Does seating depth truely matter?

[kyotekiller25]

Usually makes a big difference. This was with a 223, 28" Bartlein and 75g ELDMs with N540. I started 10 off and tried powder charges in .2g increments and could never get rid of the "flyer". So I did a seating depth test in .005" increments, from 5 to 40 off on a horizontal target. Can clearly tell it likes these at 25 off. Of course if you were to shoot a 10 or even 100 round group, they'd probably still all be within the same radius or group.

 

[William Vogel]

You should have a separate target for each shot group. Shot 4,5&6 on the shoot and see target are the best group but it doesn’t match what you wrote down. If 4,5&6 are labeled correctly as far as the holes in the paper, that’s a good group. For me, I can’t have that much chaos and attempt to draw a hold on target for data collection. I don’t know how you kept up with the holes.

 

[Tangent]

Factory rifle
max mag length is
a long ways from the lands.

Can anyone answer WHY a rifle manufacturer does this?
Or what am I missing as advantage for this?

They have to design a rifle that will work with any factory ammunition out there. The advantage of a custom is you can have it set up to work with your exact ammunition, even if it falls outside of factory norms. That said I've found some loads really don't care about a big jump. All this relates to factory expected groups i.e. 1 MOA. Obviously for things like BR or F-Class that's not going to cut it.

 

[boltfluter]

In my experience, if you don't start your testing at .020 into the rifling and work back from there, you may have already missed the boat completely! Assuming your situation, magazines, or anything else will allow this of course. Usually. 010 to .015 into the rifling will be shocking as to how small the groups are. Plus, starting into the rifling, you only have one way to go. I have never pulled a bullet out of a case .015 in, just in case you were wondering. Use Alex's method to find the true bullet contact point and go for it! You may be pleasantly surprised by what you see. Small groups!
Paul

 

[Owens85]

Here's what I believe is a good example of seating depth making a difference started at 4 in and went to 10 in the group shrunk each group when going further in. Until it hit the best seating depth

 

[Owens85]

Here's another example I just did recently before a match on some new bullets in a 30br. The 1.674 seating depth was good to go. The match yesterday I used it in I was able to shoot a 250 and 22xs.This I started at max jam and worked in the case. (Still in the lands). I believe seating depth most certainly matters.

 

[moe africa]

You should have a separate target for each shot group. Shot 4,5&6 on the shoot and see target are the best group but it doesn’t match what you wrote down. If 4,5&6 are labeled correctly as far as the holes in the paper, that’s a good group. For me, I can’t have that much chaos and attempt to draw a hold on target for data collection. I don’t know how you kept up with the holes.

I labelled 2 consecutive groups
So shot 1-6 and 4-9
The smallest vertical was 16 to 18

 

[ricco1949]

In my experience, if you don't start your testing at .020 into the rifling and work back from there, you may have already missed the boat completely! Assuming your situation, magazines, or anything else will allow this of course. Usually. 010 to .015 into the rifling will be shocking as to how small the groups are. Plus, starting into the rifling, you only have one way to go. I have never pulled a bullet out of a case .015 in, just in case you were wondering. Use Alex's method to find the true bullet contact point and go for it! You may be pleasantly surprised by what you see. Small groups!
Paul

I agree Paul however I now start at hard jam and work out. I used to work everything from touch, but now feel that that there Is no reason to even be concerned where touch is, other than for conversation comparisons.

20+ years ago my first LG LRBR rifle had a tight freebore. I was unknowingly feeling the freebore with my Sinclair gauge and shot it at 100+ jump for many matches before realizing the error. It was apparent that something was diferent since the ojive was in the neck but I was a rookie with little BR experience and this was my first custom rifle.

Surprisingly it won a few relays and matches in that configuration, and had several 3-5 inch groups at 1000 practice range. The very first 5 shot group it had at 1000 was the 2.78" never to be exceeded with any rifle since.

Working from hard jam is well defined and just seems to eliminate a lot of touchy feely requirements which really serve no purpose for me.

 

[dellet]

Factory rifle
max mag length is
a long ways from the lands.

Can anyone answer WHY a rifle manufacturer does this?
Or what am I missing as advantage for this?

Short answer is rifle manufacturers, do. Ammo manufacturers do not.

For the most part the cartridge/chamber was designed first, then the original rifle. This was done with a single bullet in mind. Then all of that is designed for a single purpose.

If you look at the history of the three most popular parent cases, all three were designed for the military where function is more important than accuracy. 30-06, 7.62 NATO, 5.56 NATO. Every cartridge designed using those cases has almost automatically been hampered with the original magazine design.

Best the manufacturer will due is make specific bullet. Consider the Palma class bullets. Designed to be shot in a specific chamber, at a limited weight. Most weigh 155 grains. The Berger 155.5 full bore certainly caters to that market.

