Before switching to 22 Creedmoor & 22 Benchrest, you may want to read about RPM limits w/ heavy bullets, jacket failure, and bullet blow-ups.

[Renomd]

For the sake of spreading this info out b/c I feel it's important before people start throwing away $$$ on a trend i'm posting this in the Bolt action forum b/c 22 creedmoor and 22 BR are becoming a trend in the tactical bolt world.

So after doing a TON of digging around, calling Sierra, Hornady, finding a bunch of info out about the berger 90 vld blowing up, here is VERY important data about shooting heavy bullets in 22 CM and 22 BR, and you should read this before deciding what you want to build.

Bullet RPM limit....

With the 22 CM and 22 BR caliber taking off in the tactical bolt rifle circuits, I ran into others on the 22 creed FB page, benchrest/accurateshooter forums, etc. talking about RPM limits before jacket failure occurs. I have numbers directly from the horses mouths in regards to heavier projectiles. Just sharing this info b/c it does matter in regards to optimal twist rate/stability; but, also balancing between velocity and jacket failure. The premise for a lot of us tactical guys going to this caliber is the speed (we have to keep it below 3200 fps for most match rules), ballistics (better wind drift and elevation than a berger 105 hybrid at the same velocity), less recoil so trace and impact signature can be fully seen. It also helps for free recoil mgmt when you are shooting off an unstable prop.

Hornady 88 ELD: 1.240" nominal length btw per Hornady technical support phone call, RPM limit from their technician is "290-300" thousand rpms before jacket failure. This is NOT actual data though, it's their suggestion to not exceed. He said as far as he knows there is no specific testing data on when the jacket fails.

Sierra 95 smk: 1.273" nominal length (per Phil sierra ballistician). From their ballistician directly, they have not tested failure; but, they have tested the maximum velocities and one of their guys has tested it to "3500-3600" fps w/o inducing failure of the jacket. I would not shoot this anywhere near this and take this with a grain of salt and on your own liability.

Berger 90gr VLD: From confirmed sources on benchrest.com forum direct from berger's technician/ballistician in 2008-2009 forum posts (just google berger 90 vld blow up) the limit is 300k as well. This bullet is known to "blow up" when exceeding 300k rpm, mostly in 6.5 twist barrels. Its important to note the blow-ups documented by berger and others on that thread from 2008-2009 on benchrest, is that jacket failures didn't occur until around the 500-600 yd mark in bullet travel. Sometimes at closer distances though. http://forum.accurateshooter.com/threads/90-vlds-blowing-up.3923489/page-2#post-37036210 http://benchrest.com/showthread.php?49336-Berger-bullet-failure-test

Just some food for thought to the tactical guys like me whom want to try something new. Before you pull the trigger and spend $800 on a barrel alone, know that shooting heavies quick 3100-3200 fps, there is little load data on the internet about it. Most 22CM data is on mid-weight bullets. So you may want to balance stability out with jacket failure w/ rpm limits.

To calculate RPM= (measured velocity x 720)/ twist rate

I'll tell you anything over 3000 fps in a 7 twist (which is recommended for all above bullets by the manufacturers) is over 300k rpm... so just think about that. Is it really worth switching over.... will for sure be a shorter barrel life compared to 6 dasher, and 6 creedmoor. So consideration for 7.5 twist is there. The stability will be marginal at sea level elevations per berger bullets stability calculator. Use the above nominal lengths to help verify this info; but, i've calculated it and at 100 fps sea level it's marginal at SG 1.27 at 3100 fps in a 7.5 twist 70 degrees, RPM is 297,600 with 6 % deterioration in BC to .559 from .600.... meaning no better than a JLK105, and pretty much the same wind drift as a berger hybrid 105 at the same speed w/o any other worrisome factors of jacket failure.

I already have a barrel on the way in 7 twist, and did all this digging in hindsight b/c I finally have a few days off. Hope you all find this helpful.

