300PRC +P Load development

[Sweet Tooth]

I tried posting this earlier, but after replacing the graphics, it was listed on waiting for approval, so I thought I would try again with a new post.

I got a custom built 300PRC +P from Defensive Edge and am trying to work up the best load for it. The +P indicates a tapered entry into the rifling which reduces pressure and allows more powder and a bit more velocity than standard: https://defensiveedge.net/300-prc-p/ for more info. The =P certainly seems to allow for significantly higher powder charges, so these loads would liely not be suitable for a standard chamber.

I used H1000 and Berger 215gr Hunting Bullets with Hornady factory load brass that my son and I had fun emptying at the range a couple weeks ago.
My first loads were at the same OAL as the Hornady factory loads which I believe now were touching the lands, and chambering the round probably seated the bullet a bit further. I started at 76gr H1000 and worked my way up to 84gr where I could see faint marks on the brass if I held it up to the light right, and the primers were getting a bit more cratered, i.e. a slight ridge around the firing pin impact, but not flattening.
Max and min velocities vs charge weight shown below:

100 yard 3 shot Group size and elevation above or below aim point shown below:

I decided to try and further refine things by trying two different seating depths between 81 and 82gr (minimal change in velocity and > 3000fps) and 83.5 and 84.1gr (3100fps+ and still relatively small dependence of velocity on powder charge). OAL touching the lands is 3.618" as near as I can tell using a modified case and Lock-And-Load tool. I am not very confident in the accuracy of this measurement as I could not get very consistent results, at least at the level of precision we're talking about here.
Results were as follows:

I was originally thinking that 84.1gr and OAL of 3.603" was going to be my load. But after graphing everything out, that same load just .005" longer quadrupled the group size and ES of velocity. Is this sort of sensitivity to seating depth normal? I was hoping to find at least some consistency in trends of powder charge variations between the different OALs, but I don't really see any.
I would certainly welcome anyone's thoughts or suggestions on how to proceed. I am getting back into reloading after several years, and what I did way back when was not nearly at the level of what I'm trying to do now.
Other information that may or may not be relevant: First loads were shot off a front and rear bag from a bench, the second two sets were shot from a bench but with a bipod and rear bag which I like better. There wasn't much wind to speak of. I am not a competition shooter, so human error may certainly be a part of the problem.
I also wonder if this is just the result of plain old probability. If I shot the exact same load over and over in 3 shot groups and each shot had a normal bell shaped two dimensional distribution about the aim point, I would expect to have some small groups, some large groups, and a lot in between. Am I just looking at that same phenomena here, i.e. is that .2" group just "good luck" and the 1.6" group just "bad luck"?

Thanks in advance for your comments.

 

[supercorndogs]

Hello Darwin? Is that you?

 

[spife7980]

Wouldnt it be easier to look at the target and see what happened?

 

[Sweet Tooth]

Hello Darwin? Is that you?

Not sure who Darwin is, but I have naturally selected a few deer over the years...

 

[Ledzep]

I also wonder if this is just the result of plain old probability. If I shot the exact same load over and over in 3 shot groups and each shot had a normal bell shaped two dimensional distribution about the aim point, I would expect to have some small groups, some large groups, and a lot in between. Am I just looking at that same phenomena here, i.e. is that .2" group just "good luck" and the 1.6" group just "bad luck"?

Yes.


Also, regarding your throat geometry and pressure... Are the claims of higher velocity with 6 grains more powder than published load data with a SAAMI chamber at safe pressure substantiated with any test equipment?

 

[Sweet Tooth]

Wouldnt it be easier to look at the target and see what happened?

I did. It just seems odd that there's no real trends like I was expecting.

 

[cast1]

3150 with 215s out of a 300 PRC is pretty spicy. Do some reading on reloading fundamentals for safety’s sake so you don’t hurt yourself. Never guess where your lands are. Find them before you start, so go back in time and do that first.

