Inconsistent Pressure Signs

[jasonc84]

I shot 4 shots today and 2 of the four showed alot more pressure that the other 2. This is a .270, I'm shooting 150 gn. Nosler Balistic Tip, this time with 49.5 gn. of IMR 4350. Nosler shows a range of 48 gn to 52 gn with this powder (actually nosler tested H4350), 52 gn. is like 2782 fps. It has showed pressure signs no matter the load or the O.A.L. But today kinda confused me with the inconsistent pressure signs, two of the primers were flattened and the other weren't. Another thing, you would think using less powder would cause the bullet to hit a little lower but it hit about 4 in. higher. Any suggestions?

[Art Eatman]

Both Hodgdon and Speer show 51.0 as max, so you're okay there. Large rifle, but not magnum primers, of course.

I dunno. You using a scale, or a powder measure? Maybe there's some sort of inconsistency in your weighing/measuring?

Variations in pressure can result in variations in barrel vibration, which can open up a group considerably. High, low, sideways...

My only loading of a .270 was eons ago, with a caseful of the old-style surplus 4831 compressed under a 130-grain bullet. Gave around 2,700 ft/sec or thereabouts. So, never any signs of high pressure...

Art

[BigSlick]

IMR 4350 & H4350 aren't the same powder.

Before going any farther with working up this load check out the load data for IMR 4350. Your stated load looks to be within recommended load data limits.

You might try giving Hodgdon a call, they have always been very helpful for me.

A good place to start would be IMR load data for 270 Win

HTH

BigSlick

[Art Eatman]

Addendum: Speer #13 sez H4350 max is 51.0; IMR 4350 is 52.0. The Hodgdon book is just the opposite! Duh?

Still, 49.5 oughta be okay.

, Art

[BillCA]

Is there any possibility those two rounds were crimped tighter?

Same brand of brass as the other rounds?

[NorWestr]

FWIW the flattened primers aren't necessarily a pressure sign unless you'r seeing other indications? A sizing die adjusted not quite right and setting the shoulder back too far will cause primers to flatten. I had that experience once,and IIRC it didn't always do it on all the cases. A headspace gauge and/or a chronograph would tell you more.
NW

[smokin54]

Cartridge overall length will affect pressure , was it consistant ? Do not load to were the bullet is touching the lands and a bullet pushed to far into the case will also raise pressure .
A light load will shoot higher , The bullet spends more time in the barrel during recoil while the barrel is rising

[jasonc84]

Thanks for the replies. The shells i was using were brand new winchester shells so they were full sized( i ususal only do partial full resizing). I ran them up the resizer just to make sure the neck was completely round. the primers also have raised ring around where the firing pin hits and tiny little dots around the whole primer(this is the case no matter the charge or O.A.L.)

Im still having problems with copper fouling. I brought this up in another thread. Since, I've been using outers foaming bore cleaner which turns blue if it detects copper. I can clean it until copper free and after the next shot copper will be coated on the lans of the rifling. someone suggested Sweet's but i can't find that anywhere but on the internet.

[LHB1]

Hi Jason,
Well you already answered my question in your last post but do BE SURE all the brass is the same brand AND is resized before loading even if it is new. A friend had problems with his first reloads, VERY hot and blowing primers with what should have been a safe load. He tried to save a few bucks by using range pickup brass. Finally I convinced him to buy a box of new brass and start over using same load. Everything was fine and high pressure signs disappeared. Seems you have already done this.

As another poster has also stated, I consider IMR4350 and H4350 to be two different powders. I found IMR4350 to be a little faster burn rate than H4350 and thus used slightly less powder in IMR4350 loads. Remember that loading manuals and loads are NOT mathematically precise calculations, they are experimentally determined using HUMAN JUDGMENT and different guns, powder, bullets, etc. Even if the guns are same brand and model, pressure and velocity may not be identical and human judgment is highly variable.

Next guess would be consistency of powder charges. Don't remember from your post but did you throw the charges or weigh them? Load some more with weighed charges and retest. If you use a powder measure, install a powder baffle in the powder hopper if it doesn't already have one. This will reduce variances of powder weight in hopper influencing thrown charge weights due to compression.

Finally, your gun may have a tight chamber or tight barrel and just use less powder to attain pressure. If so, you could be getting the same velocity with less powder than others use. Sorry, I forgot your problem was variance from shot to shot.

Regarding slower shots hitting higher. This is actually normal and is related to "barrel time". Happens because slower bullets stay in barrel slightly longer and the rifle recoils slightly higher letting bullets exit when barrel is pointing higher.

Good shooting and be safe.
LB

[jasonc84]

I use a RCBS balance scale to weigh charges. I also have a digital scale that i use to check the charges. So I weigh everything twice most of the time(takes forever.)

[mete]

Years ago I had that problem with my 44mag .Using less than max loads of Blue Dot I would get an occasional noticable hot one about every tenth round. I had not found anyone who could tell me why. But after I dumped that box of primers I never had the problem again !! So don't assume the primers are OK.....BTW a friend of mine had a problem with his 44 mag - he would get an occasional primer which would ignite with enough force to push the bullet into the barrel but not ignite the powder ! Threw out that box of primers - no more problems !!!

[Poygan]

Check your case lengths. .270 needs to be trimed to correct length regularly, more so it seems than other calibers. I have found that lubing the inside of the case necks prior to resizing reduces the case stretching.