 

[Midwestside]

I'll tell you anything over 3000 fps in a 7 twist (which is recommended for all above bullets by the manufacturers) is over 300k rpm... so just think about that.

Did any of them say why they were suggesting the 7 twist?
I see these "twist recommendations" on bullet boxes, but is this just to cover their ass in terms of stability for a huge range of caliber/cartridges' associated speeds?

I had some 88 ELDs being delivered today for my 22 creed (8 twist), so I ran some stability #'s out of curiosity with the JBM software.
It appears to check out as being stable with a huge spread of velocities and also falls under your RPM threshold of potentially blowing up per your formula above.
It doesn't mean much to me without trying a few out, but thought I would share none-the-less.

 

[Boss334OP]

Very interesting to think about. Peculiar that so many bullet manf haven't done more research into this.
If the jacket is the failure point, What about solids?
At a certain point, you would think the actual rifling in the barrel would shred/smear/deform the jacket by trying to accelerate the projectile too fast. Then again, maybe we won't see this with the standard twist rates shooters actually use. It would be interesting to see the pressure curves of different twist rates, different acceleration models, different bullets etc. Would the twist have to basically look like coarse threads before this actually becomes an issue?
These are the questions that keep me up at night. LOL

 

[Boss334OP]

Also, I believe it is fairly reasonable to assume that once anything is spun that fast, there is going to be vibration. Does some form of resonance play a factor? With some of the Bergers blowing up @ 500+, there must be an additional variable. Maybe air friction like was seen with the AMAX tips? Or is it some form of embrittlement brought on by the heating and cooling of the projectile? What is the current theory on the micro-environment/slipstream around the bullet?

 

[steve123]

On top of the other variables my theory is some rifling profiles might be part of the problem.

Barrel/throat wear, even shortly after load work is done, seems to contribute to this problem as well.

It's a catch 22, "that's an appropriate pun for this thread", because the tighter the twist, more so the optimal twist, would give a little more BC.

I think it's about time bullet manufacturers started using thicker jackets and/or bonded cores because this whole problem shouldn't have been an issue to begin with.

There's reports of the 147 eldm, the 180 eldm, the 150 SMK, others??? coming apart mid air. Heck I've had 140 hybrids and 55 grain 20 cals blow up. If the trend is longer and heavier bullets being pushed hard in tight twists then these Co's need to make sure the bullets are up to the task.

Only 125 rounds so far but the 88's are working great in my 7 twist, 6LG Benchmark, 223AI at 2800 or so.

 

[supercorndogs]

I ran 75 and 80 a maxes in my 7 twist 22-250. They ran fine at about 3150 for 700 rounds. Then it started blowing them up. I had a 7 twist AR that would blow up about any 40-55g varmint bullet you could find. I think the rifling like steve said is big contributor, and the smoothness of the launch pad. I.E the throat.

 

[Renomd]

Did any of them say why they were suggesting the 7 twist?
I see these "twist recommendations" on bullet boxes, but is this just to cover their ass in terms of stability for a huge range of caliber/cartridges' associated speeds?

I had some 88 ELDs being delivered today for my 22 creed (8 twist), so I ran some stability #'s out of curiosity with the JBM software.
It appears to check out as being stable with a huge spread of velocities and also falls under your RPM threshold of potentially blowing up per your formula above.
It doesn't mean much to me without trying a few out, but thought I would share none-the-less.

The Hornady technician didn’t say specifically why the 7 twist for the Hornady 88 eld, I can tell he was a technician and not a ballistician like the guy I talked to from Sierra. Phil the ballistician did admit though that at 3100 FPS which is what I plan on shooting the 95 smk at a “7 twist should be fine”.

