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6gt

I believe they had a different Reamer at the beginning for the GT as well because there have been quite a few that have gotten 3k on their GT barrel. I posted somewhere earlier in this thread about me pulling my first GT barrel at just over 3400 rounds more or less for piece of mind. It was still shooting the same speed with no real muzzle velocity loss and still shooting tight groups. There are several guys in the Facebook group for GT shooters as well that got 3k.
I don’t even think I’ve seen anyone that hasn’t gotten at least 2300+ before they decided to pull it and those were more or less for piece of mind cause it was their first barrel on that cartridge. I’m sure if they’re running them hot…..north of 3000fps then maybe 🤷‍♂️ I run mine right around 2850 ish and it’s been fine across 3 barrels now.
Thats amazing honestly. As I noted above, mine didn't make it to 2k. A guy I shoot with pulled his at 2k last fall, couldn't get a barrel, and ended up taking his Creedmoor to the Finale.

2850fps is where I was at as well with DTACs. By the time I shot my 3rd Pro Series match, it was down to 2770fps. Thats what the AB guys clocked it at in Montana. I shelved it after that to save it for the Finale and shot my BR. But it was toast.

Just a bad taste in my mouth I guess. Fingers crossed on the next ones.

Edit; I bought my own reamer for that from Manson. I want to say it's a .274 neck and .120 freebore
 
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Thats amazing honestly. As I noted above, mine didn't make it to 2k. A guy I shoot with pulled his at 2k last fall, couldn't get a barrel, and ended up taking his Creedmoor to the Finale.

2850fps is where I was at as well with DTACs. By the time I shot my 3rd Pro Series match, it was down to 2770fps. Thats what the AB guys clocked it at in Montana. I shelved it after that to save it for the Finale and shot my BR. But it was toast.

Just a bad taste in my mouth I guess. Fingers crossed on the next ones.

Edit; I bought my own reamer for that from Manson. I want to say it's a .274 neck and .120 freebore
I don’t know anything about reamers, I leave that to the builders. I’m just a trigger puller. Lol. My first barrel was a bartlein pre-fit from area419 but the rest have been cut by a smith. All have been bartlein though. I shoot club matches with 2 guys that were all at the 2700-2800 count at the end of this season so I don’t see why at least 2500 wouldn’t be a problem. Hopefully you get it figured out.
 
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Thats amazing honestly. As I noted above, mine didn't make it to 2k. A guy I shoot with pulled his at 2k last fall, couldn't get a barrel, and ended up taking his Creedmoor to the Finale.

2850fps is where I was at as well with DTACs. By the time I shot my 3rd Pro Series match, it was down to 2770fps. Thats what the AB guys clocked it at in Montana. I shelved it after that to save it for the Finale and shot my BR. But it was toast.

Just a bad taste in my mouth I guess. Fingers crossed on the next ones.

Edit; I bought my own reamer for that from Manson. I want to say it's a .274 neck and .120 freebore
What powder are you running? I'm convinced that some powders are throat burners. RL17 is one. Not that anyone uses it anymore, just an example.
 
I have no idea why you think I needed all of that explained to me. I understand the process quite well. The head scratcher is how you get to 2000 to 2500 rounds on a 6mm with "little" velocity change.

If you ever followed SoCal's initial 6GT thread on here when this round was in its infancy, you would see a fair number of guys pulled the first run GT barrels at <2500 rounds. Several never made it to 2k and expressed some disappointment. Though I do believe 2000 to 2500 rounds is fair barrel life for the GT, I certainly don't believe you'll get there without loss of velocity.

My BR barrels lose 70 to 80fps on average by the time they get to 2500 rounds. I've not had one surpass 3k in a functional manner. For me, that means will it survive a PRS match without losing velocity.. Nor have I heard of anyone running a GT or BR past 3k. Do I believe a guy could nurse a barrel that far? Sure. I know Morgun King ran a couple Dasher barrels to 3k running a nice easy Berger 105. But he pulled them at that point, and pulled all his other barrels sooner than that.. So that's not the norm for a competitive shooter. The large majority of competitive shooters are pulling a Dasher/GT type of 6mm at around the mid 2k round count. If nothing of significance had changed in the round characteristics by that point, why would anyone be swapping them?

