.270 win help. Cratering primers update Page 8 post 78

Well - lets see:
- magnum primers (adds the equivalent of 2-3 grains of powder over regular primers).
- copper bullets that are longer and harder than jacketted.
- undersize bore.

All the above contribute to higher pressures.
 
cosmic said:
Well - lets see:
- magnum primers (adds the equivalent of 2-3 grains of powder over regular primers).
- copper bullets that are longer and harder than jacketted.
- undersize bore.

All the above contribute to higher pressures.
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Where did you get magnum primers add the equivalent of 2-3 grains of powder? That has never been my experience.

And who is measuring bore size and with what?
 
Not "sounds strange" - is mentioned on many places on Internet - can not randomly substitute magnum for standard primers and expect no changes. Why it is intended that you work up your loads using magnum primers, if that is what you intend to use - also temperature makes difference about when you do the work up versus when you use the ammo - is a thing that you may not get equivalent muzzle velocity at minus 25 C versus plus 25 C with the same components - was a "common" thing in "old days" to use magnum primers for larger than 30-06 cases, or for colder (below freezing) shooting, or for many Ball powders.
 
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Bad Bob said:
Yes, what`s with this thing about magnum primers, sounds a little strange?
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A common "rule" is to back off 1-2grns when switching a load over to a Magnum primer. It's a dumb rule with too many variables though, like a lot of "rules" so often repeated. I am no fan of reading primers to gauge a load but damn, those are not looking good!
 
"reading pressure" by looking at primers is like a very traditional thing to do - even though is multiple examples on line to show that it does not always constantly reflect what true pressure testing equipment will show. Like "bolt lift" or "case head expansion" - can be done at home and works more often than it does not - but is still circumstances where it does not - same symptoms, but due to other causes, than are presumed.
 
I have always known the difference between mag and regular primers, but 2-3 grains, not. Yes mag primers for hard to ignite, ball powders, colder weather and larger powder charges, but never 2-3 grains variatiion.
 
I would take the cases already fired in the rifle, check them again for trim length, neck size them and start 10% BELOW minimum charge.
This will give an idea if the gun can shoot whatever powder it may be.

Either that or start out with a can of fresh unopened powder.
 
Or, give Hodgdon a call and ask their opinion. I've found them to be excellent in that respect. They'll want the lot number of the powder you have.
They may also have some suggestions re the Barnes bullets.
 
pathfinder76 said:
Where did you get magnum primers add the equivalent of 2-3 grains of powder? That has never been my experience.

And who is measuring bore size and with what?
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I measure the bore size. I took a soft piece of lead and put it through the barrel with some lube. I was then able to measure the “slug” to get the internal dimension of the barrel. I checked the slug with two different measuring tools and got the numbers I did.
 
As for the magnum primers. I have been devolving my loads to use them since the beginning. I do all of my load devolving for my hunting rifles in the cold. No point of doing them when it is warm because of the temperature difference being sometimes 50-60 degrees C (ie +25 to -30 C) I have always reduced the loads using them and started devolving the loads from the beginning with the mag primers. I am not switching part way through. I have never experience a result like this before. Powder charge below max, mono bullets and cup and core bullets doing the same thing re pressure.
 
bobjoe said:
I measure the bore size. I took a soft piece of lead and put it through the barrel with some lube. I was then able to measure the “slug” to get the internal dimension of the barrel. I checked the slug with two different measuring tools and got the numbers I did.
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Did you use calipers or do you have an actual micrometer? Calipers aren't as accurate, especially if they're not a high end pair.

If the rifling an even number of lands/grooves? If not that'll be hard to measure too...
 
Suther said:
Did you use calipers or do you have an actual micrometer? Calipers aren't as accurate, especially if they're not a high end pair.

If the rifling an even number of lands/grooves? If not that'll be hard to measure too...
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4 lands and 4 groves. Two different micrometers.
 
I thought I would post a follow up to this thread, Since it has been a year. Suspecting many things, I have checked, re checked my tools, measurements, ect. I took the rifle to a gunsmith to check my measurements, check head space ect, as recommended by savage, while the barrel is in fact undersized by about .002 based on their measurements vs the .004 that I had, I had the option of a new barrel but elected to do more digging first to see what I could find.


What I have found is that the rifle doesn’t like monolithic bullets.

I tried GMX, e-tip and different Barnes bullets. All showed signs of unsafe pressures at well below listed loads. I threw out all the brass I had and started with a fresh batch of new brass. I also changed bullet type. I checked the powder in another rifle and it performed as it should. I tried using Nosler partitions. With RL 19 I found that it was safe to work upto max loads but I did not have the accuracy one would want. When I went back to the original can of IMR4831 I found that it was much more consistent than before.

I had a 1.1 and 1.2” group with 55.5 gr of 4831 giving a velocity average of 2981 with a std dev of 15.3, zero pressure signs. Going up in .5 Gr increments produced about 20fps each step. 56.5gr showed some signs of an increased pressure and bit more recoil than one would expect. But velocity was only 3021 with a std dev of 4.6 and a 1.3” group that was more vertical stringy ( likely me). At 57 velocity jumped to 3049 and a std dev of 9.9. This was again showing a touch of pressure but nothing crazy to be worried about.

Most of the loads had a std dev in the single digits, so the powder was not the problem, I had even reached out to IMR and they found no issues with that lot number of powder.

I’ve decided that the best load is the 55.5 gr load. I still need to load up 20 rounds to head back out and confirm that the rifle is performing properly with them but it appears the end issue was the monolithic bullets.

Been a lot of email’s range trips and components for what should have been a simple load development to find this end result. But it did remind me of another rifle. My dad has a t3 in 338 and I had issues with his and running Barnes bullets. I switched to the partitions and it went away. Funny that’s been two rifles that didn’t like Barnes bullets.
 
Now I have another reason to stay away from Barnes bullets. Most unothadox that you had the same problem twice, with the same brand-name of bullet. Congrats on problem solving the issue!
 
track said:
Now I have another reason to stay away from Barnes bullets. Most unothadox that you had the same problem twice, with the same brand-name of bullet. Congrats on problem solving the issue!
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My post wasn’t bashing Barnes bullets. I use them to great effect with several other rifles and are my go too. Note in my post I also tried other brands of monolithic, this one rifle just happened to not like them.

The post was more about finding out the issues.
 
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