Help identify pressure signs. 6.5 Creedmoor with H4350 and 147 grain ELDM

[harry_x1]

Rifle is a Zermatt Arms TL3, PVA 18inch 1:8 twist barrell. I loaded 3 rounds each with below details:

Load 1: 3 Rounds with 43.4 grain H4350, 147 grain eldm, neck tension 0.004". Achieved MV 2715 fps with 6 SD, 0.5 MOA

Load 2: 3 rounds with 41.4 grain H4350, 147 grain eldm, neck tension 0.004". Achieved MV 2596 fps with 7 SD, 0.3 MOA

Please have a look at attached pictured and let me know if you see any pressure signs. Did not experience any heavy bolt lift. With these results, I am contemplating further reduction in charge weight. But will be great if people can give me some idea on how hot load 2 (41.4 grain) looks like.

thanks for all the help

PS: I am using 0.004" neck tension as this is new brass and I dont have an expander manderal to correct it. In Once fired brass I will correct neck tension to 0.002"

 

[kthomas]

Here is a good article on understanding pressure:

Understanding Pressure :: Primal Rights, Inc

Reading pressure is a required skill that all shooters must have. Whether you are shooting factory ammunition or your own handloads, you absolutely must be able to detect and interpret pressure signs on your fired brass.

www.primalrights.com

A 147 grain projectile is pretty heavy for a 6.5 Creedmoor, especially with such a short barrel. And 43.4 grains of H4350 under a 147 grain pill is a lot. I would swap to a lighter projectile - look at something like the the 123 or 130 ELD-M's, or 130 Berger Hybrids. Start at 40.0 grains and work up from there. Read that article and understand what to look for in regards to pressure signs.

A 147 projectile is much more suited for something like a 6.5 PRC.

 

[918v]

Load 40.5grs it’s a safe load

 

[Carlos Danger]

See how the primers pop out. If there's little resistance there's a good chance the new ones won't hold. Found out the hard way what hot loads can do to primer pockets.

 

[Dolomite]

Interesting as the primer edges are still round and the primer shows cratering. Are you using fed primers?

 

[harry_x1]

Interesting as the primer edges are still round and the primer shows cratering. Are you using fed primers?

CCI

 

[ITR_98_111]

Interesting as the primer edges are still round and the primer shows cratering. Are you using fed primers?

Magnum and military primers run thicker cups and you’ll rarely see flattened edges in the small rifle primers - the fact it looks like it formed around the firing pin is of concern, so are some of the markings on the brass

 

[nn8734]

For those engaged in this thread:

The exact same discussion on the exact same topic about the OP’s exact same rifle and brass is also occurring here:

6.5 Creed - 147 grain - is it safe to fire new brass with 0.004 neck tenshio

I just got a new set of lapua brass (6.5c small primer). The shoulder is already perfect for my chamber however the new brass has 0.004 neck tension. I have a match this weekend and no way to expand and then Correct neck tension to 0.002 inch (what most people recommend and I ussually fire). My...

www.snipershide.com

 

[Ledzep]

I pressure tested 43gr h4350 with a 147 once in a calibrated pressure test barrel and IIRC it was in the 80-85ksi ballpark. 41.5 was in the 70s.....

Not my face not my problem...

 

[kthomas]

@harry_x1, do you have anyone locally that can help you reload?

Reloading can be a daunting process, especially if you don't know where to start or have anyone to guide you through the process.

The first thing I do when I reload is to create a ladder of progressing powder charges, to see what charge weight gives what approximate velocity and where pressure signs begin. Usually in 0.2-0.3 grain increments when working with something like a 6.5 Creedmoor. Start with a very low/safe charge weight and go up from there.

This would be a good experiment for you. Load up some rounds in progressing charge weights from 38 grains to say 41 grains. Load in 0.2-0.3 grain increments. Fire your ladder from lowest to highest charge, taking notes of each MV as you go. Study each piece of brass carefully between each shot to look for pressure signs, using the article I linked in my first reply. If you start to see pressure - STOP. Don't proceed to shoot the rest of your ladder.