I did load development for a regular 300 PRC I built for a buddy of mine using 215s. I started him at .020” off the lands and found a nice little node around 2900 fps. Never work from a jump to jam, do the opposite and work farther from the lands as you go. I was surprised when his rig shot best at .100” jump. Single digit ES. VERY good accuracy for a lightweight rig.

 

[Sweet Tooth]

I appreciate the concerns over the higher powder charges. I haven't seen any actual pressure measurements for +P designs, but what I'm seeing is very much in line with what Defensive Edge posted with their 300PRC +P: https://defensiveedge.net/300-prc-p/
3106fps with 84.5gr H1000 and a 215gr Berger out of 26" barrel.

This weekend I hope to be able get more reliable measurements and determine more exactly where my lands are. I believe the +P design may make that a bit more difficult, but it still needs to be done.
I am working from a jam to bigger jumps, I'm just as sure of exactly how much of a jump as I would like to be.

Thanks

 

[supercorndogs]

Oh, well then. If you both put more powder in and velocity went up at relatively the same rate, it must be fine....

I believe Weatherby throated rifles in sort of the same fashion to run more pressure. I would personally just get a bigger round, I don't think you are only making 63KPSI to make 3150FPS, when with standard throating 63KPSI should be around 2870. The 300PRC doesn't have a lot of bullet in the case to begin at SAMI OAL. I just don't see making room for another 7g powder and 200FPS by throating it longer. By running overpressure, sure. But the difference in performance inst worth the squeeze.

 

[Frank Green]

I’d like to see the print/drawing of the chamber reamer that was used to chamber the barrel with.

Don’t guess on the pressure vs. velocity! Unless that load was run thru a pressure test barrel cut with that reamer…you don’t know what the pressure is running at.

Just because you don’t have hard bolt lift or any tell tale signs on the case of pressure doesn’t mean your not over pressure.

Again I‘d like to see the chamber reamer drawing.

Later, Frank
Bartlein Barrels

 

[Ledzep]

I'm with Frank. You can theorize al you want about what throat geometry will do to pressures, but if you tell me to start putting 6-7 more grains of powder in a magnum case over published max, you better believe I'm going to want to see proof that it isn't just a well-marketed pipe bomb.

In my experience, faint ejector marks on plunger ejector bolt faces begin to show up (in some guns with the softer end of the spectrum brass) around 70-72ksi. Sometimes dramatically higher (Mechanical eject bolts with smaller ejector slots, harder brass, etc.)... There's more than a few folks out there unknowingly smoking proof loads every firing... and being saved by nothing more than safety margins and fatigue life... for now.

 

[waveslayer]

@Sweet Tooth i assume your on Long Range Hunting or whateve Furman and Broz run.

There's a thread on there claiming all sorts of BS doing this +P throat.. all BS. Best analogy I saw on there was .223 or 5.56 that was like pissing in the cereal to the vanillas on that forum, especially Furman.

How many firings are you getting on your brass?

I'd listen to what others have commented already . If you want more internal case volume just switch from the PRC and go 300 Norma Ackley Improved

 

[brianf]

…with pressure there’s no free lunch…Just lack of protocol or equipment for testing

 

[Sweet Tooth]

…with pressure there’s no free lunch…Just lack of protocol or equipment for testing

I appreciate the comments on dealing with a relative unknown with the +P chamber.
I can't get prints or dimensions of the chamber, and I was using his published load with one rifle to go. There are no actual pressure measurements with this chamber, so I'm trying to use other indications the best I can.
I recently ran some loads with Reloder 26 and "measured" case head expansion before and after each shot. We have a small CNC machine in our shop we use for making electronic component plates. I cut a series of holes, each one theoretically .0001" bigger than the last. I would simply drop a case through th eholes as Go-NoGo guage before and after firing to measure the amount of expansion. I don't know how accurate or precise this machine is at that level, but it should give some sort of relative measurement before and after firing.
My cases all showed .0001" expansion this way until I could detect the faintest of ejector marks upon close examination in direct sunlight. At that point the expansion jumped to .0005" and I did not shoot any hotter loads.
While this is not an accurate measurement, it certainly seems to me to be indicative of pressures rising beyond what I want, particularly as it showed up at the same time as the ejector mark. The ejector marks were just the faintest indication by a change in the reflectivity in that spot. Primers weren't flattened to any great degree, i.e. still had plenty, I think, of radius left. I can't really go by bolt lift unless I rig up some way to accurately measure the force. I'm using Hornady brass from factory loads, and I don't have an idea of how many loads I'll get out that brass yet.
While I would like to take advantage of what the +P chambering theoretically offers, I certainly don't want to do so at unsafe pressures. I would think the expansion increase showing up at the same point as the ejector marks would be an indication that I am getting too high pressures, and would like the thoughts of those with more experience.

