Primer piercing causes

[Laurie]

Question. Does the starline 556 brass have the larger diameter hole in the primer pocket like the starline 223 brass

All the 223 / 5.56 cases that I've ever met have standard traditional 2mm (0.078-inch) diameter flash-holes. This includes Starline 223 Rem.

I think you may be confusing this with Alpha and Starline's SRP cases for cartridges where other makers such as Peterson and Lapua use the smaller 1.5mm / 0.059-inch size in SRP (eg 308 Win and the Creedmoors).

 

[ELR LVR]

I did measure the base of the case immediately above the rim groove on the first firing when conducting a pressure test ladder and there was an increase of 0.001” on all cases at all charges.

I did not have any reference to tell me how much growth is too much. Consequently, I continued with loading and paying attention to primer seating force needed after each firing.
Where is the threshold between safe pressure and over-pressure?

You provide a value of .0001-.0002 of movement is max increase in diameter before reaching excess pressure. Where did you get that number from?

I was going to post that I always remembered that if the case head expansion is .0005" or more
You have already gone into OVER PRESSURE territory
Ideally there should be none, that is the web area and is the thickest part of the case
It is also very difficult to squeeze this area down to a smaller dimension and is one reason why cases get stuck in a die.
Since you asked another person where he got the data from and Since I could not remember my source of .0005" as over pressure as well - I conducted a quick search to provide some data for you

Which states:
The first manual recommended measuring case diameter just ahead of the case web and that the expansion from fired factory rounds should not be exceeded; the second manual suggested taking the measurement just in front of the extractor groove and stated that an increase of .013mm (.0005”) be considered as an indication of high pressure; the third manual said that measurements should be taken from only once-fired cases, and cases should be used for only three reloads due to the brass hardening. Their safe pressure criteria was an average case head expansion of .008mm (.0003”) with no readings over .0005”.


One authority, a gunwriter, says that measuring the case diameter at the pressure ring and then comparing it with the measurement taken from factory rounds is the most accurate method.

Measuring case-head expansion - Sporting Shooter

Two places to measure the expansion of cartridge case heads are the solid brass base in front of the extractor groove, and the pressure ring.

sportingshooter.com.au

You may continue doing as you wish but since you mentioned you have measured .001" on all cases of all charges of your fired cases...
....I must conclude that you are over pressurizing your cases, (but you already knew that by now)
Shoot for - NO EXPANSION in the case head /web / .200" line area

 

[Hengehold]

Why are you bumping 0.002? Or should ask why are you bumping?

When I FL size the case I am pushing the shoulder back .002”

 

[Hengehold]

I was going to post that I always remembered that if the case head expansion is .0005" or more
You have already gone into OVER PRESSURE territory
Ideally there should be none, that is the web area and is the thickest part of the case
Since you asked this other person where he got the data from and Since I could not remember my source of .0005" as over pressure as well - I conducted a quick search to provide some data for you

Which states:
The first manual recommended measuring case diameter just ahead of the case web and that the expansion from fired factory rounds should not be exceeded; the second manual suggested taking the measurement just in front of the extractor groove and stated that an increase of .013mm (.0005”) be considered as an indication of high pressure; the third manual said that measurements should be taken from only once-fired cases, and cases should be used for only three reloads due to the brass hardening. Their safe pressure criteria was an average case head expansion of .008mm (.0003”) with no readings over .0005”.


One authority, a gunwriter, says that measuring the case diameter at the pressure ring and then comparing it with the measurement taken from factory rounds is the most accurate method.

Measuring case-head expansion - Sporting Shooter

Two places to measure the expansion of cartridge case heads are the solid brass base in front of the extractor groove, and the pressure ring.

sportingshooter.com.au

You may continue doing as you wish but since you mentioned you have measured .001" on all cases of all charges of your fired cases...
....I must conclude that you are over pressurizing your cases, (but you already knew that by now)
Shoot for - NO EXPANSION in the case head /web / .200" line area

Thanks for the detailed reply.

My measurements were taken on virgin brass. I was measuring the movement from zero firings to the first firing. So I guess I need to conduct it again.

I will have to take this measurement again and start with a once fired case rather than a virgin case as the reference suggests.

