Question for all of you smarter than me! Im in the process of loading for my 300 win mag with 154HHT. As ive read in this forum to do a pressure test then back off a grain or so and shoot for groups. Heres my pressure test starting low and working up with the grain and velocity produced in picture. I eventually got to 78gr of H4350 (the highest I loaded) and those are the 3 rounds with what i believe to be slight ejector marks (at top of each case slight half moon) bolt lift is still easy and smooth. Would you guys call this pressure and to stop increasing powder charge? I feel like this velocity is a lot more than what i was expecting to get too before i would run into major pressure signs but I havent. Also this is without a crimp, Im running .002" neck tension here, I will start adding 1/8 crimp to these rounds and see if i can tighten the group up. Where to go from here?
Please Help...Where to go from here???
- Thread starter AZhntr
- Start date
LightTheTower
Hammer Time Executive member
Answered in this one: https://hammerbullets.com/hammertime/threads/learning-pressure-signs.707/
BFD
Hammer Time Executive member
I see you started a dedicated thread, so I've migrated my responses here from the pressure thread:
- Yup, pressuring stoutly with flat & cratered primers. Pop them out and also look at the sides of the primers for belling out on the tops. Lapua supports the primer all the way, so the hourglass look will be another indication of most likely over pressure.
Most importantly measure the primer pocket diameter. You decide how long you want your brass to last. FWIW I only got to 76gr of XMR 4350 with 137HH in 300WM for a brass longevity load at 3350fps 24”.
- So the common ramp up to pressure then back-off method would have one beginning the precision testing of the first load that didn't show over pressure and reduce .5gr per increment loads till one or more are showing precision.
- Yup, pressuring stoutly with flat & cratered primers. Pop them out and also look at the sides of the primers for belling out on the tops. Lapua supports the primer all the way, so the hourglass look will be another indication of most likely over pressure.
Most importantly measure the primer pocket diameter. You decide how long you want your brass to last. FWIW I only got to 76gr of XMR 4350 with 137HH in 300WM for a brass longevity load at 3350fps 24”.
- So the common ramp up to pressure then back-off method would have one beginning the precision testing of the first load that didn't show over pressure and reduce .5gr per increment loads till one or more are showing precision.
Koda
Hammer Time Executive member
My short answer is yes.
You did your pressure ladder correct, good job reading pressure signs.
jrebel
Hammer Time Executive member
Lapua brass is generally a little harder brass than others. It makes it more durable but also hides pressure better than say....Nosler brass which is softer. With that said, I would say any ejector swipe would worry me a little on Lapua Brass. That with the primers dimpling (not a great measure by itself), would make me back off a bit. Your velocities are faster than I would have expected out of a 300 wsm with 154 HHT, but that could be a multitude of factors.
H4350 is very temp stable and a great powder, but I would also take into account you are shooting during the colder months. Depending on your location and temps during the fall, this could also cause an increase in pressure. I would back down to where I had no ejector swipe and work my crimp from there.
H4350 is very temp stable and a great powder, but I would also take into account you are shooting during the colder months. Depending on your location and temps during the fall, this could also cause an increase in pressure. I would back down to where I had no ejector swipe and work my crimp from there.
I'm watching 'cause I plan on loading that 154 HHT in my new to me 300 WSM. I'm going to look for accuracy around 3250-3300. Only elk I hunt is fat cows and I have been able to take broadside shots on every one I have taken. Even though this rifle is my "spare" ( right between my 338/06 Ackley Improved and my long barreled Shilen in 7x57. That 154 TT looks "intriguing". Have a ball Pard!
JustJay
Well-known member
I have found that 76-77gr seems to be top end for me with H and IMR4350's w/154-163HHT's and 160HH in my 300WM. Now every rifle different factored in, it still "somewhat" falls into most of the load data posted. 77.5 and 78 have always had slight marks with Lapua brass very similar to your photo.
its a 300 win mag. appreciate your advice im going to drop back to 75.5 and work up to 77 with 1/8 to 1/4 crimp. I will post results next week when i shoot
Also im in AZ where temps arent too cold. This data was taken it was 55 degrees
jrebel
Hammer Time Executive member
I misread the original post....those velocities make more sense now.
Side note; a few years ago I had business in Phoenix during mid November. The temp was in the pleasant low 70's. To Arizonans, they were chilly, lots of hoodies/sweaters, ha. That was the most wonderful weather I had "ever" had in Phoenix, Mesa and Scottsdale! Phew, I thought East Texas got hot!
ButterBean
Hammer Time Executive member
^^^^^^^^^^^^^^^^^^^^^^^
LightTheTower
Hammer Time Executive member
East Texas had some 110° days this sumner… still with humidity.
I grew up there ( Liberty Co) until I was 34. Worked 20yrs of that/ off and on in oilfield and midway 5 yrs Military!(2 in Germany and 3 in Tx Nat'l Guard out of Beaumont & Ft Hood) I do not miss either the heat nor the humidity, lol. This is the only place I ever lived that has Four Seasons! One can shoot all year up here if they choose ( I do). I look forward to getting my rifles back from the Smith's.
LightTheTower
Hammer Time Executive member
Liberty City
I grew up, and reside again in, Elysian Fields!
I grew up, and reside again in, Elysian Fields!
Farleg
Hammer Time Executive member
Gday @AZhntr
So glad your asking as we all learn from these questions
Advice is sound so I’ve got nothing to add to that & looking forward to seeing the final journey & that’s a smile & critter so I await that day
Side note
Ok you smart guys & @ButterBean you may come in here also on the barstool stuff you do
How about we put together a video of what a pressure load starts to look like on firing
Eg start off with a non pressure load & show bolt lift & the non click to ejecting the case showing where to look for pressure sign & measurement of case etc ( here’s a thought I wonder if you could incorporate a scale like a trigger pull or drag pressure on fishing reels to show the increased resistance on bolt lift @ pressure
)
& then do a slight pressure load showing the same process & then a pressure load
To me that would simplify a lot as pictures are great but hearing seeing a slight click of a bolt is one that a video would give a better understanding & be perfect on barstool imo as the way you explain/show things bean is simple & that’s what we need not some of the over the top things we hear about
Carry on
Cheers
So glad your asking as we all learn from these questions
Advice is sound so I’ve got nothing to add to that & looking forward to seeing the final journey & that’s a smile & critter so I await that day
Side note
Ok you smart guys & @ButterBean you may come in here also on the barstool stuff you do
How about we put together a video of what a pressure load starts to look like on firing
Eg start off with a non pressure load & show bolt lift & the non click to ejecting the case showing where to look for pressure sign & measurement of case etc ( here’s a thought I wonder if you could incorporate a scale like a trigger pull or drag pressure on fishing reels to show the increased resistance on bolt lift @ pressure
)& then do a slight pressure load showing the same process & then a pressure load
To me that would simplify a lot as pictures are great but hearing seeing a slight click of a bolt is one that a video would give a better understanding & be perfect on barstool imo as the way you explain/show things bean is simple & that’s what we need not some of the over the top things we hear about
Carry on
Cheers