have to play around with the annealing part. Do you chuck the bullet in a drill to get even heat?

 

[steffen707]

I love lee collet dies for this situation. Bushings depend on uniform neck thickness for results....or an expander. Expanders rely on the spring tension of the brass but work harden and can scratch brass.

Collet dies simply squeeze to the standard. If the standard needs to be more or less tension, a simple diameter change can be made. The part about the collet system that is hard to beat is that neck thickness can vary and the hole is still in the center of the datum.

i'll give the collets a look, thanks.

 

[wapitibob]

i chuck the brass in a drill, yes

 

[Wrench]

Many guys just chuck up a 9/16" socket and use it to hold the brass. I used to stand the case up in a pot of water.