Increases case pressure signs with Wolf 120 MPT

[Bedford]

Has anyone seen increased pressure signs with the Wolf MPT? I have been having extractor and ejector imprintations on the case head. Also, difficult extraction and loose primer pockets. I do run a suppressor, but I have been having it unsuppressed as well. I am sure the suppressor increases the pressure somewhat, but not to that degree, or it would be unsafe to run a suppressor.

My barrel is a Sabre defense chrome lined. I hope I am not having a headspace issue. I got it from Rainier Arms. I pulled some of the Wolf ammo, it is a ball powder, I was getting 29.2 grains. Some boxes had sealant on the bullets, others did not.

Any help is appreciated!

[biggdawg]

i have that happening to mine also

[Bedford]

I found this great article on "CHS" http://www.shootingillustrated.com/i...se-head-swipe/ The pictures look exactly like mine, and I am sure that this is what is happening. The timing is off between the rifle/ammo. This is probably made worse by the suppressor.

I am going to try loading new cases with mild loads of known powder, and see where things go. I may need to get an adjustable gas block.

[mongoosesnipe]

The suppresor increases back preasure that flows into the gas tube cycling the action but does not increase chamber preasure so that is not the issue It could be a hot batch from wolf or a batch with softer brass another factor could be the if it just started showing signs of over pressure temperature could also be an issue as we are getting into the warmer months also is it happening immediately or does it progress as your shooting day continues I ask because if your barrel it dirty it will generate mor friction resulting in higher chamber pressures

[ttrmike]

What buffer weight are you using?

[Bedford]

Temp is not an issue. It happens right away, so fouling not an issue.

[Bedford]

I switched to an H3 buffer when I realized it was happening, it has made no difference. It is an 18 inch mid-length.

[doug62-105]

Running a new upper, 18.5 midgas, wolf120's were showing pressure signs, but ok in my book. Shoot some 123sp, blown primer, loose primer. Wow.
Don't know if I sould try some Hornaday or not.

[mongoosesnipe]

I would try and adjustable gas block to time the dwell you gas system should be about right but your gas port may be a little on the large side I am not entirely sure what the spec should be on the as port but it would appear you are getting too much pressure into you gas system it would seem like an adjustable gas block would be your best bet.. I am going to be running an adjustable gas block on my Grendel when my barrel arrives I am getting a 21 inch barrel with a mid length gas system so as to be able to tune for any load

[Bedford]

I did a little more shooting today. With the factory load, and gas off, none of the imprintations on the case. With gas full on, and suppressor off, it had impressions on the case, but barely noticeable. I loaded up a few rounds, using pulled Wolf cases, reloading them with 129 SST's. With A2520, suppressor on, gas on suppressed, very subtle signs on the cases. IMR 4895, similar.

I was really surprised I was getting signs with full gas and with the suppressor off. Since my goal was to build a DMR type rifle, I wanted to be able to switch back and forth between suppressed and unsuppressed, and match ammo vs. ball ammo. I got the chrome lined barrel anticipating the steel cased ammo. If the rig does not work well with Wolf Gold, it will be even worse with the steel cased. I don't like the idea of having to tinker with the gas block with each load, and suppressed vs. un-suppressed. Does anyone make a click adjustment gas block?

[txgunner00]

Paladin machine, Noveske, I think there are others.

[mongoosesnipe]

Noveske switch block would the solution but I don't think the sell a Grendel version they list 5.56 and 6.8 on the website I would give them a call and see what they recommend

[Bill Alexander]

Dwell time will slightly change the visibility of the brass flow marks. The silencer is effectively decreasing the dwell time or conversely holding pressure at a higher level when the bolt commences movement. An adjustable gas block does not effect timing per se as this is primarily a function of the gas port position rather it influences carrier acceleration and speed. I do know that some of the Sabre barrels were drilled on the large size for the port and a diameter of 0.073"/0.078" is about correct for a mid gas system.

In dealing with Wolf ammunition one must consider that the brass is extremely soft in the case head versus other brands. It will therefore flow much more easily and at lower pressures than many others. Any features on the bolt not perfectly radiused and fit will then smear the brass even at normal pressures.

Before spending too much time on diagnosis try firing some loads on Hornady brass. If signs are present, measure the port diameter and correct as needed.

[Bedford]

I already have the 5.56 Noveske switchblock on. The 5.56 has the smaller port than the 6.8 version, so it should reduce pressures in the system.

Thanks, Bill for your advice! I will try some higher quality ammo. Do you think I should get a headspace gauge?

I am not sure how to measure the gas port, what type of gauge do you use?

Thanks!

[Mutt]

I agree with Bill. I've found Wolf to be much softer and show signs that my handloads (which are hotter than Wolf) do not show. I haven't had any other factory ammo show the same signs as Wolf. I wouldn't put to much worry into it, unless it's happening with other factory loads.