Spend some time to get very well acquainted with understanding what pressure signs to look for before doing this. It's easy to get carried away when reloading - we have all done it to some degree trying to chase speed. But the load you are sharing is dangerous, do not shoot anymore of those that you have already loaded.

 

[abn31c]

43.4...lapua brass....147gr. Bullet....
What could go wrong?

Buy a fucking reloading manual.

 

[Huskydriver]

OP 39-42 grs is usually where people settle with a load. How are you measuring your speeds? 2600 with 41.4 seems slow

 

[ITR_98_111]

OP 39-42 grs is usually where people settle with a load. How are you measuring your speeds? 2600 with 41.4 seems slow

If you check out the other post, you’ll see where I math it out for a 147gr bullet in an 18” barrel, but it’s slower than most of us with 24”+ and 140s

 

[Huskydriver]

If you check out the other post, you’ll see where I math it out for a 147gr bullet in an 18” barrel, but it’s slower than most of us with 24”+ and 140s

Ah skipped over the 18" barrel...2600 is basically what my 18 is doing too makes sense

 

[kthomas]

Yeah my 18" 6.5 Creedmoor shoots factory 140 Amax's at around 2660 fps.

A 147 would definitely be in the 2400's with my 18" 6.5 Creedmoor barrel.

 

[Frank Green]

41.3 to about 41.5 is what I would call a max load with H4350 and a 147/150gr bullet.

Lot of powder different from before?

The lot or brand of cases can make a difference...as well as bullet lot to lot even from the same bullet maker can make a difference. Primers.....

Other things to consider...

What reamer spec cut the chamber? This can have an effect on pressures also. What is a max load in my gun or a ammunition test barrel can be different for your gun.

Actual bore and groove size of your barrel. You can't guess! You need to know the 4th decimal place. So .2560" x .2640" is min spec. tolerance for each of those is +.0005" / -.0000".

If your barrel is at .0000" or even under....you can and will drive up pressures. I've seen Saami spec. test barrels in 6.5CM and the barrels where made incorrectly. Bore and groove size was .0005" under min spec. That drove up pressures 10k psi.

If you are seeing pressure signs at 41.4....back it off some more.

 

[Cascade Hemi]

41.3 to about 41.5 is what I would call a max load with H4350 and a 147/150gr bullet.

Lot of powder different from before?

The lot or brand of cases can make a difference...as well as bullet lot to lot even from the same bullet maker can make a difference. Primers.....

Other things to consider...

What reamer spec cut the chamber? This can have an effect on pressures also. What is a max load in my gun or a ammunition test barrel can be different for your gun.

Actual bore and groove size of your barrel. You can't guess! You need to know the 4th decimal place. So .2560" x .2640" is min spec. tolerance for each of those is +.0005" / -.0000".

If your barrel is at .0000" or even under....you can and will drive up pressures. I've seen Saami spec. test barrels in 6.5CM and the barrels where made incorrectly. Bore and groove size was .0005" under min spec. That drove up pressures 10k psi.

If you are seeing pressure signs at 41.4....back it off some more.

You must be new. SH load data doesn't even start until 65kPSI. SAAMI spec? TL;DR!

 

[Mike Casselton]

I pressure tested 43gr h4350 with a 147 once in a calibrated pressure test barrel and IIRC it was in the 80-85ksi ballpark. 41.5 was in the 70s.....

Not my face not my problem...

That pressure test barrel sure creates a healthy respect for pressure, doesn't it?

It would shock the hell out of most reloaders if they spent a day using one to see exactly how pressure changes with seemingly minor differences in brass, primers and powder charges.

