Marauder .22 barrels * May have discovered Why some are accurate, others not ?

[Motorhead]

Just may have discovered the .22 cal's barrel troubles ?


Well at least some discovery of what makes some .22 barrels good and some not so good

If reading past posts, you will have read about .22 cal barrels being hit & miss accuracy wise.
My personal .22 OEM barrel while VERY accurate with just 2 pellets it likes ... not worthy shooting anything else !!

So ... I took a leap of faith and ordered another .22 OEM barrel and once receiving it went about some lengthy measuring of Bore & Choke dimensions of bore sizing between the two, Original a 1 1/2 year old and new one a couple months old.

WOW some interesting numbers showed up that are listed below.
** Note that BOTH American Decimal and Metric Millimeter sizes are noted.
** Also measurement take with a machinists expanding ball gauge for hole diameter sizing and not pin gauges. ( So while accurate for reference barrel to barrel, not at accurate as pin gauges would be )


OK ....

BARRELS LOADING THROAT DIAMETER
Older barrel = .227" or 5.77 mm
Newer barrel = .2265 or 5.75 mm
** Very close IMO making no difference.

BARRELS BORE DIAMETER
BOTH barrels exactly same size = .218" or 5.53 mm

BARRELS CHOKE DIAMETER
Older barrel = .216" or 5.49 mm
Newer barrel = .212" or 5.38 mm **
** That's a LOT more choke present by .004"

Outside for 50 yard shooting .... well I'll be darn, new tighter choked barrels more accurate than the older shooting pellets from 14.6 Gr to 21.3 Gr inside of a dimes diameter !! 


So what does this post really mean in layman's terms ?
** Being the I.D. of barrel is .218" or 5.53 mm ..... only a larger pellet head of @ 5.52 or more is going to actually be in contact with rifling and even then NOT BY MUCH :oops:
Have a pellet who's head is just equal too rifling bore sent down the barrel it is getting very little stability in spinning concentric with bore ( wobbles like football ), compounded by a CHOKE of only @ .002" less and no "dang" wonder POI shotguns !!

The TIGHTER choked barrel having a CHOKE .004" tighter really strangles the pellet just before exit getting forced to spin concentric with bore at muzzle due to the tighter choked diameter.
No "dang" wonder again why smaller head pellets now shoot accurately 


Just discovery here .... no clue how universal others may find like differences having similar results ?
At least now I have an OEM barrel that is far more wide range pellet friendly 

Scott

[PakProtector]

Nice work there. I also noticed the 25 cal GM barrel has a fairly drastic choke; no question about when the pellet hits it. Too bad the tight choked 22 cal barrels are not available 4" longer...
cheers,
Douglas

[JerryW]

Good info. I have to wonder if this is a conscious effort by Crosman to improve accuracy or if it is just day to day production variance?

My .22 Prod barrel is also loose, but the most disturbing thing is the interior finish. The grooves don't look too bad, but the lands look like a gravel road. They have to be stripping lead from every pellet. Despite the poor finish, after some lapping with paper towels and Flitz, it is surprisingly accurate. It will only shoot 5.52 and 5.53 pellets, though.

Jerry

[Ribbonstone]

Replaced two Crosman barrels, both of them .22's. Just too rough and too shallow rifling to shoot very well, although fat pellets (like the 5.54 or 5.55MM h&N F.T.T.) do help.  Some .22 barrels are just fine, MOST .177 barrels are good...but have to say that there seem to be more "stinker-Crosmans" in .22 than any other caliber.

[pyroboy33]

Yeah. when I purchased my .22 Mrod about a month ago I was worried I would get a picky barrel so I bought four different kinds of pellets in hopes that at least one of the four would shoot well. In the end all four kinds easily shot quarter sized groups at 50 yards, while most shot about nickle sized.

[Gertrude]

Motorhead,
Excellent work, and discovery.

 When I began reading you post, you could have just as well been speaking about mine.
 Mine does shoot a couple of pellets VERY well,... just like yours.
 Mine shoots anything else horrible,....  Just like yours.

I 100% agree that the .0005 variance at the breech is insignificant. I also agree that a .004 tighter muzzle is a HUGE difference.
 I did 26 years in Aircraft Production/Repair as a QA Inspector. I'm pretty familiar with "interference fit" holes. LOL!
 I've measured off millions of them. 

