308 blown primers question

[steves86ta]

Hi All,

This is my first post asking for help, but i've been around in the classifieds for a bit. I am relatively new to this long range stuff (f-class) and have been shooting a Howa 1500 in 308. When i first started i was using the Hornady Match BHTP 168's and had no issues at 1k other than my SD and ES being extreme.

One of the guys I shoot with said to switch up to 175 SMK's. I did this and at 1k I'm struggling to get them moving fast enough to be picked up consistently with our Shot Marker targets. Last time i was at the store i saw some ELD-Match in 168 i picked up.

This is where things get interesting. The rifle is a 'stock' Howa 1500 with 24" 'heavy barrel'. I am now using Staball Match powder and the ELD-M's.

Today i figured i needed to do some load workup for the new projectiles. I know both the 168 BTHP and the 175 SMK's liked to be on the upper end of the spec on Hodgdon's site. So i loaded up groups of 5 from max down ten groups. From 44.8 - 46.8gn of Staball Match powder, the 168 ELD Match and Lapua brass (3 firings on them and annealed)

I went today to chrono the loads and started at the bottom at 44.8 gn.

The first 3 rounds shot great, seemed to be fairly accurate and felt good, the 4th round popped a primer out. The Magnetospeed measured

Series	Shot	Speed
1​	1​	2592​	ft/sec
1​	2​	2612​	ft/sec
1​	3​	2600​	ft/sec
1​	4​	2592​	ft/sec

I loaded the next charge weight of 45gn in and the next two shots popped primers out and did not register on the chrono. I stopped at this point as I figured if im popping primers at 45 there is no reason to go higher.

Hodgdon lists the data from 42.7 - 46.8 with Sierra BTHP and 42.4 - 46.4 with Barnes TTSX

My reloading process is as follows

1. Universally deprime brass
2. wet tumble with stainless media
3. lube with alcohol/lanolin oil
4. Size with Hornady full length sizing die and a 333 bushing (i think its 333 i dont remember for sure)
5. Quickly wet tumble again to remove lube
6. Load on Dillon 550 - Station 1: Wilson Expanding Mandrel, Station 2: Dillon powder die with funnel adapter, Station 3: Frankford arsenal bullet seating die

Up until now, I have never seen pressure signs this 'far' from the max that i see listed. Just figured i'd ask if anyone has any advice. I am concerned that at what my rifle seemed to put the max of 44.8gn's at im not pushing these fast enough to carry enough velocity at the 1k line for the targets to work consistently.

Thank you in advance, attached are some pictures of my fired cases the two grouped together are the 45gn - i see the ejector marks. Maybe it's me, but the 3 with primers from the 44.8 dont look over pressure to me - but like i said im new to this.

 

[nettle]

Have you checked the inside diameter of the "blown" primer pockets to see if they are oversize?

 

[whatsupdoc]

Looks like you are getting brass extruding into the ejector hole, so you are
over pressure.

Confirm your charge weights, confirm your scales calibration.

 

[steves86ta]

Looks like you are getting brass extruding into the ejector hole, so you are
over pressure.

Confirm your charge weights, confirm your scales calibration.

I just re calibrated the Scale - Creedmoor Sports TRX-925 then pulled all of the rounds down and weighed them all. They all weighed +/- .05 what they should have most were +/- 0.02 what they should have been

 

[steves86ta]

Have you checked the inside diameter of the "blown" primer pockets to see if they are oversize?

So all i have to be able to measure these are my calipers.

I will say the 'blown' ones are significantly larger than other pieces of brass. All measuring at least 0.211 or larger - Could these have opened up with the primer popping out though?

 

[mattt]

have you measured your chamber to make sure you are not jamming bullit into lands

 

[steves86ta]

have you measured your chamber to make sure you are not jamming bullit into lands

Yes, these are 20 off the lands

 

[ChrisNZ]

Have you got a borescope? I think you need to rule out a nasty carbon ring.

 

[steves86ta]

Have you got a borescope? I think you need to rule out a nasty carbon ring.

I just got one. Need to look and see what a carbon ring looks like. I only played with it a little but and it looked pretty darn clean

 

[fkimble@charter.net]

Define "popped" primers. Popped to me means they were not in the case after the shot. Did the primer fall out of case during brass ejection? They can't really come out of the pocket while the bolt is still closed. Popped could also mean what most call blown, ie: a hole in the primer where the firing pin indentation is and lots of smoke. Either way the ejector marks signal high pressure.

Frank

 

[JSH]

Who’s or what primers?
I ask because of an incident a while back. A fellow either intentionally or accidentally used pistol primers. I quizzed him and asked about primers and if by chance a pistol primer could have been used, his answer was it could have happened.
His brass exhibited all of the “classic” signs as yours did with the blanking. Don’t know about his primer pockets.

How are you determining your “jam” or “jump”?
Switching bullets and using the same OAL is of little use because of bullet designs.

I would suggest going to a book OAL length and load a couple to see what they do.

Uh, and popping/blanking/blowing what ever one wants to call it is a definite S T O P right there and make a determination of what the issue is.

If you have a carbon ring that big, you probably need a new barrel by now.

