The Learning Curve

[longgun]

Loading manuels are great and they save us a lot of problems and experimenting when working up new loads, since they give us a starting place to begin.   It is when we have no or little information on new cartridges that we have to do our work.  This is where the fun and frustration happens.

I've been working with the 6.5 grendel and it has shown some promise for small case capacity and mild recoil.  And loaded right it can be effective on rams which is mostly the standard by which we judge a particular cartridge.  To achieve the velocity that I needed for ram load I was using 29.2 g of V V N 530 behind a Norma 130 g bullet. This load is on the top end but  I have loaded hotter loads and though not as accurate was still safe.   I live on the Texas gulf coast and temperature us usually in the mid to high 90's.   I have shot this load in one match prior to going to Phoenix.
When sighting in at Phoenix the temp there was 107+ and my first shot ruptured the brass, blew the bottom of my stock out with the spring and follower.  Also damaged the bolt somewhat and broke the Sako extractor, and split the stock.
I was lucky in that I only received very minor powder burns and a couple of scratches.   The left lens of my glasses received a chip but other wise I was ok.  

What I didn't know was the the V V N 530 is not a temperature stable powder,  such as some of hodgdon's  powders are.   After the facts I found that  N 530 is a double base powder,  and probably would have been
safe had I have kept in in a cooler.  

I was able to put the gun back together enough to shoot the match using my short line loads.   I've reworked the gun and put a new stock on it and as of now is still a 6.5 Grendel.   I want to play with it some more but will be more selective in my powder choices.   FWIW,  Don

[K2]

Hi Don

Glad you came out whole!  The law of dimenishing returns indicates that going smaller and trying to get more power for the rams can be dangerous.  Even if your loads are safe one should be careful shooting next to an experimenter as well.  

Something to consider when experimenting is that you would most likely be held liable should your experimentation hurt someone else.  Going outside of published loading data would be pretty hard to defend in court if something goes wrong.  Calling a load "safe" because it hasn't blown up yet, with no emperical data will hold little sway with a general public jury.  

Be careful and be safe.  If you want more power use more gun or except that tiny cartridges will leave rams.  

Loading manuels are great and they save us a lot of problems and experimenting when working up new loads, since they give us a starting place to begin.   It is when we have no or little information on new cartridges that we have to do our work.  This is where the fun and frustration happens.

I've been working with the 6.5 grendel and it has shown some promise for small case capacity and mild recoil.  And loaded right it can be effective on rams which is mostly the standard by which we judge a particular cartridge.  To achieve the velocity that I needed for ram load I was using 29.2 g of V V N 530 behind a Norma 130 g bullet. This load is on the top end but  I have loaded hotter loads and though not as accurate was still safe.   I live on the Texas gulf coast and temperature us usually in the mid to high 90's.   I have shot this load in one match prior to going to Phoenix.
When sighting in at Phoenix the temp there was 107+ and my first shot ruptured the brass, blew the bottom of my stock out with the spring and follower.  Also damaged the bolt somewhat and broke the Sako extractor, and split the stock.
I was lucky in that I only received very minor powder burns and a couple of scratches.   The left lens of my glasses received a chip but other wise I was ok.  

What I didn't know was the the V V N 530 is not a temperature stable powder,  such as some of hodgdon's  powders are.   After the facts I found that  N 530 is a double base powder,  and probably would have been
safe had I have kept in in a cooler.  

I was able to put the gun back together enough to shoot the match using my short line loads.   I've reworked the gun and put a new stock on it and as of now is still a 6.5 Grendel.   I want to play with it some more but will be more selective in my powder choices.   FWIW,  Don

[DanDeMan]

Don,

After years of working with small case capacity 6.5mm cartridges for HP Silhouette I can say that one should NEVER use any double base powder; nitro-cellulous/nitroglycerine.  These powders are very dangerous to use when loading to top cartridge pressures.  It is the nitroglycerine that makes the powder VERY temperature sensitive with respect to pressure.  The least temperature sensitive powders out there are the Hodgdon Extreme Series, http://www.hodgdon.com/smokeless/extreme/page4.php.  The only other powders I use for HP are the VVO N100 Series, http://www.vihtavuori-lapua.com/rifle.asp#N100%20series.

The ball powders made by Winchester, all of the N500 series powders made by VVO, some of the RL powders and others that I’m not aware of have nitroglycerine in them.  They are to be avoided like the plague if one is loading to high chamber pressures as just an extra bit of ambient temperature can cause the catastrophic event that befell you at Phoenix.  STAY AWAY FROM DOUBLE BASE POWDERS!!!  As a matter of fact I’d not recommend double-base powders for ANY application.

Now, if I was loading the Grendel for rams I’d do 6 things to optimize ram performance:

1.Shoot a 139 Lapua Scenar as it has the best balance of BC and toughness or one of the heavy jacketed 140-grain Cauterucios with closed meplates.