I have no desire to spend pages debating it. I would rather just tell you I'm glad you are seeing good barrel life from your rifles and how you shoot them, and move on.
Definitely not worth arguing with someone about whether or not they believe in throat erosion 🙄
 
So, it’s now popular for long jumps in PRS.

The reason being that while it may not be the smallest groups, you get less change over the course of a 200+ round match.

Which is great. But, no one stops to ask “why.”

Well, that is very likely (without tons of money and equipment you can’t be 100% sure) due to the long jump prohibits the bullet from relying on the lands to build initial pressure.

Let’s say you’re jumping .020

How far does a bullet move forward on the initial primer strike before powder has burned enough to build more pressure.

If it moves .020, now you’re in the lands almost immediately building pressure.

After 150 rounds, your throat moves .006 and changes that.

Or let’s say you’re jumping .020” and the initial movement is .005. That’s 25% of your jump

And when the throat burns .005, your jump is now .030 and the initial movement is now 17%. That’s substantial


Now, let’s take a .070” jump. Bullet moves .005” on primer strike. That’s 7%

Throat burns .005” for .075. Your change still rounds up to 7%

That is likely why long jumps show less deviation across a 200 round match.
Damn, that is one of the best explanations I’ve ever heard. It is completely conch with the jump testing from …. The guy from short action. (I think) which was also very in depth and logical. Great read. In said article he references how Weatherby and (I’m drinking) were pioneers in long throat chambers in the 50’s and showed that the consistency was ~ mitigated, for lack of a better term, by jumping. Good post. I agree.
 
Does anyone have a load for the 108 ELD'sM with H4350 at the 2900 mark? My 109s go 2940 with 36.7, I was thinking 36. 3 or .4 may be a good start?
 
I pulled my 3rd 6GT barrel yesterday. Round count was 2445. Running speeds of 2940 fps.

My first 2 barrels were pulled at 2100 rounds. Running speeds of 3005 fps.

4th, and possibly final barrel, spun on yesterday and breaking in tomorrow.
 
Damn, that is one of the best explanations I’ve ever heard. It is completely conch with the jump testing from …. The guy from short action. (I think) which was also very in depth and logical. Great read. In said article he references how Weatherby and (I’m drinking) were pioneers in long throat chambers in the 50’s and showed that the consistency was ~ mitigated, for lack of a better term, by jumping. Good post. I agree.

Thanks for the kind words.

I will admit this is only theory. I don’t think we can actually prove a lot of this stuff as there are so many variables to try to control.

Also, seating into the lands is generally better for group size and such, but needs to be monitored throughout the day which we don’t have the luxury (might be a good thing) in practical shooting.
 
I pulled my 3rd 6GT barrel yesterday. Round count was 2445. Running speeds of 2940 fps.

My first 2 barrels were pulled at 2100 rounds. Running speeds of 3005 fps.

4th, and possibly final barrel, spun on yesterday and breaking in tomorrow.
Did you pull because of speed loss, throat erosion, accuracy diminishing, or just "playing it safe?"
 
NiteQwill: I'm curious to know if you have any actual data to support "a couple hundred rounds"?
Personal information with frequent people I shoot with (high round match shooters). Guinea pigs with modbb barrels in 6mm. Not one of them is buying another. Example of a 2700 round count Dasher barrel pull. Not worth it to me at the extra cost. I can buy one extra barrel for every 3 modbb barrels and shoot more rounds overall.

Take it as you see it. Ymmv.
 
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2 or 3 guys I shoot with running 400Mod steel are well north of 2500 rounds and still hammering.
In a conversation with Bartlein they stated in their testing that 3500 wasn't an unreasonable.
Time will tell I guess. If the couple guys I know running it in 6BR and 6GT are a testament, then they're well on their way.
 
