GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: FuzzyGrub on June 25, 2019, 04:08:40 PM
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Tom Holland over on AGN has been working with some crosman barrel engineers. He reported today that crosman went to their own barrels in early 2018. :( :'( This seems to jive with the barrel I purchased in Jan 2019, which had an extremely tight choke, that resized the 25g JSB head. I didn't have accuracy issues with it, but lost 60fps which some was barrel port not enlarged. Others reported the same tight choke around that same timeframe.
Now, outside of the tight choke, I don't recall seeing accuracy issues being reported here on GTA. What say you 2019 25 cal mrod owners?
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Thanks John! Good to know. I've got two of the original GM barrels that are very accurate, but can't help with the new ones.
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How does one know if they have a green mountain barrel on their .25 or a crosman barrel? I bought my marauder in 25 mainly cause of the better barrel.
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It would be interesting to know if Crosman changed the twist rate.... The GM barrels were supposed to be a 15.5" twist....
Bob
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Mike,
I have never seen any id markings on any of the barrels, be it crosman, GM, or LW ones supplied in their guns. What is you gun mfg date in the serial number?
Bob,
I just checked the thread where I had talked about the choke. I though I might have checked the twist rate, but wasn't recorded. Now I think of it, that was my Liberty.
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Wish this would not have happened, now I will have to find a used .25.
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John The Crosman engineer is an active member here ask him. I’m curious also
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I have a build date of 8 18 so it looks like I got a crosman barrel. It seems to shoot fine but I'm left wondering if it could've been better. I think major production changes should be shared with the consumer so they know what they're buying.
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I remember first shooting my GM and thinking something was wrong. I only saw my sight in pellet hole. Then realized I had dumped the magazine into the same hole at 25 yards. Shocked because I had one of the infamous .22 barrels that was horrific. Sold that rifle and glad I did! The .25 now sits in a bullpup and it is a very nice combo.
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I have a build date of 8 18 so it looks like I got a crosman barrel. It seems to shoot fine but I'm left wondering if it could've been better. I think major production changes should be shared with the consumer so they know what they're buying.
When you cleaned the barrel, did you notice if the choke felt very tight?
Travis,
Hopefully John will read and confirm/deny. I probably bugged him with too many IM's when he first joined GTA. ;)
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Following along, curious as well
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Following. If true, I wonder if the barrel could be ordered from GM directly? If they're no longer making barrels for Crosman, hopefully they're free to sell direct? Maybe we could even get longer blanks made?
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Following. If true, I wonder if the barrel could be ordered from GM directly? If they're no longer making barrels for Crosman, hopefully they're free to sell direct? Maybe we could even get longer blanks made?
Pick up the phone and call them! ;)
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Following. If true, I wonder if the barrel could be ordered from GM directly? If they're no longer making barrels for Crosman, hopefully they're free to sell direct? Maybe we could even get longer blanks made?
Pick up the phone and call them! ;)
I'd love to, after getting confirmation that they no longer make barrels for Crosman! ;D
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Yes I want to find out. I was on the phone with Kim today (Lil_Sis) she works at crosman I wished I would have asked I just assumed.
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I contacted GM a good number of years ago about 22 cal barrels for the Mrod. I think the minimum quantity was 1000. Far more than we would ever get with a group buy.
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yeah thats a lot
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John The Crosman engineer is an active member here ask him.
I just PM'd him and asked him to comment here....
Bob
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I contacted GM a good number of years ago about 22 cal barrels for the Mrod. I think the minimum quantity was 1000. Far more than we would ever get with a group buy.
But wouldn't that be for making a .22 custom barrel? I'm probably wrong... I'll call GM on Friday... I would make sense that we could buy a "Crosman spec" .25 barrel blank on it's own- and possibly in a larger O.D. than currently available. How awesome would that be?
What is Crosman spec anyway? 1:15.5 twist, but what's the land/groove?
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John (FuzzyGrub) –You have tons of questions left. At least 1 maybe 2….
Bob (rsterne) – Thanks for reaching out! I try and get on there as much as I can but that is not always easy! You post some awesome information and it is appreciated!