Thanks

 

[wadebrown]

I assume you are shooting this outside, I ask because if you decide to shoot the rifle at higher temps than those of February you might want to dial back the powder charge. With no direct measurement of pressure you really have no idea what it is so you don't know how close you are to disaster and the additional 40 degrees in temperature might get you to disaster, but then again maybe not kind of nice to know BEFORE you pull the trigger.

I am amazed that Defensive Edge publishes reloading data that is significantly greater than other published data for the same case, different throat geometry but the same case, with no pressure measurements. When Defensive Edge first publicized their +P chamberings for rifle cartridges I called then up re: the same for 308 W. I was interested in the 308 as Palma shooters are always looking for extra performance and due to rules are locked into the 308 or 223 cases.

I forget the name of the principle at DE but he claimed he had a patent on the throat geometry and I could not get a reamer cut to it, he did not like that fact that I laughed. I was asking for some background and would have bought a 308 +P reamer from him but he that caliber is of no interest to his business and he claimed that I had no right to use the idea for 308 +P. At the time I did not find a patent under his name for throat geometry because all I would have needed to do was to change a dimension slightly and call Kiff up and have a reamer cut. Think about 300 Blackout and 300 Whisper dimensions are pretty close.

Kiff is cutting the +P on demand as we speak. But it does not seem that the +P reamers are setting the world on fire, maybe due to a lack of testing and desire for not having to take a ride to the ER to have parts of your receiver removed from your cheek.

 

[DeathBeforeDismount]

Make sure your heirs have this information:

Shawn Carlock
15670 N Ranch Valley Rd.
Rathdrum, Idaho 83858

This way when you kill yourself they know who to serve the papers.

 

[bax]

I'm just a knothead with a computer but I thought I would run some of your computations through my stuff.

I am generally suspicious of internal ballistic tools however, I downloaded the GordonsReloadingTool and it has been working for me. I ran a prediction using the specs from your post. 26-inch barrel, 1-9 twist, Berger 215, 81.7 grains of H1000, standard 300 PRC chamber. I took defaults for other parameters. Gordon says muzzle velocity is 3019 feet per second. Based on your charts, that is good agreement. Gordon also says that max pressure is 67,575 PSI and PMAX for the round is 63,817 PSI. So if Gordon is right about pressure, you are about 6% above PMAX.

You say that you have a custom chamber that reduces pressure. Okay, I don't know about that but I'm not sure how you get more velocity with less pressure unless you stretch out the pressure impulse. But you have a 26-inch barrel and the bullet is gone in 1.3 milliseconds. That isn't much time or room to work with.

Defensive Edge says: QuickLOAD Prediction: Max load 87.0 gr. H 1000, 103.4% case capacity, 3001 fps, 100% barrel burn, 4288 ft/lbs, muzzle pressure 12639 psi. Note - there is no max pressure.

Gordon says: with 87 grains of H1000 that is 110% of case capacity, 3213 FPS, 100% barrel burn, 4928 ft/lbs, muzzle pressure 16,036. Oh, by the way max pressure is 85,903 or about 35% over pmax. Note the disagreement on load factor - 103.4% versus 110%. That should be looked into. It looks like those guys are using different density values for H1000.

BTW about that pressure. In 1972, I saw that guy at the range on Ft Richardson. They were taking him away in an ambulance. He scalped himself, blew up his gun, and bled all over the place. I don't know how much shrapnel he caught - the RO was pretty shook up and the ambulance was in a hurry.