I pulled my 3rd 6GT barrel yesterday. Round count was 2445. Running speeds of 2940 fps.

My first 2 barrels were pulled at 2100 rounds. Running speeds of 3005 fps.

4th, and possibly final barrel, spun on yesterday and breaking in tomorrow.
It looks like speed does kill. Kills barrels. 🤣
 
Well the numbers we are hearing were twice the barrel life so that's about 5-6000K for a BR or GT.

If you aren't getting that that the extra cost may not be worth it. Its ~ 25% cost increase on a chambered barrel so you would have to get atleat 3100 with the GT or 3750+ with the BR for the cost to even make it worth it.
 
That’s one of the main reasons I picked up a GT barrel. In these days of component and powder shortages I liked the idea of a cartridge that can use 4350 or Varget class powders.
 
Definitely not worth arguing with someone about whether or not they believe in throat erosion 🙄

No one said they they don’t believe in throat erosion.

There is however the erosion into the lands and the erosion at the neck/throat junction. These are not necessarily linear and have different effects on performance.
 
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No one said they they don’t believe in throat erosion.

There is however the erosion into the lands and the erosion at the neck/throat junction. These are not necessarily linear and have different effects on performance.
It is amazing that we have been shooting rifles for 100+ years and we still don’t have definite answers on this. I load close to the lands, purely for accuracy, but if you could get an extra however many rounds of match accuracy out of a barrel by jumping (spacewalking?) then I would try it. It seems the trends in reloading and in cartridge selection is forever going around in one big circle. The 6GT is really just a Swiss Match or a 6x44 with a name behind it, good to see people trying different shit anyway.
 
It is amazing that we have been shooting rifles for 100+ years and we still don’t have definite answers on this. I load close to the lands, purely for accuracy, but if you could get an extra however many rounds of match accuracy out of a barrel by jumping (spacewalking?) then I would try it. It seems the trends in reloading and in cartridge selection is forever going around in one big circle. The 6GT is really just a Swiss Match or a 6x44 with a name behind it, good to see people trying different shit anyway.

Jumping more won’t degrade a barrel less as that’s not what kills a barrel. At least not the velocity part. It’s the end of the neck area. Once that starts heavily degrading, you will lose velocity and then won’t be able to predict the next velocity loss or when it’s just too far gone.

The lands being eroded will be what affects precision (mostly). And you can keep changing them until they are just too far gone or the firecracking is just too much.

That’s why you see some toss a barrel when velocity takes a hit, and others will up the charge and keep chasing until precision falls off. Both are valid strategies if utilized in the proper way.


As far as long jump, that’s not for barrel life. That’s for the longest amount of rounds before precision or POI changes enough to affect your performance.

And it’s fairly well known that jumps are not as precise as loading into the lands. Otherwise BR shooters wouldn’t almost universally be loading into lands.

The difference is the amount of shots taken in a match. A PRS match plus match prep can be 300 rounds or so.


So, we make a trade. We trade some precision for longer round count before a *possible* degradation in accuracy enough to cause problems. And our target size is large enough the trade of precision doesn’t really matter.
 
It is amazing that we have been shooting rifles for 100+ years and we still don’t have definite answers on this. I load close to the lands, purely for accuracy, but if you could get an extra however many rounds of match accuracy out of a barrel by jumping (spacewalking?) then I would try it. It seems the trends in reloading and in cartridge selection is forever going around in one big circle. The 6GT is really just a Swiss Match or a 6x44 with a name behind it, good to see people trying different shit anyway.

Simply put, if you desire .2 precision, you will need to be close to or into the lands. But you will have to keep an eye on it.

If you desire .5, then you can load further away and let it eat for a while.

Either way, if you’re just shooting with a bipod and a rear squeeze bag, .2’s is all but impossible long term.
 
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So, it’s now popular for long jumps in PRS.

