Strange occurrence at the range today with handloads

[Calvin45]

I used it for years in a 7RM without issue. In my 243AI pressure would be normal and then stiff bolt and pressure signs from the same load. The next heavier charge would be fine again. These were not reduced loads so I doubt it was a detonation issue. Rifle acted fine with a number of other powders I tested

My experience was with a plain vanilla 243 win in a savage 99. Probably still just too fast, faster than the burn rate chart suggested it seems. Lot to lot inconsistency?

Anyway, couldn't get good case fill before intermittent pressure signs, as in one round is fine, the next is sticky, and so on. Extreme spread of over 100 feet per second. This with 90 grain Sierra fmjs. It is a ball powder, I do realize they can be like this. I had sworn off ball powders in general until i reluctantly worked with H380 in a few things…and it's not erratic at all! I love H380 now.

Oh, and the long discontinued h870.

 

[Oldschool280]

Very interesting. I used W760 for years in my 7-08 and never had any problems but case fill was very good compared to a 257 bee. I usually pick a powder that has at least 90% fill but 95-100% is better imo.

My 7/08 loves it

 

[243winxb]

The Collapsed Shoulder is in an old Speer manual. Light loads & slow powder are the cause. Use a faster burn rate of powder. Pressure is low & neck not expanding to seal. Make sure the bullets have enough neck tension. Bullets that move to soon, at primer firing, not good. Acts same as pluged barrel. Magnum primers must be used. A to long OAL, will not let powder burn correctly. Light for caliber bullets also add to the problem.

https://thefiringline.com/forums/showthread.php?t=476535
See post 22 at link.

 

[Hugnot]

W760 is a dense ball powder. Nosler load data for the .257 Wby has 64 gr W760 for 85 grain bullets & uses Fed 215 primers - a real hot primer. The primer used was not identified. Case capacity as per Nosler data with 85 grain bullet & 64 grain bullet is 79%, lots of empty space.

My best guess is that a dreaded "detonation" event occurred as previously described. In addition, upon the "large bark" event, the case neck did not expand despite excessive pressure (100K psi ?). This might have been caused by excessive brass length. The mouth of the case was jammed into the chamber so tight expansion was prevented despite powder detonation pressure spike.

Possibly, case length grew upon several reloads when brass was head spaced on the belt and necks were jammed into chamber so tight expansion was prevented. The huge pressure spike should have expanded the neck.

 

[243winxb]

Double based powders containing a high percent of nitroglycerin, have been know to detonate. They require magnum primers & are best at or near maximum loading.

 

[Oldschool280]

W760 is a dense ball powder. Nosler load data for the .257 Wby has 64 gr W760 for 85 grain bullets & uses Fed 215 primers - a real hot primer. The primer used was not identified. Case capacity as per Nosler data with 85 grain bullet & 64 grain bullet is 79%, lots of empty space.

My best guess is that a dreaded "detonation" event occurred as previously described. In addition, upon the "large bark" event, the case neck did not expand despite excessive pressure (100K psi ?). This might have been caused by excessive brass length. The mouth of the case was jammed into the chamber so tight expansion was prevented despite powder detonation pressure spike.

Possibly, case length grew upon several reloads when brass was head spaced on the belt and necks were jammed into chamber so tight expansion was prevented. The huge pressure spike should have expanded the neck.

I did size the cartridges to headspace on the shoulder and not the belt.

 

[Oldschool280]

I did size the cartridges to headspace on the shoulder and not the belt.

The throat os miles away though

 

[MagnumManiac]

I cannot put blame on the powder, its intended purpose was incorrect.
760 is a beautifully working powder when used correctly, just like 296, it must be close to 100% density, or a little compressed, to get full results.
I forget how many cartridges I have used it in over the last 30+ years, but 2 spring to mind as being almost perfect, those being the 257AI and 375 Weatherby, both having a slight compression and ballistics so uniform it was uncanny. Also used in my 7-08 with 120's and 150's with exceptional results. The only problem I ever had with it was in one of my 24" barreled 25-06's, it detonated just like yourself with a 87g Speer TNT for the only reason I can attest to is that the load was below 85% fill…it was terrible in my 45-70, but good in the 45-120.

