pressure signs

[robhinze]

So what are the pressue signs on our sav ml's? I don't have a case to measure. Does one use the flattened primer? Amount of primer deformity? Please keep in mind I don't have a strain guage to use.

[esmd]

Flattened primers and blown sabots are the first indicators, in my understanding.

[rbinar]

8-)That's a good question. Depending on who is asked the answer varies. One nameless but controversial past commenter said there are no pressure signs for the 10ML. Following that logic (or lack thereof ) I suppose if something begins to look odd while shooting your 10ML then you should keep shooting it anyway.

I prefer to listen to the rifle rather than ignore it. The rifle has said all we need to hear about pressure in the past. Was anybody listening then? I refer to what happened when many experimented with Lil Gun powder. Pressure signs sprouted everywhere yet were ignored on all fronts. Trying to bring a little sanity to bare was no simple task.

The very first thing that happened was sabots were reinforced without regard to what was the consequence. In fact a commercial product was developed to essentially allow sabots to take any pressure. If I'm honest (and I try to be ) some good came of this as we now have tougher sabots than existed many years back. But the bad was shooters had leaped into extreme pressure loads with no idea why.

The above circumstance seemed stranger to me when it became apparent 250 grain bullet speeds could reach 2600+fps with even a moderately soft sabot. The load had to be chosen correctly but high pressure was un-necessary.

Part and parcel to the "sign" of the sabot was vent liner life. It was becoming alarmingly ( to me at least ) short. When reports were given that vent liners were lasting 20 or fewer shots I cringed. When I heard of these same loads being used with 300 grain bullets I began to hope someone wouldn't have to pay a terrible price for a hard learned lesson.

It took some ill fated happenings for things to be decided in favor of sane choices. But even then I was labeled a "kook", "danger", and "un-qualified" for developing loads that shot a bullet faster but at much lower pressures. I guess my ego allowed me to be immodest because I knew the ones who backed both Lil Gun and my ill image had no idea how to develop a load, any load. In hind sight I know I should have been less vociferous.

So I shoot with two basic ideas behind my choices. First I never reinforce a sabot. If it blows the load is too hot. Now that does not mean I won't use a woolen or fiber wad on a known load. Still, I never develop a new load with trying to protect the sabot.

Secondly I look for at least 50 shots from a standard (non-hardened) vent liner. If the liner life breaks below 50 I try something else. As with the above I don't have a heart attack with a minor variance. If one vent gets only 40 or 45 shots things are still within reason. However if the average vent gets less that 50, I back up.

I'm not sure even now some would concede that these things are "signs" of pressure. However it's been proven ignoring them is a "sign" and it's not of something good.

[jims]

RBinAR nailed this on the head. I was trying some loads that just ate up ventliners. That should have been a warning sign to me but I was just too dumb and stubborn to listen. It ultimately caused me a broken barrel nut and bulged barrel.
I hope to restart my project in the nearer future but will be looking for suggestions on loads from those very knowledgeable people on this site.

[sw]

I agree with all the above and would like to add one thing. Primer integrity isn't a good indicator. I "headspace" my barrels and ream out my BPs primer insert to where the primer is totally supported and inserted in the BP. I worked up a very hi pressure load(but extremely accurate and temp insensitive load in my 40) that wore out ventliners in 40ish shots. It is in the 50,000psi range. It may stay my cold temp load. The primers come out looking like new. They are fully intact and easily come out. In my 50 cal SMI the primers start disintegrating at 40ish thousand(estimated PSI. Different primers have different thicknesses also. Don't use primer integrity as a gauge.

[ET]

Jan 17, 2009 2:04:05 GMT -5 esmd said:

Flattened primers and blown sabots are the first indicators, in my understanding.

Esmd

Your comment would definitely be a wake-up call to stop and do some research before proceeding.

But lets take some variables and have a look at them. A blown sabot say in 80-90F might not blow so easily at 40F. Higher temps will soften sabots and reduce their integrity.

The current BP from Savage has a specific cavity behind the Vent liner to cushion the returning bore pressure. Recess that vent liner and reduce the volume of the cavity behind the vent liner and here again you could see a higher pressure accessing the primer. With a book load I already had blowback developing when I recessed my vent liner. After recessing my barrel deeper to reduce blow back I will be curious if any indications will be found with my primer.

This post is not in any way to question your comment but to add a bigger picture for consideration.

Ed

[sw]

I should make a correction or at least an addition to my post. With the std Sav set up, primer loss of integrity,flattening, etc, should be some cause for concern/evaluation of your load.

[joe21a]

I have reloaded for 40 years and have read many articles that claims the primer is a poor way to tell how much pressure you are shooting. I still use it when reloading and also use it in shooting the Savage. I shoot 180 to 240 gr. (.40 cal.) bullets and have not noticed much difference in the way the primer looks. My loads are also not near max in the ML. It should also be noted that I only use CCI while loading and in the Savage this I feel makes what I see a little more consistent with the pressure I am shooting.