Are some rifles more tolerant of higher pressure?

[bobnob]

I have a new .270 Winchester. I have started developing some loads. So far I have worked up loads with 130gn and 150gn Hornady SSTs.

BUT...

Working up from minimum published, going higher until reaching signs of pressure, I have already exceeded published maximums for both powder and bullet weights by 2 whole grains in each case. I have not experienced ANY SIGNS of pressure including sticky bolt lift, flattened primers, case expansion, extra loud report etc.

Anyway I have stopped it there, if I am 2g over maximum recommended there is obviously no need to go further. In fact I won't routinely load those loads in any case until I work out what is going on.

Any thoughts? I have heard some rifles will allow greater powder loadings than others before exhibiting signs of pressure.

I must admit this is the first time I have exceeded recommended maximums generally so I am inexperienced in this regard.

I have not posted the loads in case someone goes out and copies them.

The cases are Winchester and the primers are CCI std large rifle. The bullets are seated to the cannelure.

Thanks.

 

[gamestalker]

2 grains over max published data doesn't mean anything without knowing what powder you are uysing. A super slow burning powder can be loaded to compressed charges without high pressures ever becoming an issue. On the other hand, a faster burning powder will begin to produces high pressure when it is still below maximum published data. Also, bullet seating depth is another factor in pressures.

 

[Frozen North]

Are your groups still getting tighter?

 

[243winxb]

List your load data with this warning.

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

Its possible to have a load 2 gr over maximum listed published data, seen it in 7mm Rem Mag. years ago. Seems some barrel grooves were tighter then others. Check your scale for accuracy.

 

[Sunray]

Two grains over max isn't that much over. It's not so much the rifle as it is the brass. A certain amount has to do with the age of your manual. Most of 'em are giving lower max loads than the same manufacturer used to give. I have an old 23rd Edition Hodgdon manual that shows a starting load of H4831 for a 150 that is 2.5 grains with a max that is 2.3 grains higher than the current load on their site. The same book gives a 130 starting load of H414 that is half a grain less than their current data with a half grain more for the max load. That has to do with the powder lot used on the day of the testing.
In any case, you don't work up the load looking for signs of pressure. You work up the load looking for the most accurate load.
Like gamestalker says, without knowing what powder, it doesn't mean much anyway.

 

[Clark]

I shoot some guns way over book, some right on book, and some way less than book.

The 270 for me kills big deer, bang flop or run 50 feet, out to 500 yards, with a wimpy 130 gr Ballistic tip at 2895 fps muzzle. That is s very wimpy 270 load. 50 gr IMR4895.

But the rifle deigns that really seem to take over loads are beefy break actions and Ruger #1s.

Further down are 98 Mausers.
Further down still are Rem700s.
Don't even think about it with Win 94 or SKSs.

 

[bigedp51]

Winchester cases are general the thinnest cases so the "boiler" room is a little bigger with more case volume with less pressure. Would it be safe to assume your using ADI powder and might be rubbing Vegemite on your bullets to get lower pressures.

 

[bobnob]

No on the Vegemite!

Yes to the ADI powder. AR2209 (aka H4350).


CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

Using 56.5g for the 130g SST and 55.0 for the 150g SST.

The rifle is grouping accurately considering it is new. 5 shots under 1.5 inches.
The rifle is a Zastava bolt action M70, which is a modern Mauser 98 copy. I think Remington rebadged these as the model 798.

As I said no signs of pressure. I don't feel there is an issue with the scales however I will QA this sometime in the next couple of days.

Thanks for the info so far everyone.

 

[MEHavey]

OP references pressure not powder charge. Notwithstanding the chemistry, pressure is a function of case volume, bullet jump, bullet hardness, and barel/land/groove dimensions. Every rifle therefore takes a slightly different powder charge to produce the same pressure.

That said, I would venture that (save for obviously weaker-design actions), your brass is the limiting factor, not the comparison between different rifle models.

Once your your case starts flowing into the extractor cutout in the bolt, you're done.

 

[Grumulkin]

1. It's pretty uncommon that any load you cook up is EXACTLY like what's in the manual so the maximum allowable powder charges will vary.

2. Much published load data is gathered from pressure barrels. It's quite likely that your gun will be different in things like chamber size and even in a slightly different bore size. That means your gun may tolerate a heavier powder charge without causing excess pressure.

The important thing is that the load isn't excessive in YOUR gun. In a strong bolt action gun, if you're not having signs of excessive pressure, and there are a number you should evaluate, you're OK whatever the manual says. For guns with less robust actions like revolvers, lever guns, etc., you're best off sticking slavishly to published data.

 

[OldmanFCSA]

Pressure is dependant on many features, design of rifle, design of cartridge, style & weight of bullet, powder & primer, barrel length. All must be considered.

However - that piece of brass is what determines your safety factor - if your pressure exceeds the elastic value of the brass casing - you will soon have a grenade in your face!

The brass casing seals the gas explosion into the rifle - if it fails to seal, the resultant pressure will get you - in the face!