 

[steves86ta]

Who’s or what primers?
I ask because of an incident a while back. A fellow either intentionally or accidentally used pistol primers. I quizzed him and asked about primers and if by chance a pistol primer could have been used, his answer was it could have happened.
His brass exhibited all of the “classic” signs as yours did with the blanking. Don’t know about his primer pockets.

How are you determining your “jam” or “jump”?
Switching bullets and using the same OAL is of little use because of bullet designs.

I would suggest going to a book OAL length and load a couple to see what they do.

Uh, and popping/blanking/blowing what ever one wants to call it is a definite S T O P right there and make a determination of what the issue is.

If you have a carbon ring that big, you probably need a new barrel by now.

Winchester Large Rifle Magnum Primers - no chance for pistol primers, i manually primed these

Jam-Jump:
I took 5 pieces of prepped brass, and jammed the bolt shut then measured the oal. I then took the 'shortest' one of the five and subtracted .020 from that and thats where the bullets were set at. I did this with the new bullets - FWIW the measurement was within .005 of the smk's

I took a video with the borescope, ill put links shortly. I did not know what this was and how it could form or what not. After doing some research last night, i learned that you will not get that area of the chamber clean with a bore guide, and yes i always use a bore guide. It is quite dirty there videos incoming.

 

[steves86ta]

I went ahead and ran the borescope through the rifle this morning and will link the videos below.

Forgive me if this is a stupid question as i truly dont know and dont mean it to be argumentative. If it were a carbon ring issue, the reading i read was the velocities would be all over the place. The 4 rounds i shot were very consistent and had an SD of only 9.5 and ES of 20.

Even last time out at the 600Y range, my SD was between 12-17 at the target much better than ive ever seen it (with the 175 smk's)

In my reading last night, it's my understanding that using a bore guide does not let you clean the area in which the carbon ring develops. Well i've always cleaned with a bore guide as i was not aware.

The two links below are videos i took with my Borescope. The first one is with it not being touched since firing yesterday. The second is after i just ran a wet patch down it with some patch out - no abrasives and then just a dry patch after

Before wet patch

After wet patch

 

[divingin]

I notice you have a decent ejector mark on the case without the primer, and none on the others. Either the primers reseating are preventing the mark on some, or your charges (or maybe some other pressure-inducing variable) are inconsistent. Either way though, I'd guess it's a pressure issue.

Have you compared fired to sized brass base to shoulder lengths? Short brass does weird stuff.

And yes, check for a carbon ring.

 

[59FLH]

Jam-Jump:
I took 5 pieces of prepped brass, and jammed the bolt shut then measured the oal. I then took the 'shortest' one of the five and subtracted .020 from that and thats where the bullets were set at. I did this with the new bullets - FWIW the measurement was within .005 of the smk's

Id revisit this process.

 

[steves86ta]

Id revisit this process.

Do you have a suggestion on another process?

This is how i did it for the 168 BTHP and the 175's - this is the first time im coming across this issue

Not trying to be argumentative - legitimately trying to learn here

 

[shoot4fun]

I realize when I say this that primers are still not plentiful and, when they are available, not inexpensive.
I've seen more than one bolt face after a steady diet of WW primers that showed all the signs of pierced and blown out primers.
That said, I do believe you are pretty far above the pressure limits.
There may be several causes. I would look very closely at the areas where carbon rings build up. Actually have seen a few rifles with two distinct carbon rings.
Staball Match is a relatively new powder. IS it possible your lot number is a bit faster than the testing was done with?
Many times we tend to determine publicly listed charge weights from powder manufacturers as "conservative". I've talked to lots of reloader that tend to use the maximum listed charge as their starting point. Not saying you did that but you did fail to note Hodgdon's testing was done with different bullets, primers and brass than they used. Keying on the brass, you must know that Lapua brass has a smaller internal volume than Winchester.
At this point I would develop a step by step plan for determining the cause and eliminate them one at a time.

 

[DGP4]

If the prior 3 loads on those cases were at or near maximum, some of the case primer holes may have opened up enough to seat the primers loose. I would take one of the trouble cases and see how well they hold a primer.

 

[steves86ta]

If the prior 3 loads on those cases were at or near maximum, some of the case primer holes may have opened up enough to seat the primers loose. I would take one of the trouble cases and see how well they hold a primer.

I threw them away, they measured pretty loose compared to the rest.

 

[steves86ta]

I realize when I say this that primers are still not plentiful and, when they are available, not inexpensive.
I've seen more than one bolt face after a steady diet of WW primers that showed all the signs of pierced and blown out primers.
That said, I do believe you are pretty far above the pressure limits.
There may be several causes. I would look very closely at the areas where carbon rings build up. Actually have seen a few rifles with two distinct carbon rings.
Staball Match is a relatively new powder. IS it possible your lot number is a bit faster than the testing was done with?
Many times we tend to determine publicly listed charge weights from powder manufacturers as "conservative". I've talked to lots of reloader that tend to use the maximum listed charge as their starting point. Not saying you did that but you did fail to note Hodgdon's testing was done with different bullets, primers and brass than they used. Keying on the brass, you must know that Lapua brass has a smaller internal volume than Winchester.
At this point I would develop a step by step plan for determining the cause and eliminate them one at a time.

That is helpful.

At this point, i think im going to clean the barrel and the carbon ring i found above out of it. load up again and see what happens