Air strippers - yea or nay?

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mcoulter

mcoulter

Member
Dec 16, 2015
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Syracuse, NY, USA
I picked up a very nice used Air Arms s400 MPR recently. It's a beautiful rifle!



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Wanting to know more about it's history, I emailed Air Arms with the SN and got these details back from them:



Serial No Model Details Manufactured

055xxx MPR SPORTER .177 5.1 FTLB WALNUT RH RUBBER BUTT 07.09.2005



At some point in its history, this rifle has been updated with the butt hook, a longer (and regulated) air tube and has been tuned for more power. In my cold (20f) temperatures it's shooting just under 13 fpe. So it's making a good deal more power than the 5.1 fpe it originally was designed for.

UPDATE: I just did a quick test over the chrony where the rifle was normal temperature (not 20f) and it is shooting the .177 CPHP 7.9 grain pellets at 887 fps so that's just under 14 fpe.

I'm still learning the gun so I don't want to prejudge the accuracy, but as I shoot it (with and without the muzzle brake in the pics) the gun seems (sounds) like it's pushing too much air for the power it is producing. So this is where I am wondering if this gun would be a good candidate for a Rowan Air Stripper.

Does anyone have experiences they could share regarding using one? 

Here are a few more pics just because... ;-)



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Since taking this photo I have ground down some aluminum from the bottom of the muzzle brake to give this more clearance. I am also testing to see what affect o-ring will have in the barrel band. I realize this band is a critical part with the gun's accuracy. I'm not yet sure if it will like these o-rings or not. I'll circle back on this after doing some testing! 

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my unlearned opinikn is the oring does nothing but keep the barrel from being marred if hit against the barrel band whose sole purpose is to prevent the barrel from being knocked out of alignment if bumped .. in other words it free floats, and touching the presumably makeshift 'muzzle brake' likely ruins accuracy .. as far as air strippers, i have one .. on one gun .. my feeling is it groups a little better with it .. seems to control that pesky random flyer ..
 
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An air stripper isn’t going to fix a bad tune. If it’s supposed to be a 5ft lb gun and Dr. Crankenstein turned it up to get 14, there is probably a serious dwell issue. I would think that guns design is focused on a very small tuning margin. It wasn’t designed to go from a plinker to a hunter. It’s a beautiful gun so I would do what qball said and back it down to where it should be.
 
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IMO you only need an air stripper if your gun is producing excess back pressure -- enough so that the air blast when your pellet leaves the barrel is causing your pellet to tumble. 

If your pellets aren't tumbling, an air stripper is pointless. 

So basically, air strippers are for guns that have short barrels, or guns where you're trying "too hard" to increase your pellet velocity with either too high a regulator setting, or too large a plenum / dwell time. 




 
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Have you tried shooting the rifle for group sizes without the long moderator on it? And, where in relation to the end of the air cylinder does the barrel threaded end start? (Is there room for a different moderator without grinding clearances?) That is a nice looking rig, so if you are looking to strip air and quiet it down I would suggest buying a Silent Thunder Ordinance moderator, as it is the best of both worlds from what I've read from user's on the forum.

https://www.silentthunderordnance.com/air


 
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IMO you only need an air stripper if your gun is producing excess back pressure -- enough so that the air blast when your pellet leaves the barrel is causing your pellet to tumble. 

If your pellets aren't tumbling, an air stripper is pointless. 

So basically, air strippers are for guns that have short barrels, or guns where you're trying "too hard" to increase your pellet velocity with either too high a regulator setting, or too large a plenum / dwell time. 



Click to expand...

I think the air consumption = more dwell time or less dwell time - is less influential with a good tune. A good tune is a good tune regardless how much air you using - or throwing away.

My best believe the air stripper function is to shave off and re-direct the existing and accelerating air coming out in front - pushed by the projectile. What air comes after the projectile is less important considering the object is ready to leave the muzzle, any change in sound effects is just a bonus.

To people who never tried any airstripper -> you will be surprised how much of a dust can clean from your bench table. This air turbulence is existing in any closed cylinder environment like moderators as well, imagine why nobody using anything at tournaments or where the rings scoring is important. 

My observation is that the .25 cal MK2 33.9 grain pellet hits about 1.5-2.0" higher at 100 meters with an airstripper vs nothing attached....the FX radar shows approximately same speed.
 