All – We are (and have been for a year or more) making our own .25 cal barrels. I don’t know when exactly they went into production. You can tell the difference between them by the crown. The GM barrel has a deeper, almost recessed crown where the Crosman barrel has our standard target crown. The quality of these barrels should be the same as our .22cal barrels.
I cannot comment on what our barrel dimensions/parameters are. I consider that something of a trade secret.
I don’t know if GM sells barrels in small quantities but I know others do (Lothar, CZ and some others).
Happy Shooting,
John
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John (FuzzyGrub) –You have tons of questions left. At least 1 maybe 2….
Happy Shooting,
John
Thanks for commenting and clarifying for all us GTA members.
I have to hold back and make sure my one question is a real "good" one! ;)
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John (FuzzyGrub) –You have tons of questions left. At least 1 maybe 2….
Bob (rsterne) – Thanks for reaching out! I try and get on there as much as I can but that is not always easy! You post some awesome information and it is appreciated!
All – We are (and have been for a year or more) making our own .25 cal barrels. I don’t know when exactly they went into production. You can tell the difference between them by the crown. The GM barrel has a deeper, almost recessed crown where the Crosman barrel has our standard target crown. The quality of these barrels should be the same as our .22cal barrels.
I cannot comment on what our barrel dimensions/parameters are. I consider that something of a trade secret.
I don’t know if GM sells barrels in small quantities but I know others do (Lothar, CZ and some others).
Happy Shooting,
John
Thank you for that info John! Can you give the twist rates for caliber?
Thanks...
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Gives me the excuse to buy a new barrel now.
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Thanks for the reply, John.... I'm guessing we'll have to measure the twist rate (not a difficult thing to do)….
Anyone have a cleaning rod, jag and tight fitting patch available?.... Get to it, guys, it's not rocket science....
Bob
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Thanks for the reply, John.... I'm guessing we'll have to measure the twist rate (not a difficult thing to do)….
Anyone have a cleaning rod, jag and tight fitting patch available?.... Get to it, guys, it's not rocket science....
Bob
I actually made a half-hearted attempt, last night. The mop style tip, was very hard to get past the choke. It was too tight and the rod was not rotating the way it should. It did fit the green mnt barrel and rotate they way it should, but didn't get the distance for one revolution. :-[ When I get back from vacation, I'll post what I get for 2 GM barrels, and the crosman one.
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I have both the GM and the Crosman .25cal maruder barrels.
If I remember right the GM has 10 grooves and faster twist and the Crosman has 6 grooves and a slower twist rate.
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Does this mean Crossman makes the bulldog .357 barrel to?
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Jim - We still purchase the bulldog barrel. Have you noticed an accuracy difference between the GM and Crosman barrel?
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Jim - We still purchase the bulldog barrel. Have you noticed an accuracy difference between the GM and Crosman barrel?
Ok.
Sorry, I did only use the GM barrel mounted on a discovery which I no longer have.
However both of them seems to be well made ocularly...
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I just bought mine about 2 months ago. Not sure what barrel it has but it shoots great for me. Mine has the synthetic stock.
Attached are 5 shots at 90 yards. Without going through a lot of trouble, 90 yards is max I can shoot off my deck.
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John (FuzzyGrub) –You have tons of questions left. At least 1 maybe 2….
Bob (rsterne) – Thanks for reaching out! I try and get on there as much as I can but that is not always easy! You post some awesome information and it is appreciated!
All – We are (and have been for a year or more) making our own .25 cal barrels. I don’t know when exactly they went into production. You can tell the difference between them by the crown. The GM barrel has a deeper, almost recessed crown where the Crosman barrel has our standard target crown. The quality of these barrels should be the same as our .22cal barrels.
I cannot comment on what our barrel dimensions/parameters are. I consider that something of a trade secret.
I don’t know if GM sells barrels in small quantities but I know others do (Lothar, CZ and some others).
Happy Shooting,
John
A typical non answer from Crosman. It gets OLD!
all premium barrel makers, whether AG or PB "DO give full dimensions.