By the way, I am working up loads for a 300 PR. 27-inch Bartlein, JGS reamer with extra long throat. IMR7828, Fed 215m, Lapua brass, Berger 230. So far, it seems like a shooter. Good luck with yours.

 

[Feniks Technologies]

I would seriously caution using load data that is advertised as +P while simultaneously citing bolt lift and brass condition as the metric for pressure.

I’d want to see the documented pressure testing from a credible facility.

 

[Frank Green]

In my opinion there is no such thing as a +P load for rifle ammo in the real world to my knowledge. Once you hit max working pressure that it's. Your at max. You go beyond that and your over pressure. Simple as that.

I asked for a copy of the print to be posted so I/we can look at it. I can compare it to the reamer that I used in my barrel which is a Saami min spec. Just because you lengthened the throat...and if your seating the bullets out further...and your adding more powder...doesn't mean your over pressure. Again this does not equate to anything called +P loads for rifles.

I had my ammo run thru a pressure and velocity test barrel. We made the test barrel for a ammo maker. We do a lot of work for them and know the guys pretty good. I will give you my load and ask you not to duplicate it in your gun at all. I gave them several loads. Same bullets at .010" off the lands and same lot of powder. I gave them three different charge weights. At 76gr I was right at the max. working pressure. At 78gr (which that load also just hammered the target at a 1k yards. I shot like 12 of those rounds thru my gun before I got the ammo pressure tested. No heavy bolt lift, no ejector marks etc...) but at 78gr the ammo went 5000 psi over the max working pressure. The OP is talking about running 84.5gr of powder!

Just because you don't have heavy bolt lift or marks on the brass doesn't mean the pressure isn't there.

You cannot duplicate or draw an honest conclusion from some computer formula. Unless the ammo is run thru a test barrel made to a given spec. and chambered with the modified reamer your running....it's not apples and apples. Now factor in temperature/environmental conditions etc...and things can get even more dangerous.

I know everyone doesn't have access to getting ammo tested and or have the $$$ to pay for testing like this. I've requested it a few times because of how close we work with all the different ammo and bullet makers when we've seen problems. Just last month one of the guys in the shop blew up a 9mm pistol and a 9mm AR carbine to different degrees. On the pistol he blew the extractor completely out of the slide, cracked the grip frame and damaged the trigger mechanism and the case separated and blew the primer out of it etc.... He bought reloaded ammo from a gunshop and we don't know the type of powder used etc...and my guess is the gunshop as they seem like they are a hole in the wall...didn't have any of the ammo pressure tested at all (names and type of ammo being with held here intentionally). Max working pressure for 9mm luger is like 30k psi. The ammo was run thru a pressure test barrel and the average pressure was over 47k psi. Highest peak pressure was over 51k! In a universal test receiver (it's a close breech cannon type system) with a barrel with a 2" o.d...... the round that hit 51k psi blew the primer out of the case. The ammo maker said they've never seen anything like that with a pistol round out of a pressure fixture happen like that before.

I just want you all to be safe and don't want to see anyone get hurt. Rifle ammo runs at a much higher pressure than pistol ammo does.

Later, Frank
Bartlein Barrels

 

[brianf]

I know everyone doesn't have access to getting ammo tested and or have the $$$ to pay for testing like this.

Later, Frank
Bartlein Barrels

This X 1000

if you dont have the money for proper testing and your going outside the industry parameters....keep it to yourself because its dangerous

i wouldnt pull that trigger with a string if you paid me

brian

 

[Steel head]

This X 1000

if you dont have the money for proper testing and your going outside the industry parameters....keep it to yourself because its dangerous

i wouldnt pull that trigger with a string if you paid me

brian

 

[2aBaC̶a̶]

@Sweet Tooth Its been a year, how has the +P worked out?

Have you tried any heavier bullets?

 

[waveslayer]

Have the guys over at Defensive Edge responded to any request regarding the +P throat? There is a cult like following over at Longrangeonly forum on the +P. They are now pushing a RUM +P.