The reason being that while it may not be the smallest groups, you get less change over the course of a 200+ round match.

Which is great. But, no one stops to ask “why.”

Well, that is very likely (without tons of money and equipment you can’t be 100% sure) due to the long jump prohibits the bullet from relying on the lands to build initial pressure.

Let’s say you’re jumping .020

How far does a bullet move forward on the initial primer strike before powder has burned enough to build more pressure.

If it moves .020, now you’re in the lands almost immediately building pressure.

After 150 rounds, your throat moves .006 and changes that.

Or let’s say you’re jumping .020” and the initial movement is .005. That’s 25% of your jump

And when the throat burns .005, your jump is now .030 and the initial movement is now 17%. That’s substantial


Now, let’s take a .070” jump. Bullet moves .005” on primer strike. That’s 7%

Throat burns .005” for .075. Your change still rounds up to 7%

That is likely why long jumps show less deviation across a 200 round match.
Sarcastic comment time:

WOW it's almost like the enginerds at the bullet and ammo companies know a thing or two about bullet jump when recommending SAAMI overall lengths 😛😛

Sarcasm/


But, seriously, that's a fantastically logical explanation of consistency across different lengths of jump to the lands.
 
Sarcastic comment time:

WOW it's almost like the enginerds at the bullet and ammo companies know a thing or two about bullet jump when recommending SAAMI overall lengths 😛😛

Sarcasm/


But, seriously, that's a fantastically logical explanation of consistency across different lengths of jump to the lands.

Thanks. And I could be completely wrong. But I can’t come up with a better theory. And I’ve spent way more hours awake at night thinking about it or conversing with others.

I think a big part of what’s missing on our end on the practical shooting side is asking:

- why do something
- how often do we need to do it
- what is our precision requirement
- what is our precision capability

Cause, let’s be honest, it would be very easy to load into lands (not enough to stick a bullet) and be done with it. But will that last 300 rounds before you start missing targets?

Same with the things like primer seating “nodes.” Let’s forget the debate and assume that is a real thing.

If you’re not using a neo rest or equivalent (or better)……it’s virtually impossible to consistently hold a rifle still enough to exploit that advantage.
 
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I am no expert in reloading by I try to read alot and listen to those who shoot the best. They already have it figured out so no reason to try and reinvent the wheel, or at least that's the thought process.

Now this may be bullet design dependent but it appears many bullets shoot better when they are jumped. That old jam them into the lands is quickly becoming an old wives tale.

Here is some of the of the articles that include the testing Litz and Marc Gordon did along with a recent podcast where Satterlee talks about super long freebores shooting better with high jumps



It might behoove folks to read though and watch that video and see if its changes their view on some things.
 
@DeathBeforeDismount the best absolute pinpoint accuracy with most custom match bullets is found +10 to -20 seating depth. Talk the benchest and F class guys and they will tell you this. Keeping things tuned here is much more finicky as the purest accuracy may have a small 002-003 seating depth window. The windows further back off the lands are usually quite a bit wider/more forgiving but aren't as good of accuracy. Still good accuracy, but not the stuff that breaks records at 600 and 1k yards. This info has come from some the guys that are very competitive at the deep creek 1k nationals held a few hours south of me.
 
Those running A-Tips in the GT, are you able to seat them with the RCBS Matchmaster dies without any issues?
 
I am no expert in reloading by I try to read alot and listen to those who shoot the best. They already have it figured out so no reason to try and reinvent the wheel, or at least that's the thought process.

Now this may be bullet design dependent but it appears many bullets shoot better when they are jumped. That old jam them into the lands is quickly becoming an old wives tale.

Here is some of the of the articles that include the testing Litz and Marc Gordon did along with a recent podcast where Satterlee talks about super long freebores shooting better with high jumps



It might behoove folks to read though and watch that video and see if its changes their view on some things.


You’re completely confusing things.

None of these videos or articles even remotely describe what you’re saying. Marc Gordon even says that you will get smaller groups without the long jumps.