I’ve always used the Berger stability calculator and many do as well as a checks and balances for other bullet manufacturers. The Sierra 95 smk claim of needing a 6.5 twist is based on stability calculations, I know for a fact the 7 twist will work Bc I’ve talked to a few that run them. I’ve talked to one reputable shooter whom tested the 95 smk in a 7.7 twist shooting near 3200 FPS BUT he lives at a higher altitude which plays a big role. I can get a lot of bullets to stabilize where I live at 4500 ft and in the summer time with nearly an 8 twist in the marginal stability zone ( based on calculations), but if I actually want to bring this thing to Sacramento CA which is at 100 ft, the 95 smk won’t stabilize with an 8 twist.

I wanted to put this info out there Bc before too many of us jump on the 22 train for Tactical comps based on a bunch of hype.... better someone verify it theoretically first based on actual calculations to see if it’s even feasible/ safe to do.

Rotational velocity (RPM) plays a key part into bullets failing mid flight if they heat up too much and come apart. And something I was clueless about until I decided to try 22 creedmoor.

Berger did thicken their jackets back in 2008 based on eric stecker’s thread (he was aberger ballistician).

 

[Renomd]

I ran 75 and 80 a maxes in my 7 twist 22-250. They ran fine at about 3150 for 700 rounds. Then it started blowing them up. I had a 7 twist AR that would blow up about any 40-55g varmint bullet you could find. I think the rifling like steve said is big contributor, and the smoothness of the launch pad. I.E the throat.

Yeah you are right about that searching the accurateshooter forum about bullet failure or bullet blowups what you say is exactly what has been found to be another contributing factor.

 

[culater]

You should check out the guy on 6mmbr.com in the forum in the Varminter & hunting section he created a new wild cat called 220 Red line. He pushing 75 gr bullet nearly 3950 FPS,With no issues. It's a neck down 6.5 saum to .224

 

[Butler12]

I am about to get a couple of 22-250AI chambered up I went with a Broughton and Rock Creek in 7 twist hoping the 5 grove riffling might be a little easier on the bullets time will tell.

 

[b6graham]

I have a 4 groove Bartlein 7 twist at WTO now getting chambered in 22LRV for the 95s. 3200 without a sweat

 

[Butler12]

What length will you finish the 22LRV to stay under the 3200 limit.

 

[b6graham]

What length will you finish the 22LRV to stay under the 3200 limit.

Right now I have it ordered at 26", but I'm a while out so when there's a little more data I'll shorten it as much as I can to run just under 3200 without pushing it too hot

 

[bohem]

This is a well documented behavior in hot 6mm wildcats as well.

The throat roughness definitely plays a factor. I saw it in my 6.506 AI from about 10 years ago as well as a 3006 that was setup for shooting light bullets with a short throat, mostly surplus 90gr M1 carbine pulldowns. After a couple thousand rounds the stuff that shot great early on wouldn't make it to a 50yd target.

We went around and around on this forum about it in 2009 or so when GAP started offering rifles in a 6mm Jedi as I recall; something to the effect of an improved 6mm Remington case throated for 105 VLDs to go 3400fps out of an 7.5 or 8 twist (306krpm-326krpm)

The rpm conversion factor is:

FPS*720 / twistrate per inch

3000fps *60s/min *12 in/foot / 7inch per twist ~308krpm
3400fps * 720 / 8 = 306,000
3400 * 720 /7.5 = 326,400

 

[winniedonkey]

I have a 4 groove Bartlein 7 twist at WTO now getting chambered in 22LRV for the 95s. 3200 without a sweat

That 22LRV looks like a good time. I'll keep a look out for your data. Talked to them about it and they seem to be getting happy customers.

 

[ThePretzel]

Sounds to me like the simple solution is to order barrels in a slower twist and ignore the manufacturer recommended 7 twist barrels.

If a 7 twist is shooting and spinning the bullets so fast for 22CM and 22BR that you're experiencing jacket failures, it means you're not going to have bullet stability issues when you shoot at a lower twist rate. I'd imagine they recommended the 7 twist based off someone shooting these bullets at velocities you can obtain by firing them out of a .223, not out of a higher velocity cartridge.

