Seating Depth Test Help

[Jpistolero02]

I need some help interpreting the results of a seating depth test. Would I be better off retesting the area around 1.658-1.655? The area from 1.649-1.643 seems to jump around vertically a little too much. For reference, the green dots are .5". Also, this was from 100 yards. Thanks in advance for the help.

 

[HSmithTX]

Personally I would keep going, longer if you have room before you get into the lands and shorter too. I don't like having narrow seating depth windows for good shooting. I like to find a window at least .010" long that shoots well so I don't have to sort bullets and things like that, just load and shoot. I would also retest in the 1.643-1.652 area with a tenth or two more and less powder. That area looks like it's trying to shoot well and might just need a tweak. You could try a primer substitution in that area as well.

 

[Jpistolero02]

I have room. I normally do a Hornday gauge until it can't go anymore and then back out .030". My guess is that's putting me somewhere .010"-.015" from touching the lands. It's certainly not shooting poorly, but I am always looking for more. If I do the first 18 rounds before it clearly starts to open back up, this is what they all look like together. Thanks for the feedback.

 

[nwmnbowhunter]

Your impacts are doing well and hitting very similar points of impact which is awesome.

Personally i would try to stretch out your distance. Trying to read hundreds of an inch difference at 100 yards can be chasing your tail.


Your groups are small enough its time to stretch it out.... assuming you are planning to shoot at longer distances.

 

[HSmithTX]

Yes, it looks like that rifle might be a stellar shooter instead of just a good shooter once you get it completely dialed in, a couple of those groups are really small.

 

[Rick Richard]

Looks like some great groups, but the "proof in the pudding" is what will it do OUT THERE. Tight 100 yard groups do make us feel good though….just saying.

 

[Beluebow]

It's a Dasher....somewhere between .010 in and .010 off usually works with that bullet. Not sure what freebore you have (guessing .105) but 2950-70ish is pretty decent area. Unless this is a PRS rifle and they run those sloooww.

 

[nksmfamjp]

How far off lands is 1.658"?

 

[tomcat818]

Definitely looks happier the closer to the lands it goes. I originally used the Hornady gauge to find the lands and didn't like that it was hard to get repeatable results. I changed my process to setting up a fire formed dummy using the same load development brass and use a caliber diameter mandrel to set interference fit @ ~.0005" seated long enough to impact the jams. I recommend using a mandrel and graphite dry lube and leave it in the neck to alleviate even more interference as to not stick the bullet in the rifling. Chamber the dummy round and force the bullet into the case while in contact with the jams. Some say to strip the bolt before doing this to better feel the pressure during the process but seems to work fine without this step.

I believe you could be in the neighborhood of .060" off the lands to start basing it off the Hornady gauge. . One or possible two reasons for this; first if you used the Hornady tapped case then you're not using fire formed brass and secondly the neck interference fit is positive on the Hornady cases by ~+.002" over caliber(.245" in your case). Each .001" of interference fit (neck tension) adds ~.015" of available seating depth or distance from the lands so these gauges are ~ .030" off the lands and with another -.002" (This is what I use some like more or less) interference fit then you would be ~.060 of the lands. Seems to show up in your results since most hybrid targets like a seating depth between .025-.045" off so your CBTO of 1.655 would put you near ~.045 off (assuming neck tension of .002") where I see POI and groups improving. I would continue closer with caution using same increments to near .025" and you should see additional improvement.

 

[Jpistolero02]

I did run some hotter in the 2980 range. Got two slightly tougher bolts lifts but nothing that concerned me. They didn't seem to be quite as consistent, but I might need to test going closer toward the lands. I know that will increase the pressure as well. Here are those rounds and depth tests. Did have a few left that I fired at 430 and they did ok but I was having to fight mirage so not a fair shake. They were right at 1/2 MOA.

 

[R. Cram]

I don't believe you have an groups that would give you reliable information, they are all so close to the same size and shot at 100 instead of 200 and only 3 shots

 

[dogz]

Curious George here, how heavy is your gun scoped and ready to roll?

 

[Hugnot]

Lots of numbers with measurements with .003 increments for the fire formed 6 Dasher. Did the shooting progress from left to right? If so bore fouling should be considered.
Possibly measurements having larger than .003 increments and 5 shot groups to find a good spot then expand testing with selected depth to more shot groups.
My thinking is to keep activities at 100 yards to minimize other stuff like wind. An assumption being the bullet has extremely tight ogive measurements.

 

[Jpistolero02]

Definitely looks happier the closer to the lands it goes. I originally used the Hornady gauge to find the lands and didn't like that it was hard to get repeatable results. I changed my process to setting up a fire formed dummy using the same load development brass and use a caliber diameter mandrel to set interference fit @ ~.0005" seated long enough to impact the jams. I recommend using a mandrel and graphite dry lube and leave it in the neck to alleviate even more interference as to not stick the bullet in the rifling. Chamber the dummy round and force the bullet into the case while in contact with the jams. Some say to strip the bolt before doing this to better feel the pressure during the process but seems to work fine without this step.

I believe you could be in the neighborhood of .060" off the lands to start basing it off the Hornady gauge. . One or possible two reasons for this; first if you used the Hornady tapped case then you're not using fire formed brass and secondly the neck interference fit is positive on the Hornady cases by ~+.002" over caliber(.245" in your case). Each .001" of interference fit (neck tension) adds ~.015" of available seating depth or distance from the lands so these gauges are ~ .030" off the lands and with another -.002" (This is what I use some like more or less) interference fit then you would be ~.060 of the lands. Seems to show up in your results since most hybrid targets like a seating depth between .025-.045" off so your CBTO of 1.655 would put you near ~.045 off (assuming neck tension of .002") where I see POI and groups improving. I would continue closer with caution using same increments to near .025" and you should see additional improvement.

Man, if you weren't spot on. I just did your method of using sized brass and a little sizing wax on the bullet seated really long. It gave me a measurement a CBTO of 1.700". I have some room to move things closer as a test. I will give that a go and see how she does. Thanks for all the help to everyone. I will keep everyone posted in case you are curious how things go.