Bolt Rifle loads versus AR loads question

My question is about a particular cartridge/load that I use in my bolt rifle does not show pressure signs, but the same cartridge/load in an AR shows pressure signs and pretty much trashes the primer pocket? I use an adjustable gas block and believe I have it set correctly, but I still have to back the load down by .7gr from the bolt rifle load for the brass to survive.
Both chambers were cut with the same reamer, so I guess I would like to know if this issue is somewhat normal, or if I need to look at something else.

Thanks,
Gene
 
There's a couple things I can think of here, first of all the barrels are different, even though cut with the same reamer so it could just be that.

Next, in my experience adjusting gas systems, if you shut the gas completely down you will find out what is actual pressure signs, vs what is actually a timing issue. It's really tough to walk that line with some rounds and powder selection plays a big part of it.
 
Originally Posted By: 204 ARThere's a couple things I can think of here, first of all the barrels are different, even though cut with the same reamer so it could just be that.

Next, in my experience adjusting gas systems, if you shut the gas completely down you will find out what is actual pressure signs, vs what is actually a timing issue. It's really tough to walk that line with some rounds and powder selection plays a big part of it.

204AR, I got to thinking the same thing...going to shut the gas down and see if it still loosens the primer pocket. This is what is kind of odd about this whole thing...it doesn't really hurt the rim or head of the casing, but will loosen the primer pocket...and this is with the charge backed off .7gr of powder. I realize different barrels do act differently...this barrel is twisted the same as my bolt rifle, so I wasn't expecting to have to reduce the load as much as I have and still getting loose pockets but not really damaging the brass.
The cartridge is 22-204, 1-12 twist, 22" barrel. It shoots great, just seems to be a little rough on primer pockets. My bolt rifle at .7gr more of the same powder doesn't hurt the brass at all.
Going to shut the gas off and fire a round and see what it does...not sure what to do if it is a timing issue though.
Thanks for the response and I will keep working on it.

Gene
 
Originally Posted By: DiRTY DOGWhat cartridge?

DD, it is a wildcat...22-204, 12 twist, 22" long. Powder used is IMR8208 and Rem 7 1/2 primers. Everything is the same as my bolt rifle. I run my bolt rifle at 3685fps with 53gr bullet...backing off the charge in the AR .7gr is reducing about 150fps, which is still a respectable 3540ish, but it will still loosen the primer pocket enough that after one more loading/firing, the pocket is too loose.
Rifle shoots the load really well, so not a question of accuracy, just wasn't expecting this drastic of a difference between the 2 rifles...same brass, same powder, same primer, same bullet, same bbl twist rate...the AR was built with all new components and hasn't had a whole lot of rounds thru it yet so maybe it still needs to wear in some.

Thanks
Gene
 
This is an interesting one! All I can think of is the bolt holds all in place until case pressure is nil and the semi-auto bolt starts opening while there is still pressure inside the chamber so the casing might expand and then contract past the chamber dimension and cause the issue somehow. If the gas block were closed and the bolt locked shut on firing then all should be the same. The bullet jump would have to be identical in both chambers, which I assume they are if you used the same reamer. I could see a slight diff in 2 'identical' chambers as they would not be reamed so evenly to the 1000th but what you describe is more severe.

The obvious difference is the barrels and the type of rifling and finished inside diameters but one would have to think that owuld be pretty standardized or our loading books would indicate otherwise.
 
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Reading between the lines, the barrels are from different manufacturers, so that could possibly be the difference. Some barrels will/can allow you to run more powder. Case in point, one of my 22-204's is a 5R, and I can run a half grain more powder in that barrel than my other 4 grooves.

Another thing I've seen is that custom actions may/can allow you run more pressure than a run of the mill factory gun. An AR doesn't have the tight lockup of a bolt gun with a relatively massive 2/3 lug design, which I believe is part of why the pressures are limited to the 52K range versus another 10K+ in bolt guns.

There's such a thing as the barrel not being indexed properly prior to chambering, and the runout at the base wallows out a fatter web dimension, letting the pockets open up. Measure fire brass at the base with a good set of micrometers to compare.

What ever the reason, the web is expanding more than your bolt gun is, and is expanding the primer pockets, which normally is a pressure problem.
 
Originally Posted By: alfReading between the lines, the barrels are from different manufacturers, so that could possibly be the difference. Some barrels will/can allow you to run more powder. Case in point, one of my 22-204's is a 5R, and I can run a half grain more powder in that barrel than my other 4 grooves.