As do most air gun manufacturers.
the only logical reason Crosman won't give the same info other makers do,is that either thiers are vastly superior, or as this is obviously not the case,they are flat ashamed of their product.
Judging from their track record with the barrels in .22 for years, they have ever right to duck their heads in shame and avoid any info what so ever.
With that said, my maximus is very accurate with the new in house production. One would think they would be proud enough to shout their accomplishment to the moon. Apparently they have no faith in their own product.
Worse yet, they seem totally oblivious to the fact than any one with a cleaning rod, and a mic can get the specs for themselves in minutes.
Apparently they think we are too stupid to complete such a task.
Someone is being less than intelligent regarding the matter. I wonder just who.
Not in the least impressed with Crosmean, and the way they treat the airgunning community. the AG world is becoming very sophisticated.
I would like to see Crosman follow suite. Waiting! But not holding my breath.
Knife
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Whelp, I'm gonna give GM a call on Monday then see if 1) They'll sell their .25 AG barrels to us, 2) Can we get them in other O.D.'s than .5", and or longer than 20", and if necessary 3) Put it in their heads to offer these barrels to the public.
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I would love to have .25 cal GM barrel in .437 OD and longer than 20" for sure!
My .25 cal Prod would love it!
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I would love to have .25 cal GM barrel in .437 OD and longer than 20" for sure!
My .25 cal Prod would love it!
well not even if sleeving it to .5 or larger... (.4375 -.250) /2=.00625 way to thin of barrel walls... heck I want to sleeve the .4375 .22 Mrod barrels to fit the .25 Breech to have a stiffer .22 barrel...
do agree it does feel like disrespect from any producer to not be allow to have the twist rate of barrels published... and some are published on the custom shop barrels... 1:20 for the .22 mrod crosman barrel and 1:16 for the .22 L.W.
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http://www.crosman.com/custom-shop/# (http://www.crosman.com/custom-shop/#)
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My .25 cal Prod (AKA) mini-rod has a .25 cal GM barrel turned down to 7/16" to fit the Prod breach & my .25 cal Mag. It is a minute of squirrel all day long. If I could get a longer than 20" barrel in 7/16" .25 cal barrel it would most likely it would get CF sleaved flush to the breech. The MM HF .22 cal Mrod barrel in my Prod doesn't need to be sleeved either, they both rock although they are larger dia barrels.
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yeah I have two XL725 Barrels one is turned down to 7/16 for the Crosman Breech also and then 9/16 till the muzzle thread... used it for a long barrel 2100B pump tube Hybrid 1325... shot Darn well with the FTT and Kings despite only being about 21 fpe...
plan on turning the other to .5" for the Mrod ... Hoping it will like cast...Could do a .25 Max/Disco with the 7/16 turned barrel...
will eventually sleeve a Maxi .22 Barrel with some .5" O.D. .44 I.D. T6 6061 for the .25 Mrod Breech for an about 25." .22 barrel...have an extra Max .22 barrel for the project... am thinking of just oring on the bolt and single shot... think would have to take a bit off the Breech end to get the transfer port to line up..
oh and sorry wall thickness for the 7/16 barrel is .09375...senior moment with the calc... in .22 it is about .11...
I still want a .5 O.D barrel nice to have a bit more stiffness (.125 walls)... cube rule...
.09375 X .09375 X .09375=.000823
and
.125 X .125 X .125=.00195
.00088 is 88 % of .00195...
that means the .125" wall .25 auto .5" barrel is about 12% stiffer than the .4375 .25 auto barrel ;)...given equal steel...
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http://www.crosman.com/custom-shop/# (http://www.crosman.com/custom-shop/#)
What he said.
And, if you click on the question mark "Learn more about our barrels," it says the Crosman .22 barrel has 10 lands and groves, Twist ratio of 1:20, custom crown and it is choked.
Now, that is the Custom Shop. Not sure if that translates to all their MRod barrels or not.
Me, I have a Gen I MRod. I thought it was pretty accurate out of the box.
Following Bob and NervousTriggers write ups, I polished the barrel.
Now, I think it is crazy accurate.
