7mm Rem Mag - Over Pressure ?'s

[MattM]

I worked up a load for a Savage 110 (24" Barrel) in 7mm Rem Mag that initially didn't show any signs of pressure, either on the brass, primer or with heavy bolt lift. Now I am getting heavy bolt lift after only a few rounds and am hoping you guys can shed some light on the issue. The load is as follows:

Nosler Brass (once fired, bought new and fire formed), trim length 2.485"
Berger 168gr Classic Hunter
62.5 grains of H4831SC
O-give: 2.740" (0.012" off the lands)
Primer: Fed 215

My chronograph indicates this load is running about 2810 fps with a SD of 5.3. During load development, I shot all the way up to 64.0gr of H4831SC with this same bullet (0.5 grain increments) and it did not show any signs of pressure. Seating depth was done at 0.003" at a time starting at the lands and working back until it was 0.027" off the lands. The barrel was broke in as follows: 1 shot and clean for first 5 rounds, then 5 rounds and clean until 30 rounds, and then normal cleaning after that. Load development was 30 rounds at a time and never experiences pressure issues.

The above load shot a 5 round group of 0.248" at 100 yards for verification and then a 1" group at 300 yards. 600 yards it shot at 2.5". When I was verifying the load at 300 and 600 yards, I noticed I was getting some HEAVY bolt lift. There was probably 60ish rounds thru it at this time and I figured it was time for cleaning. I cleaned the barrel and chamber thoroughly using a copper remover, nylon brush and patches.

This morning, my wife and I took it out to foul the barrel with a couple of rounds and practice before she takes it for elk season next weekend. The first 4 rounds were fine, no heavy bolt lift or flattened primers. The 5th round had a sticky bolt lift and the 6th and 7th rounds were HEAVY bolt lift again. I searched the forum and other web information for possibly causes. The loaded rounds have a brass length at trim length, o-give consistent at 2.740". Other brass measurements (neck OD, shoulder length, web diameter, etc) are all within spec. I have my sizing die setting the shoulder back about 0.002". Loaded rounds chamber and extract without issue.

I cleaned the rifle again this morning and made sure the chamber was clean and had no solvents or oil left in it...as I read this can cause excessive pressure as well. I read the overall length of the brass can cause pressure...checked this and it is at trim length. I am stuck as to what could be causing this and believe it is either carbon or copper build up that I am not getting to when I am cleaning. The borescope will be here this Wednesday.

Can anyone shed some light as to what might be causing the overpressure after only 5 rounds thru the gun? Any help is greatly appreciated. Thank you in advance!

 

[Ray123]

Your rifle is saying too much pressure....drop the powder charge down 2 grains...shoot the same bullet 20 times no pressure....go hunting. It will still kill elk with 50 fps or so, less velocity, with, as always, good bullet placement.
Also I used Nosler brass, once, along time ago, because the case heads were too soft and lasted one firing where Lapua could go 40 firings with the same powder charge, but I didn't have heavy bolt lift, just enlarged primer pockets. Informed Nosler, no reply back...don't know if it the soft case head has ever improved upon, But avoid Nosler brass like a plague, they have many other good products I use, but not their brass....others may chime in on more recent examples of their old brass issues.

 

[slm9s]

What was the velocity of the heavy bolt lift rounds vs normal pressure rounds?

 

[KMart]

Carbon ring forming just at the lands. Some Isso paste, Simichrome or something similar will work it out short stroking that area.
Nylon brushes does not do a very good job of taking carbon out or keeping it in check. Get some bronze bristle brushes and go to work.
Were you getting flattened primers on the cases that gave you heavy bolt lift?
You said that you used a copper remover. Did you use anything in the way of a carbon remover?

 

[Dkk37058]

Could it beyour barrel getting hot and your leaving a cartridge in the setting in chamber and heating up before you pull the trigger with temperature sensitive powder creating pressure

 

[AckleymanII]

Savage barrels are not smooth. You probably have a barrel slam full of copper. I Have seen serious copper fouling spike pressures many times.

Tell us about your cleaning technique, please.

 

[MattM]

Slm9s: I do not know the velocity when I am experiencing the heavy bolt lift. The above velocities were from the initial load development and the only time I used a chronograph.

