User Panel
User Panel
User Panel
|
Posted: 9/5/2020 5:07:14 PM EDT
[#1]
According to my Hodgdon 2020 manual and my Hornady 10th edition book, that's above max load for 140gr bullets.
ETA: I'd say those velocities are likely indicative of high pressures. What does your fired brass look like? |
|
|
|
Posted: 9/5/2020 5:14:33 PM EDT
[#2]
Were these foulers after cleaning the bore recently?
|
|
|
|
Posted: 9/5/2020 5:21:33 PM EDT
[#3]
Quote HistoryQuoted: Were these foulers after cleaning the bore recently? Quote HistoryQuoted: Were these foulers after cleaning the bore recently? Quoted: According to my Hodgdon 2020 manual and my Hornady 10th edition book, that's above max load for 140gr bullets. ETA: I'd say those velocities are likely indicative of high pressures. What does your fired brass look like? |
|
|
|
Posted: 9/5/2020 5:27:05 PM EDT
[#4]
Which chronograph?
How far was it from the muzzle? Even before you answer, I will suggest this if you are using an optical chronograph - place it farther down range. I have been using a target at 50 yards with the chrono immediately in front of the target. Although I am still skeptical, this seems to have solved the chrono issues (bad data). |
|
|
|
Posted: 9/5/2020 5:30:41 PM EDT
[#5]
At the stated OAL, in YOUR RIFLE, is the bullet ogive very close to the lands so that a little less that good consistency in CBTO could result is some jumping and others jamming???
ETA - TS has a good point about the chrono... |
|
|
|
Posted: 9/5/2020 5:33:39 PM EDT
[#6]
Quote HistoryQuoted: Nope. Shot foulers last night before I took it to chrono. I thought of that too, because that has given me issues in the past which is why I did that last night. Perfectly fine actually. 42.5gr seems to be very common, and my brass doesnt have flattened or cratered primers, and the bolt isnt sticky on extraction. Quote HistoryQuoted: Quoted: Were these foulers after cleaning the bore recently? Quoted: According to my Hodgdon 2020 manual and my Hornady 10th edition book, that's above max load for 140gr bullets. ETA: I'd say those velocities are likely indicative of high pressures. What does your fired brass look like? I agree with other poster. That's a hot load. Under a 140eld I use 41.6 and I get factory velocities. You're a grain higher than that. |
|
|
|
Posted: 9/5/2020 7:22:10 PM EDT
[#7]
Quote HistoryQuoted: Perfectly fine actually. 42.5gr seems to be very common, and my brass doesnt have flattened or cratered primers, and the bolt isnt sticky on extraction. What does QuikLoad say about pressure for that load? |
|
|
|
Posted: 9/5/2020 7:41:05 PM EDT
[#8]
Quote HistoryQuoted: What does QuikLoad say about pressure for that load? With the stock case capacity of 53.8gr H2O, GRT predicts 58k psi, 2800fps, 91% load density. Looks like its close to an OBT node. |
|
|
|
Posted: 9/5/2020 7:45:20 PM EDT
[#9]
This is my first use of this tool, so take it with a grain of salt.
|
|
|
|
Posted: 9/6/2020 1:06:40 AM EDT
[#10]
Quote HistoryQuoted: This is my first use of this tool, so take it with a grain of salt. https://i.ibb.co/pQMTBpC/6-5a-Creedmoor.jpg Looks similar to my result. You might check the View tab to remove the cartridge drawing and powder details off the screen. In the powder library, powders have a calibration confidence level indicated by a red-yellow-green scale. H4350 is halfway into green, so it's close to right, but be more cautious with it. Where I placed a red circle is where you can alternate between pressure over time and pressure over length.  |
|
|
|
Posted: 9/6/2020 1:32:35 AM EDT
[#11]
Looking at the peak pressures, I would say the OP's is a fairly hot load (57 ksi). The software is warning it is near max pressure, too.