Cheers.

 

[Oldschool280]

I cannot put blame on the powder, its intended purpose was incorrect.
760 is a beautifully working powder when used correctly, just like 296, it must be close to 100% density, or a little compressed, to get full results.
I forget how many cartridges I have used it in over the last 30+ years, but 2 spring to mind as being almost perfect, those being the 257AI and 375 Weatherby, both having a slight compression and ballistics so uniform it was uncanny. Also used in my 7-08 with 120's and 150's with exceptional results. The only problem I ever had with it was in one of my 24" barreled 25-06's, it detonated just like yourself with a 87g Speer TNT for the only reason I can attest to is that the load was below 85% fill…it was terrible in my 45-70, but good in the 45-120.

Cheers.

I hear you, but the data was right fron the book. I didn't exactly concoct my own load .

 

[Dean2]

I hear you, but the data was right fron the book. I didn't exactly concoct my own load .

Well, no it actually wasn't. You found data that was close. You loaded a solid copper bulltet, versus a Nosler cup and core, that was lighter than the published data. Barnes bullets, due to the grooves, usually produce less pressure due to lower bearing surface. You started at the min weight for the heavier cup and core bullet with a larger bearing surface, so you were beleow the likely min charge for an 80 grain cup and core bullet, let alone a Brnes TSX. The fill rate was already low with the 85 grain bullet. Also, which primer did you use with the load.

 

[Oldschool280]

Well, no it actually wasn't. You found data that was close. You loaded a solid copper bullte that was lighter than the published data. You started at the min weight for the heavier bullet so you were beleow the likely min charge for an 80 grain bullet. The fill rate was already low with the 85 grain bullet. Also, which primer did you use with the load.

True, good point. 215 primer , old stock

 

[Oldschool280]

I appreciate all of the input guys, lesson learned, and hopefully others will be more knowledgeable from my mistakes

 

[MagnumManiac]

I hear you, but the data was right fron the book. I didn't exactly concoct my own load .

No it wasn't, you changed a parameter by using a solid bullet that is slipperier than a conventional cup and core bullet. Extrapolation of a cup and core bullet load data is a very bad idea…as you found out.
Weight is not the only thing you need to consider.
I have a Powley (sic) printed slide rule calculator for pressure, when I was developing my own wildcats based on Improved 416 Rigby cases, using solid brass bullets, this scale, Quickload and others from RCBS did not live up to actual results and in the end I had to start from scratch, change the bullet and size/number of relief grooves until chamber pressures uniformed. 2 years this took to finalise and have good case design with uniform chamber pressure using those custom turned brass bullets. Even the bullet shape, shank length and bullet base all change pressure upon ignition, blow by is to be minimised for good bullet alignment to rifling, I didn't fully understand this when I started turning bullets, this is why boattail angle changes between some target bullets.

Cheers.

 

[Oldschool280]

Es

No it wasn't, you changed a parameter by using a solid bullet that is slipperier than a conventional cup and core bullet. Extrapolation of a cup and core bullet load data is a very bad idea…as you found out.
Weight is not the only thing you need to consider.
I have a Powley (sic) printed slide rule calculator for pressure, when I was developing my own wildcats based on Improved 416 Rigby cases, using solid brass bullets, this scale, Quickload and others from RCBS did not live up to actual results and in the end I had to start from scratch, change the bullet and size/number of relief grooves until chamber pressures uniformed. 2 years this took to finalise and have good case design with uniform chamber pressure using those custom turned brass bullets. Even the bullet shape, shank length and bullet base all change pressure upon ignition, blow by is to be minimised for good bullet alignment to rifling, I didn't fully understand this when I started turning bullets, this is why boattail angle changes between some target bullets.

Cheers.

Got it! Thanx