Known Loads too hot now..why

[clhman]

Please help! I've been reloading for about 2 years and I consider myself a careful reloader. Yesterday I had a very perplexing situation happen. Everything that I shot was too hot and I don't know why. Everything I have tested, chronographed and verfied several times. I just went out to shoot for groups yesterday. Here are my loads:

.300 SAUM
Model 7 22" barrel
200 Nos AB
61.6gr R-19
2.820 OAL
Chrono'd @ 2635fps

.300 Ultra
Model 700 26" barrel
180 Hornandy SST
99gr Retumbo
3.692 OAL
Chrono'd @3360fps

These loads were developed between temps of 20-40 degrees. Yesterday the weather was really nasty. It was 32 degrees and snowing heavily. (Yes I was out in it, you have to be to live in Alaska!)

Both loads showed giant shiny spots on the top of the brass and the bolt was hard to open. I shot a couple of each to be sure and got the same resuts. Then I picked up my 22-250 and some factory junk that I was getting rid of did the same thing!

I keep very thorough notes and I'm a careful reloader. I'm hesitant to tear these loads apart and start over.

My 2 hypothesis are:

1. My guns cooled very quickly in the weather. My ammo was on the bench but in boxes. Maybe it didn't cool as quickly, leaving a big difference in ammo v gun temp? Didn't feel like it but maybe...?

2. The blowing snow made the humidity 100% and combined 32 degrees made everything work weird...?

I don't want to question everything because I don't know where to start.
Any insight would be greatly appretiated.

Thanks
clhmangun)

 

[Buffalobob]

If you get water on the cases and/or in the chamber it will cause the rifle to act like pressures are high because the water lubes things and causes more bolt thrust.

 

[Loner]

If you get water on the cases and/or in the chamber it will cause the rifle to act like pressures are high because the water lubes things and causes more bolt thrust.

+1 Even if you kept your loads dry with the high humidity and the heat of firing,
rapid barrel cool you would get condensation, that sure accounts for the bolt swipe.
If this is the case your pressures were actually ok.

 

[Boss Hoss]

If you get water on the cases and/or in the chamber it will cause the rifle to act like pressures are high because the water lubes things and causes more bolt thrust.

That is a good one!!!!! LMAO!!!!!!!!!

 

[Pdvdh]

Any insight would be greatly appretiated.

Thanks
clhmangun)

You didn't state if these cartridges were loaded back at the time of original load development, or if you loaded them up at a different cartridge reloading event. Are you using the same powder scale, brand and model number primers, the same brass casings, the same Lot of gun powder? Do you have a weight to calibrate your powder scale with and have you checked it's accuracy?

Change any of these components and if you were already operating near max you could begin to experience excessive pressure signs.

"Both loads showed giant shiny spots on the top of the brass and the bolt was hard to open." What's a giant shiny spot on the top of the brass mean? Are you describing a relatively small (compared to the entire case head) shiny spot on the case head from a bolt face plunger hole or extractor slot?

Hard bolt lift is subjective also. I've had everything from noticable stiff bolt lift to having to slam the bolt handle up with the palm of my hand - or it wouldn't budge.

If you're experiencing a huge increase in pressures, I'd check the powder scale for calibration first, after confirming you haven't switched any of the other components or swapped over to a new Lot and container of powder.

Report back after you figure it out?

 

[MR.SWIFT]

pull one round from each cal. and verify load if the same as data quoted on box reshoot loads to verify press need only shoot two rounds each

 

[clhman]

Thanks for info. All components the same. I use a Lyman III digital powder thrower/scale, RCIV and RCBS dies. CCI 250 primers, powder and bullets same lot.

Come to think of it, everything was wet.

With the RUM pressure was seen at 99.5gr so I should be near the top.

With the SAUM I went all the way to 63gr with no signs of pressure, settled on 61.6gr because of a really good e.s.

Maybe I'll try them again now that the weather cleared up.

 

[clhman]

By the way, I said giant spots because they were big and round, not faded or distorted. Bolt was stiff, enough to get your attention that there was a problem...

 

[clhman]

By the way, I said giant spots because they were big and round, not faded or distorted. Bolt was stiff, enough to get your attention that there was a problem...

 

[gcamp54]

I'm not knowledgeable enough to give you any advice but I remembered an article I read that may shed some light on your issue. Others here can better clarify this, if it's even to be considered. Charles Ballard wrote an interesting article that's posted on 6mmbr about his load development for his .284 where he states, "between 100 to 300 rounds, as the barrel gets broken-in, the velocity climbs significantly". Even if it doesn't help you it's a great read at http://www.6mmbr.com/gunweek088.html. You didn't mention how many rounds you had through your barrel.

Gordon

 

[Buffalobob]

Come to think of it, everything was wet.

Water is called the universal solvent because many chemicals will dissolve in it. It has also been used for centuries as a lubricant for normal temperature applications. If you have a elementary school child in need of a science project you can do the old coefficient of friction experiment of the block on the inclined plane and test the viscosity of water versus various motor oils, gun oils and gear oils. The only thing that is better is powdered graphite and it is not a liquid and has no viscosity.

Shooting with a wet cartridge is like shooting with oiled cartridges.

There are other possible explanations of what occurred to you, but it is what jumped into my mind being as I sometimes hunt and shoot F-class in the rain. The fact that the factory loads also caused a the same problem in a different rifle seems to point to something such as wet cartridges and chamber.

 

[jwp475]

A different LOT of powder? My original 180 grain load for my 300 RUM was 99 grains of Retumbo. My next batch of powder only allowed 97 grains and I settled on 96

 

[bigngreen]

I would agree with Buffalobob, in Black Powder Cartridge shooting you really have to watch for moisture in your chamber because your blow tubing every shot. If you start to get moisture back into the chamber you will get high pressures and you can some times see patterns in the side wall of the case where the moisture was in comparison to a dry area.
Chamber moisture will absolutely cause this problem cause your bolt is carrying the entire thrust of the load. Just like firing a super stiff load in a fresh case.
I use a 20 gauge bore mop to clean my chamber after any cleaning also.

 

[Boss Hoss]

Water is called the universal solvent because many chemicals will dissolve in it. It has also been used for centuries as a lubricant for normal temperature applications. If you have a elementary school child in need of a science project you can do the old coefficient of friction experiment of the block on the inclined plane and test the viscosity of water versus various motor oils, gun oils and gear oils. The only thing that is better is powdered graphite and it is not a liquid and has no viscosity.

Shooting with a wet cartridge is like shooting with oiled cartridges.

There are other possible explanations of what occurred to you, but it is what jumped into my mind being as I sometimes hunt and shoot F-class in the rain. The fact that the factory loads also caused a the same problem in a different rifle seems to point to something such as wet cartridges and chamber.

Bob---in a rifle barrel under the extreme pressures that exist the powder is ignited and pressure develops the projectile is the least restrictive path of resistance and is forced down the bore. Water or oil if it exists has to be DISPLACED (just as anything in the bore because it has mass) which creates resistance therefore increasing pressure. Do not know how much water was present in the bore but there is no doubt that it will increase pressure.

If the humidity level is high when a match starts say 90% and in afternoon relays it is 30% the POI shift will have to be adjusted because moisture laden air is denser therefore slowing the projectile faster than dry air. I think you have it backwards.