None of the guys can answer questions about the pressure and advantages of it. I've been basically banned for questioning one of their self proclaimed experts and how dare I say CA isn't a top rifle! But I digressed.

 

[2aBaC̶a̶]

Just curious does the +P stand for +Pressure?

 

[Frank Green]

None of the guys can answer questions about the pressure and advantages of it. I've been basically banned for questioning one of their self proclaimed experts and how dare I say CA isn't a top rifle! But I digressed.

To back up what waveslayer says......

If a source will not disclose some sort of data on pressures and changes and have a print/drawing of the reamer spec...you have to question it as you cannot compare it to a standard.

Look at Sierra, Hornady, BlackHills, Barnes, Hodgdon powder etc...these places all adhere to a industry standard and make bullets, make powder and test the stuff so they have data to back it up. Yes you will see slight variances here and there and or things can change over time...that's why testing is always being done. To ensure that things don't get out of whack for the box ammo and for published reloading data.

If there is no standard type of testing being done with a pressure test barrel set up......how can you trust the data?

 

[BCX]

Wasn't Weatherby the first to experiment w + P throats? To my understanding its a long free bore w a swallower leade angle.

 

[Frank Green]

Wasn't Weatherby the first to experiment w + P throats? To my understanding its a long free bore w a swallower leade angle.

It's never been referred to a +P throat or loads for WBY. Keep in mind those typically have a really long throat. As an example if I recall correctly on the 375WBY the bullets jumped .375" before they hit the rifling. Yes this long jump helps the pressure in my opinion but if so...it doesn't help when a shooter runs a heavier powder charge and seats the bullet out further to have the case capacity but he's running the bullet close to our touching the lands/rifling. Your not gaining anything in my opinion.

Guys do this with the 300WM. They think because you cut the throat longer so they can seat the bullet out further that it means they can run a heavier powder charge. It doesn't work that way.

Also if you do jump the bullet a lot...accuracy usually will suffer. You don't get your cake and eat it too as the saying goes.

 

[Steel head]

Wasn't Weatherby the first to experiment w + P throats? To my understanding its a long free bore w a swallower leade angle.

They certainly had a good amount of freebore

I did something similar, ran a longer freebore in my 260 to get all that the 2.96 magazine and a bit of jump woul get me back when I was shooting it way out there a lot.
With roomy brass it did get me a bit extra speed.
Certainly not a game changer.

 

[Frank Green]

Here is a good one for you all....a couple years back I was at a meeting at Shot Show. I questioned the ammo/bullet maker if they test they're stuff with ammunition pressure test and accuracy test barrels and who they used for the test barrels out of curiosity?

I got nah...don't need to do that. We run the numbers thru quick load and using hunting rifles to test the stuff. It all works out fine!

I just shrugged my shoulders and walked away from the meeting. Factory rifles....yes there is a min. spec. standard but most factory built rifles are built with production tolerances. The barrel and chamber could be at min. spec.... or I've seen the stuff at +.002" over min spec. So how in the heck do you know what is good data?

Unless you know what your running the stuff thru and collecting good data... again how do you know what you are getting is even in the ball park?

Doesn't matter if you by a bolt gun blank from us or an ammunition test barrel. We run Saami min spec. + .0005" tolerance on the bore and groove size. Yes in some cases we make barrels to tight bore spec's also but not the norm and usually per customer requests. If we make a ammunition test barrel the end user gets an inspection report with actual bore and groove sizes to the 4th decimal place so .xxxx" as well as we reference the actual chamber spec reamer used as well. So they know exactly what we did to the inside of that barrel. If they have any issue with anything and I get a phone call I can pull the inspection report and I know exactly what we did. If they send the barrel back and I reinspect it I'll compare the original inspection report that a guy did in the shop to what I get for measurements. We are human and can make mistakes. Or a chamber reamer can be made wrong or even if it measures to spec...it can not cut to spec. I've measured and checked the reamers as well looking for errors and have found issues.