The data indicates he should be getting about 2,800 fps and he is measuring an average of 2,865 fps. OP, did you hand weigh those powder charges or were they thrown charges? |
|
|
|
Posted: 9/6/2020 8:48:30 AM EDT
[#12]
Quote HistoryQuoted: Looking at the peak pressures, I would say the OP's is a fairly hot load (57 ksi). The software is warning it is near max pressure, too. The data indicates he should be getting about 2,800 fps and he is measuring an average of 2,865 fps. OP, did you hand weigh those powder charges or were they thrown charges? My load development goal was 2850fps for this as it were. I knew they were hot, but they are accurate when I shot the ladder and didn't exhibit pressure signs. |
|
|
|
Posted: 9/6/2020 10:00:35 AM EDT
[#13]
Quote HistoryQuoted: I agree with other poster. That's a hot load. Under a 140eld I use 41.6 and I get factory velocities. You're a grain higher than that. I use 42.7 with fantastic results and have tried up to 43. |
|
|
|
Posted: 9/6/2020 11:04:48 AM EDT
[#14]
OP,
If you trickled your charges of same-LOT H4350 and controlled neck tension/seating depth, your chrono may have given you false readings as previously posted. Just finished loading 143GR ELD-X and 147GR. ELD-M loads seated 0.010 off the lands in FGMM primed neck turned Hornady brass with H4350. When I worked up the loads in the RPR with 762-SD can attached, SD was in the low teens at a slightly lesser charge weight than you are using. Only other variable I can think of that has not been discussed is work-hardened brass in need of annealing. Just as a note, several of the Hornady case primer pockets (approx. 1 per 100) were WAY shallow so were scrapped. HTH Just for reference, some of the early Hornady 6.5 CR boxes actually had the load listed on them. It is a useful load level to keep in mind IMO. I did not understand why Hornady discontinued putting the load on the label until one of the "insiders" posted that Hornady is currently using several non-canister/blended propellants.  Attached File |
|
|
|
Posted: 9/6/2020 11:47:40 AM EDT
[#15]
Quote HistoryQuoted: OP, If you trickled your charges of same-LOT H4350 and controlled neck tension/seating depth, your chrono may have given you false readings as previously posted. Just finished loading 143GR ELD-X and 147GR. ELD-M loads seated 0.010 off the lands in FGMM primed neck turned Hornady brass with H4350. When I worked up the loads in the RPR with 762-SD can attached, SD was in the low teens at a slightly lesser charge weight than you are using. Only other variable I can think of that has not been discussed is work-hardened brass in need of annealing. Just as a note, several of the Hornady case primer pockets (approx. 1 per 100) were WAY shallow so were scrapped. HTH Just for reference, some of the early Hornady 6.5 CR boxes actually had the load listed on them. It is a useful load level to keep in mind IMO. I did not understand why Hornady discontinued putting the load on the label until one of the "insiders" posted that Hornady is currently using several non-canister/blended propellants. https://www.AR15.Com/media/mediaFiles/42284/Hornady_box_with_load_data_png-1579644.JPG I'm going to load up another 5 and move the Chrono back past 25 feet and see what happens. |
|
|
|
Posted: 9/6/2020 12:20:16 PM EDT
[#16]
How much neck tension did you wind up with? Measuring a loaded VS unloaded case will be close enough. One guy had 0.006" which was far too much. He used the wrong bushing in his sizing die. I keep it at 0.001-0.002" in a bolt rifle.
|
|
|
|
Posted: 9/6/2020 12:32:24 PM EDT
[#17]
Try it again with once fired and I bet it goes back to normal.
Common with virgin, I always fireform before gathering data. |
|
|
|
Posted: 9/6/2020 2:23:51 PM EDT
[#18]
I'd bet money on false chrono readings. Even overpressure shots won't exhibit that kind of variance. My HMR loves 42.2 grains 4350 with a 140 eldm btw. I know it's over max (according to Hornady) but I see absolutely zero pressure signs in my gun. Gives 2756 FPS with a sub 5 SD.
