6 PPC bullet seating depth

R

rodauto

Guest
I'm trying to get my Berger column bullets to "jam" and it looks like I will have 1.760 from the base of the cartridge to the ogive according to my Hornady tool.
My Lapua 220 russian brass is trimmed to 1.490 so this will only give me .082" of bullet in the case. Is this normal? Seated bullets are not loose so I am not terribly concerned but still wondering?
Bought the rifle used and haven't done a chamber cast yet so not sure of the dimensions.
To get my ogive measurement I seated a bullet long and chambered it to touch the lands.
Barrel stub that came with the rifle shows that I am indeed into the lands but that would only be a rough check as the lands move a bit as the round count goes up?

Rodney
 
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Correction #2.....you mean your Lapua brass is trimmed 1.490", right?

And can you show your overall calculation on the 0.08"? I don't know the Berger Column's length offhand. That said, I bet you have more than 0.08" in the neck.

-Lee
www.singleactions.com
 
Rodney,
Slow down, take a breath, and zero your calipers with the jaws touching each other. As was said earlier, it is highly likely that your trimmed brass is 1.490. If you seat a bullet long enough that it will be pushed into the case as the bolt is closed, remove it and measure the loaded round, what you should have is the jam length for that particular, barrel, bullet, and neck tension. If you add the tip to base length of the bullet, to the mouth to head length of the case (probably 1.490) and subtract the tip of bullet to case head measurement of the round that you chambered, you will have the amount that the bullet is in the case neck. Unless you want to actually shoot with your bullets seated at jam, you then can set your seating die so that it shortens the round by the amount that you require, and then you can take a measurement of the round using a tool that contacts the bullet on its ogive, near where the rifling will make contact when it is chambered. Let us know what you come up with. As it stands, your numbers have been a bit jumbled. If you really do have that little bullet in the neck, either your chamber has an unusually long throat, or your barrel is quite worn.
Boyd
 
Thanks all,
Corrected the original post again. Sorry guys!
The brass is trimmed to 1.490
The berger column bullets are .808 on average
My loaded rounds average 2.215 on average from Base of cartridge to tip of loaded bullet in order to touch the lands
To figure out the jam I put a column bullet in a case sized just enough to keep the bullet from falling out and closed the bolt on it. The case was sized so slightly that the bullet doesn't even show a mark from the lands where they touched.

I bought this gun used at a gun shop and it came with the Wilson neck sizing die, wilson seater die, and over 100 Lapua 220 russian brass. (talked to Harrels Precision today about a full length sizing die as I now have some brass that is tight to chamber)
Claimed round count when I bought it was 327 rounds. I now have 882 total rounds through the rifle. I think this is my first attempt at doing a different seating depth than what the die was originally set for when I purchased the rifle.... should have been the first thing I did I guess.
First precision rifle, my other 6mm ppc was a Sako I had for at least 10 years.
My groups have ranged any where from .137 to .714 trying to work up a load, the majority though are in the 2s and 3s using H322 and Berger 68 grain Molly, and now using LT 32 and Berger columns

I don't compete so 2s and 3s are OK for me right now as I am just trying to learn to shoot better before spending money on a new barrel that I would wear out learning to shoot properly.

Rodney
 
If you know someone with a bore scope, you might take a look at the chamber and bore a few inches in front of it. If the chamber was cut with a long throat, and the condition of the barrel warrants it, you might consider having the barrel set back. If the throat length appears to be due to wear, and there is much checking in the throat and in front of it, the round count was fiction.
 
Thanks Boyd,
I checked the barrel stub that came with the rifle with my hornady tool and the cartridge base to ogive is 1.748, just .012 less than the actual rifle. I wonder if they were trying to shoot heavier bullets in it? It appears to be a 1 in 13 twist when I use my cleaning rod and a nylon brush to check so I expect it is somewhere between 1 in 12 and 1 in 14 twist. I have a reamer I bought from PTG a couple years ago to rebarrelmy Sako so might get the smith to cut and rechamber this one.IMG_20140502_204832.jpg
 
In benchrest tuning, don't think in terms of bullet seating depth. Think in terms of bullet position in the chamber.
 
Hi Jerry,
Are you reffering to distance into or from the lands and don't worry how much bullet is in the case?

Just got back from the range, my rifle definately doesnt like to be into the lands with the column bullets, loaded 50 rounds at 1.670 to the ogive with various powder charges that I used before and my groups opened up quite a bit. will now start backing off on the length.
I know I,m into the lands with this measurement as I had to stop shooting after 45 rounds when I opened the action on a loaded round and dumped powder all over the action!! Bullet was easy to push back out of the rifling but didn't have enough cleaning equipment with me to clean out the action.

Rodney
 
rodauto said:
Hi Jerry,
Are you reffering to distance into or from the lands and don't worry how much bullet is in the case?

