I bought the bolt, gas block and barrel from Competition Shooting Sports.
I bought the LaRue rail from G&R Tactical.
I bought the Colt M4 upper receiver from ADCO.
I bought the TPS rings from Brownell’s.
I bought the Leupold 6.5-20 LR/T Illuminated Mildot from AR15.com EE.
I bought the LMT Defender 2000 from Denny’s Guns.
I am still waiting on the ammo…
I hear that Bill Alexander is testing the Wolf Gold ammo now, and it appears Midway and Competition Shooting Sports expects their AA factory ammo at the end of this month.
I’m a little disappointed though, as I wanted to take this rifle to Wyoming next week to hunt antelope.
Anybody have any news on the 6.5 Grendel ammo situation??
Well, I have the Ammo(100 Rounds) but I’m waiting on the LaRue Billet Upper and finalizing my lower…But the ammo situation right now is a little frustrating. I would have hurried with assembly, but since the ammo situation is blek Im not in a hurry.
Is that upper modified for the 6.5 in any way? When I looked into a 6.5 a long time ago, I saw some stuff about needing to mod the ejection port for 100% ejection. Of course, that may well be BS.
If it requires a bigger ejection port, I guess I will break out a file and make it happen. I was unaware that the ejection port needed to be modified, if that is true.
I’m not saying that it’s true but I do recall reading it somewhere. I think it was on the Grendel forum. Anyway, hopefully someone more knowledgeable can answer definitively.
Arne (Competition Shooting sports, and the developer of the 6.5 PPC who worked with Mr. Alexander to develop it into the 6.5 Grendel) is selling upper kits (Barrel, Bolt, Gas Block) and says they will work with any “In Spec” upper receiver.
Midway did this every month or two with 6.8 Ammo.
In the end, it took 18 months or so until they had it in stock.
There were short periods of time, where they would get 20K to 100K rounds in stock, but it would always sell out within hours.
Whenever someone saw ammo in stock, it got posted in the “Big” 6.8 thread and we went and bought it all.
Now, 6.8 Ammo is easy to get about anytime you want.
I don’t mean to turn this into a 6.8 vs. 6.5 thread, but without standardization in the industry, fewer ammo and gun makers are interested in producing ANY new cartridge or rifle.
6.8 Has SAAMI acceptance and you can buy at least 4 different brands of dies, 3 brands of brass and 3 or 4 brands of ammo.
Also, several different companies offering barrels.
One of these days, I’ll even get around to finishing my license agreement with AA and actually produce some barrels.
Standardization is the single biggest reason that I have kept a grip on the design. Without a level of supervision the design can quickly spiral out of control. Did you know that there are currently 47 different prints for a “standard” 6mm PPC. In the early days of the Grendel we had a least one gunsmith who though he knew better and re-engineered the chamber. He built a bolt gun that shot groups like buckshot and could not tell enough people how the cartridge was inacurate and that the loads were too hot.
If the 50 S&W and the 6.8 are examples of what SAMMI can achieve I think I will be very slow in moving down this path of standardization. For the 6.8 the initial work was both delayed and confusing, which led to the chamber neck diameter being given out at a size that was smaller than the cartridge neck diameter. This was then followed by a discrepancy in shoulder refererence. Beyond the simple dimensional problems we have seen a raft of changes for chamber pressure and the measurement method. Initially 51,300 psi was cited but in the absence of a defined measurement route this was assumed to be conformal transducer, although some took this to be NATO. Then a value of 55,000 psi for conformal tranducer is given. The last iteration of a formal method has been the CIP certification. This is set at just shy of 62,000 psi by direct reading tranducer or 58,000 psi NATO. With this it is now quite possible that CIP and SAMMI loads will not be interchangable. Beyond the institutionalized standards there are now several home grown standards evolving. There are standard loads, combat loads, SAMMI chambers and now we are seeing modified SAMMI chambers designed to cope with the combat loads, both of which violate both SAMMI and CIP. The customer may now begin to see his gun as not suitable for certain brands of ammunition, a situation that has not existed since the days of the blackpowder 50-70 Government cartridge.
Happily in the absence of such standardization I have but a single 6.5 Grendel chamber, which is capable of digesting all loads both hunting (short ogive) and match (long ogive) bullets while reporting acceptable accuracy. pressure is set at 50,000 psi MAOP from direct measurement (CIP method) and we have ring gauge reference points for loaded ammunition to ensure that changes in ogive reflect ammunition that will chamber with adequate freebore. The growth of the caliber is certainly slower in the absence of SAMMI but the foundation for the long term application of the 6.5 Grendel is set.
Pressure measurement for cartridges is not a precise science and there are correspondingly a number of techniques that are employed. Perhaps the oldest is measurement of Copper Units Pressure or CUP. This method employs a cylinder of copper that is compressed by pressure from the cartridge acting directly upon a piston. Cartridges are usually drilled for this method but the position and size of the hole required varies. LUP (lead) is similar but is employed for lower pressure cartridges such as shot shells.
The newer techniques employ the use of pitzo electric tranducers typically the direct output type which can limit the linear responce of the guage. SAMMI typically calls for a conformal tranducer, in which a piston that conforms to the wall of the chamber sits at around half way down the main body diameter. The case is not drilled but deforms under the piston to create an output. Cases must be calibrated for offset in this method as the brass will effect the readings, equally the finished barrel has to be calibrated by static hydraulic pressure. Headspace, throat and rifling design will all influence the output but the case volume is in effect unchanged.Headspace and throat design "should be specified but rifling vary rarely is. By contrast CIP uses a drilled case with a specified transducer mounted again about half way down the case body. Readings are not effected by the brass properties but for small cases there is an effective volume increase that can squew the results. Again it is rare to see the rifling for specified. The last technique is the Nato measurement. The transducer spec is similar to CIP but measurements are taken at the case mouth, not within the case body. The technique has the advantage that it is independent of brass properties, the rifling form is defined in conjunction with the chamber and the case volume is unchanged, but the gas flow will alter the results and the reading does not represent either the case pressure and equally the loading on whatever mechanism that is used to keep the weapon in battery cannot be easily assesed.
Beyond this we have strain guage techniques and head thrust measurements. Strain guages are generally well known but are poorly understood. If applied correctly the results can be extremely accurate and the linear nature of the guage is outstanding. Being driven by external excitement the response rate is also well suited to the work. Newer temperature stable gauges have been a huge advance. The down side is that the technique places a huge reliance on the correct placement of the guages to resolve the principle and the thick cylinder analysis has to have good values for the modulus. Head thrust measurements (usually from an S cell) are strictly a lab technique but the results are ideal for weapon design.
There is rarely any reasonable relationship that can be use to convert between the reading type.
Thanx for explanation. I was aware of CUP and strain gauge measurement techniques, but I’ve never heard of the differences between CIP, NATO and the transducer system.
Given these techniques, which system allows the max absolute pressure? Meaning, if there were a way to design test barrel employing all three measurement techniques concurrently, which system would record the highest pressure?
This answer is not really a lot of help but honestly it depends on the cartridge you are testing, and the quality of the equipment.
Part of developing a cartridge is to examine the pros and cons of the testing methodology and then pick the best definition for what you are trying to acheive. One of the huge advantages we had with the Grendel in the AR platform is that there is a whole lot of historical data on the bolt and barrel extension combination, so we could sort of work backwards and pick out a test route that we knew would look after the gun.
