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300 PRC update
- Thread starter DAVETOOLEY
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I ran those calcs before I ordered the blank. In this morning’s conditions(24.60/ 20 deg), a 208 eld would have an sg of 1.8. Even at sea level in 20 deg its a 1.5. This barrel will be going on a DTA as well.
I'm waiting on a Bartlein left hand 9.75-8.75 gain twist. I just had to make it interesting...
Not sure. Whatever the reamer was he already had is what he used. Can't speak to the specs.
Yes I did. I have another ordered with a shorter throat.
Would you say the 1.3 is the low end cutoff for most practical uses? And on the other side, I don't care much for the 8 twist in 30 cals, as I personally think its overkill.
I picked a 10 twist for 212 eldx / 215 burgers for a hunting rig as the majority of the hunting is done at 8-10k feet. In the rare case it is at sea level at 32 degrees its a 1.40. At 9k feet at 0 degrees its 1.82. Increasing the altitude and temps even increase that number much further. Think Ill be fine with the 10 twist here. Would you agree?
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From personal experience I've shot a combination of a 1-14 30 cal. with 187 Gr. FB bullets. @3100 FPS in 1k comps. It wasn't supposed to work but it did. When I ran the numbers back then I came up with an Sg of 1.1. I shot it from Quantico to Byers CO. never had a problem with stability. Fantastic consistent accuracy. Now take that same barrel and put a 200 Gr. SMK in and you had a difficult time hitting a sheet of notebook paper at 200 yds. I was on the edge with that combo.
Most, just about all of you, are to young here to remember that Sierra made a 30 cal. 250 gr. SMK. I'm sitting here looking at a box with the lot number of #2-87. Trying to cheat the wind is nothing new. I'm sure most were shot in 1-10's. Several lots had a propensity to disappear when shot in magnum large calibers.
Just my opinion here but anything on either side of 1.5 works and doesn't bring any of the negatives that can creep in with extreme RPM's . All this is with using cup and core bullets. I have very little experience with solids.
From all my testing looking at the effects of the meplat on BC/stability that's were I would spend my money. I want a bullet that flies right with no yaw as soon as it leaves the muzzle. I want each and every bullet to have the same BC or at least as close as humanly possible. Combine that with superb accuracy and I can learn to read the wind out to a reasonable distance.
As always YMMV
Most, just about all of you, are to young here to remember that Sierra made a 30 cal. 250 gr. SMK. I'm sitting here looking at a box with the lot number of #2-87. Trying to cheat the wind is nothing new. I'm sure most were shot in 1-10's. Several lots had a propensity to disappear when shot in magnum large calibers.
Just my opinion here but anything on either side of 1.5 works and doesn't bring any of the negatives that can creep in with extreme RPM's . All this is with using cup and core bullets. I have very little experience with solids.
From all my testing looking at the effects of the meplat on BC/stability that's were I would spend my money. I want a bullet that flies right with no yaw as soon as it leaves the muzzle. I want each and every bullet to have the same BC or at least as close as humanly possible. Combine that with superb accuracy and I can learn to read the wind out to a reasonable distance.
As always YMMV
Many times nothing at all. Lately it’s been the in thing to do, as it’s been shown to increase BC slightly. It’s pretty hard on the bullet though. What may work initially on a fresh barrel, may start showing issues as the thoat become rough from erosion. There’s also a chance the core could shift in the jacket.
Read Dave’s post a few above yours, he outlines his priorities there.
Doing two things at the same time can lead to some confusion. At least temporarily. I've tried aggressive gain twists and never had any luck. 14-10 The bullets didn't like it. Crazy unexplained vertical. Probably doing some damage to the bullet. Wind drift calls will be different if you make them on the fly. The rifle will torque differently. I would never change the twist greater than 1 turn. Probably get any benefit going .5
With all seriousness, I cannot wait for everyone to start the 300PRC what works and what doesn't thread. I appreciate the folks handling this newer frontier.
I appreciate your reply...
I get that ppl state bullet busting loose at the seams from over rotation...
Its does seem to be the direction things are going with faster rates...
partly my question..ppl talk about over rotation and the issue of it...what are the issues and why...
Will a throat kno the difference between an 8" twist over a 10"..? And if so how? Normally pressure doesn't change with twist rates, correct?
Forcing the projectiles to twist faster may put more strain on everything...in my mind...I dont kno...
I read Dave's post and understand his liking is a 1.5.....that's what lead me to the question....I'm looking for an explanation...some science or something as to why over 2 is not a good thing....or might could lead to not a good thang...
And please understand I'm not here trying to be a pain in the neck or be argumentative....I'm here to learn and understand....
I'm one of those that wants the how, when and why.....not just the answer...