 

[Nortex]

My 22 creed with a 7 twist broughton slings 90gr vld out over 3k (two nodes one at 3106fps and 3350fps) with ease and I've yet to have a jacket separate. Hunted with 80gr vld this last season running 3180fps with no issues either.

 

[Renomd]

My 22 creed with a 7 twist broughton slings 90gr vld out over 3k (two nodes one at 3106fps and 3350fps) with ease and I've yet to have a jacket separate. Hunted with 80gr vld this last season running 3180fps with no issues either.

Can you post your load data on the 22 creed thread in the reloading depot? Thx, will help me and others

 

[Ledzep]

For the fast 22s you don't need 6.5 twist. 7-7.5 will work. I have a 1:8 22-250 that stabilizes 90 vlds at 2800fps no problem, and run them at 3000. Can't speak for sea level. I'm at about 2700ft.

As far as bullets blowing up there are a couple of contributors. Heat, spin, and rifling are the big ones.

Opposing groove (even # lands and grooves) sharp square rifling causes stress concentrations in the jacket. 5r rifling appears to be less prone to splitting bullets. These are general trends.

Heat is the other issue that can blow them even at lower rpm. Tight or dirty bores and rough throats and super fast speeds build up heat in the jacket and if you get the bullet hot enough to melt the lead inside the core separates, they destabilize rapidly and can come apart. These are likely the ones that blow up down range. Remember air at mach Christ causes heat build up, too.


Then obviously there's a limit on rpm before the bullet can't hold itself together.

 

[spife7980]

It obviously wont help with the rpms or grand canyon firecracking but could running molly or hbn be beneficial in reducing the friction/heat from rough barrels?

 

[kthomas]

Interesting thread. I've seen a lot of interest in .22 cal PRS rigs all of a sudden, especially from the Utah PRS crowd.

I've personally thought about getting a rifle or barrel spun up for myself and/or the wife a .22br/.22bra - but I can't justify it over a 6mm.

In my opinion, the short 6mm's (6br and associated 6br variants) seem to be the best suited cartridges for PRS and intermediate range shooting. They seem to strike the best balance between BC, recoil, velocity, tuneability and splash signature down range.

The low recoil of the fast .22's are awesome, but you are given up splash signature down range and with potential bullet reliability issues - I'm not sure if I can justify the minimal savings in recoil.

 

[supercorndogs]

I ran 75 and 80 a maxes in my 7 twist 22-250. They ran fine at about 3150 for 700 rounds. Then it started blowing them up. I had a 7 twist AR that would blow up about any 40-55g varmint bullet you could find. I think the rifling like steve said is big contributor, and the smoothness of the launch pad. I.E the throat.

26" BHW polyaganl rifled barrel.

 

[Nortex]

Interesting thread. I've seen a lot of interest in .22 cal PRS rigs all of a sudden, especially from the Utah PRS crowd.

I've personally thought about getting a rifle or barrel spun up for myself and/or the wife a .22br/.22bra - but I can't justify it over a 6mm.

In my opinion, the short 6mm's (6br and associated 6br variants) seem to be the best suited cartridges for PRS and intermediate range shooting. They seem to strike the best balance between BC, recoil, velocity, tuneability and splash signature down range.

The low recoil of the fast .22's are awesome, but you are given up splash signature down range and with potential bullet reliability issues - I'm not sure if I can justify the minimal savings in recoil.

I've ran my 22 creed in a prs match when I was waiting on my 6mm barrel to show up. Running the 90's st 3106 was very similar to running a fast 6mm with 115dtac or 110smk. Mine is primarily a hunting gun but it worked great since I was in a bind.

 

[steve123]

26" BHW polyaganl rifled barrel.

Even with a polygonal ??? I would have thought this would have provided the best type of rifling for not etching a bullet.

Sure would be nice to know what the most reliable rifling type is?

 

[supercorndogs]

Even with a polygonal ??? I would have thought this would have provided the best type of rifling for not etching a bullet.

Sure would be nice to know what the most reliable rifling type is?