 

[brianf]

the same OP keeps asking the same questions about pressure signs and basic info that is found on the web in 2 min

either he is a troll, or he is giving advice to people who should not be listening to him

both of which are no good

 

[nn8734]

the same OP keeps asking the same questions about pressure signs and basic info that is found on the web in 2 min

either he is a troll, or he is giving advice to people who should not be listening to him

both of which are no good

 

[Frank Green]

You must be new. SH load data doesn't even start until 65kPSI. SAAMI spec? TL;DR!

Your killing me smalls! Just killing me!

 

[harry_x1]

Hi all...firstly thanks for the feedback as well as the jokes. It is quiet evident that the almighty while being thrifty in his IQ endowment, did give me a tremendous amount of luck.
I have a match this Saturday and due to shortage of time just loaded 41.2 grains for now. I will explorelower charges next week, but hopefully this charge does not blow up in my face.

I would also like to take some time to explain some decisions regarding short barrell, heavier bullet, excessively hot load etc. They do sound a bit crazy.

Currently my build is a 18 inch barrell in TL3 short action with XLR chassis and a leupold scope. The total weight of rig is 9.8 lbs. My aim is to build one rifle which can be all purpose (PRS Matches/Hunting/Tactical etc etc). I am not a big fan of 20lbs+ rigs with lighter bullets that I generally see in PRS matches. Yes, they help win matches but IMO serve limited practical purpose. I also like to focus on one caliber which can do all tasks reasonably well (6.5c)...objective is that over a period of time I will become good at it. I chose a heavier bullet (147 grain) because of two reasons: 1) wind 2) to hunt and participate in NRL hunter matches (meet minimum power factor).

Why a hot load? 1) meet minimum power factor for NRL matches 2) enough MV for bullet stabilization.

One surprising (pleasantly) learning has been that a shorter barrell has more precision vs longer barrell. I had the same barrel in 26 inches (which I cut down to 18), and the accuracy has doubled in shorter form. I beleive it is because a shorter barrell tends to be more stiffer and has better harmonics.

Hope this explains some of my crazy sounding choices. Feedback/jokes/comments are all welcome.


PS: I had to start two threads as the first thread was concentrating on feedback for first (thermonuclear load) and this particular thread was primarily for getting feedback on the lower charge weight load. In hingsight maybe I could have avoided a new thread...but as they say, hindsight is always 50:50 (but lesson learnt)

 

[spife7980]

Why a hot load? 1) meet minimum power factor for NRL matches

380,000/147=2,585
Using the smallest chambering possible and then cutting its legs out from under it with a short barrel is the wrong way to go about meeting the minimum power factor.
Factory ammo removes the power factor equation, just fyi.

2) enough MV for bullet stabilization.

Your barrel twist is going to be the primary decider on whether your bullet is stable, not the muzzle velocity, if you have to chase muzzle velocity to keep the bullet from tumbling you fucked up way earlier when you chose the wrong barrel twist.

One surprising (pleasantly) learning has been that a shorter barrell has more precision vs longer barrell. I had the same barrel in 26 inches (which I cut down to 18), and the accuracy has doubled in shorter form. I beleive it is because a shorter barrell tends to be more stiffer and has better harmonics.

In theory but in practice its just that you changed the barrels harmonics and now you found that it likes what you are doing a bit more. Had you kept the barrel long and changed the load instead of vice versa you would likely have found the same results.

 

[Baron23]

It is quiet evident that the almighty while being thrifty in his IQ endowment, did give me a tremendous amount of luck.

John Wannamaker as reported by Dale Carnegie:

God has not seen fit to distribute the gift of intelligence…equally.

Haha

 

[Doom]

About 6" too short!

 

[harry_x1]

380,000/147=2,585
Using the smallest chambering possible and then cutting its legs out from under it with a short barrel is the wrong way to go about meeting the minimum power factor.
Factory ammo removes the power factor equation, just fyi.


Your barrel twist is going to be the primary decider on whether your bullet is stable, not the muzzle velocity, if you have to chase muzzle velocity to keep the bullet from tumbling you fucked up way earlier when you chose the wrong barrel twist.