KMart: I was getting flattened primers when the heavy bolt lift occurred on every case. No other indicators of pressure...such as ejector marks etc. Just the heavy bolt lift and flattened primer. And I did not use anything for a carbon remover. I used Hoppes copper remover and regular Hoppes #9.

Dkk37058: I thought about this too, however I do not chamber the round until I am ready to shoot. The cartridge sits in the chamber for maybe 10 seconds prior to firing. I usually take more than one rifle with me when I shoot so I don't heat a barrel up too much during the course of fire. Usually about 9 rounds then switch rifles so the previously rifle will cool down for approximately 20 minutes or so. I can usually touch the barrel without issue.

Ackleymanll: I have several Savage barrels and this is the first I have had this issue with. I am leaning towards it being copper or carbon fouling and have read this can be a problem. I've just never had a barrel do this after so few rounds.

When I cleaned the rifle, it went as follows:

I run a patch soaked with copper solvent thru the barrel. I let it sit for 30-45 minutes then I will run another soaked patch. This sits for about 30 minutes then I run a dry patch until it shows clean. Then I run another patch soaked and then I ran a brush thru the bore. I patched this out and then ran another soaked patch thru the barrel, allowing it to sit for 30 minutes or so. I continued this for about 4-5 hours...admittedly it is not a set routine for cleaning. I thought I had all the copper out of the barrel when I ran a soaked patch, let it sit and then patched it out with very little to no color on the patch...it was the same color as the soaked patch. I tried to scrub the chamber (8-10 strokes) and throat area with a nylon brush and Hoppes 9 and then patched this out as well.

Afterward, I ran a patch with a light coat of oil thru the barrel once.

 

[slm9s]

When I have had a carbon ring issue, it made it hard to chamber a round as the bullet squeezing into the carbon ring created a lot of resistance. He says rounds chamber with no issue.
Also, a carbon ring would behave the same for all of the rounds for the last shooting session, not let several act normal and then give heavy bolt lift on the last couple.
IMO something else is going on here.

 

[big5ifty]

If you have any virgin brass, measure the bottom of the belt with a 1/10,000 micrometer, and measure the same spot on your fired brass.

If you don't, it's worth getting a few pieces and testing.

That will tell you how far over pressure you are. You want to see around 8 / 10,0000 expansion there.

You passed the max pressure mark some time before you got to the sticky bolt.

 

[std7mag]

NEVER run a borescope down a factory Savage barrel!!

You'll end up throwing away a barrel that shoots!

Sounds over pressured to me.
Hard bolt lift & ejector marks on the case head are my first indicators on my Savages.

 

[KMart]

When I have had a carbon ring issue, it made it hard to chamber a round as the bullet squeezing into the carbon ring created a lot of resistance. He says rounds chamber with no issue.
Also, a carbon ring would behave the same for all of the rounds for the last shooting session, not let several act normal and then give heavy bolt lift on the last couple.
IMO something else is going on here.

He said that he is jumping the bullet about .027", so his rounds may chamber without any problem

 

[Edd]

Do you not have any H1000 powder?

 

[barefooter56]

I worked up a load for a Savage 110 (24" Barrel) in 7mm Rem Mag that initially didn't show any signs of pressure, either on the brass, primer or with heavy bolt lift. Now I am getting heavy bolt lift after only a few rounds and am hoping you guys can shed some light on the issue. The load is as follows:

Nosler Brass (once fired, bought new and fire formed), trim length 2.485"
Berger 168gr Classic Hunter
62.5 grains of H4831SC
O-give: 2.740" (0.012" off the lands)
Primer: Fed 215

My chronograph indicates this load is running about 2810 fps with a SD of 5.3. During load development, I shot all the way up to 64.0gr of H4831SC with this same bullet (0.5 grain increments) and it did not show any signs of pressure. Seating depth was done at 0.003" at a time starting at the lands and working back until it was 0.027" off the lands. The barrel was broke in as follows: 1 shot and clean for first 5 rounds, then 5 rounds and clean until 30 rounds, and then normal cleaning after that. Load development was 30 rounds at a time and never experiences pressure issues.

