7mm Rem Mag and Barnes Pressure Problem


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Shadowstalker
July 1, 2014, 12:41 PM
Here's what I have:
-Newer Savage 114 with maybe 200 rds through it
-Brand New Federal Premium Brass, Winchester LRM primers, 67.0g H4831, Barnes 120 TTSX to a COAL 3.230 =/- .002 Books Maximums are 68.5g and 3.240 COAL
Past History
I started a load work up for the 150g about 2 yrs ago. I also found 2 sweet spots for a 120g that I noted and left to finish the 150g. I started at the beginning with once and twice fired brass and ultimately ended up having the same pressure problems that I'm having now with charges well below the max. During the last 1 1/2 yrs I sent the rifle into Savage twice to make sure it wasn't a headspace problem and after a blown primer broke the ejector pin. I got the rifle back late last year and its sat until a few days ago
So I draw my antelope Tag after 19 yrs and am going back to the 120g sweet spots (67.1 and 68.2) but this time with brand new brass to make sure it wasn't a primer pocket issue
I had 6 loads of 67.0, 67.1, 67.2, 68.1, 68.2, and 68.3 with book max being 68.5.
Fired 2 shots of Factory ammo to verify Zero with no problems
67.0g-I shoot all 4 rds of with no problems but certainly not the accuracy I had before.
67.1g-I shoot 3 of the 4 and the 4th has a slight leakage on the primer pocket, with poor accuracy on all
67.2g- I shoot the first one and the primer leakage is more significant and I stop the test.
I shot 3 of the same factory ammo with no problems.
I notice two burn marks on the bolt head one very slight and one a bit more, one that created some pitting

This morning I spoke with Barnes and there load for H4831 is 65-69g of IMR 4831. I told him specifically that Iím using H4831 and he said he uses it as well
My question is it possible that some rifles wonít take anywhere close to max values???

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WestKentucky
July 1, 2014, 12:51 PM
That is indeed why we use ladder tests. I suggest backing off from 67 slowly as it sounds like your just barely past your sweet spot now for some reason (new lot of powder or primers?)I'm betting 66.6 or 66.7 is your new spot.

steveno
July 1, 2014, 12:53 PM
considering all of the tolerances involved with different rifles yes it is possible for a load good in one rifle to cause problems in another rifle

jmr40
July 1, 2014, 02:24 PM
My question is it possible that some rifles wonít take anywhere close to max values???

Absolutely.

This is why you need a chronograph. If the books say a max load is 68.5 and you should be getting 3000 fps at that charge, then 3000 fps is your max load, not 68.5 gr. You might reach 3000 fps at 66.5 gr. That is where you stop with that rifle. In another rifle 68.5 gr of powder might be needed to reach 3000 fps. Some may only reach 2950 fps at 68.5gr

gamestalker
July 1, 2014, 03:52 PM
Other than primer leakage, what other signs did you notice?

How was bolt lift?

GS

ironworkerwill
July 1, 2014, 04:11 PM
Savage rifles have been known to have "dished" bolt faces. I have not looked at your load data, but if you are using Federal brass and have the classic dished bolt face, then that may be your problem.

gamestalker
July 1, 2014, 04:41 PM
I would be doubtful that it has anything or everything to do with the load, I've loaded a bunch of Barnes in 7 mag. and never had a pressure problem. Barnes does have it's own exclusive data though, and it's for a good cause. Reason being that it's a solid copper, which gives it a much longer bearing surface. The longer bearing surface creates a significant increase in bore friction, which increase pressures.

But what your describing so far, it sounds like it may be an issue with the bolt face.

How was bolt lift?

And other than leaking / blown primers, what do they look like, do they flow completely out to the edges of the pocket?

GS

Shadowstalker
July 1, 2014, 06:18 PM
The Bolt Face and Lift are Fine, They rounds chamber and unchamber easily. I bought a Cartridge Length (or sizing) gauge ????. someone told me they think I could have the bullet seated to close to the lands, but I'm under what Barnes publishes for the COAL by 0,010
The primers are not flattened, I stopped where I did because I know by jumping to the next load the primers will blow.
I should also say that I weigh each charge twice; first on a RCBS chargemaster, than on a beam scale. (Yes, Im anal)
I should have Chrony'd them, but I didn't have the setup time. My next step I think is to back the H4831 down and try a different powder (with a new ladder test), and Chrony them

ironworkerwill
July 1, 2014, 07:31 PM
So you took a straight edge .535" wide and set of feelers to determine if the bolt face is not dished? If it is, it will not be visibly apparent.

climbnjump
July 1, 2014, 09:00 PM
...someone told me they think I could have the bullet seated to close to the lands, but I'm under what Barnes publishes for the COAL by 0,010

Have you checked to see how far off the lands you ACTUALLY are?