 

[Hengehold]

With that chamber and 32-inches, your pressures should be fine at 2,790 fps. Top US FTR competitors run their 90s at 2,800 - 2,850 fps from 30-inch barrels, mostly with VarGet for the lower value and H4895 for the higher (at a cost in case-life though!). The one remaining question mark is Starline 223 case capacity. (I bought some recently to give them a try, but have yet to load and fire any, so don't have the fireformed-case 'water overflow capacity' yet to compare to Norma or Lapua 223. Their case weights are however relatively low which usually results in greater internal capacity.)

So, it looks like it may be a primer cup toughness allied to firing pin diameter and its clearance in the bolt face issue. Although Federal says its 205/205M 22.5 thou' thick cups are NATO standard, every other maker uses heavier 25 thou' cups for higher pressure applications. My own limited experience of the F205M is that is much more robust than thin Rem 6 1/2 / CCI-400 models, but not as tough as CCI-450/BR4s and (maybe) the Rem 7 1/2BR. So, before exploring firing pin turning / bolt bushing, I'd at least try one of them with your existing load.

There is a great deal of information about long-range 223 / 90gn FTR loads on the forum. Do a search of '223 90gn FTR' and also of @Ned Ludd who is a prolific source of good information on this combination on the forum.

Since my throat is .200-.300” longer than the load manual, I can presume than my chamber pressure is lower.

How much lower?

A huge amount! That's why Dave Kiff at PT&G and Manson produce the 223 ISSF and T15 respectively to accommodate 90s seated right out.

As an example of the difference between loads for the 90gn SMK provided by Vihtavuori and Sierra at their short COALs based on CIP and SAAMI standard 223 Rem chambers (25 thou' throat in the latter case) and your throat giving a 2.620-inch COAL, I ran QuickLOAD for Sierra 6th Ed manual's 2.43-inch COAL and H. VarGet in a 30.5 gn water capacity case (what Lapua comes out at with my minimum-SAAMI match chamber) in a 32-inch barrel. And then again at 2.620-inch. (Unlike N150, QuickLOAD's default powder values are pretty good for 223 and heavy bullets, and this is probably the favourite powder for the application anyway on your side of the Atlantic.)

2.43-inch COAL ....................... 23.3gn: 55,243 psi / 2,785 fps

Run that combination in your T15 chamber at 2.620-inch COAL, and the 23.3gn charge is calculated to produce 46,892 psi / 2,703 fps.

Using the pressure reduction produced by the long throat (not to forget the extra room in the case for powder below the bullet, and the charge increases to:

2.62-inch COAL ....................... 24.6gn: 54,770 psi / 2,827 fps

This is of course just a computer model and the usual caveats apply, but I'd reckon the PMax / MV differences won't be far out. @Ned Ludd may care to comment as he has considerable experience with actual loads and MVs for this powder and 90s in long throated chambers.

Great info. Thank you so much for taking the time to post this.

I’ll get the case H2O capacity and case weight of Starline 5.56 for you.

 

[ELR LVR]

Thanks for the detailed reply.

My measurements were taken on virgin brass. I was measuring the movement from zero firings to the first firing. So I guess I need to conduct it again.

I will have to take this measurement again and start with a once fired case rather than a virgin case as the reference suggests.

Yes, so you could fire a factory round which would be a safe gauge to measure and reference
then use that to compare to your reloaded cases

 

[big5ifty]

I did measure the base of the case immediately above the rim groove on the first firing when conducting a pressure test ladder and there was an increase of 0.001” on all cases at all charges.

I did not have any reference to tell me how much growth is too much. Consequently, I continued with loading and paying attention to primer seating force needed after each firing.
Where is the threshold between safe pressure and over-pressure?

You provide a value of .0001-.0002 of movement is max increase in diameter before reaching excess pressure. Where did you get that number from?

I've seen reference to the Speer #12 manual, I understand Vernon Speer used this method in compiling his load manual.

Reduce your charge to 2/10,000 expansion on virgin brass, and the primer problem should go away.

If that is the problem, and you feel that's not fast enough, increase the charge incrementally from there and stop at the point before you encounter the problem again.

 

[Webster]

Question. Does the starline 556 brass have the larger diameter hole in the primer pocket like the starline 223 brass. Just curious. A larger hole might suggest a brass change to a small hole might help.

A second thought. Take a really good look at the tip of the firing pin. And look for wear. The pin indent looks a little irregular in the pictures. Had that issue with a few firing pins along the way. The irregular shape and can initiate local stretching of the primer cup.

Lots of good info here. Two comments which probably don’t help.