In theory but in practice its just that you changed the barrels harmonics and now you found that it likes what you are doing a bit more. Had you kept the barrel long and changed the load instead of vice versa you would likely have found the same results.

1) using factory ammo would have been akin to using those super heavy prs rifles with puny bullets. I believe the power factor requirements serve a practical purpose.

2) you are correct. Hindsight is always 2020. If I knew in my teens what I know now, life would have been very different.

3) not sure about your comment regarding barrell length. Even in 338 lapua my 20 inch barrell shoots way better than the 26 inch one. Most revealing are the ladder tests.. with the shorter barrell the vertical spreads are way narrower.

 

[harry_x1]

John Wannamaker as reported by Dale Carnegie:

God has not seen fit to distribute the gift of intelligence…equally.

Haha

Raises an interesting question… if the maker offered one to choose between a super high iq and super high luck, what should one choose ?

 

[Doom]

not sure about your comment regarding barrell length. Even in 338 lapua my 20 inch barrell shoots way better than the 26 inch one. Most revealing are the ladder tests.. with the shorter barrell the vertical spreads are way narrower.

And that's why all the bench rest and high-power shooters are shooting 20" barrels?

 

[Cascade Hemi]

1) using factory ammo would have been akin to using those super heavy prs rifles with puny bullets. I believe the power factor requirements serve a practical purpose.

2) you are correct. Hindsight is always 2020. If I knew in my teens what I know now, life would have been very different.

3) not sure about your comment regarding barrell length. Even in 338 lapua my 20 inch barrell shoots way better than the 26 inch one. Most revealing are the ladder tests.. with the shorter barrell the vertical spreads are way narrower.

Get another barrel and swap them as needed. Do the work up on a different load for each barrel.

 

[BuildingConceptsllc]

@harry_x1, do you have anyone locally that can help you reload?

Reloading can be a daunting process, especially if you don't know where to start or have anyone to guide you through the process.

The first thing I do when I reload is to create a ladder of progressing powder charges, to see what charge weight gives what approximate velocity and where pressure signs begin. Usually in 0.2-0.3 grain increments when working with something like a 6.5 Creedmoor. Start with a very low/safe charge weight and go up from there.

This would be a good experiment for you. Load up some rounds in progressing charge weights from 38 grains to say 41 grains. Load in 0.2-0.3 grain increments. Fire your ladder from lowest to highest charge, taking notes of each MV as you go. Study each piece of brass carefully between each shot to look for pressure signs, using the article I linked in my first reply. If you start to see pressure - STOP. Don't proceed to shoot the rest of your ladder.

Spend some time to get very well acquainted with understanding what pressure signs to look for before doing this. It's easy to get carried away when reloading - we have all done it to some degree trying to chase speed. But the load you are sharing is dangerous, do not shoot anymore of those that you have already loaded.

It really is a huge thing to have someone experienced actually teach you how. This is how I was taught to load. Start very low and work up doing nothing but a pressure test. You can shoot at a target doing it and see how it shoots but you only need to load 1 per so there's no grouping. This is step #1 and the only purpose is to see when you start hitting pressure so you know where that place is. Then you can load a powder ladder and have a range to test what the most accurate load is. Then you can make another ladder with seating depth to fine tune the charge you settled on. (A charge that you know is safe from your pressure testing phase). This is the basics of how to find a load for your rifle. Step #1 IS ALWAYS STEP #1.

What's safe in my rifle may not be safe in yours, and so on with my brass, bullet, primer, and even my powder lot. The guy who taught me the basics over about 3 weekends, stressed all of these things to me and gave examples of how they can change things so I'd understand how big that change can be. I'd highly highly recommend finding someone to do the same for you. I would think wherever you get your supplies locally could hook you up, as most loaders are very happy to teach someone else.

 

[Oldloser]

New brass shows less pressure signs than fired. Fired brass will add 2 to 3k Psi easily to your pressure with same loads. You did not say your seating depth or the ambient temperature. With those we can run QL or GRT.

