106 TAP for hunting?

[ddowning]

Berger has specs on their site. If you are able to grab a measurement for what you have, I can compare it to mathing out from their listed specs for the bullet you have. I think if those numbers match, I can math out for the other Bergers and be comfortable assuming they are correct for my purposes.

So, yes please!

I measured 3 random bullets. I don't have a way to measure the chamfer depth on my comparator, so I can't compensate for that. These are 108 BT Target

OAL - 1.207", 1.211", 1.205"
Nose length - .530", .534", .528"
Bearing surface - .516" all
Boat tail length - .161" all

Also, I don't know the diameter of the hole in my comparator, but it is the 6mm hornady.

 

[ddowning]

I haven't specified a jump measurement. I'm open to and encourage suggestions from anyone knowledgeable. The barrel and dummy round are in the mail. Is jump a consideration for a person who doesn't clean barrels anymore? Does chasing lands extend usable barrel life?

In my experience, you only chase the lands when it stops shooting. If you do it before that, you are chasing your tail. When a barrel stops shooting I look for things that are loose, check scope, clean to bare metal (need borescope for this one), seat bullet closer to the lands. SOMETIMES this will make a barrel shoot acceptably again. For max performance/accuracy, when a barrel quits shooting and cleaning won't fix it, I am done with it for anything serious. I am not taking a barrel with a reworked load on an important hunt or shooting it at a national or regional level match. I use them for practice, local matches, culling does.

Compared to the cost of a 2 day match or a back country hunt, a barrel is damn cheap. That said, I would throat it to around a .020" jump when designing the reamer. Bore/groove dimensions and reamer dimension variance as well as bullet diameter variance will have some effect. If chambering to a dummy cartridge with a throater you can get it nuts on.

I have not shot any 106 yet. With 115 dtac and Hornady 105 bthp and 108 berger target I would have the smith run the throated to get a .040" jump.

I honestly don't custom throat my chambers. Many of them, especially the 243AI have a lot of bullet in the case. Unless you are worried about case capacity, I have had no issues with accuracy or donuts, even with brass fired 30x+ the way I size. I get 3200fps+ with 105s in 26" 243AI barrels. This is with h1000 and n165, so more speed is probably there for the taking with a different powder, even with the short throat.

If it is a fun gun and not a serious one, I would throat it to touch with the bt junction in the correct spot. You can seat deeper for jump and seat longer for wear for max rounds of playing around. For something serious, I would throat to my liking, and, when accuracy dropped, I would scrap it for a new one.

 

[sndmn11]

Is jump a consideration for a person who doesn't clean barrels anymore? Does chasing lands extend usable barrel life?

I was hoping you'd tell me!

 

[Jimbee]

I was hoping you'd tell me!

Hopefully we can find an adult to help us

 

[Wrench]

I haven't specified a jump measurement. I'm open to and encourage suggestions from anyone knowledgeable. The barrel and dummy round are in the mail. Is jump a consideration for a person who doesn't clean barrels anymore? Does chasing lands extend usable barrel life?

Chasing the lands is a secant ogive technique. On a tangent or hybrid it becomes typically unnecessary. The main reasons to get the bullet up to the shoulder junction are doughnuts and case capacity.

If you form a doughnut but never seat the bullet to the doughnut....it basically has zero effect...seat into the doughnut and pressure can spike.

I'd shoot for a kiss at 20 over the shoulder if you have room and if not, just gauge the brass to see if flow is going to bite you.

 

[wind gypsy]

Does anyone have in hand:
-Berger 105/108/115
-Hornady 103/108
-Sierra 95/100
?

If so, could some take a measurement from the back of the bearing surface where it meets the boat tail to the ogive?
View attachment 660588

I have a bunch of these 106mysterys and will have my throat cut from a dummy round that has as short of a jump as possible. I may hunt with any of the above bullets, and I think I'd likely seat that dummy round like I do all my cartridges with the bearing surface/boattail junction at the base bottom of the car neck.

If I understand which of the above bullets has the longest measurement, I can know it's a no-go or plan in advance. I do understand that your measurement will be less than precise, but it gives me an idea without buying a full bow of each sku.

Quick and dirty single bullet measurements of what I have on hand using a caliper and single hornady bullet comparator (only have one .243 bushing) - 108 Elite hunter, 115 DTAC, 106 TAP

108 EH	BT 2 Tip	1.096​	BT	0.168​
	Base 2 OG	0.665​	Nose	0.599​
	OAL	1.264​	bearing	0.497​
106 TAP	BT 2 Tip	1.142​	BT	0.165​
	Base 2 OG	0.702​	Nose	0.605​
	OAL	1.307​	bearing	0.537​
115 DTAC	BT 2 Tip	1.109​	BT	0.211​
	Base 2 OG	0.750​	Nose	0.570​
	OAL	1.320​	bearing	0.539​

Compared to the 108 EH, the TAP bullets take up a fair bit more powder space and would benefit more from long freebore.

