Home Forums Hunting & Shooting Ask The Gunwriters IMR Enduron Powders - Pressures???

G'day,

This is for John B. but all responses are welcome.

I was looking online at the IMR reloading data with the new Enduron powders in the .257 Roberts (100gn bullets). Hodgdon list the pressure readings in CUP for both 4451 and 4955.

Why would they still be measuring pressures in CUP rather than PSI with these modern powders?

Also, the data lists 50gn 4955 with a 100gn bullet for 3152 fps at only 46,700 CUP. That's good velocity for a fairly mild pressure. Does this sound right?

What velocity could be achieved if they used the +P pressure load of 50,000 CUP or even 52,000 CUP (.270 Win)?

It just seems a bit odd to me. Have they actually fired these loads or have they been guesstimated on a computer? If that is so, why not use the modern PSI pressure readings since we are well into the 21st century?

Thank you very much.

SAAMI still lists crusher and transducer measurement standards for the Roberts. Maybe since the Roberts is a relatively "back burner" cartridge Hodgdon's lab hasn't bought a new test barrel set up for it and continues to use the crusher equipment they already had.

Anybody have heat content values for those powders?

Elvis,

The situation is similar with the the data for IMR 4955 and the 6.5x55 as well. As in, it's one of the top powders velocity-wise for most of the range of bullet weights. However, my own tests showed that I couldn't use Hodgdon's max load data without exceeding their predicted velocity by 100-120 fps. I've gotten decent accuracy with that powder, but so far with two different bullets, the velocity spreads have been larger than I care to see. The velocity swings were tamed a bit by using a Winchester WLR primer (also tried: CCI 200, Federal 210, Federal 215).

I know that is a bit off-topic, but I hope that is helpful to you in some way

Elvis,

What mathman said: Powder companies often keep using their copper-crusher pressure barrels for older cartridges, because there's not as much demand for data as in newer/more popular rounds, and piezo-electronic test barrels cost quite a bit. CUP data is still perfectly valid.

Azar,

I recently had a discussion with the top tech guy at Hodgdon, and he mentioned they like Winchester LR primers (both standard and magnum) for pressure-testing, because they provide the most consistent results. You may have noticed that the primer Hodgdon used in the 6.5x55 data was the WLR.

John,

I did indeed notice they used the Winchester WLR, which is one of the reasons I decided to give it a try again. It was one of my favorite primers when I first started hand loading but I haven't used it at all for a few years after the "snafu" that Winchester had with their primers (I had also become a big fan of the Federal 210 prior to that). I did call and ask Winchester about my lot # and all they said was "there haven't been any reported issue with that lot as of yet." It was small comfort and I stayed a bit leery of it until I tried it with IMR 4955. That experience definitely reminded me why I liked it so much originally.

Yeah, I used a LOT of WLR's before the problem. Am now waiting to see if they've really solved the problem.

Before "The Problem" I loaded an awful lot of 308 Win plinking ammo in LC Match brass with a 168 and 41.5 grains of 4895 lit by a WLR.

I have bought several thousand Winchester primers the past few weeks. They include a couple different lot numbers. I know my sample size is tiny but out of those several thousand I have shot a couple hundred with no issues.

Ok, thanks everybody. Good to know.

Although there is no direct conversion table between CUP and PSI, this formula will get you in the ballpark ..

1.516 x CUP minus 17,902. Use it only if you are curious as it is not totally reliable.

Denton's paper that includes the details of the above relationship:

https://www.shootingsoftware.com/ftp/psicuparticle2.pdf

Mule Deer, I use WLR primers in my Winchester brass. I have the 308 ME, the 307 Win, and many single shot 30-30's in the H&R single shot.
The H&R's are the old slim Topper barrels mated to newer receiver. All use Winchester brass except for the 308 ME which is Hornady.

I sent back two bricks of primers and immediately bought another after calling from Cabelas and checking the lot#. I still had one brick that was ok to use according to Winchester.
I have tried both lot#'s in the 308ME and the 307 with no problems to report.

I had already loaded 200 of the returned lot# in the 30-30 with LE powder and the 170 grain Sierra FN that the grandkids shoot. Winchester indicated that since the CUP
was at 34,700 they weren't concerned about those loaded rounds. Those rounds were fired by me with no problems arising.

I have no concerns using WLR primers but YMMV. The WLR's are very accurate in my loads. I use RP primers in my RP brass with no problems to report there either.

What concerns me most about them is that while they did a good job of owning up to the problem, they didn't, according to the dealers I've asked, make any attempt to get the suspect lots off the shelf. That makes any to be found in stores suspect, given the turnover in a lot of places. Rather than risk trouble, I've stayed away from them, and with thousands of others on hand, may not ever even buy any more LRs, period.

I ALWAYS get better velocity.... prob 40-50 fps with WLR's than CCI or Fed 210's. Not sure why but I use a LOT of them.

10-18-2017 in the sagebrush with my truck, camper, and laptop with quickload, 900 miles from here:

2) Sighted 257 Roberts Arisaka in at 200 yards.
1" 3 shot group at 200 yards
100 gr nosler ballistic tip 46 gr IMR-4451 2.963" OAL jammed into the lands
63.4 kpsi 3231 fps Quickload
2926 fps chrono
2936
2911
Pressure on primers looks very high

I don't know what went wrong. The chrono and pressure agree on Quickload for 6.5-06 and 7mmRM with the same jug of IMR-4451.

Clark

First, I have no answers for you but would like to make a few observations and ask 1 or 2 questions.

1" group at 200 yds, that great IMO.

OAL jammed into lands..... 'usually' generates more pressure. THEN we expect higher velocity.

M D tells us that 'primer appearance' isn't a good indicator of pressure. Firing pin size and how hard it hits as well as firing pin hole in bolt face and the hardness of the primer cup affect the appearance of the primer.

Quickload data is not absolute but mathematical predictions (suggestions).

? # 1. What's your barrel length?

? # 2. Have you compared velocities in THIS rifle with KNOWN velocity loads? The reason I ask is that, THIS rifle is not the 6.5-06 or 7 Mag


Sometimes things just don't turn out like we think they should. Sometimes we don't figure out why.

Good Luck

Jerry