I would be willing to be bet mine was more about heat cracked torched out throat than the rifling. I used it for prairie dogs that year. What I mean is
I got it hot and dirty often, with long strings of fire. It actually only took me about a month and 100 pieces of Lupus brass, I still use, to do it. I ran them up to about 3400 when it was new and I never saw one blow up, out of a small sample. Toward the end 3300 would blow them all up.

 

[steve123]

I would be willing to be bet mine was more about heat cracked torched out throat than the rifling. I used it for prairie dogs that year. What I mean is
I got it hot and dirty often, with long strings of fire. It actually only took me about a month and 100 pieces of Lupus brass, I still use, to do it. I ran them up to about 3400 when it was new and I never saw one blow up, out of a small sample. Toward the end 3300 would blow them all up.

Ahh, that would be a good reason.

 

[thehartofthings]

On top of the other variables my theory is some rifling profiles might be part of the problem.

Barrel/throat wear, even shortly after load work is done, seems to contribute to this problem as well.

It's a catch 22, "that's an appropriate pun for this thread", because the tighter the twist, more so the optimal twist, would give a little more BC.

I think it's about time bullet manufacturers started using thicker jackets and/or bonded cores because this whole problem shouldn't have been an issue to begin with.

There's reports of the 147 eldm, the 180 eldm, the 150 SMK, others??? coming apart mid air. Heck I've had 140 hybrids and 55 grain 20 cals blow up. If the trend is longer and heavier bullets being pushed hard in tight twists then these Co's need to make sure the bullets are up to the task.

Only 125 rounds so far but the 88's are working great in my 7 twist, 6LG Benchmark, 223AI at 2800 or so.

I did a 22LBC 24” 7 twist and blowing up 75grn match at 3250. They do fine at 2900 tho. I’m hoping t can get 2850 with the 88s and 90s

 

[Ranger188]

This is an old thread and bullets are better than they were in 2008-9 quote from Berger. A lot of people are running the
88's 90's and 95's without any problems above 3100 fps.
Why would the bullet come apart farther out, it's slowing down in speed and RPM's.
Might have more to do with barrel condition.

 

[Wheres-Waldo]

Just and FYI, BHW “polygonal” rifling is not true polygonal rifling. 2.5 seconds with a bore scope will reveal its a 3 groove barrel.

So don’t think that POLYGONAL might not be an answer, but 3 groove isn’t it.
With that said, my BHW 243LBC shot VERY well.

 

[FALex]

This is an old thread and bullets are better than they were in 2008-9 quote from Berger. A lot of people are running the
88's 90's and 95's without any problems above 3100 fps.
Why would the bullet come apart farther out, it's slowing down in speed and RPM's.
Might have more to do with barrel condition.

The bullet would come apart at further distances due to the fact that it is covering so much ground from the time of ignition. That bullet is getting to 5-600 yards within half a second, even slighly less. It's not like a bunch of time has transpired. It's fired, it begins to degrade immediately, and has already covered several hundred yards when it goes full on nuclear.

 

[steve123]

FYI to all, the Hornady 88's have started to do weird things at distance now at 250 rounds down my 7 twist 6 groove barrel, no problems until 2 weeks ago. That is with throat maintenance with JB and cleanings not exceeding 50 rounds. Barrel has never been "hot" and the load is in the low node at 2814 fps.

I'll try the Sierra 95's and the 90's at some point.

 

[Ledzep]

Barrel make, and caliber?

 

[THEIS]

Hi,

I will take "The problems monolithics solve" for $1000 Alex.......

Sincerely,
Theis

 

[padom]

Interesting...no issues here with 88's or 90smk in a 7 twist 6 groove at 800rds

 

[Ledzep]

I've been trying to follow as closely as I can bullet blowup issues and it seems to be typically heavy-for-caliber bullets with even numbered grooved barrels, trending towards tight bore/groove diameters, and in the couple of barrels I've looked at that blew bullets up there are steps/tapers in the bore, or just overall rough internal surface finish either from manufacture or from lack of cleaning, or heat erosion.