• Guys talk about primer cup hardness. Hardness isn’t thickness. The primer manufacturers have the cup material cold rolled to a specified hardness. Of course, thickness also matters.
• Been shooting a Rem 700 since 1969. No problems with FP hole diameter. I use the appearance as a pressure indicator. Bushing the hole only hides signs of pressure it doesn’t eliminate the pressure. Spend the money if it makes you happy.

 

[kyotekiller25]

I'm not overly convinced that it's always an over pressure issue... Never was before you have the bolt bushed. And my 223 loads were doing it on the low to middle end, so it's definitely not just a pressure issue...Shooting 75s at 3K and 80s at 2950 from Bartlein 28" 8 twist. Bolt bushed, totally fixed it. To each their own, some guys are way over complicating this.

 

[LRPV]

Many years ago I read about bushing a firing pin. At that time guys were turning old 308 700’s into 6.5X47 and blanking primers. Then, the problem wasn’t so much a sloppy pin to hole fit. It was supposedly widely known to be because of the large diameter firing pin displacing too much material in a small rifle primer. Of course BR4’s and 450’s will help this a little as well as reducing loads but it is not fixing the problem as much as it is masking it. I admit I haven’t tried shooting many small rifle primers with a big diameter pin. I had my stuff bushed or simply bought with small firing pins from the get go.

There are so many different things that can cause primers to dimple and or pop. A weak firing pin spring can cause a big dimple when it bounces, effectively striking twice and making a guy think it’s one problem when it’s actually another.

 

[LCazador]

The number one reason for blanking primers is over pressure. How do you measure over pressure on a fired round? You start by measuring the head diameter at the .200" line on the virgin case. Then if you have an over pressure situation you measure the fired case. Any expansion over .0008" is over pressure. That load of 25.1 is over pressure IMO. The VitaVouri site lists a maximum load of 22.8 grains with N150. What is case head diameter now?

 

[Laurie]

Many years ago I read about bushing a firing pin. At that time guys were turning old 308 700’s into 6.5X47 and blanking primers. Then, the problem wasn’t so much a sloppy pin to hole fit. It was supposedly widely known to be because of the large diameter firing pin displacing too much material in a small rifle primer. Of course BR4’s and 450’s will help this a little as well as reducing loads but it is not fixing the problem as much as it is masking it. I admit I haven’t tried shooting many small rifle primers with a big diameter pin. I had my stuff bushed or simply bought with small firing pins from the get go.

There are so many different things that can cause primers to dimple and or pop. A weak firing pin spring can cause a big dimple when it bounces, effectively striking twice and making a guy think it’s one problem when it’s actually another.

I 100% agree. To illustrate this, here's a pic I've shared many times before. It was from a 308 Win FN SPR (Special Police Rifle) I had rebarreled to the then new 6.5X47mm. The actions on these things were selected Winchester M70 with pre-64 external extractor type bolts. Very well made; little pin to aperture clearance. It never, ever produced even the mildest of craters in its original 308 Win form (all LRP type back then) with the softest LR primer despite some stiff heavy-bullet handloads. However, it did have the fattest firing pin tip I've ever seen on a commercial rifle. Beautifully smooth and perfectly rounded, but really large diameter.

When I had a 'proper' FTR 308 built, I didn't have much use for the rifle, and rather than sell it, it seemed a good idea to have it rebarreled to the then new and very 'hip' 6.5X47L. Result: every primer was cratered to some extent and two or three in a box of 50 'blanked'. Ah ..... 'High pressures!' I hear @LCazador say. Only this was with 123 Scenars and Viht's very mild starting loads. The chronograph confirmed these were weak as water low-MV, hence pressure rounds.

After several primer model changes without significant improvement, the barrel was rechambered to 260 Rem and only ever loaded with LRP brass. Again, despite some stout loads, no cratering never mind 'blanking'.

 

[Laurie]

The first manual recommended measuring case diameter just ahead of the case web and that the expansion from fired factory rounds should not be exceeded; the second manual suggested taking the measurement just in front of the extractor groove and stated that an increase of .013mm (.0005”) be considered as an indication of high pressure; the third manual said that measurements should be taken from only once-fired cases, and cases should be used for only three reloads due to the brass hardening. Their safe pressure criteria was an average case head expansion of .008mm (.0003”) with no readings over .0005”.