Just got back from the range, my rifle definately doesnt like to be into the lands with the column bullets, loaded 50 rounds at 1.670 to the ogive with various powder charges that I used before and my groups opened up quite a bit. will now start backing off on the length.
I know I,m into the lands with this measurement as I had to stop shooting after 45 rounds when I opened the action on a loaded round and dumped powder all over the action!! Bullet was easy to push back out of the rifling but didn't have enough cleaning equipment with me to clean out the action.

Rodney
Click to expand...

Seat to a good square mark on the bullet and work from there. Most barrel/bullet combinations will not shoot at that point so seat the bullet about 0.010" deeper in the case. Then in 3-shot loadings shoot groups backing off 0.003" with each one. Generally you will find a bullet seating in the 4 or 5 groups.'

Try this with a medium load of powder, say 28.6-29.3g of V133 or about 28.5-29.2g of LT-32..Somewhere in the 3250-3375 fps the barrel. if it is going to shoot, will show improvement Then work from there using good windflags. And remember, what worked great today may not shoot worth crap tomorrow!!
 
JerrySharrett said:
Seat to a good square mark on the bullet and work from there. Most barrel/bullet combinations will not shoot at that point so seat the bullet about 0.010" deeper in the case. Then in 3-shot loadings shoot groups backing off 0.003" with each one. Generally you will find a bullet seating in the 4 or 5 groups.'

Try this with a medium load of powder, say 28.6-29.3g of V133 or about 28.5-29.2g of LT-32..Somewhere in the 3250-3375 fps the barrel. if it is going to shoot, will show improvement Then work from there using good windflags. And remember, what worked great today may not shoot worth crap tomorrow!!
Click to expand...

Thanks Jerry,
Will try that for next weekend.
 
Use that guage sparingly

I never owned one of those gauges and have been reasonably successful.

In terms of how much seating depth you have compared to how much you need can be boiled down to how much you need. I had a barrel, that I won a bunch of matches with, where the bullet seated just barely into the case. The tension didn't matter much since the bullet didn't use but a bit of the neck. I had to make sure that the neck had a good grip on the bullet but still had several bullets that fell out when a loading frenzy was necessary..or I thought was necessary which was usually the case. I'm saying that if you pushed sideways on the bullet it would pop out of the case.

Bottom line is that if the rifle shoots well with the bullet just barely into the case that's a good thing. When you start trying to accomplish something different with a rifle that is already competitive as it is, you're looking to goof up.
 
Wilbur said:
I never owned one of those gauges and have been reasonably successful.


Bottom line is that if the rifle shoots well with the bullet just barely into the case that's a good thing. When you start trying to accomplish something different with a rifle that is already competitive as it is, you're looking to goof up.
Click to expand...

Wilbur, tell the group about the loads you, Tommy and Ted used to shoot where you simply dropped the bullet down on the powder.
 
Seating depth views

different strokes for different folks. But: Several hall of fame shooters determine jam by using the same sizing button that they load with, seat the bullet long so lands and groves push bullet into case. measure do 3-4 times and take average. If bullet pushes way back - adjust the initial long setting so only .010 or so bullet is pushed back as you determine jam. You will be amazed at how much difference there is for jams with no neck tension and moderate neck tension. for example 262 neck with 261 bushing versus 262 neck with 257 bushing is QUITE A BIT. GOOD LUCK.
 
We're starting to talk "jam" here

Had to say this....there's no specific jam for rifles. Each rifle has its own preference and I'm thinking that you have to find it. "Thinking" is a key word as I just don't know whether or not a rifle will shoot better with a specific seating depth. I am sure that given components, fired in a given rifle, at a given time will shoot best with a given seating depth. What I don't know is what all those givens mean......:)

I do know this - the rifle you win the most with will care the least about seating depth.
 
ok doka!

Wilbur said:
Had to say this....there's no specific jam for rifles. Each rifle has its own preference and I'm thinking that you have to find it. "Thinking" is a key word as I just don't know whether or not a rifle will shoot better with a specific seating depth. I am sure that given components, fired in a given rifle, at a given time will shoot best with a given seating depth. What I don't know is what all those givens mean......:)

I do know this - the rifle you win the most with will care the least about seating depth.
Click to expand...

Wilbur: I Agree that each " barrel" will have a unique jam on a certain receiver. change the barrel or the receiver and you may not get same with same bullets and neck tension. Also I am convinced that neck tension has a direct correlation to jam. initial item referred to little or no neck tension to find jam thus my comments. I agree that hummers or great barrels are not as sensitive to bullet seating depth. I also think there to more than one way to begin tuning to find seating depth - for example you can begin with: square mark on bullet, no mark on bullet, or from jam. although I have tried these three (and others) I still prefer starting from jam and I was taught that way by Bart, Billy and Tony . My limit experience tells me my best tune is found within a few thousands of jam. I know hall of famers who shoot way off jam in fact never look for jam while others shoot 4 to 10 thousands off jam and find their best tune there 90% of time. Wilbur when are you going to start shooting and showing us again versus talking? LOL Jim Casey
 
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