I would love to R & D and test everything myself but things hinder that....kids...work...wife...etc. etc.
One reason I'm on this thread...
I'm excited to be involved in this phase of the 300 prc...and the hide...
One thing I kno for sure is I have a rifle chambered in the 300 prc with an un-favored 8" twist coming....
Now I just need pills and dies
There are far too many variables to nail down exactly what you’re looking for. Also, there is no wall, no threshold, that delineates exactly at what SG things may go bad, because of all those variables. Adding twist has a negligible effect on pressure. The physical forces obviously go up. Going from 10 to 8 twist adds roughly 50k rpm for example.
The throat doesn’t “know” anything, but it’s surface finish changes due to erosion. Between a fresh throat, and a hammered throat, it’s easy to imagine that the bullet is going to have a harder time engraving the hammered throat, and the bullet jacket is probably going to take some additional damage. Lots of evidence to support this. Many here have talked about combinations working well, then late in the barrel’s life, bullets start vaporizing, or behaving erratically. Generally those are hotrod cartridge combinations. I shoot varmint bullets out of many of my rifles, and they’re all fast twist. Some of the SG’s are well into the 3’s, and I don’t recall ever having a bullet blow up, go figure.
Obviously it’s difficult to evaluate bullet failures on your own, since you cant directly observe the behavior or failure. You have to rely on performance, and the experience of others who have done the work.
You’re about to find out what all the fuss is about. Maybe it’s nothing at all.
I see it as an experiment and learning experience, hopefully in a positive way. I'm not a fan of fast twists for caliber anymore. Did not see the results I was looking for with a 7 SAUM this past year and running a 7 twist. Decided just fast enough was where I wanted to be and then started reading some good things about gain twists.
Bartlein recommended not going more than 1" on gain due to caliber. Makes sense. Being aggressive would most likely cause some strange things to happen especially on heavier bullets. I see is as starting off the projectile slowly and then hammering it as it's leaving the bore possibly causing a slight pitch of the nose up which further down range may show up as vertical on target. Maybe that explains what you were seeing. An analogy that comes to mind is a car under acceleration that has an aggressive shot of nitrous causes the front end to want to lift off the ground and the rear end to squat.
Shooting out at a mile or longer the spin drift from the left hand twist will completely cancel out the horizontal component of the coriolis effect and the rifle will torque away from the shooter instead of into the shooter and which over extended strings of fire with a large caliber my cheek will be happy.
So pretty much all speculation on my part as I have never shot a LH gain twist rifle and there will most definitely be a learning curve involved but one I feel is worth it, at least today anyway.
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There's always a long story behind things like this. One person convinces another that something works better then it begins to spiral out of control until the opinion is now fact. Before anyone jumps on me, yes there is a benefit to faster twists. Does a small increase in BC out weight the negatives. I don't think so.
For 40 years now I've participated in shooting competition. All disciplines were accuracy centered. Short range BR, 1K BR, 600 Yd. BR and then throw in ELR varmint hunting in the early 90's. My relationship with shooters there lead to my association with Accuracy International. Now 10 years later here I'm here. Taking what I learned and applying it to yet another shooting discipline.
Here is what I've seen, witnessed with paper targets measured over those 40 years.
In short range BR people , myself included, would try faster twist barrels. Standard was a 1-14 for the bullets we use. We tried everything from 1-12 to 13.5. Occasionally we would get a 13-13.5 to shoot with the 14's. 14's dominated. A 65 gr. Berger bullet @3300 FPS in a 1-14 has an Sg of 1.07. I've been away from that game for some time now. Frank Green will see this and maybe he can add something about current trends but I doubt it's changed much. We've been on the ragged edge decades but it works.
In 1K BR the 30's were king when we started the IBS 1K Yd. program. Williamsport had been shooting a long time before we started and they were predominately 30 cal. We shot 10 and 11 twist barrels mostly with Sierra MK's, Berger 210's or a custom bullet. For myself I shoot a 187 gr. FB bullet in anything from 1-10 to a 1-14. They shot better, more accurately in a 1-12 and slower. In my 14 twist the Sg was about 1.04. We have rifle, barrel and bullet combinations that are capable of easily agging under 5". We weren't looking for a solution because we didn't have a problem to solve.
In 600 Yd. many of us migrated over from 1K competition. I shot my 30 there for several years. Set one world record which is laughable now compared to what's currently being shot. The 6's quickly dominated. 105 Berger's, twist rate 1-8 with a Sg of 1.44 using Berger's twist rate calculator. The records for the IBS 600 Yd. light gun single target .336", 3 target agg 1.3458" heavy gun single target .404", 3 target agg 1.3359". I'm on the records committee and have personally measured each of those targets. The accuracy required to compete is well just hard to fathom unless you're there and see it for yourself. They see no need to go with a faster twist. Again they have an Sg of 1.44 with the 105 Berger's and other custom bullets.