At least one of these is from the older Speer manuals. Go back far enough to when copper crusher pressure measurement was the norm, and the bullet makers (all small companies at that time) used this method for most if not all chamberings for cost reasons.

I first read of this in my earliest Speer manual back sometime in the early 80s. Apart from describing the methodology, it noted that a special blade micrometer had to be used whose readings were regularly verified and that doing this job consistently required considerable experience and skill.

Here's what Speer's #10 (1994) says about this method after covering the copper crusher and Piezo crystal methods the company now used:

"When the cartridge is a non-SAAMI cartridge like a wildcat, an obsolete or obscure foreign cartridge, normal crusher or Piezoelectric opressure testing will likely not be possible. In these cases, an older and less precise method of pressure assessment is used.

.................... [after describing the point on the case where measurements should be taken, ie as per @ELR LVR's description and immediately above the extractor groove.] ..........

"Case head expansion testing should be made with once-fired cases of the same make and from the same production lot. The hardness of cartridge brass varies; a softer lot of brass will will deform at lower pressures than a lot made from harder brass. For measurement a blade micrometer accurate to 0.0001" is mandatory. .....................

"New cases can give deceptive readings. The first firing of any case will usually cause more deflection of the brass than subsequent firings. .................

"........... Once-fired cases are loaded and each one is carefully measured. After firing, each case is measured again and the difference in diameter is calculated. We look for an average expansion of 0.0003" with no individual reading over 0.0005". You can see this is very slow and precise work. Case-head exapnsion is measuring 0.0003 to 0.0005" is generally accepted as representing pressures in the 50,000 c.u.p. range with typical cases.


Note the use of cases (plural) and average readings (plural), same lot and so on as well as the base unfired measurement mustn't be used as a base value. This isn't as simple a method or issue as some posts imply.

Re the '.200' line, a quote from a post in another topic by @Alex Wheeler

This number has caused a lot of confusion. When you are designing a reamer and a die you are concerned with the brass just above the solid web. This is where it expands to fit the chamber and where clickers usually come from if the design is not right. This is not always at the .200 line. The .200 line is just a spot on the print. They could have made it a .250 or .300 line. It doenst mean anything. In some cases the .200 line is still solid brass and doesnt expand so if your measuring it you will get into trouble. In other cases if you measure the widest part of the case and you want to compare it to the chamber you need to do the math to know what the chamber measures in that spot. Just some thing to consider for those playing with this stuff.

As Alex points out, this line may or may not be on the solid web. For the chamber / reamer designer this shoul;d be above the web for a good case to chamber fit and avoidance of 'clickers'. However, according to Speer and others when case-measurement is used to judge loads for safe or excessive pressure, measurement must be on the solid web.

For those who've posted that a factory cartridge's expansion should be used as a base for comparison, note what Speer's technicians say about the micrometer method requiring same make and lot of brass throughout. Introducing a factory round would potentially produce an 'apples and oranges' comparison. (Speer and others note that the modern electronic measurement results need to be compared to specially loaded industry standard reference cartridges that they purchase in order to calibrate the individual transducer unit's outputs.)

 

[Webster]

I would like to know what can be the root cause of pierced primers.

I pierced two primers today and two more had primer flow back into the firing pin hole. I can feel it raised up over the rest of the primer. I was doing load development in a new-to-me cartridge.
Day 1: I shot about 40 rds with this load, the temp was 70 degrees outside. No primer or pressure signs on any of the cases.
Day 2: I shot 25 more rds of the same load when it was 40 degrees. I pierced two primers (see pic) and two additional cases had primer metal flowing into the firing pin hole (see second pic). No additional signs of pressure were experienced (no sticky bolt lift, no ejector swipe on the brass, primer pockets are still tight after day 1, etc)

Cartridge specs:
-223 Rem,
-Starline 5.56 brass,
-Fed 205M,
-25.0gr of N150,
-90gr Sierra SMK (naked).
-Loaded rd NK has .004” clearance on either side.
-Brass times fired: 2, 3, & 4 times fired, segregated into separate lots.
-OAL without comparator: 2.620”
-Muzzle velocity: 2790

I believe the primer issues are from something other than excessive pressure. Although, I acknowledge that I am toeing the line for max pressure. Maybe someone can check my chamber pressure with quick load?