Measure youre brass on case web before and after firing - if it increases by over 0.001", you are exceeding the elasticity of the brass and a failure is coming. All casings are different in hardness - keep a good safety value - look for the most accurate loading.

Some of us idiots have purposely blown up rifles in search for the fastest velocity possible, I have achieved 6300 fps in a special built rifle, rifling only lasts about 500 rounds, brass lasts only 5 firings with annealing every firing, and accuracy normally sucks, shotgun style - shoot and hope for the best - spray and pray - sounds like some semi-auto pistol shooters I know. Rifling is burnt and abraided out of barrel by powder erosion thru throat of rifle as entire barrel becomes the chamber while firing this type of loading.

 

[redneck2]

Measuring case head expansion has proven to be extremely inexact at best and dangerous at worst. Same with other "proven" methods (primer flattening, bolt lift, etc.).

Why do you feel the need to exceed proven loads? You get very little if any velocity increase and risk damaging the firearm and yourself.

 

[gamestalker]

Clark. Hey, which powder do you load the .270 win. with when your trying to break the world record for velocity? Is it RL19, RL22, H1000, or IMR4350 or what ever. I'm loading RL19 and it will flat send those 130 gr. BT sailing at 3250 fps using a compressed charge of RL22. Of course that's beyond any published load, but because its a slow powder for that cartridge, pressures are reasonable.
Just like everything else, I use the data as a guide by which we work with until we have either blown the gun to pieces, or found the perfect load that sometimes requires two cases welded together for all the powder to fit, ha! ha!
By the way, I just put some Speer 110 gr. TNT's together for my 700 CDL 7mm RM. Wow, 75.0 grains of RL22 and those puppies are chronoing in the 3500 fps range. I couldn't get them much faster because they start to come apart. The Sierra 100's hold together and they were hitting 3700 fps respectfully. Talk about rabbit stew when I blast one of our giant Arizona jacks at several hundred yards. I just get this massive explosion of fur and blood every where.

 

[bigedp51]

Once your your case starts flowing into the extractor cutout in the bolt, you're done.

This telltale imprint is what the competition shooters use on their custom built rifles as the cut off point pressure limit and back off one or two grains.http://www.accurateshooter.com/ It is the cool period or "winter" in Oz and the local temperature might have something to do with your loads. (yes I know your ADI powder is very temp stable)

In my .270 I used IMR-4350 with 55 grains and 130 grain Hornady spire point and 52 grains with the Hornady 150 grain round nose in a Remington 700.

Your rifle was made in Serbia at the Zastava plant as was my old 24/47 military Mauser. If you slug your barrel it will tell you more about your powder loadings and pressure. In the end without pressure measuring equipment your brass decides what pressure it likes and if you switch brands of cartridge cases you could be getting different pressure signs depending on the softness of the brass.

In the older Lyman reloading manuals the loads were tested in a universal receiver, 26 inch barrel, 1-10 twist, and groove diameter of .277. The newer manuals use specific rifles in each manual and these rifles vary with each loading manual. (which are conservative readings)

If I take a Winchester case and a U.S. military Lake City 30-06 case and neck it down the pressure signs would be quite different due to the construction of the cartridge case. In the end YOU have to decide what is safe, its your face next to the action when you pull the trigger.

In your posting I did not see what cases you were using which is another factor.

Are you happy with your .270, the stock bedding or as you say in Oz the stocking up. Below Australian Enfield stocking up variations.

Cheers

 

[RandyP]

Other than seeing if you can develop a load large enough to wreck your rifle, what is your goal? What were the groupings like, firing from a rest, when you were below published max data? IMHO anything beyond good groups just wastes powder and under 2 inch groups should serve well as a hunting round.

 

[Grumulkin]

I would agree that anything beyond good groups just wastes powder but you accept 2 inch groups???

 

[Jim Watson]

"The Past is a different country, they do things differently there."

Jack O'Connor loaded .270 heavier than any present manual approves of. I never heard of him blowing up a rifle.

Rocky Gibbs said the maximum load was the most that would give ten (10) loadings of the brass without enlarging the primer pockets too much to hold a primer.

Speer's old criterion, pre small company pressure test equipment, was to load until one "pressure sign" was seen, then reduce the load 6%. Note that is ONE sign from a list including heavy bolt lift, cratered primers, ejector imprint on the brass, and casehead expansion, not multiple symptoms. And a full 6% reduction, which amounts to 3 or 3.5 grains in .270; not the hobbyist "load her up til she binds, then back off half a grain."

I have not "worked up" very heavy loads but have been guilty of "shopping for data." Different outfits have different equipment, different barrels, and different lots of components, so it is not surprising that they come up with different maximum load listings. So you can pick and choose to find a stout load that was laboratory tested... somewhere.

 

[45ACPUSER]

You gotta compare apples to apples. Are you using the exact same components as the data source? Any case bigger then 223( yes there are some extreme case out there but most are in small case capacity range ) you have to respect each will have varying water capacity hence different load data. Case in point Sierra used Federal 308 cases to work up their data and Hodgdon used Win cases to work up their data!

