seating depth increments

[bstomper]

After finding my OCW for my 7mm rem mag, I try to bring the groups together by adjusting the seating depth. I have been doing my initial testing with a COAL of 3.370" because that is the max that will fit nicely into my magazine. For my seating depth test I have been loading the bullets in 0.010" shorter incriments (3.360, 3.350......) all the way down to the manuals 2.329" spec. Because of slightly decreasing the case capacity with each decrease in COAL I have been watching for pressuere signs just to be safe. Is the 0.010" incriments to much to be able to fine better accuracy. Should they be smaller increments.

 

[WeiserBucks]

It all depends on the bullet you're using and what your bbl likes . You may see good results with a .010" adjustment, you may need to adjust .050" at a time to see results.

I don't have a link , but there's an article on Bergers site regarding seating depth , it's very informative .

 

[243winxb]

I find max and minimum, then set 2 oal inbetween the two.

 

[rcoody]

I have had good luck with this one

Getting the Best Precision and Accuracy from VLD Bullets in Your Rifle | Berger Bullets Blog

 

[brentc]

It's a sticky.

http://www.longrangehunting.com/for...accuracy-berger-vld-bullets-your-rifle-40204/

 

[FearNoWind]

Relying on OAL (bullet base to bullet tip) to fine tune jump is akin to chasing your tail. Even if you're separating your bullets by length out of the box before seating, your measurements won't be accurate enough to be useful and you'll end up frustrated..
You'll have better results using CBOL to do comparative testing of seating depths.
IMO, .010 increments will put you in the ball park so that you can use the overall spread of groups on target to show you where to concentrate your fine tuning efforts but once that's done I'd use .003 increments to obtain final data.
After that you can play with .1 gr adjustments in the load to really fine tune it.
I've used Berger's "Getting the Best Precision and Accuracy from VLD bullets in Your Rifle" (stick previously mentioned) and it works fairly well - with VLD bullets. I've found it's not the perfect solution for every bullet.

 

[FNA3G]

If the OCW is done properly it is usual in my experience that no seating depth adjustments will be necessary for most bullets, in Dan's description of OCW he also agrees on this. I usually seat them .010-.020" off the lands to start and i rarely have to adjust seating depth. If seating depth adjustments are needed then its best to follow the instructions for the berger bullets. .010" or less adjustments are meaningless. On fast 6mm throat erosion can be measured .001" per 100 rounds so the .003" adjustments are pointless in my opinion.

 

[woods]

Because of slightly decreasing the case capacity with each decrease in COAL I have been watching for pressuere signs just to be safe.

Your case does not hold the pressure the chamber does. Because you are giving your bullet more and more of a running start, your pressure will decrease when seating deeper, at least within the range of normal seating depths (.00" off to approx. .250" off)

To your original question, I prefer increments of .015" and I am looking for low Extreme Spread and Standard Deviation in velocities as much if not more than grouping

 

[FearNoWind]

Your case does not hold the pressure the chamber does. Because you are giving your bullet more and more of a running start, your pressure will decrease when seating deeper, at least within the range of normal seating depths (.00" off to approx. .250" off)

(image)

To your original question, I prefer increments of .015" and I am looking for low Extreme Spread and Standard Deviation in velocities as much if not more than grouping

(images)

Just wanted to say how impressed I am with your generosity in providing all that data. The more "valid" learning tools we include in posts to this site the faster we all improve in our shooting skills. gun)

 

[coyotezapper]

After finding my OCW for my 7mm rem mag, I try to bring the groups together by adjusting the seating depth. I have been doing my initial testing with a COAL of 3.370" because that is the max that will fit nicely into my magazine. For my seating depth test I have been loading the bullets in 0.010" shorter incriments (3.360, 3.350......) all the way down to the manuals 2.329" spec. Because of slightly decreasing the case capacity with each decrease in COAL I have been watching for pressuere signs just to be safe. Is the 0.010" incriments to much to be able to fine better accuracy. Should they be smaller increments.

If your OCW is actually a true flat spot / node then your seating depth window should be fairly wide so .010" will work fine. Seating depth windows can be .010-.030" or more. Once I determine my window I seat to the long side to allow for throat erosion.

 

[Pharmseller]

Another vote for the Berger method. I use this technique for all bullet types.

An illustration. Pay attention to OAL.


First group

Second group

Third group

I didn't even try the fourth loading.





P

 

[Brad615]

I shoot berger vld & they like to be pushed into the lans, at least in my 7mm & 300 RUM. I load to max per loading book. Nosler brass, federal primer & that produces a ragged hole @ 200 yds.

 

[coyotezapper]

I shoot berger vld & they like to be pushed into the lans, at least in my 7mm & 300 RUM. I load to max per loading book. Nosler brass, federal primer & that produces a ragged hole @ 200 yds.

If you are jamming bullets into the lands and loading to book max then you are most likely over pressured. Jamming adds 5-6K pressure. What load manual are you using?

 

[rcoody]

If you are jamming bullets into the lands and loading to book max then you are most likely over pressured. Jamming adds 5-6K pressure. What load manual are you using?

Lots of.misinformation out there about loading into the lands. I do it regularly.

Read about the competition benchrest shooters and the loads they use. I will put your mind at ease.