Pressure signs

jshepherd61

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Joined
Dec 28, 2015
Messages
289
Location
Parker
I’m trying to identify pressure signs and I think I have too many variables in the mix.

The easiest sign to identify seems to be bolt lift. A heavy bolt is hard to not identify. The question is whether a heavy bolt lift is a pressure sign or something else? What causes heavy bolt lift? I assume it’s the case expanding at the shoulders and the shoulder rubbing as it’s rotated to free the bolt when the handle is lifted? If this is true, it has to be a relative amount because all cases expand, so some expansion is ok and the bolt doesn’t get heavy, but excessive Pressure causes excessive expansion which causes heavy bolt lift?

Last night i shot virgin h1000 and 1x reloaded rl26 out of my 7 Saum. I was trying to find pressure and got a stiff bolt immediately from the 1x fired rl26. I had bumped the shoulders back .002-.003 and the bolt closed easily on the loaded rounds. I find it hard to believe I was hitting pressure already but the bolts were noticeably stiff (starting load 59.1gr and 2576fps out of a 20” barrel.

On my last round of h1000 I got a stiff bolt but no other signs of pressure. I just measured the shoulder and it was longer than the other virgin h1000 shoulders that I fired last night by .002”. So I assume I hit pressure there? That was with 64.6gr h1000 in adg brass with a 180eldm out of a 7saum. No ejector smear, no flat primer. A little mark where the cutout on the bolt face where the extractor is.

I never saw any extractor smears or flat primers or cratering on any brass h1000 or rl26. Just variations in bolt lift.

Im not even sure what help I’m asking for…I’m just confused! I am FL sizing and shoulder bumping, but am I doing something wrong on the 1x fired brass to cause the bolt lift? Should I ignore bolt lift and keep an eye out for primer/ejector signs?
Here are a couple of pictures. Not sure if they’ll help.

the gun shoots great, just trying to get into the 2700-2750fps range. The ladder test was 625 yards. The wind shifted from north to south at the end of the h1000 which explains the last 3 hitting far left.

I got out of order on the h1000 at the end as you can see on my note pad. Smh
Normally in magnums you’ll have a slight primer flattening you can only see after punching the primer before your bolt lift is pressured! That is a good notification you are getting close, but you can’t see it unless you punch the primer. If you can see the primer flattened or protruding crater on the primer before you punch it you normally already have a slight restriction on bolt lift! Just what I have found
 

Tiny Tim

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Joined
Jan 26, 2015
Messages
973
Along with oil in chamber, is it possible that your brass had lube on it from sizing? You did not specify if virgin brass was sized. Also, how far off the lands are you. Too close or jammed can cause issues. Forgive me if I missed it.
 

Jeffrey Van Zandt

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Joined
Feb 26, 2013
Messages
524
Location
tok
I’m trying to identify pressure signs and I think I have too many variables in the mix.

The easiest sign to identify seems to be bolt lift. A heavy bolt is hard to not identify. The question is whether a heavy bolt lift is a pressure sign or something else? What causes heavy bolt lift? I assume it’s the case expanding at the shoulders and the shoulder rubbing as it’s rotated to free the bolt when the handle is lifted? If this is true, it has to be a relative amount because all cases expand, so some expansion is ok and the bolt doesn’t get heavy, but excessive Pressure causes excessive expansion which causes heavy bolt lift?

Last night i shot virgin h1000 and 1x reloaded rl26 out of my 7 Saum. I was trying to find pressure and got a stiff bolt immediately from the 1x fired rl26. I had bumped the shoulders back .002-.003 and the bolt closed easily on the loaded rounds. I find it hard to believe I was hitting pressure already but the bolts were noticeably stiff (starting load 59.1gr and 2576fps out of a 20” barrel.

On my last round of h1000 I got a stiff bolt but no other signs of pressure. I just measured the shoulder and it was longer than the other virgin h1000 shoulders that I fired last night by .002”. So I assume I hit pressure there? That was with 64.6gr h1000 in adg brass with a 180eldm out of a 7saum. No ejector smear, no flat primer. A little mark where the cutout on the bolt face where the extractor is.

I never saw any extractor smears or flat primers or cratering on any brass h1000 or rl26. Just variations in bolt lift.

Im not even sure what help I’m asking for…I’m just confused! I am FL sizing and shoulder bumping, but am I doing something wrong on the 1x fired brass to cause the bolt lift? Should I ignore bolt lift and keep an eye out for primer/ejector signs?
Here are a couple of pictures. Not sure if they’ll help.

the gun shoots great, just trying to get into the 2700-2750fps range. The ladder test was 625 yards. The wind shifted from north to south at the end of the h1000 which explains the last 3 hitting far left.

I got out of order on the h1000 at the end as you can see on my note pad. Smh
 

timkaul

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LRH Team Member
Joined
Feb 24, 2020
Messages
2
Location
Arizona
I have a 7SAUM using RL26 and ADG brass. Had the same problems with over pressure signs. My gunsmith told me that the short fat cartridges can get "sticky" on reloads when the shoulder is not bumped enough. I bumped back more (in my I bumped .004-.005) and it solved issues. Accuracy is still fine.
 