 

[ma smith]

My $0.02 cents here is worth what you pay for it, but...

The reloading issues are really downstream of rifle design issues.
In particular, the barrel choice 18" creed for NRL Hunter is a bad idea.

Trying to make PF is causing selection of components and load
that are heavy+slow+hot to make PF.

The issue is an arguable mismatch of rifle, ammo, and use case.

 

[harry_x1]

And that's why all the bench rest and high-power shooters are shooting 20" barrels?

Never shot benchrest, so not sure what barrell lengths they use and why. Have you shot benchrest competitions? If yes, request share details on what they choose and why in-terms of barrell length.

 

[harry_x1]

My $0.02 cents here is woth what you pay for it, but...

The reloading issues are really downstream of rifle design issues.
In particular, the barrel choice 18" creed for NRL Hunter is a bad idea.

Trying to make PF is causing selection of components and load
that are heavy+slow+hot to make PF.

The issue is an arguable mismatch of rifle, ammo, and use cae.

Thanks for the comment. I am curious why you think 18inch is a bad idea for NRL hunter… thanks !

 

[harry_x1]

New brass shows less pressure signs than fired. Fired brass will add 2 to 3k Psi easily to your pressure with same loads. You did not say your seating depth or the ambient temperature. With those we can run QL or GRT.

What is Ql/grt?

 

[2aBaC̶a̶]

Just load it and send it. caution is for pussies. some of us need to figure things out the hard way. when you have to beat the bolt open with a 2x4 thats when you went too far.

 

[ma smith]

Thanks for the comment. I am curious why you think 18inch is a bad idea for NRL hunter… thanks !

If NRL lets you use factory ammo, the dark horse choice is 130 AR hybrid. Take a look at the chart and crunch your own numbers.

Good luck either way!

A

 

[msgriff]

What is Ql/grt?

QuickLoad and Gordons Reloading Tool

 

[Cascade Hemi]

Thanks for the comment. I am curious why you think 18inch is a bad idea for NRL hunter… thanks !

Because you're loading to the moon for an 18" barrel trying to achieve what a longer barrel can do with lower pressure. 1" is generally 25fps so you'd get roughly 200fps more velocity with a 26" barrel.

Get another barrel for NRL. You didn't say which NRL Hunter division you're in but you have at least 2lbs to work with in Open Light.

 

[Doom]

Never shot benchrest, so not sure what barrell lengths they use and why. Have you shot benchrest competitions? If yes, request share details on what they choose and why in-terms of barrell length.

Not trying to be confrontational, but It seems you spend a lot of time on forums so I'm surprised you claim that you haven't read more about shooting at long range and reloading, especially sine you claim that you do. In fact some of your post actually seem a little scary.

First off, benchrest and high power shooters often have 30" or longer barrels to achieve high velocity. Most reloading data is presented for a 24" barrel. In 6.5CM I'm guessing it's similar to 308 and you lose 25-30 fps on average per inch of barrel length. This puts you down ~150fps for an 18" barrel. That's equivalent to over 2 grains of powder and probably not something you want to try to do on a cartridge that doesn't have a lot of margin on PF. If you want to shoot an 18" barrel you need to pick a cartridge that will support it.

Shooting a bunch rounds and then posting on a forum looking for analysis of your brass is not the way to look for pressure signs. That's something you need to do at the range. Your middle round in the first post is not a load you want to be shooting. Any reloading book will show you that. A search of the internet will also show you this but then you get both informed and uninformed opinions.

Many of your post claim that you are shooting at long range but some of you questions do not reflect a level of knowledge that reflects that. If you are serious about shooting LR and reloading for that purpose, you need to either get some formal training in shooting, ballistics, and reloading or acquire a mentor before you hurt yourself or someone else.

 

[2aBaC̶a̶]

Not trying to be confrontational, but It seems you spend a lot of time on forums so I'm surprised you claim that you haven't read more about shooting at long range and reloading, especially sine you claim that you do. In fact some of your post actually seem a little scary.