It's been my experience that longer, thin skinned bullets, over the life span of a barrel with excessively fast twist can have issues. Can you go with a little faster twist? Sure but do the positives out weigh the negatives. I have a 1K customer, an anal engineer that tracks everything,. He has found over several decades of testing that 30 cal bullets work best around @200,000 RPM's. My heavy gun is a tight neck 300 PRC. It's a 9.5 twist and has shot and can shoot 5" 10 shot groups at 1K. Would an 8 twist help? Not likely.
30 cal. RPM example
220 Gr. SMK @2900 in a 1-11 = 189,818 RPM's
220 Gr. SMK @2900 in a 1-10 = 208,800 RPM's
velocity X 720 divided by twist rate= RPM's
Per Berger/Litz minimum twist rates
6MM 105's 1-8
6.5MM 140's 1-8
30 cal. 215-230 1-10
30 cal. 210's 1-11
Take a look at the results from last years IBS matches for the data you're looking for. It's all there.
https://internationalbenchrest.com/results
For 40 years now I've participated in shooting competition. All disciplines were accuracy centered. Short range BR, 1K BR, 600 Yd. BR and then throw in ELR varmint hunting in the early 90's. My relationship with shooters there lead to my association with Accuracy International. Now 10 years later here I'm here. Taking what I learned and applying it to yet another shooting discipline.
Here is what I've seen, witnessed with paper targets measured over those 40 years.
In short range BR people , myself included, would try faster twist barrels. Standard was a 1-14 for the bullets we use. We tried everything from 1-12 to 13.5. Occasionally we would get a 13-13.5 to shoot with the 14's. 14's dominated. A 65 gr. Berger bullet @3300 FPS in a 1-14 has an Sg of 1.07. I've been away from that game for some time now. Frank Green will see this and maybe he can add something about current trends but I doubt it's changed much. We've been on the ragged edge decades but it works.
In 1K BR the 30's were king when we started the IBS 1K Yd. program. Williamsport had been shooting a long time before we started and they were predominately 30 cal. We shot 10 and 11 twist barrels mostly with Sierra MK's, Berger 210's or a custom bullet. For myself I shoot a 187 gr. FB bullet in anything from 1-10 to a 1-14. They shot better, more accurately in a 1-12 and slower. In my 14 twist the Sg was about 1.04. We have rifle, barrel and bullet combinations that are capable of easily agging under 5". We weren't looking for a solution because we didn't have a problem to solve.
In 600 Yd. many of us migrated over from 1K competition. I shot my 30 there for several years. Set one world record which is laughable now compared to what's currently being shot. The 6's quickly dominated. 105 Berger's, twist rate 1-8 with a Sg of 1.44 using Berger's twist rate calculator. The records for the IBS 600 Yd. light gun single target .336", 3 target agg 1.3458" heavy gun single target .404", 3 target agg 1.3359". I'm on the records committee and have personally measured each of those targets. The accuracy required to compete is well just hard to fathom unless you're there and see it for yourself. They see no need to go with a faster twist. Again they have an Sg of 1.44 with the 105 Berger's and other custom bullets.
It's been my experience that longer, thin skinned bullets, over the life span of a barrel with excessively fast twist can have issues. Can you go with a little faster twist? Sure but do the positives out weigh the negatives. I have a 1K customer, an anal engineer that tracks everything,. He has found over several decades of testing that 30 cal bullets work best around @200,000 RPM's. My heavy gun is a tight neck 300 PRC. It's a 9.5 twist and has shot and can shoot 5" 10 shot groups at 1K. Would an 8 twist help? Not likely.
30 cal. RPM example
220 Gr. SMK @2900 in a 1-11 = 189,818 RPM's
220 Gr. SMK @2900 in a 1-10 = 208,800 RPM's
velocity X 720 divided by twist rate= RPM's
Per Berger/Litz minimum twist rates
6MM 105's 1-8
6.5MM 140's 1-8
30 cal. 215-230 1-10
30 cal. 210's 1-11
Take a look at the results from last years IBS matches for the data you're looking for. It's all there.
https://internationalbenchrest.com/results
Hi Guys,
Been watching this thread with interest for a couple months now. I decided to put a new barrel on my 300 WM and chamber it in 300 PRC - I should get it in about a week. Fortunately It's been raining almost non-stop for the past few weeks, so my anticipation has been tempered. Still, can't wait...
Anyway, my issue is brass. The necks on Hornady brass are less than consistent and I want to neck turn the cases. The problem is that many cases start with a thickness of .0115, meaning that's about the thickest I can turn to. Why is that a problem? The only dies available for 300 PRC are Hornady, and the smallest applicable bushing they make for the dies is .329".