I have a 7mm RM rifle where the suggested COAL in a bullet manufacturer's (not Barnes) manual is about .010 INTO the lands so in that case, COAL minus .010 would be right on the lands. Rifles - and the reamers that cut their chambers - do vary some.

witchhunter
July 7, 2014, 07:27 PM
Shadow, take a sharpie and mark a bullet, chamber it and look for rifling marks on it. That could be your problem as seating a bullet into the lands will spike pressure.

tightgroup tiger
July 7, 2014, 08:05 PM
Shadow, take a sharpie and mark a bullet, chamber it and look for rifling marks on it. That could be your problem as seating a bullet into the lands will spike pressure.

That's what I was thinking also. You at least need to eliminate that as a possibility.

gamestalker
July 8, 2014, 02:47 PM
If you are up close to the lands, or into the lands it will most definitely drive your pressures through the roof. And with Barnes bullets it will be even more significant.

And not that I think it has anything to do with your problem, but the data for IMR v.s. H-4831 is very different. But it's still something to be aware of, and can no doubt have an effect on pressures.

There are two ways to go about this. First you can take your powder charge all the way down to 65.0 grs. and work back up until you get what your looking for regarding velocity and accuracy. Or you can decrease the OAL to a definite .020"+ off the lands and start from around 66.0 grs. working up until accuracy and velocity are acceptable. But in this respect, and in my experience Barnes don't fare as well regarding accuracy when up close to the lands. I have chased the lands with them, and I learned that they don't do as well as does a lead core projectile, at least not in my rifles anyway.

GS

climbnjump
July 8, 2014, 04:42 PM
But in this respect, and in my experience Barnes don't fare as well regarding accuracy when up close to the lands. I have chased the lands with them, and I learned that they don't do as well as does a lead core projectile, at least not in my rifles anyway.

GS

Yep, same with my rifles. If you call Barnes, they will suggest that you start about .050 off the lands. That distance gave the best accuracy for one bullet that I tried. I did go to .030 for another.

nastynatesfish
July 10, 2014, 11:07 AM
Ya I load a bunch of 140 trac bullets in my rifle and I seat a normal aol. I don't use Barnes info. I just start 2 gr under suggested and work. I'd start at a factory loaded round pal for your bullet. I've went I to gunstores with calipers and asked to open and measure rounds. Get funny looks but... Are you shooting the old x bullet or the newer banded bullets?

918v
July 10, 2014, 12:10 PM
Barnes copper bullets NEED a lot of bullet jump. You CANNOT treat them like conventional bullets. Barnes' .050" off the lands is the MAX OAL you should be using. I almost sploded my HiWall doing what you're doing.

ArchAngelCD
July 10, 2014, 04:58 PM
I looked at the Barnes load data and it seems you are well within their limits and using the same OAL they did. If it were me I would try backing the bullet away from the rifling a bit more. From everything you said it seems most likely your pressures are spiking because your bullet is too close to the rifling.

Andrew Leigh
July 11, 2014, 05:41 AM
@Shadowstalker.

I have simulated your load in the QuickLOAD ballistic software program. Indeed there is something odd going on here. Although I have needed to use the SAAMI standard H2O case capacity the simulation should be representative. At your load of 67.2gr H4831 you should be producing a MV of 3 052fps at 49 494psi. So something is indeed most odd seeing that your are experiencing pressure problems.

You have not confirmed if your trimmed case lengths are within spec. I can only see case length and being on the lands as being the culprit. Having said which QuickLOAD recommends that 7 500psi is added to the pressure calculation if seated on the lands so theoretically you would still be within SAAMI limits which really only leave case length. Another question, are you uniforming your primer pockets? A final question is what is your jump with a COL of 3.23"

QuickLOAD also shows that your load is inefficient and that your are only burning 92% of your powder.

I can do a full simulation for your particular rifle if you would care for it. It will require some basic measurements on your part.

627PCFan
July 11, 2014, 10:32 AM
If the only signs of pressure are a leaky primer, I gotta ask how are you seating your primers? Hand primers or press?

Also have you tried taking that 3 samples of brass for this current test and using it for another known load you have worked up to see if the leak occurs with that load as well?

918v
July 11, 2014, 12:49 PM
QuickLOAD also shows that your load is inefficient and that your are only burning 92% of your powder.

Most loads with slow burning powders are inefficient.

918v
July 11, 2014, 12:52 PM
Having said which QuickLOAD recommends that 7 500psi is added to the pressure calculation if seated on the lands so theoretically you would still be within SAAMI limits which really only leave case length.

QL assumes you are using conventional bullets. Solid copper bullets do not engrave as easily and need more jump. The ttsx grooves don't help all that much.

Factory chambers allow .040" to .050" of case growth before the case mouth pinches the bullet.

Andrew Leigh
July 11, 2014, 01:22 PM
The point was to illustrate to the poster that after he has solved his problem that there are other powder that may well prove to be more efficient for his purposes.