First off, benchrest and high power shooters often have 30" or longer barrels to achieve high velocity. Most reloading data is presented for a 24" barrel. In 6.5CM I'm guessing it's similar to 308 and you lose 25-30 fps on average per inch of barrel length. This puts you down ~150fps for an 18" barrel. That's equivalent to over 2 grains of powder and probably not something you want to try to do on a cartridge that doesn't have a lot of margin on PF. If you want to shoot an 18" barrel you need to pick a cartridge that will support it.

Shooting a bunch rounds and then posting on a forum looking for analysis of your brass is not the way to look for pressure signs. That's something you need to do at the range. Your middle round in the first post is not a load you want to be shooting. Any reloading book will show you that. A search of the internet will also show you this but then you get both informed and uninformed opinions.

Many of your post claim that you are shooting at long range but some of you questions do not reflect a level of knowledge that reflects that. If you are serious about shooting LR and reloading for that purpose, you need to either get some formal training in shooting, ballistics, and reloading or acquire a mentor before you hurt yourself or someone else.

Everyone knows all you need to shoot long range is a 338 Lapua Magnum rifle.

 

[Mike Casselton]

Not trying to be confrontational, but It seems you spend a lot of time on forums so I'm surprised you claim that you haven't read more about shooting at long range and reloading, especially sine you claim that you do. In fact some of your post actually seem a little scary.

First off, benchrest and high power shooters often have 30" or longer barrels to achieve high velocity. Most reloading data is presented for a 24" barrel. In 6.5CM I'm guessing it's similar to 308 and you lose 25-30 fps on average per inch of barrel length. This puts you down ~150fps for an 18" barrel. That's equivalent to over 2 grains of powder and probably not something you want to try to do on a cartridge that doesn't have a lot of margin on PF. If you want to shoot an 18" barrel you need to pick a cartridge that will support it.

Shooting a bunch rounds and then posting on a forum looking for analysis of your brass is not the way to look for pressure signs. That's something you need to do at the range. Your middle round in the first post is not a load you want to be shooting. Any reloading book will show you that. A search of the internet will also show you this but then you get both informed and uninformed opinions.

Many of your post claim that you are shooting at long range but some of you questions do not reflect a level of knowledge that reflects that. If you are serious about shooting LR and reloading for that purpose, you need to either get some formal training in shooting, ballistics, and reloading or acquire a mentor before you hurt yourself or someone else.

My reply is strictly related to barrel length, because I 100% agree with everything else you posted.
When you say benchrest shooters often use 30" barrels, I'm wanting to know specifically which form you're speaking of.

I know from experience that Benchrest vs benchrest type of shooting makes a difference.
So does the Benchrest discipline.

For short range, Benchrest (emphasis on the upper case B) is shot at 100, 200 and 300 yards. Most all of the competitors use barrels that range between 21.5", 22" (most popular length) and for heavy gun, often it'll be 24".
The rifles are Light Varmint and limited to 10-1/2#. Heavy Varmint is 13#.


Now, if you're talking 600 plus yards and weight limits exceeding 16lbs, then I would agree with the statement that barrels are typically 30-ish (paraphrasing) inches.

This would also be considered Benchrest, but it's "Long Range".

Then there's benchrest (emphasis on the lower case b) which is shooting off of a bench using rests, but not a formal competition.


With all of that ^^^^^^ said, I know the intent of what you wrote, and really, I just posted this for clarification.
I'm sitting inside bored. It's raining and I'm not going out there...

 

[Schütze]

I'm sitting inside bored. It's raining and I'm not going out there...

So get some rounds ready for next week, that’s what I’m doing. Or are you done already?

 

[Mike Casselton]

So get some rounds ready for next week, that’s what I’m doing. Or are you done already?

That sounds like a good plan.
Instead, I'm sitting in the kitchen watching Rebecca cut up veggies and other stuff for tonight's chicken noodle soup.
Oh, and I'm hanging out on the Hide and also texting with these four other buttholes.