Another thing I've seen is that custom actions may/can allow you run more pressure than a run of the mill factory gun. An AR doesn't have the tight lockup of a bolt gun with a relatively massive 2/3 lug design, which I believe is part of why the pressures are limited to the 52K range versus another 10K+ in bolt guns.

There's such a thing as the barrel not being indexed properly prior to chambering, and the runout at the base wallows out a fatter web dimension, letting the pockets open up. Measure fire brass at the base with a good set of micrometers to compare.

What ever the reason, the web is expanding more than your bolt gun is, and is expanding the primer pockets, which normally is a pressure problem.

Nothing special on the rifling...the bolt gun is a Muller barrel and the AR is an Xcaliber...neither are 5R or Polygonal rifled. From what I am getting on headspace measurement wise between the 2 rifles is that the AR has about .002 more headspace than the bolt gun which isn't really bad when the rifles were done by 2 different gunsmiths with the same reamer. The bolt gun is a Rem 700 action, so not custom.
I did re-adjust the gas block today doing some experimenting and I think the AR might have been over gassed. I took 3 pieces of new brass and started out .5gr below my bolt gun load. Closed the gas off and fired the 3 pieces of brass about 8 times till the bolt would cycle properly and lock open on last shot. Primer pockets remained as new on 2 of the 3 pieces and the 1 loosened slightly but was still good. This gas block is designed to be adjustable with a throw lever for running suppressed and non-suppressed, so I then loaded the same 3 pieces of brass 3 more times getting the gas block set for suppressed...all 3 primer pockets stayed the same...then went to firing suppressed and non suppressed another 4 loadings on the same 3 pieces of brass and they are still going strong. Everything on this build was new and I think the initial settings on the gas block needed adjusted some more after the rifle got wore in some...and I may not have had it adjusted very close either. For now it seems to be doing fine with .5gr less than the bolt rifle...I can live with this...especially with the brass holding up to 15 reloadings and still staying good on primer pockets. I will experiment with bumping the load up a little closer to the bolt rifle load and seeing what it does, but for now it seems to be OK where it is. I really think I had to open up the gas more when everything was new and as it wore in it was getting too much gas. I now go only 3 clicks on the gas lever from suppressed to non-suppressed and it originally took 5 clicks to fully function both ways.
Thanks to all for the insight...appreciate it very much.

Gene
 
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Originally Posted By: tesoroThis is an interesting one! All I can think of is the bolt holds all in place until case pressure is nil and the semi-auto bolt starts opening while there is still pressure inside the chamber so the casing might expand and then contract past the chamber dimension and cause the issue somehow. If the gas block were closed and the bolt locked shut on firing then all should be the same. The bullet jump would have to be identical in both chambers, which I assume they are if you used the same reamer. I could see a slight diff in 2 'identical' chambers as they would not be reamed so evenly to the 1000th but what you describe is more severe.

The obvious difference is the barrels and the type of rifling and finished inside diameters but one would have to think that owuld be pretty standardized or our loading books would indicate otherwise.
tesoro, I agree with everything you said...barrels are different manufacturers, but no special rifling type...just standard 12 twist rifling. See my write up below after doing some experimenting/adjusting today.
Appreciate the feedback...thanks

Gene
 
Bore dimensions can vary as well, so a tighter bore could yield higher velocities/pressures with the same loads between barrels.

Different lot numbers of bullets can be a factor too. I've seen 1 thou difference in diameters before.
 
Well there ya go! I guess the casings were over expanding at the web from not being fully contained by the chamber when there was still significant pressure.
 
Originally Posted By: tesoroWell there ya go! I guess the casings were over expanding at the web from not being fully contained by the chamber when there was still significant pressure.
Ya, but the only thing that was throwing me off was the fact that the brass wasn't getting torn up. Usually in an over gassed rifle the rims get torn up and the case heads get some swipe marks. I wasn't getting any of this...just loose pockets after firing. Just goes to show that the normal signs don't always show up.

Gene
 
Originally Posted By: alfBore dimensions can vary as well, so a tighter bore could yield higher velocities/pressures with the same loads between barrels.

Different lot numbers of bullets can be a factor too. I've seen 1 thou difference in diameters before.
Yes, different barrels will not always perform the same due to dimensional discrepancies. I am fine if I have to stay at .5gr under my bolt rifle load as long as I can get more than 2 loads out of a piece of brass before the pocket goes away...and it appears that this is working now.