Ucsdryder

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Joined
Jan 23, 2016
Messages
324
Along with oil in chamber, is it possible that your brass had lube on it from sizing? You did not specify if virgin brass was sized. Also, how far off the lands are you. Too close or jammed can cause issues. Forgive me if I missed it.
I’m way off the lands…whole different story!
Have you shot this rifle before this? Any problems?
New rifle. Gunsmith was supposed to custom throat off supplied dummy rounds. I wanted the bullets 020” off the lands. Gun came back .120” off the lands with 175 eldx, probably the longest bullet made in that class. So it’s jumping a ton. I’m not happy about it…
 

KSAv8r

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Joined
Dec 5, 2014
Messages
54
Location
Colorado
I assume your 7 SAUM is a custom build. I had a similar problem with a factory Savage 110BA .338 Lapua Mag with a heavy bolt lift with even light loads. According to a thread on another forum, Savage cut the chamber to minimum SAMMI specs. Bumping the shoulder back .004-.005" on Lapua brass solved the problem.

As some noted previously, it could be a combination of several things like a tight chamber, slight amount of oil left in the chamber from cleaning, differences in brass, etc. Please let us know what you find with your testing.
 

Finsta

Member
Joined
Jul 14, 2021
Messages
21
Location
Pa
Normally in magnums you’ll have a slight primer flattening you can only see after punching the primer before your bolt lift is pressured! That is a good notification you are getting close, but you can’t see it unless you punch the primer. If you can see the primer flattened or protruding crater on the primer before you punch it you normally already have a slight restriction on bolt lift! Just what I have found
Me too with my Kimber wissum. But not my Browning in the same cartridge. For a last resort I might have the lugs lapped and chamber polished. Maybe have .001 taken off chamber in a spot or two.
 
Last edited:

MagnumManiac

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Joined
Feb 25, 2008
Messages
3,941
All good info so far.
To eliminate possibilities, you now need to take measurements.
First off, measure these points on a NEW piece of brass.
.200” up from the base, you can use you caliper to scribe a line there.
The neck diameter, without a bullet, and with a bullet.
The shoulder position with a set of headspace comparators.
With a fired case, measure all of these again.
Regarding neck clearance in the chamber, it should be a MINIMUM of .003” LARGER than a neck with a bullet in it. My personal max is .005”, but I see many at .006”.
The measurement at .200” up from the base is critical, it should not be more than .005”. And, it should measure the same ALL THE WAY AROUND THE CASE DIAMETER. If it changes, your chamber is an egg shape. I use a micrometer accurate to .0001” for measuring case diameter, a caliper is not accurate enough.
Check how a fired case feels when you chamber it after firing when the case is cold. If there is resistance, then your chamber may not be round. In that case, use a sharpie and colour in the entire case and carefully chamber it and carefully remove it, I normally do this with the firing pin assembly removed and the plunger ejector, if one is fitted.
Look to see if only one side or the ink rubs off.
Give all this a go, and get back to us with before and after measurements, the answer lies there somewhere if it truly isn’t a pressure issue.

Cheers.
 

Carlos88

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LRH Team Member
Joined
Dec 16, 2020
Messages
660
Location
Benbrook TX 76126
I’m trying to identify pressure signs and I think I have too many variables in the mix.

The easiest sign to identify seems to be bolt lift. A heavy bolt is hard to not identify. The question is whether a heavy bolt lift is a pressure sign or something else? What causes heavy bolt lift? I assume it’s the case expanding at the shoulders and the shoulder rubbing as it’s rotated to free the bolt when the handle is lifted? If this is true, it has to be a relative amount because all cases expand, so some expansion is ok and the bolt doesn’t get heavy, but excessive Pressure causes excessive expansion which causes heavy bolt lift?

Last night i shot virgin h1000 and 1x reloaded rl26 out of my 7 Saum. I was trying to find pressure and got a stiff bolt immediately from the 1x fired rl26. I had bumped the shoulders back .002-.003 and the bolt closed easily on the loaded rounds. I find it hard to believe I was hitting pressure already but the bolts were noticeably stiff (starting load 59.1gr and 2576fps out of a 20” barrel.

On my last round of h1000 I got a stiff bolt but no other signs of pressure. I just measured the shoulder and it was longer than the other virgin h1000 shoulders that I fired last night by .002”. So I assume I hit pressure there? That was with 64.6gr h1000 in adg brass with a 180eldm out of a 7saum. No ejector smear, no flat primer. A little mark where the cutout on the bolt face where the extractor is.

I never saw any extractor smears or flat primers or cratering on any brass h1000 or rl26. Just variations in bolt lift.

Im not even sure what help I’m asking for…I’m just confused! I am FL sizing and shoulder bumping, but am I doing something wrong on the 1x fired brass to cause the bolt lift? Should I ignore bolt lift and keep an eye out for primer/ejector signs?
Here are a couple of pictures. Not sure if they’ll help.

the gun shoots great, just trying to get into the 2700-2750fps range. The ladder test was 625 yards. The wind shifted from north to south at the end of the h1000 which explains the last 3 hitting far left.

I got out of order on the h1000 at the end as you can see on my note pad. Smh
Their are several indicators used to identify excessive pressure with no hard and fast rules. Flattened primers, hard bolt lift, higher than "normal" velocities, harder than normal recoil, blown primers,etc.

The hard bolt lift can also be rough bolt recess, misaligned lugs or 100% lug contact, improperly drilled chamber with an almost imperceptible bulge, a tight neck,etc. I had a factory .270 Win. that had that condition (bulge) and rebarreled it, had a 6.5x55 that had a "crooked" neck. Rebarreled it as well. The brass rotates when you raise the bolt so also inspect the extractor and the extractor groove. I had a Remington with an out of spec extractor and it was ruining the groove.

Measure the web of the cartridge before and after firing, look for scratches or bulges on the brass and an sufficient bullet release (narrow neck or case not too long). Also inspect the bolt face for any irregularities. It can also be a trigger reset issue.

Hope you figure it out.
 

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