Monolithics will solve the blowup problem but come with their own set of limitations. In the future, my opinion is that fin-stabilized projos will be the LR/ELR go-to. Ditch the spin-related problems altogether.

 

[hwy1strat]

Awesome info! Thanks for the write up

 

[Ranger188]

Steve, you said the 88's are doing weird things at distance, like what and
how far out did you start to notice this?
Stopped using the 88's early cause could get a grouping I liked.
Went to the Bergers 90 vld's and now have 350 down the pipe with no issues yet.
7 tw 4 groove HH

 

[308pirate]

You should check out the guy on 6mmbr.com in the forum in the Varminter & hunting section he created a new wild cat called 220 Red line. He pushing 75 gr bullet nearly 3950 FPS,With no issues.

His "no issues" will end when he gets enough throat erosion to start affecting the jacket's integrity margin or when he rebarrles and his new barrel isn't as smoothly finished inside as his current one

There is no fucking way this guy knows something new or that no one else knows about bullets' structural integrity.

 

[spife7980]

Its a pretty interesting read on a guy playing around trying to push the limits to get as much velocity as he can.
Hes also using a slower twist rate to avoid spinning them more than they can stand at the high velocities and hes using slightly lighter than max weight bullets to stabilize easier with that slower twist.

At a scorching 3950 fps (already established), a 75 from the 1:9 REDLINE is spinnin' 316,000 RPM, which is well below where my .22-243AI is churning from a 1:8

Link

The Birth Of The .220 REDLINE – Coyote Stuff

coyotestuff.com

Given a MV of 3750 fps, a 75gr VLD is “marginally stable” from a 1:9 twist barrel, with a factor of 1.2. That is @ sea level & 30°F, atmospherics toward the lower end of intended use. Given that conservative MV estimate for this project, I’m OK with a stability factor of 1.2. so that finalizes the twist rate for this .224 SAUM @ 1:9.

The .220 Redline Lives! – Coyote Stuff

coyotestuff.com

 

[DisplacedTexan]

I have a 1-6.5" 4 groove bartlein ready to be chambered for 22BR and this thread makes me sweat.

 

[steve123]

Barrel make, and caliber?

I think it's a Benchmark, IIRC. .224. It's very accurate and cleans easy.

 

[steve123]

Steve, you said the 88's are doing weird things at distance, like what and
how far out did you start to notice this?
Stopped using the 88's early cause could get a grouping I liked.
Went to the Bergers 90 vld's and now have 350 down the pipe with no issues yet.
7 tw 4 groove HH

This 223AI has been a good one, impressive at distance, low recoil, had no complaints until a few weeks ago. Symptom was hugely errant shots once in a while at 792Y, like every 10 shots or so. No bullets blew up per say, as in not making it to the area of the target.

I cleaned the barrel, went out a few days later, shot 30 rounds, and things were fine like before??!! I have another box of 100 left to use so I will get back here to report in a month or two.

 

[Lowlight]

 

[steve123]

The dreaded comet!

This is what happened with my 20x47L with 55gr Bergers. Another long bullet going 3830 fps. That barrel started doing this at about 250 rounds. Went to 40 vmax at 4100 fps which worked but I took that barrel off and only used it once since so no longevity report.

 

[Fig]

?HMIC? Valk?

The premise for a lot of us tactical guys going to this caliber is the speed (we have to keep it below 3200 fps for most match rules), ballistics (better wind drift and elevation than a berger 105 hybrid at the same velocity), less recoil so trace and impact signature can be fully seen. It also helps for free recoil mgmt when you are shooting off an unstable prop.

Couple of things. My .220 Swift sends 32gr Spitzers (tried everything and this is what it likes) @4200+ but it's like a 12 twist. It is obviously NOT a long range rifle. It's a laser at 300 yards and still good to about 600 yards (on varmints) and then it really falls apart. So I get shooting heavies to get more range, but...

