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Topic: Seating depth testing (Read 780 times) previous topic - next topic

Seating depth testing

I post this as a good demonstration on how seating depth testing is arguably as, if not more, important as proper charge weight.  I had muffed up a distance to lands measurement and had been shooting matches at 600 and 1000yds with a much less than optimal seating depth.  I had extensive course and fine powder charge tests on this bullet/case using a couple of known good powders for the cartridge but still I was getting erratic results; sometime great, sometimes average.  I remeasured my distance to lands after finding my problem with the previous measurement and ran through a test of 0.010, 0.013, 0.016 and 0.019" off light touch (I started at '10 off' as the Berger 184 hybrid is known to shoot well near 0.015" in most guns).  Here are the results:

0.010" off



0.013" off



0.016" off



0.019" off



You can see how, when you get close and you in the powder charge ball park the groups go horizontal with low vertical.  Once in the optimum seating depth it pulls together.  These were shot at 300yds.

Robin



Re: Seating depth testing

Reply #1
I couldn't agree more about seating depth being more important than charge weight once you're close.

I split between +.004 & +.005 out in MN last weekend making + .0045 my targeted seating depth. I really wanted to seat at .004 but had never shot +.003 on the new Lilja barrel before and was worried it was too close to the lands or on the edge of the node and didn't want to risk it coming out of the seating tune.

I'll be looking for scores on AS this weekend! I wanted to be in Harris MN shooting one more 600 yard match before Nationals but had business today I couldn't ignore.
Dave

Re: Seating depth testing

Reply #2
IBS Nats Dave?  Where are they this year?

Re: Seating depth testing

Reply #3
IBS Nats Dave?  Where are they this year?

Yes IBS 600 yard Nationals

Harris MN, October 12 - 13 with the 14th saved for a weather day.

https://internationalbenchrest.com/events/2019/01/31/long-range-600-yard-nationals-9-21-9-22
Dave

Re: Seating depth testing

Reply #4
I suppose that is not too far of a drive for you.  Would that be your 'home range' if you have such a thing considering your location?

Re: Seating depth testing

Reply #5
I suppose that is not too far of a drive for you.  Would that be your 'home range' if you have such a thing considering your location?

Has to be 7 hours to Harris from home, 9 hours from my place up north according to Google

I've never been to Harris before. Elbow Lake MN last week is closer. Hunter's point in Humboldt SD is about 6 hours from my home but I've never been there either. All 600 yard venues but they're trying to expand to 1000 at Elbow Lake.
Dave

Re: Seating depth testing

Reply #6
I guess I've got it good; I have 3 1000yd ranges within 4 hrs (closest 2.5hrs) and 3 600yd ranges within 3 hrs..  I need to stop complaining about the 3 hr runs :-[ .

Re: Seating depth testing

Reply #7
I would imagine Eric shoots at most of the Minnesota ranges.

Re: Seating depth testing

Reply #8
quick correction- Hunters Point is near Humbolt SD, approximately 25 miles west of Sioux Falls.  :)   Great place to shoot. 

Re: Seating depth testing

Reply #9
I've been reading the thread and I think you might just be the guys to question.  I have no problem measuring the base to lands on new barrels, but as they wear, not worn out, I start getting erratic measurements.  I have thought that this may be caused by a raged throat and lands.  Any tips on this?  Also, how do you get such close measurements?  I get erratic +- .003" with my BTO seating measurements.  I'm using the Hornady comparator and have tried several calipers including Starret and Mitutoyo with the same results.  I am using Hornady seating dies with their micro seating accessory and bullet specific seating stems. 

Re: Seating depth testing

Reply #10
I've been reading the thread and I think you might just be the guys to question.  I have no problem measuring the base to lands on new barrels, but as they wear, not worn out, I start getting erratic measurements.  I have thought that this may be caused by a raged throat and lands.  Any tips on this?  Also, how do you get such close measurements?  I get erratic +- .003" with my BTO seating measurements.  I'm using the Hornady comparator and have tried several calipers including Starret and Mitutoyo with the same results.  I am using Hornady seating dies with their micro seating accessory and bullet specific seating stems.

Before measuring distance to lands it's critical to clean the barrel paying close attention to the throat. Use a brush to get the throat clean. If you still don't get consistent measurements take several readings writing them down and throw out any high or low readings and average the rest.

The exact number is irrelevant you are just looking for a baseline number to make adjustments on to work into the node.

As your throat wear progresses sometimes it's easier to shoot ladders seated longer at small increments to creep back into the node to come up with your B to O measurement.

I've switched over to Sinclair comparator inserts because I feel they measure closer to the actual ogive and have a more uniform hole.

Lastly sorting bullets by base to ogive into lots of .001" has helped me maintain a tighter degree of seating depth accuracy. Set your die to seat .003' long then measure and then seat to desired depth.

Seating depth is the easiest accuracy to obtain once you are close on the powder. .003"-.006" can cut your groups in half.

Many people will wear a barrel out seated at .020"off (because the guys on the internet said that's where to seat) chasing powder and never do a thorough seating depth test.
Dave

Re: Seating depth testing

Reply #11
quick correction- Hunters Point is near Humbolt SD, approximately 25 miles west of Sioux Falls.  :)   Great place to shoot.

Duly noted and thanks for the catch! I'm going to try and shoot there this season. I heard the 2020 600 yard Nationals are going to be there. I was close they are 7.4 miles apart LOL
Dave