What's going on here?

O

olddav

New member
What's going on here?

I am trying to develop a load for my 338-06 using Barnes 160 grain TTSX. Using info I received from Barnes I performed a ladder test staring at the min and progressing to the max in .01 grain incriminates. During the ladder test I saw no signs of pressure with any load. I settled on 61.3 of H 335 (best node) and began testing seating depth. Using a bullet comparator I seated the bullets at 3.595 to 3.635 in incriminates of .005, and loaded 3 of each.
Started shooting the shorter bullets first (3.595) and progressed to the longest (3.635). Everything was going as it should (no signs of pressure) until I got to the final six. The first three were a little tight ejecting and the final two I shot blew out the primers. Stopped right there! Keep in mind I shot these very same loads without any problems not more than 20 minutes prior to blowing the primers out. Any ideas as to why this is happening?

Here are the details for the loads
Remington Brass (30-06 new and resized)
Winchester WLR primer
Barnes TTSX 160 grain bullets
H335 powder (61.3 grains)
Barnes Manual states min to max are 57.0- 62.0 of H335
All measurements given are to the Ogive of the seated bullet.
 
Did you use the comparator to determine the max COL for your chamber?
Sounds like the bullets were on the lands resulting in higher pressure.
 
You could argue that point except I fired the very same COL, and some longer, within 20 min before blowing out primers.
 
Barnes bullets will give you better accuracy AWAY from the lands, they might be slightly slower, but the accuracy improvements are worth it.

All solid copper rifle bullets behave very differently from a conventional cup and core bullet. Especially when pushed close to the lands.

Barnes bullets need a certain amount of "freebore / leade " ( away from the lands ) in order to keep the pressures down. That little space gives a gentle push prior to developing full pressure.

Just like the Weatherby rifles. Lots of rifles chambered in various Weatherby calibers can behave nasty without that freebore.... Weatherbys have it from the factory, other brand rifles do not.

Who made your rifle ? How much freebore does the barrel have ?

How many of each OAL length did you fire before you had pressure issues ?

I can't tell if I understand exactly when this happened during your testing.

Maybe your loads were just at the edge of pressure and the heated barrel / chamber was enough to show bad signs.
 
I can't tell you the freebore but the rifle is a savage with a Shilen barrel (338-06). The test consisted of 3 bullets per seating depth, I fired 2 of the 3 sets before blowing primers. I fired the shortest to the longest , one each as a set. Once a set was fired I repeated the process a second time except On the second set I started with the longest and worked down the the shortest. On the Thrid set I started in the middle and move out to the from there.

Shot sequence,
3.595, 3.600, 3.605, 3.610, 3.615, 3.620, 3.625, 3.630, 3.635. (10 min break)
3.635, 3.630, 3.625, 3.620, 3.615, 3.610, 3.605, 3.600, 3.595. (10 min break)
3.600, 3.605, 3.595, 3.625, 3.620, 3.630,( 3.615, 3.610 blown primers).
 
SO within all of your testing have you cleaned your barrel?

Could be the build up of fouling is giving your bullets more resistance and causing added pressure.

Also what were the temps while you were working through these, and did you have any of the ammo sitting in the sun?

It doesn't take a lot of added temp to raise pressures with some loads. We shot some 300 RUM loads that were wicked accurate and had shown no issues what so ever with regard to pressure, when the temp was 75'ish degrees...When it bumped up to the low to mid 80's it raised up enough to lock up the bolt.

Not saying this is whats going on just throwing out a couple of thoughts.
 
While I understand you are Using a bullet comparator.... what is the shortest and longest actual COAL of your reloads ?

I am positive you are over pressure, obviously since you blew primers, but not knowing how much the bullet comparator is adding to your measurements is adding to your figures is complicating the issue. ( no offense intended )

Could you place a bullet into the comparator and measure... then one without a bullet so we could do the math and deduce the additional length that the comparator is adding.

Your other rounds may have had tighter primer pockets ?! ... that combined with "heat" might be the issue.

I suspect your barrel is tight chambered and you may have found your max... a fired empty non-primed case and a loosely seated bullet ( snug enough to be able to cycle into the lands, but tight enough to eject ... will show your max length prior to hitting the lands of your barrel. I also mark the bullet with a black marker so I can see it has hit the lands.

Or use the snug fired empty non-primed case and bullet, gently cycle and insert a dowel / cleaning rod ... marking where the end is on the dowel and measure the whole measured dowel and "test round" COAL.... that should suggest your max seating depth.... measure with the bullet comparator... and let us know the results.

I hope that makes sense.

Hornady makes a gizmo specifically designed for this purpose....

https://www.youtube.com/watch?v=WCPgKNp8i7o
 
I know I am not on the lands, can't remember the numbers but I am well off the lands. However when I performed my ladder test it was a bit cooler, I could be on the edge with a increase in temp.
I have another node approx .7 grains lower. I'll give them a try.
 
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