I don't get the first part of your premise. There is a speed limit, and you can make a 6mm reach it, so why would I want to shoot a lower BC bullet at the speed limit, granted, they are so close as to almost be indistinguishable, but I'm not getting the attraction. Seems like splitting hairs when I can shoot a 108gr or a 115 gr 6mm at the speed limit too... This is not a cut on .22 heavies, because they're damn near the same, but I just don't see advantage here.

The recoil is so low on a heavy 6mm I am wondering how much of an advantage that is too.

Not MFing your thread, and you go girl if you think this is giving you an edge, but I sort of thought 6 and 6.5 mm was dominating because it was in a sweet spot of the ballistic physics of rifle shooting. Looking at the numbers it looks to me like your going backwards with the heavy .22s even if it's ever so slightly. I seriously doubt I'd notice either way shooting heavy .22s or the heavy 6mm I favor. .223-.236-.256 obviously these are all a little different and at the high end generally aren't run at the speed limit, but coming from some smoking varmint rounds I kind of feel like I want the highest BC bullet run at 3100 with no signs of pressure, and that just seems to be the 6mm.

I'll add that I'm not a fan boy or anything. If I had to pick a favorite caliber and bullet it would be 300WM shooting 230s @ about 2,750. Not going to shoot that in a match!

 

[Nortex]

I've ran about 300 88 eld through my 7 twist broughton 22 creed with no issues. I prefer the 90gr vld and will switch back to them now that they are more available. I've only ran the 88's to 3100 but the 90gr bergers have ran great at 3350.

 

[twm134]

Every time I read discussions on this topic I look for anyone that has experience with what Bartlein Barrels refers to as "T" style rifling. What many learned as gain twist. For anyone who doesn't know, gain twist is rifling that starts at a slower twist and finishes at the muzzle at a faster twist. Bartlein claims they can rifle a barrel starting at basically any twist at the breech and have the twist at the muzzle as fast as requested.

The idea is to start the bullet into the rifling at a less stressful rate of twist and ease it into the the faster rate to maintain jacket integrity while also achieving adequate stabilization. Does anyone have any experience with this using these heavy match bullets at high velocity that require faster twists than the jackets can withstand?

 

[Ledzep]

The common denominator as far as I've seen is almost always 4 groove square rifling barrels. If it's not a 4 groove, it's 6. I've never seen/heard of 5R style rifling doing it, gain twist or not. Not all of them do it, and they seem to only do it with certain lots of bullets/ammo. Good with most, occasionally a lot that doesn't jive. In conjunction with the square rifling & opposed grooves is usually tapered bores, tight spots, fire cracking, poor cleaning cycle, etc..

 

[twm134]

The common denominator as far as I've seen is almost always 4 groove square rifling barrels. If it's not a 4 groove, it's 6. I've never seen/heard of 5R style rifling doing it, gain twist or not. Not all of them do it, and they seem to only do it with certain lots of bullets/ammo. Good with most, occasionally a lot that doesn't jive. In conjunction with the square rifling & opposed grooves is usually tapered bores, tight spots, fire cracking, poor cleaning cycle, etc..

Have you ever heard of 5R rifling not having this problem and working well, and if you have in how many instances? Also, do you have any experience with transitional or progressive or gain twist?

 

[Ledzep]

I don't think I have the answers to your questions.

In theory, maybe GT helps but I don't know how you'd prove it. Understand I'm talking about cases where it's not obvious that the rifle would pop bullets (under 300,000 RPM). Of the 4 barrels I've personally seen blow bullets all of them were 4-groove. Of everything I've read online of blowing bullets all but 2 or 3 were 4-groove. Those other 2-3 were 6 groove. I've never heard of it in 5r.

People running 22-243's, 22 creeds, 22-250AI, etc... with anything faster than 8 twist I don't really keep track of because it's almost expected that at some point a few of them will blow bullets just on the basis of how fast they spin bullets. What I'm talking about is more along the lines of 8 twist 6.5's and 8-9 twist 7mm's.