The above load shot a 5 round group of 0.248" at 100 yards for verification and then a 1" group at 300 yards. 600 yards it shot at 2.5". When I was verifying the load at 300 and 600 yards, I noticed I was getting some HEAVY bolt lift. There was probably 60ish rounds thru it at this time and I figured it was time for cleaning. I cleaned the barrel and chamber thoroughly using a copper remover, nylon brush and patches.

This morning, my wife and I took it out to foul the barrel with a couple of rounds and practice before she takes it for elk season next weekend. The first 4 rounds were fine, no heavy bolt lift or flattened primers. The 5th round had a sticky bolt lift and the 6th and 7th rounds were HEAVY bolt lift again. I searched the forum and other web information for possibly causes. The loaded rounds have a brass length at trim length, o-give consistent at 2.740". Other brass measurements (neck OD, shoulder length, web diameter, etc) are all within spec. I have my sizing die setting the shoulder back about 0.002". Loaded rounds chamber and extract without issue.

I cleaned the rifle again this morning and made sure the chamber was clean and had no solvents or oil left in it...as I read this can cause excessive pressure as well. I read the overall length of the brass can cause pressure...checked this and it is at trim length. I am stuck as to what could be causing this and believe it is either carbon or copper build up that I am not getting to when I am cleaning. The borescope will be here this Wednesday.

Can anyone shed some light as to what might be causing the overpressure after only 5 rounds thru the gun? Any help is greatly appreciated. Thank you in advance!

You ever grease the back side of the bolt lugs?

 

[searcher]

It is possible your shoulders were not fully blown forward when you set them back .002". I'd measure your shoulder-to-base measurement on your reloaded ammo and compare it to a factory cartridge if you happen to have one. If your case is more than .010" LESS than the factory cartridge - this could easily be the culprit. What happens is your cartridge has enough space in the chamber to slam rearward on ignition, striking the bolt face, thereby causing the base of your brass to mushroom a bit, enough to cause the sticky extraction that is otherwise common to too hot of a load.

 

[MattM]

Searcher: The original new Nosler brass fed and fired without issue. The base to shoulder measurement was 2.102" on the new brass, 2.119" on the fired brass and when I sized it, I set it to 2.117". It is the reloaded brass that I have been experiencing the over pressure with...but not every shot. The first 4-5 shots after cleaning are fine but then it begins to show the signs of overpressure.

I still have about 50 new pieces of brass and thought about shooting 5 of those, then 5 of the reloads, and then another 5 reloads but setting the shoulder back to 2.110" just to see if it is a sizing issue.

Barefooter56: I had a light coat of oil on the bolt. I can't say for certain if I greased the bolt lugs.

Edd: No I don't have any H100....been looking but no luck so far.

 

[Coyotefurharvester]

I have some new brass, Rem, 2.493 length. I wouldn't trim under length. Set die to 0.004 under your max shoulder length and try 5. If still a tight extraction, revisit your ogive length(seems long). Something other than powder charge is off. No oil on bolt body, light grease on back side of lugs(handle side).

 

[MattM]

Just an update for anyone curious:
I loaded up some brand new brass with the same load combo to see if there were pressure signs. I ran some patches thru the barrel last night in order to see if the pressure signs went away. This morning I headed to the range with the new brass and some of my previous reloads that were showing the pressure signs.

I shot the previous reloads (once fired and shoulder set back 0.002") first. The first round was fine, no indications of pressure. The second round had heavy bolt lift. This continued thru all 10 rounds....the only good news is the 5 round group (including the cold bore shot) measured 0.184" when I was done. I then switched to the new brass with the same powder charge, o-give, bullet, etc. I had heavy bolt lift with ejector swipe on the first round. The second round the primer blew out of the casing. I stopped there.

This afternoon, the borescope showed up, so I was finally able to see what was going on inside the barrel. I have never used a borescope before but I figured a black carbon ring should show up. I will post photos of below. At the beginning of the barrel was a HEAVY black line that went all the way around the inside diameter of the barrel. I believe this is the carbon ring causing me the overpressure.

