Bipolar seating depth test results today

[Gregor.Samsa]

Today I tested what I was hoping To be the final leg in load development for my 6.5 and 308 rifles. It was hot as hell, fairly windy and uncharacteristically humid in Sacramento today.

The 6.5 seems to be very good and forgiving.
tikka 6.5 CTR
140 ELDMs
41.5g H4359
Tested seating from .005” to .050” from the lands. Which depth would you pick?

 

[Gregor.Samsa]

Now this is where shit gets ugly!
The rifle is a Howa 1500. 150 rounds down the pipe. I’ve been having troubles with feeding. I’ve made progress but I’d still occasionally have to break my cheek welder fuck around getting it to feed. I think this was a big aggrevation and broke focus. I’m not a great shot but this didn’t help. I’m having trouble interpreting the test due to the fliers.
The load is:
New lapua brass
210m primers
43.2g varget
175 RDFs
Seated .005” to .050” in .005” increments.
I chose this load as it was in a really good es/sd node and seemed to have less vertical dispersion. I’m pretty new to precision handloading and test interpretation does maybe this is a crap load. What are your thoughts?

 

[Gregor.Samsa]

I didn’t use a chrono today. Previous average speeds for the 6.5 and 308 loads respectively were 2702fps and 2614 FPS. Thanks

 

[TheOfficeT-Rex]

Tikka: somewhere in the 25 to 35 range. I'd load closer to 25 and let throat erosion keep you in the sweet zone. Load up some at 25 and lob some 5 or 10 round groups, and maybe try some at 60 or longer as well, just to confirm. There also likely be another sweet spot a little further out.
Howa: 35 to 40, but I would also look at some loads with more jump. I find the RDF profile really finnicky, so don't get discouraged quite yet.

I prefer to do jump tests with two sets of three rounds at each length (Berger protocol). When i think I have a couple lengths to explore, I nail it down with 5 round clusters.

 

[Gregor.Samsa]

Tikka: somewhere in the 25 to 35 range. I'd load closer to 25 and let throat erosion keep you in the sweet zone. Load up some at 25 and lob some 5 or 10 round groups, and maybe try some at 60 or longer as well, just to confirm. There also likely be another sweet spot a little further out.
Howa: 35 to 40, but I would also look at some loads with more jump. I find the RDF profile really finnicky, so don't get discouraged quite yet.

I prefer to do jump tests with two sets of three rounds at each length (Berger protocol). When i think I have a couple lengths to explore, I nail it down with 5 round clusters.

thank you for this advice. I'm not sure if I can load much further out on the tikka, but I like the idea of loading closest to the lands in that series. The RDF was really baffling. High winds, feeding issues and a mediocre shooter make it hard to figure out. appreciate the advice

 

[Jordanwickham]

As the last guy said I personally would run the ELDms at .30". Based on my loadings for these, obviously different gun and all that, but my experience is that the ELMs run well at 30-45k.

As for the RDFs I don't have much first hand experience but through the grapevine I have heard you want to hail Mary those things to the lands. Don't be afraid to get all the way out with them.

If it were me I would run them rough at like 20 increments as far out as you can.

I know I'll probably get a little flame for suggesting a 20k jump increment but I did a rough test today with 30ks and found a good starting point for some tinkering I'm doing.

 

[Gregor.Samsa]

As the last guy said I personally would run the ELDms at .30". Based on my loadings for these, obviously different gun and all that, but my experience is that the ELMs run well at 30-45k.

As for the RDFs I don't have much first hand experience but through the grapevine I have heard you want to hail Mary those things to the lands. Don't be afraid to get all the way out with them.

If it were me I would run them rough at like 20 increments as far out as you can.

I know I'll probably get a little flame for suggesting a 20k jump increment but I did a rough test today with 30ks and found a good starting point for some tinkering I'm doing.

I need to get a mag without a binder plate to seat much closer. One of the issues I’m having with the howa is the bullet tip gets caught under the feed ramp lip. I’ve adjusted the KRG bravo stock to gain as much clearance as possible but I’m still not there. I’m considering having a gunsmith notch the ramp if that’s a kosher practice. Thanks

 

[Jordanwickham]

I need to get a mag without a binder plate to seat much closer. One of the issues I’m having with the howa is the bullet tip gets caught under the feed ramp lip. I’ve adjusted the KRG bravo stock to gain as much clearance as possible but I’m still not there. I’m considering having a gunsmith notch the ramp if that’s a kosher practice. Thanks

I'm not saying seat closer to the lands with the RDFs, I'm saying lob that thing in from about .250" back. Alot of people are +.120" to get them to shoot great groups.
I'd obviously start at mag length and do .020" further from lands jumps till I ran into compression. If you are loading hot already this will boost your pressure when you get out past about .050" so you may have to drop a 10th on the powder charge. It'll help if your throat already has a plethora of freebore. Not sure what your mag length to lands relationship is for jump.
At any rate I would test any jump I could get out of it safely.

 

[Gregor.Samsa]

Gotcha! Thanks

 

[Ryridesmotox]

Ditch the RDFs. My Howa doesn't like them either. 175 sierra SMKs are easy mode, get them and load em up.

 

[Jordanwickham]

Ditch the RDFs. My Howa doesn't like them either. 175 sierra SMKs are easy mode, get them and load em up.

He has a point. Tangents are the training wheels of bullet design, hybrids are when you first take off the training wheels, secants are like riding a 1 mile wheelie.

 

[Dthomas3523]

First one: .027 off (gives you .002 error to .025) and you have plenty to cover erosion.

Second: keep moving away from lands. None of those are acceptable.

