Bullet seating depth

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Ken Green
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Bullet seating depth

Post by Ken Green » Mon Aug 07, 2017 5:32 am

How far or close do you seat the bullet away from the lands on a 7mm-08? I am thinking around .020 thousands off the lands or is that too much?

What about for a .243 winchester? Is 0.020 too far away? I have read that the .243 should be about 0.005 or either jamed tight basically touching. Thanks Ken

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Re: Bullet seating depth

Post by cedestech » Mon Aug 07, 2017 5:51 am

As with most things firearm related... it depends... .some barrel/bullet combo's like a certain amount of jump or no jump, some just don't care... part of load development.

YMMV, IMHO, etc, etc...

I will say use a ogive tool to measure off the ogive... COL isn't accurate enough.

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Re: Bullet seating depth

Post by Ken Green » Mon Aug 07, 2017 6:58 am

I use a Hornady OAL gauge with a dial caliper to measure from the ogive of the bullet. I don't go by the OAL of the loaded round at all.

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Re: Bullet seating depth

Post by OldRanger » Mon Aug 07, 2017 8:26 am

For all things 7mm-08 you need an answer from The Guru before its a done deal. You out there Bob? Is this thing on!?
My poor knowledge of greek mythology has always been my achilles elbow.

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Re: Bullet seating depth

Post by Bob Mc Alice » Mon Aug 07, 2017 4:06 pm

I agree with what cedestech said. Only testing will prove what your rifle prefers. Me, I seat .012 the off lands on every gun I have. It's worked well right away with no need to tweak it more by testing different gaps. I adjust COL every 500 shots to compensate for erosion.

My two match guns with the high round counts still delivered very good bench accuracy at Ridgway last month. With both rifles I have been chasing the lands...or what is left of them. The COL is now .135 longer than when they were new. No powder added to comp for increased case volume. You would never notice any significant bullet drop, at least I haven't. I am no fan of jamming bullets into the steel.

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Re: Bullet seating depth

Post by Ken Green » Mon Aug 07, 2017 4:50 pm

Thanks Bob. I loaded some test rounds .020 off the lands on my .243 Winchester, but I could not get a good group at 100 yards. I just loaded some test loads with the 95 grain Nosler BT hunting bullet. I seated them at .010 off the lands. I haven't been able to test them yet. I do need to get some more 7mm-08 rounds loaded.

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Re: Bullet seating depth

Post by Jerry G » Mon Aug 07, 2017 7:20 pm

The VLD bullets in a fast twist gun won't group as well at 100 as they will at 200 in my tests with the 107 Speer bullet in a 243. You need to play with the seating depth to the ogiv and not with the overall length. .020 sounds like too much but don't put them in the lands or you will pull bullets if you don't fire the gun before you open the action. Who wants a trigger full of powder?

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Re: Bullet seating depth

Post by jask » Sat Aug 12, 2017 8:32 am

Just a reminder that if anything at all is changed about the cartridge, seating depth, bullet, then a new load workup is needed to determine any accuracy changes.

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Re: Bullet seating depth

Post by Bob Mc Alice » Sat Aug 12, 2017 9:46 am

Interesting, that has not been the case for me when adjusting seating depth. A couple of shots from the bench before the start of a match shows no changes even worth resetting a scope knob for. Accuracy has remained the same with my loads for years. My only requirement is checking for acceptable bullet tip run out after adjusting the Redding comp seater die. Still, some may want to go through this exercise.

After the St.Louis regional both my 7-08 match guns will have 6000 shots each on them. When will they give up the ghost?

( a shameless plug for the regional, your welcome Snake.) :mrgreen:

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Re: Bullet seating depth

Post by jask » Sat Aug 12, 2017 10:52 am

The vibration pattern of a barrel is basically fixed by the dimensions. Any changes in the cartridge that alter pressures or cause The bullet to exit the barrel in a different phase of vibration will change the grouping for acuracy.

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Re: Bullet seating depth

Post by jask » Sun Aug 13, 2017 4:09 am

McAlice "Interesting, that has not been the case for me when adjusting seating depth. A couple of shots from the bench before the start of a match shows no changes even worth resetting a scope knob for."

It alters the pressure curve effectively changing the time the bullet has to travel before exiting the barrel. That is a change you do not want to make after a load work up if you strive for accuracy.
The following is an accepted fact.
"Pressure change can be produced with bare copper bullets by changing seating depth and/or neck tension in most calibers."

The final step I always did when reloading was to neck ream the cases for a .002 bullet tension. With the same seating depth and neck tension, I had a very accurate bullet.

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Re: Bullet seating depth

Post by jask » Sun Aug 13, 2017 8:43 pm

McAlice "After the St.Louis regional both my 7-08 match guns will have 6000 shots each on them. When will they give up the ghost?"

I got 5000 out of my .308 before it died and I used light loads except for rams at 500. We used a reduced size animal for our local range so I used light loads most of the time. 6000 is really good. Does stainless act the same way for barrel erosion as the chromoly? If you find someone with a bore scope, they can check it out for you.

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Re: Bullet seating depth

Post by Bob Mc Alice » Sun Aug 13, 2017 9:22 pm

Jask, I do not have the intellect to make a long post of this. My typing is still one key at a time although I do occasionally use my left finger if it is near the needed key. :) I have 54 years of reloading experience. I shoot more than anyone you might know. :|

I do not fuss much with assembling my ammo. No case cleaning, weighing , indexing or sorting nonsense either. I shoot mixed lots of bullets and powder with no concerns. I do pay attention to bullet run out and keep this tight. This is an off hand game, not bench rest shooting for top prize money and glory. All I want is for the projectile to go in the same general place each time from a rest . The projectile is the most important component in the accuracy equation.

The two rifles have 5925 shots on them now. They are stainless Douglas XX match and our Hawkeye shows significant wear. It is less sever looking than a carbon barrel with similar round count. The alligator skin appearance is faint compared to carbon.There is much missing steel burned away. A half dozen carbon barrels were toast in 4500 shots, two went 5400 with marginal accuracy. I have yet to retire a stainless barrel for poor accuracy. I expect to get 7500 or more accurate shots according to some people that have been there. That will be sooner than later.

In preparation for the regional next week I benched them this past week. Each put it's shots in tight clusters as usual. No real accuracy chances worth noting or adjusting for. 500 meter 2.5 inch groups to this day. That is real good.

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Re: Bullet seating depth

Post by jask » Mon Aug 14, 2017 12:31 am

Run out is an important component for accuracy. What steps are you taking to minimize the run out? Do you check all cartridges? How much run out do you find unacceptable? What brass are you using? Are you using standard dies?

Your group at 500 with both of those rifles is impressive. Thanks, Jim

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Re: Bullet seating depth

Post by Snake » Mon Aug 14, 2017 9:06 am

Thanks Bob, I have the wind machine all fired up just for you :ymhug: Except for a Weatherby I had projectiles rarely like being more than .015 from the lands. I fireform with a slightly lower charge and up against the lands just make sure the new case is tight against the bolt face. Ninety percent of the time .010 thereafter about does it. Every barrel bullet combination is different. Neck tension is also a significant factor...unless you have precise consistent release in the neck a large bullet jump may be detrimental...less jump less influence neck tension..generally speaking

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