Was the data worked up in a universal receiver vs a real gun? All these factors come into play!

So, a prudent reloader will have to evaluate what works for their gun based on case head expansion, bolt lift, accruacy, safety, and reliability.

No game animal is going to know it got hit with bullet going 50 fps more then staying within normal loading prarameters! If you need more gun then get more gun!

I can not point to where I sourced this info, but most proof loads are at 25 percent more then Std operating pressures specs So if spec 50K then proof loads would be 62.5K . Unless you have Oheler 43
http://www.oehler-research.com/model43.html You as a reloader have no way to accurately measure pressure!

 

[bigedp51]

Jack O'Connor loaded .270 heavier than any present manual approves of. I never heard of him blowing up a rifle.

Jack O'Connor did in fact blow up a converted 03 in .270 Winchester and lost a thumb when the receiver came unglued.

I don't load heavy and inspect my primers with a magnifying glass to watch for flattening as the load progresses upward. The Gentleman from Australian sounds like he has common sense and is asking a legitimate question. And sometimes a given rifle doesn't fit standard rules.

He could have a bore that is slightly oversized, a bore that is very smooth, or a batch of powder slower than normal or all of the above.

I will say it again if you go to accurateshooter.com and read about their custom rifles you will see wide variations in loadings on these custom rifles. Chamber size, type throat, bore size, etc will all effect pressures. The big question is did the Serbs build this rifle to SAAMI standards or the European CIP standards.

CIP chamber standards differ from American SAAMI standards.

Delta L Problem

http://en.wikipedia.org/wiki/Delta_L_problem

 

[bobnob]

Thanks all for the info and views. To answer a few of the points raised:

- The rifle seems to be grouping quite well regardless of the powder charge. Last time out I shot a nine shot group, which had 9 different powder charges, from 52.0 grains of AR2209 all the way to 55 grains of the same with a 150SST. The group was less than 2 inches at 100 metres, with just a little vertical stringing.
- If anything the groups were slightly larger with under maximum book charges than with over maximum charges
- Why am I pursuing above recommended loadings? Because it appears there's a bit more this rifle can do - and I mean to achieve that in complete safety - by exceeding what's in the books.
- I went down this road because I have seen many of those old articles and reloading manuals that listed what were held out as safe loads, that had velocities much higher than those listed in modern manuals. I had to ask, "Why?"
- The cases I am using are all Winchester, and they are all new or once fired at this stage. Super long case life is not that big an issue because eventually most of mine get lost in the bush, shooting at pigs, goats or deer (on a good day).
- Today I checked my scales. They are working properly.

My question is really prompted because I have already pushed a lot further than I thought I would be able to, and have still not encountered any things that indicate pressure is too high. I really was just wondering if that happens more than I thought. I have usually only ever loaded to below recommended max because I am naturally cautious with my shooting.

But, nothing ventured, nothing gained 'eh?

 

[Haxby]

It sounds like you need to chronograph those loads. If you are over the max load in the books, and over the velocity you'd expect, it's time to back off.

 

[RandyP]

"But, nothing ventured, nothing gained 'eh? "

Nothing blowed up either - lol

 

[bobnob]

Yep RandyP hard to argue there.

Anyway, why did you guys bother landing some bloke on the moon?!

Seriously, there is no way I want to blow up anything, which is why I am looking for assistance.

I agree that I need to chrono the loads Haxby. Have got my hands on one for this weekend so they should tell me a lot more than I know at this point.

 

[MEHavey]

When working near "published" max loads I cross check between multiple reference points:

1. The books. Even then, multiple modern editions have multiple max's. I look carefully at the bullets and seating depths they reference.

2. QUICKLOAD. My touchstone to compare and contrast between what the books say for particular bullet designs, case volumes, seating depths and barrel lengths. QL tells me what I theoretically "should" be getting as velocity for a specific burn rate.

3. Chronograph. Only the chronograph allows you to make sense out of what QL tells you as compared to the books. If you get significantly faster speeds than predicted, you are likely operating at higher pressures that QL would predict for the specific factors fed into it. Assuming all else is correct, adjust your burn rate/temperature data to match and look at the predicted pressure again to make decisions.

4. Brass. No matter what books, QL, or the chronograph tell you, your brass/extractor-cutout/primer pocket tell you what the weak link thinks about all this. Different brass reacts differently (including different volumes and strength). "Generally" Lapua is considered the strongest, Federal the softest.

As before, however, ..."Opinions vary"

 

[gamestalker]

I'm guilty of brass flowing into the extractor hole, all the time. I commonly get 12 or more cycles from brass that has 12 or more extractor rings in the case head. I'm a mad man when it comes to running max loads of slow powders through my Rem. 700's. I've yet to blow a primer or separate a case head. I will admit the determining factor in case life for me is visable head separation just short of through and through.