Gene
 
Glad you got it figured out, and I want to hear more about this round. Basically a 222 mag, improved, I always figured it should work but haven't heard of anyone doing it in an AR. That's pretty impressive speed and about 100 fps more than I'm getting out of my 223AI with RP (soft) brass and 8208 with 53's.

I'm also curious what brass you're using.
 
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Originally Posted By: 204 ARGlad you got it figured out, and I want to hear more about this round. Basically a 222 mag, improved, I always figured it should work but haven't heard of anyone doing it in an AR. That's pretty impressive speed and about 100 fps more than I'm getting out of my 223AI with RP (soft) brass and 8208 with 53's.

I'm also curious what brass you're using.
204AR, I am using Winchester brass. You might call it a 222mag improved, but if you looked at a 222mag and 204 case together you would see that the 204 case has quite a bit more powder capacity...the 222mag has a long neck, where the 204 has a short neck by comparison and will get you more powder. The start of the shoulder/body on the 204 is at the neck shoulder junction of the 222mag...if posting pics wasn't such a pain on this site, I would show you a pic of them side by side.
I have gotten over 3700 from this cartridge and so have a few others that have tried this wildcat...most dispell it as just a 222mag because when the 204 came out, it was reported that it was based off of the 222mag cartridge...yes, it might have been based off of the 222mag but it definitely holds more powder than the 222mag. I have yet to see any load data for a 222mag that will get 3700fps...not even close.
The few of us that have tried this wildcat have gotten benchrest type accuracy, phenominal velocity and no fireforming necessary...this is just simply necking up 204 brass to .22, nothing else changes on the cartridge. It basically gives 22-250 velocity with a lot less powder. My bolt rifle does 29.5gr of 8208 and I am doing 29.0 in the AR. I have had zero feeding issues and am using ACS 223/556 magazines in the AR.
If you frequent Accurateshooter web site, search 22-204 and you will see a lot of info and the pics on there...as well as a lot of naysayers BS. I was skeptical at first with the velocity claims, but myself and a friend had JGS build us a reamer and I can say that it has done everything it was reported to do and has done it well. I killed around 50 coyotes with it last year and that is why I decided to try it in an AR for thermal night hunting. Going to be using it here shortly for night hunting now that I have it set up correctly.

Gene
 
FkvqZ6.jpg


center 222 Rem Mag next two to the right 22-204

Great little round, I've been killing coyotes with it for 15 years, I was surprised to see it in an AR I would have thought it too long for an AR but I understand that some metal AR mags will take longer rounds. Nice work.

AxVnvZ.jpg
 
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I hadn't considered the shoulder was blown that far forward, thanks for clarifying. I'm all for it, can you fit a 53 vmax at 2.3"?

Is rechambering an already built 223 barrel feasible?

IIRC I'm pushing 53's in RP brass at 3420 with 27.8 gr 8208 in a 24" 223AI ar, Remington take off barrel, to give you some reference. If I could squeeze another 180 out of a 204 case that would be impressive.

Have you ever tried n133? I got some last winter and worked up a load easy peasy in another 223AI with 55 vmax. I can't remember the details on speed but that stuff was much cleaner than 8208 iirc. I wouldn't be surprised if it gave more speed also and I want to try it with 53's and see how hard it can be pushed.
 
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I had to do some testing with a 204 case, and no you can't seat a 53 vmax at 2.3 in it without seating it too deep. I suspect Gene is using hollow points?
 
Originally Posted By: 204 ARI had to do some testing with a 204 case, and no you can't seat a 53 vmax at 2.3 in it without seating it too deep. I suspect Gene is using hollow points?
204 AR, you are correct...the 53 Vmax will be too far down in the case to fit an AR magazine. The 53vmax works extremely well in my bolt rifle, but it is too long for the AR. I am using the 52gr Berger bullets...both the Varmint and the Target variety and have been doing some load work up with 53gr Hillybilly HP Flat base bullets. All 3 of these are doing real good. The 55gr Sierra HPBT #1390 does real good as well. I know it isn't much but I am staying with the 52-53gr bullets to keep the velocity up there a little bit, but the 55gr Sierra is very accurate. I experimented with some H4895 yesterday in the AR with the 52gr Bergers and was getting an average of 3610fps and SD was 4.5 and it was an accurate load...and the primer pockets were staying tight as well.

I have a brand new 22NXS barrel that I would sell if that may be of interest to you. I built the 22NXS a few years ago and liked it so much that I went ahead and got another new barrel so I would have it in the future, but now that I have been using the 22-204 I doubt that I will be needing this other barrel.

Gene
 
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