The TAP in this pic are actually seated with 20 thou’ish less jump than the 108 EH.

 

[eoperator]

I called hornady 2 more times inquiring about these 106's. Both guys were quite sure having interlock ring and eldx'ish jacket they are 106 tap not the dod version. They said 7.5 twist is recommend but over 3k 8 twist is likely ok.

Neither of the guys were 100% sure of the translucent tips. One of the guys said the original version of the 106 tap had a semi clear/red tip that infringed on pattent stuff and was changed. He was geussing that they are old contract overrun or possibly original prototype production that have been released.

 

[sndmn11]

Quick and dirty single bullet measurements of what I have on hand using a caliper and single hornady bullet comparator (only have one .243 bushing) - 108 Elite hunter, 115 DTAC, 106 TAP

108 EH	BT 2 Tip	1.096​	BT	0.168​
	Base 2 OG	0.665​	Nose	0.599​
	OAL	1.264​	bearing	0.497​
106 TAP	BT 2 Tip	1.142​	BT	0.165​
	Base 2 OG	0.702​	Nose	0.605​
	OAL	1.307​	bearing	0.537​
115 DTAC	BT 2 Tip	1.109​	BT	0.211​
	Base 2 OG	0.750​	Nose	0.570​
	OAL	1.320​	bearing	0.539​

Compared to the 108 EH, the TAP bullets take up a fair bit more powder space and would benefit more from long freebore.

The TAP in this pic are actually seated with 20 thou’ish less jump than the 108 EH.
View attachment 661191

Ohhh you earned two honey holes and a backpack ferry.

 

[wind gypsy]

Ohhh you earned two honey holes and a backpack ferry.

The thing is, the bullet measurements dont really align with differences when I found distance to lands so I don't know if I jacked up a measurement somewhere or if that can be attributed to the lands being a different diameter than the hornady comparator and the geometries of the bullets at that location being significantly different?

 

[sndmn11]

The thing is, the bullet measurements dont really align with differences when I found distance to lands so I don't know if I jacked up a measurement somewhere or if that can be attributed to the lands being a different diameter than the hornady comparator and the geometries of the bullets at that location being significantly different?

One honey hole demerit.


I'll just go buy a box of each and see what I come up with. I also haven't talked to Fritz about my uneducated assumption about the distance to lands and if that is when a barrel dies.

 

[wind gypsy]

One honey hole demerit.


I'll just go buy a box of each and see what I come up with. I also haven't talked to Fritz about my uneducated assumption about the distance to lands and if that is when a barrel dies.

My understanding is it is not at all distance to lands but rather when the lands get degraded enough in the throat that it doesn't shoot well anymore. Which is why I tend favor having a longer throat if a guy isn't going to chase lands. You can live with lower pressures from the start and never have to seat a bullet's bearing surface below the donut area.

If it was distance to lands, all of the long throated hornady and weatherby designs would have way worse barrel life than cartridges with comparable capacities but short throats. I don't believe that is the case.

 

[sndmn11]

My understanding is it is not at all distance to lands but rather when the lands get degraded enough in the throat that it doesn't shoot well anymore. Which is why I tend favor having a longer throat if a guy isn't going to chase lands. You can live with lower pressures from the start and never have to seat a bullet's bearing surface below the donut area.

If it was distance to lands, all of the long throated hornady and weatherby designs would have way worse barrel life than cartridges with comparable capacities but short throats. I don't believe that is the case.

If the lands started at A and then degraded, could the throat then be reamed at D to crisp up the lands to make it new-ish?

 

[wind gypsy]

One honey hole demerit.

I'm a "one honey hole" man anyway.

If the lands started at A and then degraded, could the throat then be reamed at D to crisp up the lands to make it new-ish?

I dont know. It makes sense to me that cutting away some of the jacked up lands and creating fresh(er) ones could help. People set barrels back frequently to freshen things up but it seems it's done often before the barrel is toast. There's got to be a limit. I imagine having an inch of freebore to lands that are firecracked anyway isn't going to be a great answer.

 

[MThuntr]

Not my rifle but a friend did some basic load ups with the 106 TAP. Best was 29gr A2520 in 6mmARC with a 20" barrel. He doesn't have a chronograph for some reason but he seems happy for the bullet cost

 

[sierracharlie338]

What seems to be the consensus with the following info:

Im at 500 feet ASL
243 with 8 twist
**SHOULD be able to get them into the 2900-3000 range if they dont pressure out lower than the 105s Im testing

Am I wasting time and components with this setup and just wait til I get my GT up and running with a 7.5 or is it worth trying?