|
|
|
|
Posted: 9/6/2020 8:01:30 PM EDT
[#19]
Quote HistoryQuoted: I'd bet money on false chrono readings. Even overpressure shots won't exhibit that kind of variance. My HMR loves 42.2 grains 4350 with a 140 eldm btw. I know it's over max (according to Hornady) but I see absolutely zero pressure signs in my gun. Gives 2756 FPS with a sub 5 SD. You bring up a good point. Surprisingly, overpressure can produce MV variation exactly like that when some of the primers leak. I unwittingly documented just that while testing thermal variation of different propellants in 5.56MM 77GR. SMK handloads in new #41 primed LC brass. The last string of (5) handloads artificially heated to +135F then quickly fired had (3) MV measurements that were relatively close. But the other (2) measurements were unreasonably low. I thought I might have a couple of bad chrono readings until I picked up the brass. The (2) low readings were from cases with very positive evidence of primer leakage around the flattened primers. If the OP did not get false chrono readings, he needs to check his spent brass for any primer leakage just to rule it out. But I would not expect any primer leakage in new brass at that charge level. |
|
|
|
Posted: 9/6/2020 8:43:50 PM EDT
[#20]
My money is on moving the chronograph farther down range.
|
|
|
|
Posted: 9/6/2020 8:48:05 PM EDT
[#21]
Quote HistoryQuoted: I use 42.7 with fantastic results and have tried up to 43. Quote HistoryQuoted: Quoted: I agree with other poster. That's a hot load. Under a 140eld I use 41.6 and I get factory velocities. You're a grain higher than that. I use 42.7 with fantastic results and have tried up to 43. You loading to the same length as OP? I know I ventured above 42, but I haven't checked my load book. I do recall getting high SD as I moved upward. |
|
|
|
Posted: 9/6/2020 10:04:32 PM EDT
[#22]
That is interesting. I usually read about people whose SD collapses to a small number as they reach book max charge weights.
|
|
|
|
Posted: 9/9/2020 2:37:35 PM EDT
[#23]
Quote HistoryQuoted: Which chronograph? How far was it from the muzzle? Even before you answer, I will suggest this if you are using an optical chronograph - place it farther down range. I have been using a target at 50 yards with the chrono immediately in front of the target. Although I am still skeptical, this seems to have solved the chrono issues (bad data). Probably this. Once I switched from an optical chronograph random mysterious results like this went away. You're rocking your chrono with your muzzle blast. Also, I'm not a big fan of virgin brass. You're running hot. Not stupid-hot, but hotter than you really need to. Run a ballistic calculator to determine at what distance you go subsonic; you'll be amazed how little benefit pushing the pressure for that last extra 50 FPS really buys you. |
|
|
|
Posted: 9/19/2020 6:32:46 PM EDT
[#24]
Update from today.
Set the Chrono back to about 30 feet. 5 shots, same charge and OAL as before were: 27292706 2695 2707 2716 Much more consistent but significantly lower velocity than I had expected. I had expected these to be at least 2750+ if not closer to 2800. The saga continues... |
|
|
|
Posted: 9/19/2020 7:04:08 PM EDT
[#25]
Yes, much better - 2711 fps mean; 13 fps SD.*
Use a ballistics program to estimate the velocity loss while traveling the distance from the muzzle to the chronograph. Add that lost velocity to the measured velocity to get the muzzle velocity. My guess is you need to add 30-50 fps to get the true muzzle velocity. I use a 50 yard distance and add about 80 fps (for my distance and bullet). Why do we worry so much about velocity when accuracy is what we are after? * The people who sell these optical chronographs do everyone a disservice when they imply these instruments can be used for rifles and then give only a 10' cord. It would be better had they just said, flat out, "When used with center fire rifle, set the chronograph X distance (25 or 50 yards) down range". Then explain why. A much longer cord would be good, too. |
|
|
|
Posted: 9/19/2020 9:13:40 PM EDT
[#26]
With my atmos, JBM says 2730fps.
"Why do we worry so much about velocity when accuracy is what we are after?" Do you mean a target average velocity? |
|
|
|
Posted: 9/20/2020 12:59:20 PM EDT
[#27]
As a general rule, you lose something on the order of 1 fps/ ft of chrono of distance. Obviously this varys.
That's one thing I really like about the LabRadar. is since it gets 20+ readings over a spectrum of distances per shot, it's able to extrapolate pretty accurately back to the muzzle, which it does automatically for you. |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
