switching to TSS - 3 questions from a neophyte

[C M Wings]

Hmmm, that is worrisome. I thought I was using CMwings' pressure tested load. He reported:



Reviewing your "ultimate load 12GA Waterfowl load" thread, your longshot load that failed the pressure test was:

3” cheddite hull
28 grains longshot
TUPRW123 wad
2 x 1/4” 20ga felt
273 gn tss under 273 gn steel
20ga OSC
fold crimp
1407 FPS, 15290 PSI

Is that correct?


CMwings can you weigh in here?

There is a published load

80611-370H in the cheddite manual

3 inch Cheddite hull and primer
31 LS powder
X12x
Tps41
OS12
9/8 steel shot

10600@1420

Your shot column at 50/50 tss/steel at 10/8 total weight is no longer than this one, but 1/8 heavier. I don’t see that building 5K psi, especially with a shorter wad. I’m not saying your data is bad, in fact I trust it over this published load for your build 100%. Just giving a point of reference. Fold crimps are the devil. I had a tested 10k 10 bore load come back at 18k because my fold crimps were too deep.

 

[duckrogers]

I tested 500 gns @ 34gns of Longshot. Shorter shot column for sure, but all I see in those wads is the gas seal going cockeyed against the wad. The gas seals themselves look fine. If it were over pressure you’d see the seals cracked, they are designed to fail like that, for that. Now, you might say yeah but at 3.5 inch gun pressure. That I don’t know, but these don’t show sign to me of being hot. They look like they got some typical blow by. But OP could always back off the shot column and add felt. That would def drop pressure. I agree steel powder is a better option. I used ls because I couldn’t find steel. Also why I tested this and another at 437/38 which came back 1600@11k.

Ok, thanks for that feedback. I guess I survived 8 rounds of an untested load. Am I safe in assuming my barrel is no worse the wear for the experience? Being the rank noob that I am, I'm going to stick with exact replicas of tested loads or do my own testing going forward.

 

[C M Wings]

Ok, thanks for that feedback. I guess I survived 8 rounds of an untested load. Am I safe in assuming my barrel is no worse the wear for the experience? Being the rank noob that I am, I'm going to stick with exact replicas of tested loads or do my own testing going forward.

Your setback looked perfect. That exact load isn’t tested but well within specs for two that are. I’ve shot that load but saw no need to test it. My results are similar to yours but my TSS is on top. I just went to all TSS after playing with some duplex. One ounce TSS is all you need for pretty much anything.

 

[A5B]

Your setback looked perfect. That exact load isn’t tested but well within specs for two that are. I’ve shot that load but saw no need to test it. My results are similar to yours but my TSS is on top. I just went to all TSS after playing with some duplex. One ounce TSS is all you need for pretty much anything.

Agreed. One once of tss is awesome.

Some 1/4 cork down in the wad would bring the pressure down as well. Probably have to increase the charge of longshot to get the speed back up. But the pressure would come down and it would do away with the steel shot effecting the pattern dispersion.

Csd078 wad would work perfect with some 1/4 inch cork inside to hold 1 once of tss.

 

[cd2]

I don’t see 29 Longshot having more pressure than 35 steel, especially in a roll crimp, but it def has a different burn rate. Op could back it off a grain or so. But I agree steel powder is a better overall option for taller shot columns.

I respectfully disagree. From my testing 29 grains of longshot has a MUCH higher pressure than 35 grains of steel with a 1-1/4oz payload. The tested data I have is very close to the load we are discussing here.

Referencing other data and making assumptions is a good way to begin development of a load. It is not good enough to rely on, however

OP - if you’re wanting to load in 2-3/4 hulls go to a 1 oz or 1-1/8 oz total load payload. 1-1/4oz belongs in a 3” hull. Ditch the longshot

 

[A5B]

I respectfully disagree. From my testing 29 grains of longshot has a MUCH higher pressure than 35 grains of steel with a 1-1/4oz payload. The tested data I have is very close to the load we are discussing here.

Referencing other data and making assumptions is a good way to begin development of a load. It is not good enough to rely on, however

OP - if you’re wanting to load in 2-3/4 hulls go to a 1 oz or 1-1/8 oz total load payload. 1-1/4oz belongs in a 3” hull. Ditch the longshot

Longshot and 1 1/4 loads. Work just fine in my 2 3/4 hulls and my pressure is nice and low. 9k range and making 1450fps.

I'm running 33 grains of longshot in that load. Useing number 8 tss and number 4 tss buckshot. Shot 5 of the buckshot loads just a few mints ago.

 

[cd2]

Different story with straight tss A5B, we are talking steel duplex

 

[A5B]

Different story with straight tss A5B, we are talking steel duplex

That's right. My bad i forgot OP was duplexing loads.

 

[C M Wings]

I respectfully disagree. From my testing 29 grains of longshot has a MUCH higher pressure than 35 grains of steel with a 1-1/4oz payload. The tested data I have is very close to the load we are discussing here.

Referencing other data and making assumptions is a good way to begin development of a load. It is not good enough to rely on, however

OP - if you’re wanting to load in 2-3/4 hulls go to a 1 oz or 1-1/8 oz total load payload. 1-1/4oz belongs in a 3” hull. Ditch the longshot

I would agree that 1.25 belongs in a 3-inch hull. You can look at my prior posts from well forever to see my general dislike of Longshot, but I’m working with it now because it’s all I can find. As you know shot volume drives pressure more so than weight, which is why steel shot is so tricky. TSS takes up a lot less volume than even lead, and there are several 10/8 lead recipes for Longshot that run from 31 to 35 gns in a 2-3/4 hull, one with a CLBC and a few with the old PT wads which were steel wads. I’m not a “it’s published so it must be true” recipe believer, but as I’ve learned to really manage my crimps the testing I’ve done pretty much tracks the published data I use in load development. My experience, poor fold crimps cause far more pressure issues than anything else in loads that make sense (there are plenty that don’t). And once or more fired hulls are the worst. I’ve had loads I know where all but identical internally come back with 2k pressure deltas between shells when using fired hulls. New hulls typically come back with in a few hundred pounds max. That’s why I asked if he had used new hulls. You can as a rule of thumb add 1500 psi to a load that calls for a new hull if you load it in one pre-fired.

 

[C M Wings]

That's right. My bad i forgot OP was duplexing loads.

It’s still about volume. If you do the math you’ll see that 5/8 TSS and 5/8 steel have the same volume as 10/8 lead.

28*10/8*1/11 = 3.18 cm^3 for 1.25 lead

(28*5/8*1/18) + (28*5/8*1/8) = 3.17 cm^3 for TSS/steel duplex.

So using a lead recipe that calls out a steel rated wad should give you a pretty good idea of the internal ballistics of the OPs TSS/steel duplex load. This is where I started in working up my Longshot loads and it has tracked with testing. The TPS wad and gas seal are a little stickier than the old PT wads, but the recipes for those pushed 35 gns of Longshot. I should really just built and send some to test. Now I’m just overly curious. But I’d have no worries shooting the OPs shells, especially roll crimped.

Someone check my match and make sure please at this point I’m biased as to how I did it.