 My ball gauges and calipers are getting dusted off tomorrow.

THANKS for the time, effort, and clear reporting.
 I will post my muzzle diameter for comparisons, when I have measured it.

[Rescue35]

Motorhead,
Excellent work, and discovery.

 

I agree, Thanks!

I may have to take down both the Mrod and Prod to see what they look like. If needed I might even try to add more choke to the Mrod since no one wants to buy it. I might just give Crosman a call and try my luck with another .22 barrel too.

[Gertrude]

Ok, I've done my initial measurements,... and I think I'm going to

My CHOKE is measuring in at a SOLID .217 !! (leaning towards .2175 !!)

and the best "guess-timate" for the BARREL/BORE is .218, (I did not remove my barrel for these measurements),... so I was going thru the muzzle to get to the bore with my ball gauge, then had to index the ball gauge, loosen it before pulling thru choke,remove from muzzle, retighten to index mark, and then measure.
 SOoooo, that means the it's a reasonably accurate, but not perfect, call on the bore size.

Certainly with the barrel removed from the breech,... a more perfect measurement of the bore, could be made from the loading port.
either way for me,...
 It Really Doesn't Freakin' Matter !,....
I LITERALLY HAVE ONLY .001 CHOKE, at BEST !!! That sssSUUUUUCKKS !

To give some readers (who may not be familiar dealing with interference fit holes), a loose comparison,...
 When building aircraft, we had a acceptable range requirement of .003 +0/ - .001 on about 90% of the interference fit type fasteners,... (think pellets here).
but here's the kicker,... That's with driving a STEEL Fastener thru aluminum.

Now in Air Guns/Pellets,... its a different case for sure.
 We are driving LEAD thru steel.
 In other words,... we,... by design and physical property's,... should have AT LEAST .003 interference fit.
 Heck,... even .0045-.005 would not be too radical, for a straight lead pellet, going thru approx. 1" of Rifled Choke.

So what does this mean for Tri-5-ron
 It means I THOUGHT I had a decent barrel,.... but as it turns out, I'm basically sitting on the knifes edge of having a crappy barrel !
No Wonder I can sometimes get 3 to 5 "Flyers" in a single 10 shot clip...    

DANG,.. Now I suppose I'm going to have to try and call Crosman,... and see if I can talk to someone in "Technical dept" (or something),... and see if I can get them to verify a .003 to .004 interference barrel/choke before sending it out to me.
 What are my chances of that ... I Dunno.

[Rescue35]

Yeah now I am really curious as to what my early 2012 barrel measures. I might just slug mine.

[Motorhead]

Wanted to add some FYI data to this while my mind was further pondering this ....

If you don't have a machinists ball gauge ? ... a 7/32" drill ( Using it's Shank ) can be utilized as a Go / No Go gauge.
Being 7/32 = 0.2187" you could slide the drills shank into breach end and see if it go's in confirming @ bore diameter.
Then test it into muzzle end seeing what degree of choke is present ?

**As stated in OP, pin gauges are more accurate and just recently having this idea of the 7/32" drill, TRIED IT.
Sure enough 7/32" drill shank slid right in at BREACH end.
Tried again at MUZZLE end and to my surprise it JUST fit the old barrel firmly sliding in giving a more exact diameter at choke.
New barrels muzzle / choke would not take the 7/32" shank BTW.

So with some correction on OLD BARRELS choke size confirmed via a pin gauge ( Drill Shank ) it could be used to give a rough idea if barrel you have is loose or tighter in choke specs 

KNOW A MACHINIST ? ... hit em up to see if they have Pin Gauges, it hands down the most precise way in measuring a hole.

Regards,
Scott

[FuzzyGrub]

Scott,

Thanks for a layman way of checking the barrel.  As luck would have it, my 7/32" drill has some slipping scars about 1/2" up from the shank end.   I checked my "bad" prod barrel first.  I had to push too hard to get past o-ring, so should remove that before measuring.  Glad that wasn't a "good" barrel!    That "bad" prod barrel, it would slide in on the muzzle end the full 1/2".   On a new replacement mrod barrel, received within the last week from crosman, it would not slide in at all.   