I broke out the cleaning supplies and used PATCH OUT as directed on the packaging. It sat in the barrel for about 2 hours and then I ran dry patches thru the barrel. I was amazed at the amount of junk coming out on the patches. I took another peek with the borescope and the HEAVY black line was starting to come out...some parts were still heavy but other areas were showing clean metal. I then used IOSSO bore cleaner paste with a brush and began scrubbing as directed on the packaging. Followed this with several patches and then borescope again. The line was now even more faded and not near as heavy.

The pics below are not the best but I think y'all will get the gist. I want to thank everyone for their insight and help!!

 

[PhilC]

Get some Boretech C4 and reduce your clean times. Boretch recommends nylon brushes, I do not, and instead use quality phosphor bronze brushes and flush with lacquer thinner or Brakleen immediately after use. Dirty to clean in less than an hour, and that's with 15min soak times in between brushing.

Wouldn't be a bad idea to get a chamber length guage and measure your actual chamber length (will need to sacrifice ONE case) so you know when you need to trim your brass. Carbon build up at the end of the chamber can cause problems too. You can just barely make out the area I'm referring to in your middle pic in top row.

 

[searcher]

Searcher: The original new Nosler brass fed and fired without issue. The base to shoulder measurement was 2.102" on the new brass, 2.119" on the fired brass and when I sized it, I set it to 2.117". It is the reloaded brass that I have been experiencing the over pressure with...but not every shot. The first 4-5 shots after cleaning are fine but then it begins to show the signs of overpressure.

I still have about 50 new pieces of brass and thought about shooting 5 of those, then 5 of the reloads, and then another 5 reloads but setting the shoulder back to 2.110" just to see if it is a sizing issue.

Barefooter56: I had a light coat of oil on the bolt. I can't say for certain if I greased the bolt lugs.

Edd: No I don't have any H100....been looking but no luck so far.

Searcher: The original new Nosler brass fed and fired without issue. The base to shoulder measurement was 2.102" on the new brass, 2.119" on the fired brass and when I sized it, I set it to 2.117". It is the reloaded brass that I have been experiencing the over pressure with...but not every shot. The first 4-5 shots after cleaning are fine but then it begins to show the signs of overpressure.

I still have about 50 new pieces of brass and thought about shooting 5 of those, then 5 of the reloads, and then another 5 reloads but setting the shoulder back to 2.110" just to see if it is a sizing issue.

Barefooter56: I had a light coat of oil on the bolt. I can't say for certain if I greased the bolt lugs.

Edd: No I don't have any H100....been looking but no luck so far.

Seems you have the shoulders dialed in. Barring your cases exceeding trim length for your actual chamber- or bullet being unknowingly jammed, it could be that the load is simply too hot for that load in your rifle. I looked in my Berger manual and it does not list the Classic Hunter 168 bullet - only the VLD target and VLD hunting bullets with H4832 SC as the powder being tested. I then looked on Berger's site - and I didn't see where they gave out load data for that bullet either. What they do show for the 168 bullets is 63.4 grains with approx. 2,904 fps max velocity. If you are substituting the classic hunter bullet for the VLD in any of the max loads - that could be a problem if the bearing surface is longer on the Classic Hunting bullet than the VLD versions - which is quite possible. That would take the pressure even higher than the "max" they publish in their manual. In my own experiences, the loads listed in the Berger manuals are quite tame compared to many of the manuals - but taking a near-max load and substituting the bullet with one which has a longer bearing surface could make it go from tame to pretty stiff. In a properly operating rig with a load that is not excessive, it can be completely void of lubricants and still open without hard bolt lift. While lube is great for reducing wear - the lack of it is not likely the source of your problem. I'd back the load off a full two grains and see where that gets you. If you are doing load development in warm weather and will hunt in cold weather - that would probably do it. If hunting in hot weather, I'd probably drop yet another grain. Good luck

 

[Bubba Boomstick]

I had an issue following book loads with a custom rifle I had built chambered in 300 PRC. Went through all kinds of gyrations to sort out the pressure issues with my Hornady brass.

I switched over to Peterson brass in 300 PRC and instantly, I was able to run the same gun and same powders without pressure signs following safe factory loads from the Hornady manual.