I've seen test barrels made by other makers where the bore and grooves where just a .0005" undersize and it drove up pressures 10k psi and velocity up +150fps. The barrels where out of spec and that was causing the issues.

 

[Steel head]

I investigated the 338 edge +P they promote when I was planning my 338 edge.
No solid pressure or load data scared me off.

Just relying on QL data is just asking for issues.

 

[waveslayer]

I investigated the 338 edge +P they promote when I was planning my 338 edge.
No solid pressure or load data scared me off.

Just relying on QL data is just asking for issues.

And how often is QL correct without truing it? I have never had it be near what my real life data is telling me, when compared to QL

 

[Steel head]

And how often is QL correct without truing it? I have never had it be near what my real life data is telling me, when compared to QL

I now use a different program
P-max, it’s been far better and works well with solids.

 

[waveslayer]

So guys I was banned from Long Range Only forum today, I consider it a badge of honor! guess Defensive Edge is a major sponsor over there and any questioning isn't allowed so much for trying to save an eyeball or ask what the advantage is.

 

[Sweet Tooth]

I appreciate all of the responses and wish I had had time to respond sooner.

It seems to me the situation boils down to this: I have a 300PRC with a modified chamber theoretically allowing increased powder charges and velocity due to the throat geometry. This may be real. It may just be marketing hype. I can't get any actual test data to back up the claims, and the only load data published relied on qualitative pressure signs such as bolt lift to indicate excessive pressure rather than actual pressure measurements.

Max load data are readily available for standard chambers. However, I'm sure there are rifles out there with out of spec or tolerance chambers for which these max loads are beyond safe. For that reason, it is highly recommended to start with lower charges and work up towards or possibly to that max load but stop if signs of excessive pressure are seen. For example, if I had a 30-06 that showed flattened primers, ejector marks, etc. at 60gr of H4350 and 150gr bullets, I couldn't safely go to 61.5gr even though that were still under the "Max Load" weight. How much different is working toward the max for a +P chamber than that scenario?

It sounds like I have two options: One- Ignore the +P chambering and stay at published max limits for the 300PRC or Two, work my way above those loads as long as I know I'm not exceeding safe pressures. Obviously Option One is the safer route, but if I can safely take advantage of the +P chamber and get a significant performance boost, I'd like to do that.

To do that, I need a reliable indicator that I'm approaching safe pressure limits. Flattened primers are somewhat subjective to begin with and can be caused by pressures within safe limits. Ejector marks seem a bit more reliable but not enough to go by on their own. Bolt lift, for me anyhow, is right out as it's somewhat "stiff" already and enough pressure to cause a noticeable difference in this rifle would be cause for serious concern.
What about case head expansion (CHE)? I used our CNC machine to cut several holes in plexiglass, each one theoretically .0001" bigger than the last. I'm measuring each loaded case before and after firing using the series of holes as a Go-No Go gage. Almost all of my cases have about .0001" CHE judging by this method, including factory ammo. In testing some loads recently with RL26, I got the typical .0001" CHE up to and slightly over theoretical max load as well as no signs of an ejector mark. However, a very faint ejector mark was present at the same load as the CHE jumped from .0001" to .0005".
I know CHE isn't typically used as a pressure indicator as there are so many variables, but is this method giving me any relevant data? Is there anything else I can use to indicate pressure reliably enough for what I'm trying to do?

Again, thanks for all of the responses above.

 

[Feniks Technologies]

It appears the main source of the extra powder is via long throat + a steeper angle. Which allows the bullet to be seated further, and in some cases allows enough extra powder to increase speed.

Which is still under the safe operating pressures.

At least that’s what I’m gathering. And it would only be capable with case/powder combinations that can take advantage of the increased capacity.

So, I believe the wording in the initial post “may not be suitable for a normal chamber” may have implied the operating pressure would be unsafe. When it basically would be impossible because not enough case capacity without the longer throat/lead. Not that the chamber wouldn’t be able to handle the pressure.

 

[Feniks Technologies]

I am however a bit confused.