 

[Jimbee]

What seems to be the consensus with the following info:

Im at 500 feet ASL
243 with 8 twist
**SHOULD be able to get them into the 2900-3000 range if they dont pressure out lower than the 105s Im testing

Am I wasting time and components with this setup and just wait til I get my GT up and running with a 7.5 or is it worth trying?

Please try and let us know!

 

[ddowning]

What seems to be the consensus with the following info:

Im at 500 feet ASL
243 with 8 twist
**SHOULD be able to get them into the 2900-3000 range if they dont pressure out lower than the 105s Im testing

Am I wasting time and components with this setup and just wait til I get my GT up and running with a 7.5 or is it worth trying?

Hornady 4dof app gives gyroscope stability at 1.25 in 1:8
1.43 in 1:7.5
1.64 in 1:7.

This is at 500' ASL give or take if you use standard atmosphere (DA 500') for that elevation. If you are at 500' elevation, but have a low pressure front and cold weather (below 50 deg) the numbers will look worse.

It is generally agreed upon that sg=1.5 is stable with no loss of bc. I have had good accuracy all the way down to sg=1.0 at 100 yards. Those combos tend to do crazy things in wind at long range. They are also hell to get the calculator to line up because as the temps change, so will the bc. I experienced this a bunch when shooting DTACS in a Criterion "1:8" that was probably actually a 1:8.3". The gun would shoot great even at distance as long as sg=1.3. The BC would get better all the way to sg=1.5. It was pretty frustrating to try and track at matches. It would be even worse to track while hunting.

Based on the sg numbers, if I was building a gun to shoot these bullets in the 3000fps range, I would use a 1:7 or custom order a 1:7.25 cut rifled barrel from someone that has really tight tolerances for twist rate like Bartlein.

A 1:8 might work, but you will want to test the shit out of it in conditions where the sg drops below 1.5. Given my experience, I try to avoid that as much as possible.

 

[eoperator]

Hornady 4dof app gives gyroscope stability at 1.25 in 1:8
1.43 in 1:7.5
1.64 in 1:7.

This is at 500' ASL give or take if you use standard atmosphere (DA 500') for that elevation. If you are at 500' elevation, but have a low pressure front and cold weather (below 50 deg) the numbers will look worse.

This makes sense my 1:8 6cm shot much better yesterday in temps 40+deg warmer than previous outings.

Where do you find gyroscopic stability within 4dof?
-Edit- found it

7.25 twist 6prc at 3200fps would be about 320k rpm, 7.5 twist would be about 308k rpm.

 

[sierracharlie338]

Hornady 4dof app gives gyroscope stability at 1.25 in 1:8
1.43 in 1:7.5
1.64 in 1:7.

This is at 500' ASL give or take if you use standard atmosphere (DA 500') for that elevation. If you are at 500' elevation, but have a low pressure front and cold weather (below 50 deg) the numbers will look worse.

It is generally agreed upon that sg=1.5 is stable with no loss of bc. I have had good accuracy all the way down to sg=1.0 at 100 yards. Those combos tend to do crazy things in wind at long range. They are also hell to get the calculator to line up because as the temps change, so will the bc. I experienced this a bunch when shooting DTACS in a Criterion "1:8" that was probably actually a 1:8.3". The gun would shoot great even at distance as long as sg=1.3. The BC would get better all the way to sg=1.5. It was pretty frustrating to try and track at matches. It would be even worse to track while hunting.

Based on the sg numbers, if I was building a gun to shoot these bullets in the 3000fps range, I would use a 1:7 or custom order a 1:7.25 cut rifled barrel from someone that has really tight tolerances for twist rate like Bartlein.

A 1:8 might work, but you will want to test the shit out of it in conditions where the sg drops below 1.5. Given my experience, I try to avoid that as much as possible.

This is what I figured I would run into. Granted 99% of my shooting is done above 65 degrees. I may see if I can find a 100yard load for shooting pigs and varmints but probably won’t waste time and components on any long range stuff until I have a faster 6mm.

 

[ddowning]

This makes sense my 1:8 6cm shot much better yesterday in temps 40+deg warmer than previous outings.

Where do you find gyroscopic stability within 4dof?
-Edit- found it

7.25 twist 6prc at 3200fps would be about 320k rpm, 7.5 twist would be about 308k rpm.

I have run Hornady 105 bthp to 309,600 rpm in a 243AI. It is a Bartlein 5r, but I haven't vaporized any bullets in mid-flight...yet.