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Sorry for neglecting my own post for this long... things just got super busy! Anyhow, I spent some quality time with the s400 this past weekend and logged some good info regarding it's performance. Again, this is a used Air Arms s400 mpr which was originally designed as a 10 meter gun. It now has a longer air tube (roughly 15.5 inches long vs. the 12 inch original tube) and it has been regulated.

Without changing anything on the gun, I found it was getting about 75 to 80 shots from a 200 bar fill before falling off the reg at about 100 bar. Here are some chrony numbers with different weight pellets:

AA 8.4 = 882 fps / 14.5 fpe
AA 10.3 = 817 fps / 15.3 fpe
JSB 13.4 = 714 fps / 16.3 fpe

I shot two full strings with some different pellets (7.9 grain crosmans and H&N ftt) at this tune and the results were pretty similar. Accuracy with pretty much all pellets were OK, but not great. Wind was not good until later in the day... But I couldn't help shake the felling that this gun just does not like this extra energy that it's putting out now. I really was expecting the JSB monsters to put out less FPE than the lighter pellets and that makes me think it's really pushing and wasting more air than it needs to with lighter pellets.

So I decided to play with the port restricting screw. It's just to left of the end of the air tube here. (There is a little plastic donut in there that serves no real purpose that I can see.)

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Well I ended up turning that in 14 turns before it made any change in velocity. From the 14th turn in to the 16th turn in it went from 891 fps to 842 fps. Given that I'd like to try field target with this rifle, I think I'll get it shooting at the <12 fpe level. From this point it was easy to make some small adjustments to get it in that range. Accuracy with Air Arms 8.4 and 4.52mm FTT were pretty good now! By the end of the day a storm had passed and I took my 1st 50 yard shots with the rifle. 

I had been zero'd at about 35 yards and I wanted to see the drop at 50. The stickers I use are 1/2 inch diameter.

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The FTT were shooting at 778 fps (11.6 fpe) and the AAs were shooting at 795 fps (11.8 fpe).

Worth noting is that I bought a tin of cheap "Excite Hammer" pellets to test doing shot strings, but they were getting hung up trying to feed them into receiver. It felt like they're catching on the transfer port. Being a used gun that has been tuned up, I wonder if if that port has been made larger...

Anyways, it's a really fun gun to shoot and I look forward to testing some longer strings with this reduced power level. Ultimately, I'll be opening it up sometime in the future to drop the power level properly. But that'll be another chapter for later!

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Air strippers on lower powered airguns may not do much. But if you shoot high powered ones with pellets only they serve a purpose. Slugs are more forgiving but it doesn’t take much to upset a pellet and especially an imperfect pellet. most shrouded guns at least have a provision for a stripper if not included, and many suppressors have them built in. But the jury’s in and they are helpful when all else seems to be failing.
 
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Looks like the air stripper is homemade? and looks like it could be touching your air cylinder? It also appears that someone chamfered the cylinder air gauge for clearance? Try removing it and see if groups improve or worsen.

Either way a great looking rifle!
Click to expand...

No, what's there is more of a simple muzzle brake than anything else - I think it came standard on the early MPRs. There's not any air stripping (or air baffles) that are part of it. However, it does moderate the sound a little bit. 

I did grind away some aluminium from the brake to make it (barely) clear. I don't think any grinding was done on the gauge. Before de-tuning the gun I did shoot groups with and without it. Not much difference then. I have not tried that test since taking it down to 800 fps.

Since it was so easy to de-tune the gun, I'll experiment at this power level for a while. However, if I do bring it back up to the "higher" power, I will likely invest in the Rowan air stripper. The barrel is NOT threaded but has a flat area where a grub screw will hold it. I am not sure I'd find a moderator/ldc that would work for this. (I'll take and post some pics later for context.)

Oh, I almost forgot to post target pics from how the gun shot before tuning it down. These are 7.9 grain Crosman Hollow Points at 35 yards (@ 886 fps) when I was shooting the 80-shot string over the chrony. As you can see they're not good. The H&N and AA pellets were about the same as these CPHPs at this velocity.

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Why would any man in his right mind be opposed to strippers doing aerobatics? ;-)
Click to expand...

Hmm... got nothing for you on that one! 

;-)

Here the pics of the barrel without the muzzle brake:

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And the clearance between the brake and the tube end:

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To do:

1) test with and without the muzzle brake

2) remove the o-ring from inside the barrel band to see if allowing it to be free improves accuracy 
 
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