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The stiffness of a rod is proportional to the 4th power of the diameter.... For a tube it is therefore proportional to (OD^4 - ID^4)…. For two .25 cal barrels , of the same material but different OD's, the ratio of stiffness is:
1/2" OD.... (0.5^4 - 0.25^4) = (0.0625-0.0039) = 0.0586
7/16" OD.... (0.4375^4 - 0.25^4) = (0.0366-0.0039) = 0.0327
Therefore the 1/2" OD barrel is (0.0586 / 0.0327) = 1.79.... ie the 1/2" OD barrel is 79% stiffer than the 7/16" OD barrel.... not 12%....
Bob
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The stiffness of a rod is proportional to the 4th power of the diameter.... For a tube it is therefore proportional to (OD^4 - ID^4)…. For two .25 cal barrels , of the same material but different OD's, the ratio of stiffness is:
1/2" OD.... (0.5^4 - 0.25^4) = (0.0625-0.0039) = 0.0586
7/16" OD.... (0.4375^4 - 0.25^4) = (0.0366-0.0039) = 0.0327
Therefore the 1/2" OD barrel is (0.0586 / 0.0327) = 1.79.... ie the 1/2" OD barrel is 79% stiffer than the 7/16" OD barrel.... not 12%....
Bob
Yea, what Bob said... LOL
Man Bob, when you say it that the .5" OD barrel is a lot stiffer than the .4375 OD barrel.
Thanks for putting it into perspective for me.
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Yep, and a 9/16" barrel would be (0.5625^4 - 0.25^4) = (0.1001-0.0039) = 0.0962.... That would make them 64% stiffer than a 1/2" OD barrel, and 163% stiffer than a 7/16" barrel.... over 2.5 times as stiff (all in .25 cal, same material and length).... A 16mm LW barrel would be (0.630^4 - 0.25^4) = (0.1575-0.0039) = 0.1536.... which is over 4 times as stiff as a 7/16" Crosman barrel.... :o
When I sleeve my 14mm TJ's barrels up to 20mm, the stiffness also increases over 4 times.... 8)
Bob
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I guess treating wall thickness as a solid rectangular bar is way to simplistic... was just what I remembered off the top of my head... and it is basically the cube of the thickness... just did not think would be that far off as an estimate...
so found a calc cause was not sure you could treat as a solid round bar either... brain just does not remember right...
so hanging a 5# weight off of a 24" .4375 hollow tube with .09374 walls it deflects .478"
all same but .5 tube with .125 walls it deflects about half as much .267"...
so yep about 90% stiffer...
https://www.engineering.com/calculators/beams.htm (https://www.engineering.com/calculators/beams.htm)
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Yep.... 0.478 / 0.267 = 1.79....
Once the bore is less than half the OD, you can almost ignore it.... and just use the 4th power of the ratio of the OD's.... (OD2 / OD1)^4.... close enough....
Bob
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GM barrels essentially told me to frak off. >:(
the crosman spec would be handled as a "custom barrel" and therefore would require a minimum order of 100.
They said that the barrel specs are "proprietary" to Crosman, but I tried to counter with "since you're no longer supplying the barrels to crosman, couldn't you just add the barrel spec to your regular barrel selection?" so that GM could then offer the barrel as a normal (and inexpensive) blank. She came back with "it's proprietary, it's a custom order, minimum order size 100" in not so nice a tone. The contempt in her voice was palpable.
SMH, why do companies always do this once they hit a certain size?! I'll stick with TJ's barrels. Jeeze.
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I bought a 25 Mrod barrel from crosman in August of 2018, thinking that it was a GM barrel. It has 6 grooves and the last 1/2" of the bore on the muzzle end looks more like it was drilled, rather than reamed. I don't know if I can get a good picture of it.
I haven't shot it yet, but it sure ain't pretty. I paid $78.44 plus $10.63 shipping, plus tax.
