16ga.com ~ View topic - Tom Roster article in Shooting Sportsman magazine

Joined: 21 May 2015 Posts: 135

The article was about modifying 2-3/4 loads for 2-1/2 hulls.

Roster mentioned that changing, i.e. removing felt spacers and such used to improve crimps in 2-3/4 loads to fit 2-1/2 hulls could increase chamber pressures by 1500 to 2000psig.

I'm not sure that I understand his logic...

So, I'm reaching out to some of you that have maybe done so and had your loads tested.

TIA,

Bob

Joined: 08 Feb 2009 Posts: 1356 Location: Western WA

Bob, I am unable to view the latest online editions of Shooting Sportsman, but there is a grain of truth (pun intended) to Roster’s remark. Some of the 16 ga load databases contain exact comparable loads in 2 3/4” and 2 1/2”, hulls, and the reported pressures are typically modestly higher in the shorter hulls, but not necessarily by the amount mentioned by Roster.

There have been occasional outbursts of fear mongering about 2 1/2” load pressures, but most are overblown. Simply put, if one is concerned about higher pressures in 2 1/2” hulls, merely reduce the powder amount. How much? Consult the published tables, or have your loads lab tested, or obtain a Pressure Trace II strain gauge system and test it yourself.

One writer went so far as to imply that roll crimped 2 1/2” loads using 2 3/4”recipes would likely be above SAAMI max pressure limits, which is a sweeping over generalization. In fact, some data shows roll crimped 2 1/2” loads can have lower pressure than equivalent 2 3/4” fold crimp loads.

I’ll put this question on my Pressure Trace II to do list. It will give us some solid numbers to work with. I think I can dig up some 2 3/4” hulls for testing, as almost all have been cut down to 2 1/2” or otherwise discarded as unneeded. Just as a point of reference, to date I have tested a good range of 2 1/2” and 2 3/4” loads, including factory and reloads, and nothing yet has come close to the peak pressure generated by what is perhaps the most popular 16ga factory field load on the market.

B.

Joined: 21 May 2015 Posts: 135

B,

Thanks for the reply...

I was just coincidentally sorting through some hulls for trimming and tried a trimmed one with a recipe that has always required a filler.

I got a nice crimp and then read the article.

I'm not concerned, because I'm at about 6kpsi, so Roster's worst case is still conservative.

But, his logic is confusing.

Take care,

Bob

Joined: 04 Mar 2019 Posts: 1913 Location: Central ND

This is what I know.

If you use a 2 3/4" load in a 2 1/2" hull, do not change any component and roll crimp the chamber pressure will be same or slightly less than that load in the 2 3/4" hull. I have seen up to 500 PSI less in the roll crimped load.

If you use a 2 3/4" load in a 2 1/2" hull, you change the wad column height by changing the plastic wad(as long as you use the same brand plastic wad just a different version) or taking out fillers and fold crimp the load, you will normally see a slight increase in the chamber pressure. I have seen a chamber pressure increase up to 1,000 PSI. 1,000 PSI is not really a very large change and I wouldn't get all that concerned about it. Changing the plastic wad can really change the chamber pressure to the point that maybe you should consider having the load tested.

Personally I like the idea of roll crimping for this situation.

Joined: 04 Mar 2019 Posts: 1913 Location: Central ND

Roster wrote that article after he said something stupid in a previous article about 2 3/4" loads in a 2 1/2" hull. He is just covering his butt. Roster does not own a pressure gun and no one is quite sure who does the testing for him now. I know who doesn't do the pressure testing for him.

Joined: 21 May 2015 Posts: 135

Basically, I have a tested 2-3/4 recipe that didn't mention I've had to use a spacer to fold crimp nicely.

So, I figured maybe it would crimp cleanly in a 2-1/2.

No other changes.

Powder is 572 and pressure around 6kpsi, so I am not alarmed.

But, in general that department of Shooting Sportsman mag doesn't impress me.

That said, if it is a 1000psi higher pressure, might it burn a little cleaner?

Joined: 04 Mar 2019 Posts: 1913 Location: Central ND

That load will be fine. It might help it burn cleaner, but I wouldn't expect miracles.

I am generally not a big Roster fan. I think his work with steel shot is very good. The rest, IMO is biased towards his opinion and doesn't always follow the facts.