If you look at 150/147 grain 30 caliber bullets, you’ll have about 75-100 choices. I have no idea how many 30 caliber chamber there are, but that’s a lot of combinations in a single weight class.

 

[tom]

Yes, it matters quite a lot.

Even when in this context where you're stuck jumping a bunch. I still recall it coming and going in "nodes" even tuning Weatherby chambers. When jumping much past 15, I believe you can widen the gaps you're testing as the zones will increase in width. You may not achieve a tune that can win any Benchrest matches, but you should be able to find 1/4 - 3/8 moa with solidly stable poi.

Tuning into the lands, I would consider moving .003 as pretty coarse.

Tom

 

[Bill Norris]

In my experience, if you don't start your testing at .020 into the rifling and work back from there, you may have already missed the boat completely! Assuming your situation, magazines, or anything else will allow this of course. Usually. 010 to .015 into the rifling will be shocking as to how small the groups are. Plus, starting into the rifling, you only have one way to go. I have never pulled a bullet out of a case .015 in, just in case you were wondering. Use Alex's method to find the true bullet contact point and go for it! You may be pleasantly surprised by what you see. Small groups!
Paul

I am leaning more and more towards working into the lands with seating depth with all my rifles.

 

[rwj]

I am leaning more and more towards working into the lands with seating depth with all my rifles.

Do you need to decrease powder charge weight when moving from jumped to jammed?

 

[Idaho-Lefty]

Do you need to decrease powder charge weight when moving from jumped to jammed?

YES,. I lowered my Powder charge 1/2 a grain AFTER "Jamming" the 107 gr. SMK, Bullet.
I like to, Find the Rifles Max, Powder charge ( best Velocity ) at .025 - .030,.. "Off Jam",.. FIRST.
Then, I move the Bullet inwards and then, "outwards",.. IF NOT, Happy with, group's @ Near or, @ "Jam point".
My Tikka Hunting Rifles, seem to Like,.. .070 to .110 Jump ( Hybrid or Classic Hunter,.. "Design" ).
My Short Free Bore, 6 XC likes em',.. Jammed to, close in ( Bullet "Design", HAS, a LOT to Do with What, a Rifle,.. "Likes" IMO ! ).

 

[Bill Norris]

Do you need to decrease powder charge weight when moving from jumped to jammed?

Yes, it is very important to reduce the charge and work back up once you are jamming to lands .

 

[wright brothers]

This chamber is to fit long factory rounds,
but the mag is too short to fit sane rounds.

Ok, I will go back to lurking.

 

[dellet]

This chamber is to fit long factory rounds,
but the mag is too short to fit sane rounds.

Ok, I will go back to lurking.

If the chamber is a SAAMI chamber and the ammo is also to SAAMI specifications, then it sounds like the rifle manufacturer is at fault.

Even as a wildcat cartridge building a rifle as a magazine fed rifle that won’t accept the cartridge in its magazine sounds like they weren’t thinking things all the way through.

Knowing the chamber/cartridge might be helpful, sounds like you have something specific. I was certainly generalizing and do not include anything Weatherby related which is known for long free bore chambers. But as far as I know, a Weatherby round will load in a Weatherby magazine.

Being longer than magazine length in the bore is certainly safer than being shorter. Hornady found this out publishing the 9th edition of their loading manual about the same time as 300 Blackout hit the market. It became pretty clear very fast they had not actually tested about a half dozen of their loads. They couldn’t be chambered because they jammed at less than magazine length loads. The couple that did chamber with only a small jam, caused some serious problems of over pressure with minimum loads.

 

[ricco1949]

Do you need to decrease powder charge weight when moving from jumped to jammed?

Used this approach to tune a 222 for an egg/pool chalk match in ND:

1. Pressure ladder at hard jam
2. Pick a preliminary powder load based on the ladder
3. Shoot two shot seating depth ladder moving back from hard jam
4. Shoot another two shot group powder sequence with the chosen seating depth to finalize the load.

Worked well enough to win with some noteable LRBR competitors in attendance.

 

[SKWERLZ]

Does seating depth truely matter?​

On a podcast called {Believe the Target) with Erik Cortina and Wayne Campbell who now has the second largest number of Hall Of Fame points (second to Tony Boyer only) Wayne positively says seating depth matters more than powder charge. He explains in detail why this is true.

I have to agree with Wayne that seating depth does matter a lot. I have no proof as to whether it matters more than powder charges but I would not question Wayne's ability to test and give his findings.

I believe him.

 

[wright brothers]

"1. Pressure ladder at hard jam"

What is meant by this pressure ladder?

 

[Bill Norris]

"1. Pressure ladder at hard jam"

What is meant by this pressure ladder?

Searching for the max powder charge