I will be getting a new drill today, and "measure" the muzzle in my mrod and prod this evening.  Didn't have time this am to remove shrouds.  One has a new prod barrel, and the other has older mrod barrel.  The mrod was purchased used, so won't have a good build date.  Think barrel was replaced at some point.

[tobar832]

I watched a YOUTUBE video on this subject of 22 mrod barrels that cover this very subject, worth a watch.

[Rescue35]

Interesting video. I think I would have returned the "new" barrel as soon as I saw it was bent. The only real comment I can make is Don't leave the chuck key in the chuck of your lathe.

[Gertrude]

very interesting video, Thank you for posting it.

 I'm thinking I might try to contact the maker of that video and invite him to the GTA, as well as ask him to join this discussion.
 I would also like to get his thoughts on the other thread I started, asking for a knowledgeable/experienced discussion   on the available aftermarket barrels. Boy,.... wouldn't it be nice if Crosman was influenced enough by such a discussion, to at least offer up a barrel replacement of higher quality. Something that they themselfs were involved in with the assurance that they had recognized the problem, and were stepping up to offer a real solution. Heck,.. I'd gladly buy it.

 Do that,.... and I can guarantee my collection will grow wearing the Benjamin brand.
The way I'm going,... a P-rod, Rouge, and .25 Mrod are possibly in the wish list.

Sure would be nice to hear them chime in here.
 Yeah,... I know,.... "wishful Thinking"
 

[PakProtector]

hey-Hey!!!,
Just measured two new barrels. Alledgedly from two different runs. Bore diameter at 5.52 on both. One choke at 5.46 and one at a slightly tighter 5.44. I still have one barrel at home that came on my first Marauder, but it is currently installed and I didn't want to take it out. 5.44 x .039374 is .2142" so a fairly good choke of ~.003" Measured with pin gages.
cheers,
Douglas

[Gertrude]

Today I sent a letter to Crosman Customer Support, explaining the findings, measurements, and considerable variances between our OEM .22 barrels. I told them I would like to get another barrel, and would be happy to pay for it,... but I want to be assured I will get a barrel with an acceptable degree of choke.
 I mentioned our discussion on the subject here, and invited them to join the discussion.
I will let you know what they say when they reply.

has anyone else measured their barrels and chokes ?
post 'em up, so we can get an idea up the range between various barrels.

[Raizer]

A member on the kiwi forums mrod came from the factory with the choke at the breech end, that sure didn't help accuracy lol

[Bill G]

OK.  For those of you who want to measure this really closely, you can purchase individual gauge pins from MSC.  ZZ class will run about $3ea plus shipping.  ZZ is .0002" tolerance, you designate + or - .  X class are about $ 11+shipping and have a tolerance of .00004".  Holding these in your hand long enough to warm them will alter their fit so use a plug gauge handle.  with this new found knowledge, I can see .22 owners becoming curious about their barrels.  Buying these gauges in .001" graduations isn't practical for most of us but could be useful for those who tune these guns for money.  Just having the ability to accurately diagnose this would help greatly. 

 Now here is another idea to kick around.  Could one build a roll form that could reprocess the barrel and further constrict the choke?  I don't see why not other than not being able to recoup the cost of builing the roll form.  The barrels are so cheap it isn't worth the investment i'm affraid. 

Bill

[PakProtector]

Yeah...I am quite tempted to get after Crosman and I'd even send them the pins; a 5.42- no-go and a 5.40- go for the barrel I'd be buying. But the barrel is short, and If I am going to go and mess with it, I'll spend the 5x increase in cost and get another BSA or L-W.
cheers,
Douglas

[Motorhead]

What we are LACKING is enough information on HOW MUCH reduction in diameter between Bore and Choke is near optimum ?
* Also in the case of Crosman/Benjamin barrels that are BORE OVERSIZE generally ... how much choke in them honestly required to get pellet stabilized ?

Read on QUALITY barrels .001 - 002" is considered Choked ... on a C/B barrel that just does NOT work obviously.
( My second barrel which prompted this thread chokes .006" ) and it shoots most all pellets pretty dang well where as the .002" choke barrel ONLY like a couple heavy big head pellets.

We really need more DATA !!

Scott