Please check my math, but at .308 bullet diameter + .0115x2 next thickness = .331 - .003 neck tension - .001 spring back = .327. That is 2 thousandths smaller than their smallest bushing.
Anyone have any ideas other than just sorting brass based on neck consistency and waiting for Redding or other die manufacturer to come out with a die/bushing that will allow me to size the neck appropriately (or wait on better brass, which I'm not holding my breath for)?
Been watching this thread with interest for a couple months now. I decided to put a new barrel on my 300 WM and chamber it in 300 PRC - I should get it in about a week. Fortunately It's been raining almost non-stop for the past few weeks, so my anticipation has been tempered. Still, can't wait...
Anyway, my issue is brass. The necks on Hornady brass are less than consistent and I want to neck turn the cases. The problem is that many cases start with a thickness of .0115, meaning that's about the thickest I can turn to. Why is that a problem? The only dies available for 300 PRC are Hornady, and the smallest applicable bushing they make for the dies is .329".
Please check my math, but at .308 bullet diameter + .0115x2 next thickness = .331 - .003 neck tension - .001 spring back = .327. That is 2 thousandths smaller than their smallest bushing.
Anyone have any ideas other than just sorting brass based on neck consistency and waiting for Redding or other die manufacturer to come out with a die/bushing that will allow me to size the neck appropriately (or wait on better brass, which I'm not holding my breath for)?
Building a 9 twist here but planning to use same bullet and same barrel length...
Loaded ammo is .338 that I just measured. I use a .336 bushing for most of my .30 cals. I wouldn't get too caught up in your numbers until you load a round, and measure it. I guess if the necks are that bad and you have to turn them way down, then you have to look for other options.
Going from a typical .336 bushing down to .329, that would mean you are turning 9 thousands off the neck. Are they that bad?
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Until there are better options you could fire form the RWS 8x68s brass. You won’t be sorry you did. I posted a link some where in this thread on how
Set your neck turner to clean up 50% of the neck and go with it. Redding and Wilson bushings also work in the Hornady dies.
Dave,
Thanks. This is good info, and something I didn't know. Redding makes an appropriate sized bushing, and I just ordered one. I'm still not sure why Hornady doesn't make a smaller .30 cal sized bushing with their brass tending toward the thinner side of available offerings. I ran into the same thing when playing with my 300 WM brass. I finally just ditched it all and went with Norma.
I'm hoping Lapua decides to make the 300 PRC case, but I know that will be a long while off if they do. I do very limited prep on my new 6mm CM Lapua brass. In fact, it shoots better its first shot than the Peterson I had previously been using did after being fired and appropriately sized, seated, etc. I'm likely going to do a new custom build this year, and I'm still unsure of which cartridge I'll be going with. All I know is that it will definitively be in a be one for which Lapua makes brass.
https://www.vanceoutdoors.com/products2.cfm/ID/213584
Vance outdoors has 6 boxes left if ppl are still looking for factory ammo...
Vance outdoors has 6 boxes left if ppl are still looking for factory ammo...
$20 cheaper ($64.55) at https://vizardsgunsandammo.com/horn-544349-match-grade-die-set-300-prc/
Though $12 shipping eats up some of that.
I have to chuckle.
It takes a village to get a rifle to go boom.
It takes a village to get a rifle to go boom.
Just a FYI... Dane @ DMR rifles will be receiving a reamer soon. So he's another great option for a build.
And Midsouth shooters supply is out of the 225 ELD Match rounds. Isn't taking long to sell out. I just received the email yesterday afternoon that they had stock.
Just got a new box of 225 gr ELD-M from Midway. Getting consistent C.O.L. between 3.6615 and 3.662".
Anyone else getting the same measurements with this new lot?
What's your lot number. I just got 100 more on the last Midway run. I'll measure in a minute
Pure speculation here... But at that COAL they just allowed all the 3.775 magazine guns to run this ammo as it's under the 3.675 COAL. The CIP 3.850 mags were needed for the 225 factory rounds at the 3.685 length. May have just seated them 23 thou deeper to allow a more variety of guns and manufacturers to run 300prc without needing CIP bottom metal and mags. Just a guess if that is the new standard for this ammo going forward.
Certainly. Now DOD can just rebarrel all their 300 Win Mags. I couldn't figure out for the life of me why they didn't do this from the beginning. I raised all kinds of hell a couple months back about the COAL being too long for most actions and switched my order to accommodate CIP length and they changed it anyway.
I think going CIP length was the right choice though especially if you hand load. But overall probably a good business choice to get the 300 PRC in the most hands possible.
Agree on both points. I'm sure they have received a lot of backlash since the release, especially with the military trying to adopt it.
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