His method is about getting the most consistent precision across PRS round counts.
 
It is amazing that we have been shooting rifles for 100+ years and we still don’t have definite answers on this.
Likely because we have never been able to actually measure many aspects of what is happening when you launch a bullet out of a tube. But that's changing with technology and we should be seeing some real science behind the process. Then things will get really interesting.
 
Question for you guys:

I took some time off from matches in the fall for coaching football. Started up again recently and saw a weird thing happen to my rifle.
In the summer before my hiatus my GT was running 105 hybrids with 4350 at around 2870 with 35.5 gr.
Now in the winter with the same load last weekend my chrono was clocking 2900 fps. I may need to trim brass, it’s been so long I can’t remember. Can long brass cause the higher speed due to higher pressure or is there something else I need to be looking at?
 
Question for you guys:

I took some time off from matches in the fall for coaching football. Started up again recently and saw a weird thing happen to my rifle.
In the summer before my hiatus my GT was running 105 hybrids with 4350 at around 2870 with 35.5 gr.
Now in the winter with the same load last weekend my chrono was clocking 2900 fps. I may need to trim brass, it’s been so long I can’t remember. Can long brass cause the higher speed due to higher pressure or is there something else I need to be looking at?

I doubt it’s a trim length. But have a few questions:

- How many rounds since last cleaning?
- Newly loaded ammo or was this ammo you loaded and left on shelf? If left on shelf, was it inside house or some sort of climate controlled area?
- Same jug/lot of powder? If yes, where/how was it stored?
 
I doubt it’s a trim length. But have a few questions:

- How many rounds since last cleaning?
- Newly loaded ammo or was this ammo you loaded and left on shelf? If left on shelf, was it inside house or some sort of climate controlled area?
- Same jug/lot of powder? If yes, where/how was it stored?

Fair questions,
-Recently cleaned the chamber and a few patches down the barrel but nothing deep or intensive. Probably 100 rounds I guess.
-Newly loaded the night before
-same lot/jug of powder, stored in a cool dry place in my insulated garage
 
Fair questions,
-Recently cleaned the chamber and a few patches down the barrel but nothing deep or intensive. Probably 100 rounds I guess.
-Newly loaded the night before
-same lot/jug of powder, stored in a cool dry place in my insulated garage

I got nothing then. At least no immediate and obvious answer.

Except depend on the sample size and what not, could be on either end of your ES area on chrono each time.

In typically don’t worry about fairly small fluctuations like this unless they are erratic. So many things that could be contributing.
 
From a FB post by George Gardner:

Latest 6mm GT News

Adopted by SAAMI Jan 23 2022

Hornady is well into production of the 109 gr ELD ammo, I’ve tested 3 different pre production samples and found a great load that produces silly accuracy out of several test rifles. Target Speed is 2900 out of a 26” barrel. This will likely be 2880-2920 depending on your rifle and type of barrel. The power is temp stable and burned very clean. I cannot tell everyone what it is as it’s a powder that is not sold in canister line. But Burn Rate seems to between Varget and H4350. SD average was under 10 for an average across 4 different rifles and several 5 shot groups per rifle. I am super happy with the results.

I did test it with a couple Gas Guns and it ran well with very minor pressure signs. Didnt note any primer issues or and major Edjector marks.

Production should be completed in Feb with ammo and bullets shipping prior to March 1st.
 
I got nothing then. At least no immediate and obvious answer.

Except depend on the sample size and what not, could be on either end of your ES area on chrono each time.

In typically don’t worry about fairly small fluctuations like this unless they are erratic. So many things that could be contributing.
True, Ill go out and shoot it again this week. I guess if its consistent then it probably doesn't matter much. Still groups well. If I wanted to adjust the speed and back it back down to 2880, how much H4350 should I anticipate taking out from my current 35.5? I guess I am asking how many grains of 4350 change the speed 20 fps or so
 
And now back to your regularly scheduled programming of load development....