2. The only other cause of pierced primers that I am aware of is excessive space in firing pin hole.

Action specs: (Pierce, Rem700 clone). I have only fired 150 rds through the action so can’t say if this a trend associated with the action yet.
Barrel: 32”

I am thinking the root cause of the primer piercing is due to excessive space in the firing pin hole and not pressure. Am I wrong? Is there another causal factor that I am not aware of?

-Trevor

Can someone comment on why the pieced primers have the metal pushed into the hole. You would think 55,000 PSI would push outward? I guess the cup slams against the bolt face, does the gas then push the FP backward compressing the spring then it hits twice?

 

[shoot4fun]

I 100% agree. To illustrate this, here's a pic I've shared many times before. It was from a 308 Win FN SPR (Special Police Rifle) I had rebarreled to the then new 6.5X47mm. The actions on these things were selected Winchester M70 with pre-64 external extractor type bolts. Very well made; little pin to aperture clearance. It never, ever produced even the mildest of craters in its original 308 Win form (all LRP type back then) with the softest LR primer despite some stiff heavy-bullet handloads. However, it did have the fattest firing pin tip I've ever seen on a commercial rifle. Beautifully smooth and perfectly rounded, but really large diameter.

When I had a 'proper' FTR 308 built, I didn't have much use for the rifle, and rather than sell it, it seemed a good idea to have it rebarreled to the then new and very 'hip' 6.5X47L. Result: every primer was cratered to some extent and two or three in a box of 50 'blanked'. Ah ..... 'High pressures!' I hear @LCazador say. Only this was with 123 Scenars and Viht's very mild starting loads. The chronograph confirmed these were weak as water low-MV, hence pressure rounds.

After several primer model changes without significant improvement, the barrel was rechambered to 260 Rem and only ever loaded with LRP brass. Again, despite some stout loads, no cratering never mind 'blanking'.

View attachment 1706104

If your SPR was made well before they got the word that FN was closing the CT factory then it was "special" but the one I had was definitely NOT. After three scopes would not zero at 100 yards (all three shot 2 feet right of the X) I sent it back. I got a call from a fellow industry guy who was straight up with me. The receiver had been drilled incorrectly, making the scope base point away from the barrel and the rifle was junk.
The first thing that strikes me in your pic is the off-center strikes on all primers. The cratering, IMO, is not pressure as I see no leakage around the primers and they are not flattened from over pressure.
If I am looking at this all wrong please enlighten me, as you are very knowledgeable .

 

[shoot4fun]

I would like to know what can be the root cause of pierced primers.

I pierced two primers today and two more had primer flow back into the firing pin hole. I can feel it raised up over the rest of the primer. I was doing load development in a new-to-me cartridge.
Day 1: I shot about 40 rds with this load, the temp was 70 degrees outside. No primer or pressure signs on any of the cases.
Day 2: I shot 25 more rds of the same load when it was 40 degrees. I pierced two primers (see pic) and two additional cases had primer metal flowing into the firing pin hole (see second pic). No additional signs of pressure were experienced (no sticky bolt lift, no ejector swipe on the brass, primer pockets are still tight after day 1, etc)

Cartridge specs:
-223 Rem,
-Starline 5.56 brass,
-Fed 205M,
-25.0gr of N150,
-90gr Sierra SMK (naked).
-Loaded rd NK has .004” clearance on either side.
-Brass times fired: 2, 3, & 4 times fired, segregated into separate lots.
-OAL without comparator: 2.620”
-Muzzle velocity: 2790

I believe the primer issues are from something other than excessive pressure. Although, I acknowledge that I am toeing the line for max pressure. Maybe someone can check my chamber pressure with quick load?

2. The only other cause of pierced primers that I am aware of is excessive space in firing pin hole.

Action specs: (Pierce, Rem700 clone). I have only fired 150 rds through the action so can’t say if this a trend associated with the action yet.
Barrel: 32”

I am thinking the root cause of the primer piercing is due to excessive space in the firing pin hole and not pressure. Am I wrong? Is there another causal factor that I am not aware of?