 

[Doom]

I was specifically thinking 1000yd benchrest, Palma. I agree that I wasn't specific enough.

 

[Mike Casselton]

I was specifically thinking 1000yd benchrest, Palma.

Figured you were.

 

[Cascade Hemi]

F-Open guns are commonly straight profile 32".

 

[harry_x1]

Not trying to be confrontational, but It seems you spend a lot of time on forums so I'm surprised you claim that you haven't read more about shooting at long range and reloading, especially sine you claim that you do. In fact some of your post actually seem a little scary.

First off, benchrest and high power shooters often have 30" or longer barrels to achieve high velocity. Most reloading data is presented for a 24" barrel. In 6.5CM I'm guessing it's similar to 308 and you lose 25-30 fps on average per inch of barrel length. This puts you down ~150fps for an 18" barrel. That's equivalent to over 2 grains of powder and probably not something you want to try to do on a cartridge that doesn't have a lot of margin on PF. If you want to shoot an 18" barrel you need to pick a cartridge that will support it.

Shooting a bunch rounds and then posting on a forum looking for analysis of your brass is not the way to look for pressure signs. That's something you need to do at the range. Your middle round in the first post is not a load you want to be shooting. Any reloading book will show you that. A search of the internet will also show you this but then you get both informed and uninformed opinions.

Many of your post claim that you are shooting at long range but some of you questions do not reflect a level of knowledge that reflects that. If you are serious about shooting LR and reloading for that purpose, you need to either get some formal training in shooting, ballistics, and reloading or acquire a mentor before you hurt yourself or someone else.

Well, I am sorry for hurting your butt. That was not the intention. Given you ducked my simple Q, I presume you dont actively compete in benchrest competitions but extraplote based on what you see them using. thats fine.

 

[harry_x1]

My reply is strictly related to barrel length, because I 100% agree with everything else you posted.
When you say benchrest shooters often use 30" barrels, I'm wanting to know specifically which form you're speaking of.

I know from experience that Benchrest vs benchrest type of shooting makes a difference.
So does the Benchrest discipline.

For short range, Benchrest (emphasis on the upper case B) is shot at 100, 200 and 300 yards. Most all of the competitors use barrels that range between 21.5", 22" (most popular length) and for heavy gun, often it'll be 24".
The rifles are Light Varmint and limited to 10-1/2#. Heavy Varmint is 13#.


Now, if you're talking 600 plus yards and weight limits exceeding 16lbs, then I would agree with the statement that barrels are typically 30-ish (paraphrasing) inches.

This would also be considered Benchrest, but it's "Long Range".

Then there's benchrest (emphasis on the lower case b) which is shooting off of a bench using rests, but not a formal competition.


With all of that ^^^^^^ said, I know the intent of what you wrote, and really, I just posted this for clarification.
I'm sitting inside bored. It's raining and I'm not going out there...

Mike - seems you have experience shooting "benchrest". Everyone in this forum seems to look upto benchrest shooting for precision/accuracy. Hence seeking your input on this interesting 'experience'. I cut down my 26Inch 6.5c barrell (heavy palma) to 18 inch and found that 1) the ladder test is way way flatter for shorter barrell (similar charge weights from 34 to 43.4 grain with 0.4 increment). 2) my groups have become way tighter for similar charge weights and seating depths.

I am trying to understand what could cause this? should I expect slightly more precision from a shorter barrell? or I have messed something up in testing (remote possibility as I tried being meticulous) or is it something else ...?

 

[Doom]

Barrels vibrate. A shorter barrel is stiffer (assuming the same barrel profile) and the magnitude of the vibrations is smaller so the muzzle moves less. Since the scope is not dependent on sight radius this reduction movement of the muzzle usually results in smaller drops. Cutting the barrel can also move the center of gravity that may help with recoil control. Look up "Optimal Barrel Time" and you will see discussions on barrel vibration.