2.Moly-coat the bullets as one can get about 40 fps more MV at the same chamber pressure with moly-coated bullets due to reduced peak pressure

3.Use VarGet powder for rams

4.Use Lapua brass as it will withstand higher pressures

5.Use Rem 7 ½ primers, they will add about 15 fps to the MV

6.Use an 8-twist barrel.  Longer is NOT better as 24” will probably give the highest MV’s for a particular load because the cartridge is under-bore by a large margin.  The bullet actually starts to slow down in the barrel if it is too long when using an under-bore cartridge like the Grendel.  In testing with the 6.5mm TKS, about 10% more case capacity than the Grendel) a 24” barrel gave higher MV’s compared to a 26” barrel of about 20 fps for rams loads.  Both barrels were made one right after the other by Hart.  The recommendation is to use an 8-twist barrel with a # 5 or 5 1/2 contour with a finish length of 24”.  Coupled with a trued Remington 700 Short action, that would make a dandy HP Hunter bedded in one of the Pharr-out HP Hunter stocks.

If one follows the above, given the reamer was properly designed for the 140-grain class VLD’s, not a trivial issue for silhouette, one should be able to launch the 139 Lapua Scenars to about 2,625 fps (maybe a bit more) with no excessive pressure.  If any of you are interested in having a HP Hunter Grendel reamer ground contact me and I will help with the design.

Speaking of Hunter Class cartridges, a new version of the 7mm BR has been designed with reamer currently being made by JGS.  It is a standard 7mm BR but with the front-end optimized for the 176-grain VLD’s made by Cauterucio.  With about 32 grains of VarGet and the 176 Cauterucio out of an 8-twist barrel that load will knock down rams like no 260 ever will.  I personally know that the 176 C bullet launched at 2,325 fps out of my 7mm PPC Improved (5% less case capacity than the 7mmBR) is totally devastating on rams, much more so than a 139-grain 6.5mm Scenar launched at a MV of 2,800 fps.  And, the recoil from the 176-grain, 7mm bullet launched at 2,325 fps is noticeably milder than the higher MV 139 Scenar.  Projected loads for the 7mmBR / TPP (Theodore (reamer & load designer)/Pearson(master smith)/Perry(master trigger-puller) are:

CPT: 30 grains of VarGet under the 139 Hornady SST, MV 2,400 fps
Rams: 32 grains of VarGet under the 176 Cauterucio, MV 2,350 fps

More to come when the rifle is built by our one and only MetalHead, Marvelous Marvin Pearson, proprietor and head guru, or is that grunt, of Precision Target Sports, maker of world-class silhouette SB and HP rifles.  For those interested in such a Hunter HP Silhouette rifle Marvelous will have access to the reamer, as rumor has it.

[Tony Tello]

Dan, thank you for your advice.  

I was going through the Hodgdon Web site rifle success stories and found one letter sent to them by David Tubb and with Hodgdon's permision I wanted to share it with the rest of you.
 
                                                  David Tubb

"Dear Hodgdon Employees,

I have used Viht powders with good success since the mid 90's and until then end of the 2001 shooting season believed that the Viht was as good a powder as could be for my type of highpower rifle shooting.

I visited with my friend, Middleton Tompkins in the summer of 2001 about temperature sensitivity and from that conversation I began to look for shooting conditions where powder performance was temperature related (most of the time in Texas the temperature is very warm when I am competing, but not always the case at Camp Perry,Ohio during the Nationals).
Needless to say I proved to myself that the Viht powder didn't perform nearly as well in the 70 degree range as it did in the 90 degree range.

Consequently, at the start of last year's shooting season I traded twelve - 8# containers of Viht powder for ten - 8# containers of Hodgdon powder with a local reloading supplier.

I have now used your powder for the last year and a half and am very pleased. Last month I shot some (all 10 shot groups) tests with 4 different Schneider polygonal rifled barrels with the temperature in the 40's (out of my machine rest) and even though the groups aren't quite as small as my summertime groups they still hovered around 3 inches at 600 yds which fits my parameters for accuracy.


Sincerely,
David Tubb"

[dwl]

I'd like to thank Don for sharing this information with us.  I'd heard about the incident after I got home from the smallbore matches.  Don has done us all a favor by sharing with us the details of what happened.  I know because I deal with solid propellants and energetic materials in the course of my work and incidents are reviewed with great concern.

Thanks, Don for detailing what you did, what happened and what was learned.   Thanks to everyone else for supplying additional information regarding liability and solutions to the problem.  Tony even supplied some information on the effectiveness of the solution via Hodgden and David Tubb.  It's indicative of intelligent people that you've done what a professional Cause and Corrective Action process would have.

Considering that non-incidents in California were propagandized into the closings of the Huntington Beach and Long Beach shooting ranges to the public, I think we all owe it to our own selfish interest to share information and reduce the comparitively few incidents we have.

By the way, I was very impressed at Phoenix, all that expensive equipment and I didn't hear of a single theft.  It sure was nice to be with gun owners at and event run by the gun lobby.

DWL