-Trevor

5.56 brass, IIRC, generally has less internal volume than .223 brass. It appears to me that the cratered/not pierced primers leaked gas around them and, per the cthart provided above, the 205M has the smallest diameter of any of those listed. If you happened to loosen the pockets in previous firings then that could be a reason for both cratering and piercing.
I have a R700 that is bushed to .060 and chambered to shoot the 90's (long throat). Like you, I load to a much longer COAL than the manuals show their testing with. I know my bullet seating depth isn't taking up a lot of space but is still slightly crushing RL15.5 powder. Initially, I built the rifle thinking that there shouldn't be a great difference in powder charges (using Varget) than I used successfully for years with the 80 grain 223 loads. WRONG!!!! The difference was greater than expected and velocity was so much lower than I could get with the other rifle, a 7.7 twist, that I was actually losing ground with the 90's in both elevation and windage. Why? I surmise it was due to the new barrel being a 6.5 twist and the arguably longer bearing surface of the 90's.
Now, here's the thing about having a bolt bushed; I've had other rifles with bushed bolts (using large primers) that never showed pressure signs but ruined primer pockets by over expansion due to excessive pressure.
Those loads were with published data!

 

[Hengehold]

My bolt is nitride coated so I will have to call Pierce to see if bushing the firing pin is even possible.

 

[Hengehold]

With that chamber and 32-inches, your pressures should be fine at 2,790 fps. Top US FTR competitors run their 90s at 2,800 - 2,850 fps from 30-inch barrels, mostly with VarGet for the lower value and H4895 for the higher (at a cost in case-life though!). The one remaining question mark is Starline 223 case capacity. (I bought some recently to give them a try, but have yet to load and fire any, so don't have the fireformed-case 'water overflow capacity' yet to compare to Norma or Lapua 223. Their case weights are however relatively low which usually results in greater internal capacity.)

So, it looks like it may be a primer cup toughness allied to firing pin diameter and its clearance in the bolt face issue. Although Federal says its 205/205M 22.5 thou' thick cups are NATO standard, every other maker uses heavier 25 thou' cups for higher pressure applications. My own limited experience of the F205M is that is much more robust than thin Rem 6 1/2 / CCI-400 models, but not as tough as CCI-450/BR4s and (maybe) the Rem 7 1/2BR. So, before exploring firing pin turning / bolt bushing, I'd at least try one of them with your existing load.

There is a great deal of information about long-range 223 / 90gn FTR loads on the forum. Do a search of '223 90gn FTR' and also of @Ned Ludd who is a prolific source of good information on this combination on the forum.

Since my throat is .200-.300” longer than the load manual, I can presume than my chamber pressure is lower.

How much lower?

A huge amount! That's why Dave Kiff at PT&G and Manson produce the 223 ISSF and T15 respectively to accommodate 90s seated right out.

As an example of the difference between loads for the 90gn SMK provided by Vihtavuori and Sierra at their short COALs based on CIP and SAAMI standard 223 Rem chambers (25 thou' throat in the latter case) and your throat giving a 2.620-inch COAL, I ran QuickLOAD for Sierra 6th Ed manual's 2.43-inch COAL and H. VarGet in a 30.5 gn water capacity case (what Lapua comes out at with my minimum-SAAMI match chamber) in a 32-inch barrel. And then again at 2.620-inch. (Unlike N150, QuickLOAD's default powder values are pretty good for 223 and heavy bullets, and this is probably the favourite powder for the application anyway on your side of the Atlantic.)

2.43-inch COAL ....................... 23.3gn: 55,243 psi / 2,785 fps

Run that combination in your T15 chamber at 2.620-inch COAL, and the 23.3gn charge is calculated to produce 46,892 psi / 2,703 fps.

Using the pressure reduction produced by the long throat (not to forget the extra room in the case for powder below the bullet, and the charge increases to:

2.62-inch COAL ....................... 24.6gn: 54,770 psi / 2,827 fps

This is of course just a computer model and the usual caveats apply, but I'd reckon the PMax / MV differences won't be far out. @Ned Ludd may care to comment as he has considerable experience with actual loads and MVs for this powder and 90s in long throated chambers.

Starline 5.56:
Case weight without primer: 95.4, 95.0, & 94.6gr
H2O capacity: 29.2 gr

Lapua 223 for comparison (lot 4PH5003):
Case weight: 96.4, 96.4, & 96.3gr
H2O capacity: 29.0 gr

 

[tommeboy]

556 brass has more volume not less. 7.62x51 brass is where it has less case volume. Change your firing pin spring to a extra power one and then go from there if you need the bolt bushed.

 

[SeabeeKen]

Your load is 25 gr n150
Vv data for 90 gr berger and sierra is 22.8 and 22.5 gr
The load is hot by over 2 gr
I agree with Laurie, n150 is not the best choice here