If the goal is to allow more powder, and you seating bullets to the same OAL length as factory ammo and think that was touching lands….

Unless the bullet in the factory ammo was significantly longer than your loaded ammo…….

Then I’m failing to see how this reamer allows for the case to fit more powder than a standard 300PRC chamber.

 

[Sweet Tooth]

The modifications to the throat are a bit involved. Essentially, it's a two step reduction to bore diameter that reduces the initial pressure spike and better aligns the bullet with the bore. The patent describes it in more detail of course: https://patft.uspto.gov/netacgi/nph...ock&OS=Shawn+AND+Carlock&RS=Shawn+AND+Carlock

It sure sounds good in theory, I'm just trying to figure how to test it for real.

 

[b6graham]

The modifications to the throat are a bit involved. Essentially, it's a two step reduction to bore diameter that reduces the initial pressure spike and better aligns the bullet with the bore. The patent describes it in more detail of course: https://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=Shawn&s2=Carlock&OS=Shawn+AND+Carlock&RS=Shawn+AND+Carlock

It sure sounds good in theory, I'm just trying to figure how to test it for real.

get a pressure test barrel for 300PRC with and without a '+P'

 

[Steel head]

It will be interesting if the OP can get the advertised speed boost with a load that has decent brass life.
I for one an hoping he comes back with lots of data.

 

[b6graham]

It will be interesting if the OP can get the advertised speed boost with a load that has decent brass life.
I for one an hoping he comes back with lots of data.

i'd like to add a 30 Sherman Magnum into this mix with the +P

 

[Tokay444]

I appreciate the comments on dealing with a relative unknown with the +P chamber.
I can't get prints or dimensions of the chamber, and I was using his published load with one rifle to go. There are no actual pressure measurements with this chamber, so I'm trying to use other indications the best I can.
I recently ran some loads with Reloder 26 and "measured" case head expansion before and after each shot. We have a small CNC machine in our shop we use for making electronic component plates. I cut a series of holes, each one theoretically .0001" bigger than the last. I would simply drop a case through th eholes as Go-NoGo guage before and after firing to measure the amount of expansion. I don't know how accurate or precise this machine is at that level, but it should give some sort of relative measurement before and after firing.
My cases all showed .0001" expansion this way until I could detect the faintest of ejector marks upon close examination in direct sunlight. At that point the expansion jumped to .0005" and I did not shoot any hotter loads.
While this is not an accurate measurement, it certainly seems to me to be indicative of pressures rising beyond what I want, particularly as it showed up at the same time as the ejector mark. The ejector marks were just the faintest indication by a change in the reflectivity in that spot. Primers weren't flattened to any great degree, i.e. still had plenty, I think, of radius left. I can't really go by bolt lift unless I rig up some way to accurately measure the force. I'm using Hornady brass from factory loads, and I don't have an idea of how many loads I'll get out that brass yet.
While I would like to take advantage of what the +P chambering theoretically offers, I certainly don't want to do so at unsafe pressures. I would think the expansion increase showing up at the same point as the ejector marks would be an indication that I am getting too high pressures, and would like the thoughts of those with more experience.

Thanks

Cast the chamber and mic it.

 

[Sweet Tooth]

I'll do what I can for data. It's hard to find the time to load and shoot these days so it'll be slow to come unfortunately, but I'll post what I get.

 

[4O6shootist]

So guys I was banned from Long Range Only forum today, I consider it a badge of honor! guess Defensive Edge is a major sponsor over there and any questioning isn't allowed so much for trying to save an eyeball or ask what the advantage is.

Talk shit about nightforce or Richard Sherman on the longrange hunting forum they'll do the same, commi shit bags.

 

[abn31c]

Look at the Sherman page on fukbook, it's always good for a laugh. Bunch dudes running pressures that scare most sane people. But hey......it's been Shermanized...SMDH.

 

[4O6shootist]

Look at the Sherman page on fukbook, it's always good for a laugh. Bunch dudes running pressures that scare most sane people. But hey......it's been Shermanized...SMDH.