 

[Gregor.Samsa]

First one: .027 off (gives you .002 error to .025) and you have plenty to cover erosion.

Second: keep moving away from lands. None of those are acceptable.

thank you. Not second guessing your recommendation at all, but how do you determine whether to move closer or further away from the lands?

 

[Dthomas3523]

thank you. Not second guessing your recommendation at all, but how do you determine whether to move closer or further away from the lands?

Didn’t you test .005 - .050? I thought that’s what you tested. None of that worked. So you have no choice except to keep moving.

 

[Gregor.Samsa]

Didn’t you test .005 - .050? I thought that’s what you tested. None of that worked. So you have no choice except to keep moving.

yes. Makes sense lol. I thought there was some pattern that you identified but common sense obviously escapes me some times. Thanks for the advice.

 

[Dthomas3523]

yes. Makes sense lol. I thought there was some pattern that you identified but common sense obviously escapes me some times. Thanks for the advice.

Lol, nope. Start close and keep moving until it shoots and you have a node that will allow for some erosion.

For PRS type stuff, you can usually find a node that’s good for the life of the barrel or close to it.

 

[clcustom1911]

Today I tested what I was hoping To be the final leg in load development for my 6.5 and 308 rifles. It was hot as hell, fairly windy and uncharacteristically humid in Sacramento today.

The 6.5 seems to be very good and forgiving.
tikka 6.5 CTR
140 ELDMs
41.5g H4359
Tested seating from .005” to .050” from the lands. Which depth would you pick?

Stay at .015 off and you should be able to maintain good groups until it erodes back to .040-045".

Make sense?

 

[clcustom1911]

I'm not saying seat closer to the lands with the RDFs, I'm saying lob that thing in from about .250" back. Alot of people are +.120" to get them to shoot great groups.
I'd obviously start at mag length and do .020" further from lands jumps till I ran into compression. If you are loading hot already this will boost your pressure when you get out past about .050" so you may have to drop a 10th on the powder charge. It'll help if your throat already has a plethora of freebore. Not sure what your mag length to lands relationship is for jump.
At any rate I would test any jump I could get out of it safely.

Yes. RDF's like a looooooong jump. As long as it shoots well, the amount of jump is moot.

 

[spife7980]

Every rdf (70,85,105,115,130,140) I’ve ever tried has shot just fine .015-.030 off the lands. That’s from touch, not arbitrary jam.

 

[Steel head]

Yes. RDF's like a looooooong jump. As long as it shoots well, the amount of jump is moot.

Every rdf (70,85,105,115,130,140) I’ve ever tried has shot just fine .015-.030 off the lands. That’s from touch, not arbitrary jam.

The 140 and 185 RDF’s did well with plenty of jump for me.

 

[Gregor.Samsa]

Thanks. I’ll load some shorter and post results. Thanks

 

[Raffy]

Not trying to change the topic/hijack but it seems pertinent. How much throat erosion do you usually see out of an average barrels life? Besides accuracy, how do you decide when to seat to x depth vs y depth knowing that you will see erosion from a new barrel over its lifespan?

 

[TheOfficeT-Rex]

Not trying to change the topic/hijack but it seems pertinent. How much throat erosion do you usually see out of an average barrels life?

How long is a piece of string? It depends on caliber, load, how fast you shoot, and what you consider "acceptable life." Assuming you reload, its not particularly relevant as long as you're not running into issues with magazine length.

Besides accuracy, how do you decide when to seat to x depth vs y depth knowing that you will see erosion from a new barrel over its lifespan?

Tune accuracy with seating depth. For me, the only limiting factors are long throats and magazine lengths. If you have 25-60min to burn, I found part 1 &2 of Cortina's vids pretty well done. Listen to his method/concept, don't focus on his rhetoric/semantics/presentation style. He could be considered technically 'chasing the lands,' but he's trying to make a point that knowing exactly where they are is irrelevant. If you accept that and move on, there are some good ideas there.
Chasing the Lands Part I

 

[Raffy]

How long is a piece of string? It depends on caliber, load, how fast you shoot, and what you consider "acceptable life." Assuming you reload, its not particularly relevant as long as you're not running into issues with magazine length.


Tune accuracy with seating depth. For me, the only limiting factors are long throats and magazine lengths. If you have 25-60min to burn, I found part 1 &2 of Cortina's vids pretty well done. Listen to his method/concept, don't focus on his rhetoric/semantics/presentation style. He could be considered technically 'chasing the lands,' but he's trying to make a point that knowing exactly where they are is irrelevant. If you accept that and move on, there are some good ideas there.
Chasing the Lands Part I

Thanks I will check it out. So it sounds like throat erosion is irrelevant as long as you can load out further to where the bullet/gun likes? Would you switch to a bullet with a longer profile if you could get the ogive of a different bullet to a sweet spot after excess throat erosion? (Provided you still had magazine capacity to fit them)

Hope that makes sense...

 

[TheOfficeT-Rex]

So it sounds like throat erosion is irrelevant as long as you can load out further to where the bullet/gun likes?

The fact it is occurring is not irrelevant, but knowing exactly where you lands are is. Using the Cortina method, you would have a rough idea based on how far you've moved your seating depth.

Would you switch to a bullet with a longer profile if you could get the ogive of a different bullet to a sweet spot after excess throat erosion? (Provided you still had magazine capacity to fit them)

Only if you wanted to - You could also seat the original bullet deeper to find another seating depth 'node' if you ran out of magazine length.

If I didn't like tinkering with it so much, I would just buy one lot of bullets when I bought the barrel and shoot it out using those.