Andrew Leigh
July 11, 2014, 01:42 PM
[QUOTE=918v;9541744]QL assumes you are using conventional bullets. Solid copper bullets do not engrave as easily and need more jump. The ttsx grooves don't help all that much.[QUOTE]

Quickload does no such thing. The 120gr TTSX has a start initialisation pressure of 4 351psi while a conventional 120gr Sierra has a start initialisation pressure of 3 626psi. This directly from the QL database.

Quickload also does not factor jump into the equation, there is no provision in QL for jump only COL. So QL calculates the pressure change in the case due to seating changes and not distance from the lands. As one approaches the lands QL does nothing to change the pressure increase resulting from the increased inertia, when you touch the lands you need to manually add an 7200psi to the Start Initialisation Pressure.

A while ago I loaded up and went to the range as this was puzzling me. The the graph I plotted indeed showed that pressure slowly reduces as one moves towards the lands but barely reduces from 2.00 to 0.5mm off the lands, but from about 0.50mm off the lands the pressure from meeting the lands is far greater than the pressure reduction from increasing the COL. I unfortunately lost a bunch of info due to rebuilding my PC, it was a costly exercise that having already proved I am not about to do so again.

Check your copy of QL and tell me I am wrong.

918v
July 11, 2014, 01:56 PM
You don't understand what I wrote.

I did not write what QL factors in bullet jump. You're putting words in my mouth.

What I wrote is that the OP needs to back off the OAL because solid copper bullets do not engrave as easily as conventional bullets and cause the primers to blow when seated too close to the lands.

You are correct about the start up pressure being different, but that's not enough to overcome what's happening.

Andrew Leigh
July 11, 2014, 02:53 PM
You don't understand what I wrote.

I did not write what QL factors in bullet jump. You're putting words in my mouth.
And apparently they did not fit :D.

What I wrote is that the OP needs to back off the OAL because solid copper bullets do not engrave as easily as conventional bullets and cause the primers to blow when seated too close to the lands.
Agreed in principle but in this particular instance even if the op was on the lands I believe that he is still way under pressure.

You are correct about the start up pressure being different, but that's not enough to overcome what's happening.
Agreed.

To the OP, it would be nice to see a pic or two, and also to know how big your jump currently is.

gamestalker
July 11, 2014, 04:47 PM
Although I have seen a significant increase in pressure with Barnes bullets seated up to the lands, I've also been successful in maintaining consistent acceptable pressures by adjusting the powder charge. It can be accomplished, but that doesn't mean it will be the most effective oal and could result in loss of accuracy, velocity, and even blown primer seals.

However, blown primers can happen with bullets like this without excessive pressures. To elaborate, because Barnes and other similar solid bullets don't engrave as quickly or as easily as common jacketed types, peak pressures, although possibly within acceptable range, are sustained while the bullet is staged against the lands for an extended period of time, I are referring to milliseconds. In other words, it can effect the pressure curve.

Being a land chaser, I have experienced this on occasion with different load make ups. It hasn't happened but just a hand full of times, but almost always with solids when seated up to the lands, and even when no other pressure signs were exhibited. And when using the same powder charge, primer seal failure was resolved when I reduced the oal by .020"+.

GS

ironworkerwill
July 11, 2014, 07:01 PM
I'm still goin with the dished bolt face. Federal brass is known soft especially with belted mags. The op has shown he is below max Col there is no way he is in the lands unless the throat was cut short. After the rifle has been sent to Savage twice I'd think it would have been caught.

Soft brass coupled with a dished bolt face=leaky primers.

Often times I'll get ejector extrusion before the primer leaks. Unless it's been reloaded several times. This was virgin brass.

gamestalker
July 12, 2014, 01:21 AM
Ya, your probably right ironworker, and especially since his oal suggests it would be very unlikely he is close to the lands.

GS

41 Mag
July 13, 2014, 06:02 AM
Personally with my 7mm Rem Mag and my 7mm STW the Federal brass has been the worst to work with in regards to being "soft" and causing similar issues.

I don't know if it is simply a Federal thing, or simply due to the brass they used, but I have had this happen several times with once fired Fed cases in both, and the cases were originally either new, or from factory ammo and fired in these two rifles only. Both of them are Rem Sendero's, and have shot other brands just fine.

On the other hand I also believe the OAL is a bit long and would really look into seating a bit shorter. Most of my previous experience with Barnes has been with the original X, and not the newer TSX versions. I know for sure and certain the older ones have to be seated .050 back to start with.

918v
July 13, 2014, 11:04 AM
How far off the lands is the OP?

rogn
July 14, 2014, 10:39 PM
There has been some recent history of Winchester primers having soft or easily perforated cups. If your boltface is pitted then you are likely seeing this phenomenum. You may want to try another brand of primer and see if the problem persists.

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