Dude.......I built 3 Shermans. Never got the speeds advertised. Went on there discussing velocity and psi. How does said 6.5mm Sherman case with 71gr capacity somehow out perform 6.5mm case with 74gr capacity? No geometrical magic but HIGH PSI. Richard booted me from the Facebook group. Fuck that guy......he says he'll never persue saami, hell no he wont, saami performs psi testing. All his "efficiency" will be proven as just excessive psi.

 

[4O6shootist]

+p is actually nothing more than a stepped throat, it only changes your bto touch to lands about 10k over existing throat if done right. I've spoken with Shawn about it. It has multiple lead angles built into it that drop the land engagement psi with general 1.5° leads that have become the norm. It does drop chamber pressures enough to where a guy can run more powder within same psi levels and achieve more velocity. An extra 70-100fps before psi signs may get you into the next optimal barrel timing node that was over psi in the saami throat. If maximum performance from given XX case capacity is your persuit, than it makes sense. But increased powder charge over standard is more fire and potential energy in the case, barrel life will be same or less. How does the stepped throat erode compared to standard 1.5°?, Idk. There are a lot of unknown or thoroughly tested data there that needs be evaluated.

 

[abn31c]

Dude.......I built 3 Shermans. Never got the speeds advertised. Went on there discussing velocity and psi. How does said 6.5mm Sherman case with 71gr capacity somehow out perform 6.5mm case with 74gr capacity? No geometrical magic but HIGH PSI. Richard booted me from the Facebook group. Fuck that guy......he says he'll never persue saami, hell no he wont, saami performs psi testing. All his "efficiency" will be proven as just excessive psi.

The guy is a con man. I read his shit telling guy's "that's not pressure...it's bolt slap..."
And on and on, yet the lure of velocity just keeps em coming......"but why are my pockets fried after 2 firings?"......

 

[FLIGHT762]

**DISCLAMER** I'm currently immersed in an Old Forester 1897 & Knob Creek Single Barrel 120º " Sensory Evaluation", but Every fucking time I see this +P bullshit trying to make a 300 PRC into a 300 /378 Weatherby Magnum / 260 / 6.5 C/M into a 6.5 / 06- 6.-5 / 284, 338/ 06 A.I. into a 338 Lapua etc.

Get the right cartridge for the caliber you want for that velocity. Go ahead and burn the barrel out under 1K. It's your money. But doing all this stupid shit to squeeze every FPS so you can toast your primer pockets on the first firing is Lunacy.

**EDIT** I'm finding I prefer the Knob Creek S/B 120º to the Old Forester 1897. It's not quite fair though, since I should not be comparing O/F 1897 to Knob Creek S/B 120º , I should be comparing it to Old Forester 1920 115º.

Stand by.

 

[4O6shootist]

**DISCLAMER** I'm currently immersed in an Old Forester 1897 & Knob Creek Single Barrel 120º " Sensory Evaluation", but Every fucking time I see this +P bullshit trying to make a 300 PRC into a 300 /378 Weatherby Magnum / 260 / 6.5 C/M into a 6.5 / 06- 6.-5 / 284, 338/ 06 A.I. into a 338 Lapua etc.

Get the right cartridge for the caliber you want for that velocity. Go ahead and burn the barrel out under 1K. It's your money. But doing all this stupid shit to squeeze every FPS so you can toast your primer pockets on the first firing is Lunacy.

**EDIT** I'm finding I prefer the Knob Creek S/B 120º to the Old Forester 1897. It's not quite fair though, since I should not be comparing O/F 1897 to Knob Creek S/B 120º , I should be comparing it to Old Forester 1920 115º.

Stand by.

I know nothing of knob creek, but am in agreement on the Shermanized inproved +P bore rider whiz bang extra grain of powder +70fps stuff gets old. Want fast speed? Get a bigger case....like a 30 nosler or 300 norma if you want an extra 75-100fps over PRC.

 

[abn31c]

Nope....all you gotta do is dick out yer chamber and if you really wanna scorch the earth go
SHERMAN MEGA......