Seating depth - does it even matter?

[Dobeman887]

I will try to be the second voice of reason. I tried chasing the lands when long range shooting was much less popular and knowledge was not as readily available. I did it for 2 barrels. It made accuracy WORSE, as the powder charge needed to be changed to bring it back.

Sometimes I throw the barrel away after the initial load stops shooting. If it is a screamer barrel, or I am being cheap, I can usually get more rounds out of it by moving the bullet out and adding powder. This is after 100s or 1000s of rounds though. Also, it is with chasing sub 1/2 moa for 10 rounds. I have never owned a hunting rifle/caliber that would consistently put nearly all 10 round groups under 1/2 moa. For very good 3/4 - 1 moa rifles it is not very easy to see. For good to average 1.25 moa to 2 moa rifles it is very difficult to see a difference. This is with 10 shot groups or more. Shooting less than 10 shots will definitely lie to you. 10 shots will occasionally, but I rarely shoot more as I feel it is "good enough."

TLDR version, only do it if you love to experiment and prove things to yourself. Chasing the lands is not beneficial to accuracy. It is detrimental.

Thanks for the input. I have only made 10 rounds so far to test, so maybe I won't take it any further than that.

 

[Dobeman887]

To update all of you on a lesson I learned from "chasing the lands", be very careful when increasing bullet seating depth. There are 13 pages of posts here, and I wish I had read them all before increasing my OAL. Bottom line, THE CLOSER THAT BULLET GETS TO THE LANDS, THE HIGHER THE PRESSURE BECOMES. I was lucky with my 270 and it simply destroyed the primer, rear of case. It could have been much worse. At this point, I will not chase the lands anymore and just stick to suggested OAL's.

 

[Fireflyfishing]

Yes, it matters.

 

[JGRaider]

To update all of you on a lesson I learned from "chasing the lands", be very careful when increasing bullet seating depth. There are 13 pages of posts here, and I wish I had read them all before increasing my OAL. Bottom line, THE CLOSER THAT BULLET GETS TO THE LANDS, THE HIGHER THE PRESSURE BECOMES. I was lucky with my 270 and it simply destroyed the primer, rear of case. It could have been much worse. At this point, I will not chase the lands anymore and just stick to suggested OAL's.

Yep, that's why you should start at max mag box length, or just off the lands, then increase charges until pressure is found. Only one way to go from there, and that's to seat deeper if need be.

 

[parshal]

If increasing COAL brings you to destroyed cases you're load is overpressure already.

 

[Harvey_NW]

Yes, it matters.

13 pages and only 1 example that falls outside the expected variability with a 17 cal that has a super short bearing surface.

If you claim that it matters, please provide proof.

 

[Fireflyfishing]

13 pages and only 1 example that falls outside the expected variability with a 17 cal that has a super short bearing surface.

If you claim that it matters, please provide proof.

Here ya go. Here’s a 15 shot group after I completed a seating depth test. This was obviously the winner. I only used 6 shots each on the 3 different seating tests I completed each load was 0.015” difference. According to the Hornady app, this is 15 shots under 1 moa.

 

[Harvey_NW]

View attachment 937461
Here ya go. Here’s a 15 shot group after I completed a seating depth test. This was obviously the winner. I only used 6 shots each on the 3 different seating tests I completed each load was 0.015” difference. According to the Hornady app, this is 15 shots under 1 moa.

Awesome, please also post the test results so we can factor in sample sizes and apply the statistical variabilities to see if your results align. Otherwise, this proves nothing besides you and your rifle shoot well.

 

[Fireflyfishing]

Awesome, please also post the test results so we can factor in sample sizes and apply the statistical variabilities to see if your results align. Otherwise, this proves nothing besides you and your rifle shoot well.

Unfortunately, I didn’t shoot photos of the test loads. What I can tell you is the other groups that didn’t make the cut were over 1 MOA with 6 shots. That led me to pick the load with the group above.

The bottom line, I’ve found it to be very beneficial after I have found a good powder and bullet combo. I go through the seating depth test process after the before mentioned combo is found. I consistently have good results in several different rifles.

As others have mentioned, sometimes it doesn’t matter. I have an AR that shoots mag length 77SMKs just over 1 MOA with a 30 round mag. I produce those loads in large quantity from my Dillon press, not individually from a single stage press.

I think it’s worth mentioning several of the bullet manufactures have a published method they recommend for a seat depth test. Berger being one of them. That’s the test I used. Erik Cortina has a vid with his version of a seating depth test.