GA Precision PPR rifle 6gt 260 rounds fired. I have been working loads with several powders, primers, and bullets. Here are best results in my rifle. Please note only testing combustion, not tuning. Seating depth with group analysis will be next. Here I focused on speed, ES, and SD.

112MB, alpha brass, Cci450, Coal 2.540, Rl16
36.8 2885fps 13Es 6Sd 5rds fired
37.0 2884fps 5Es 2Sd 5rds
37.2 2910fps 6Es 2Sd 5rds
37.4 2919fps 9Es 3Sd 4rds

105Berger Hy, horn brass, S&B primer, Coal 2.560, IMR4166
34.0 2979fps 21Es 8Sd 5rds
34.5 3018fps 17Es 7Sd 5rds *no obvious signs of pressure*
--same as above but Cci450 primers--
33.5 2942fps 11Es 4Sd 5rds
34.0 2972fps 26Es 9Sd 5rds

105 hornady Bthp match, horn brass, S&B primers, Coal 2.500, IMR4166
32.4 2865fps 6Es 3Sd 5rds
*group was one hole .3 or less


All brass was on second firing and first resizing. Shoulder bumped .002 with RCBS FL .266neck bushing. Trim 1.720.
 
And now back to your regularly scheduled programming of load development....

GA Precision PPR rifle 6gt 260 rounds fired. I have been working loads with several powders, primers, and bullets. Here are best results in my rifle. Please note only testing combustion, not tuning. Seating depth with group analysis will be next. Here I focused on speed, ES, and SD.

112MB, alpha brass, Cci450, Coal 2.540, Rl16
36.8 2885fps 13Es 6Sd 5rds fired
37.0 2884fps 5Es 2Sd 5rds
37.2 2910fps 6Es 2Sd 5rds
37.4 2919fps 9Es 3Sd 4rds

105Berger Hy, horn brass, S&B primer, Coal 2.560, IMR4166
34.0 2979fps 21Es 8Sd 5rds
34.5 3018fps 17Es 7Sd 5rds *no obvious signs of pressure*
--same as above but Cci450 primers--
33.5 2942fps 11Es 4Sd 5rds
34.0 2972fps 26Es 9Sd 5rds

105 hornady Bthp match, horn brass, S&B primers, Coal 2.500, IMR4166
32.4 2865fps 6Es 3Sd 5rds
*group was one hole .3 or less


All brass was on second firing and first resizing. Shoulder bumped .002 with RCBS FL .266neck bushing. Trim 1.720.
I know this no surprise to many but in this clambering I have found 4166 to work as well if not better than Varget. Just my experience in this specific case.
 
Has anyone ran the Berger 108 elite hunter in a GT? It’s still a high bc Berger hybrid so I figured I’d run them until I can accumulate some more 109 hybrids. Going to run either varget or h4350. Thanks.
 
Has anyone ran the Berger 108 elite hunter in a GT? It’s still a high bc Berger hybrid so I figured I’d run them until I can accumulate some more 109 hybrids. Going to run either varget or h4350. Thanks.
I have run 1500 of them through my GT along with the 108 match. They run pretty much exactly the same. Same accuracy, same DOPE to 1400 yards, same charge weight, same CBTO.
 
I see a lot of references to the Berger Hybrids, but haven’t been able to find them. I did pick up some 105 VLDs. Has anyone had luck with them? Any tricks or things to watch for loading these?
 
I am no expert in reloading by I try to read alot and listen to those who shoot the best. They already have it figured out so no reason to try and reinvent the wheel, or at least that's the thought process.

Now this may be bullet design dependent but it appears many bullets shoot better when they are jumped. That old jam them into the lands is quickly becoming an old wives tale.

Here is some of the of the articles that include the testing Litz and Marc Gordon did along with a recent podcast where Satterlee talks about super long freebores shooting better with high jumps



It might behoove folks to read though and watch that video and see if its changes their view on some things.

Agreed.