Steve
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Green Mountain has never sold individual barrels, other than 10/22, 77/22 and AR barrels for the most part. I don't know how this can be a surprise to anyone. I am actually impressed that they stick to their agreement, unlike the Chinese than tell you it is your design and we will only make it for you, and then turn around and make it for anyone that pays them. Since they actually started reaming their barrels, instead of just buying tubing with I.D. specs they have been making quality barrels, so I hate to complain too much until I get one that won't shoot. Lots of old guns out there, for anyone that has to have a GM barrel. Might want to hold off on the panic until you see the fire. it might just be a quality barrel.
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Green Mountain has never sold individual barrels...
They offer barrels and blanks, sold to the individual... It's literally on their website... I'm confused as to why you say this... :o
I know we're not privy to the contract between crosman and GM, but I kinda feel like once you're contract is done, the product is good for sale on the open market- kind of like when a patent runs out. I'm sure I'm wrong, as I'm not a lawyer. But it makes sense to me.
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I'm sure I'm wrong, as I'm not a lawyer. But it makes sense to me.
Tom - good thing you are sure you are wrong, because you are wrong ;)
Unless the company that is doing the purchasing (Crosman here) is buying a standard spec item from the seller (Green Mountain), they define all the terms in the contract that they want. And if they have any input on specs, they can choose to keep them buried forever if they want. OF course the seller does not have to agree to that, but if they want the business they usually will as this is pretty standard practice.
If you think it is bad here, just imagine car and appliance parts - unless those parts were authorized by the original manufacturer, in most cases they are retro-engineered from the original physical parts , not the original specs or CAD data . . . . and since cars and appliances always need parts, and manufacturers eventually stop making parts, all the non-OEM parts out there were never validated to the original specs.
Obviously I have not seen the contract between Crosman and Green Mountain, but if Crosman wanted those specs kept hidden and forbade the sale of the barrels after the contract was done (as I expect they would have done), then Green Mountain would be opening themselves up to a guaranteed loss in a lawsuit that would likely follow.
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I'm sure I'm wrong, as I'm not a lawyer. But it makes sense to me.
Tom - good thing you are sure you are wrong, because you are wrong ;)
Unless the company that is doing the purchasing (Crosman here) is buying a standard spec item from the seller (Green Mountain), they define all the terms in the contract that they want. And if they have any input on specs, they can choose to keep them buried forever if they want.
If you think it is bad here, just imagine car and appliance parts - unless those parts were authorized by the original manufacturer, in most cases they are retro-engineered from the original physical parts , not the original specs or CAD data . . . .
Obviously I have not seen the contract between Crosman and Green Mountain, but if Crosman wanted those specs kept hidden and forbade the sale of the barrels after the contract was done (as I expect they would have done), then Green Mountain would be opening themselves up to a guaranteed loss in a lawsuit that would likely follow.
I get all that- but the fact that they're willing to make/sell (in batches of 100) barrel blanks with the same barrel specs as the crosman barrel shows that this isn't necessarily the case. If the "crosman spec" is to be forever barred from sale, then they wouldn't entertain selling that barrel spec at all. Hence the confusion.
Bottom line, it's their policy/agreement w/Crosman. It's not THAT big a deal.
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I am sorry YEMX but I disagree... keeping your agreements is a big deal... Plus there are many ways to make a very good barrel that following Crosman Specs is not needed anyways...
I do think by not making some aftermarket air rifle barrel Blanks they are missing a good market...
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often when doing work for a corporation there is a no compete clause that says for a given period of time you can not make a competing product...
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I am sorry YEMX but I disagree... keeping your agreements is a big deal... Plus there are many ways to make a very good barrel that following Crosman Specs is not needed anyways...
I do think by not making some aftermarket air rifle barrel Blanks they are missing a good market...
I meant "it's not a big deal", as in "it's not a big deal that we can't buy crosman spec barrels direct from GM". I'm not saying GM honoring their contract w/crosman (whatever that entails) is a bad thing.
often when doing work for a corporation there is a no compete clause that says for a given period of time you can not make a competing product...
I figure its something like that, but again, why the ability to sell "a custom barrel" with the same exact specs as the crosman?
Never mind, I'm just gonna drop it. There's other options out there. The GM barrel isn't the be-all end-all of .25 barrels.
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I bought my 25 Mrod barrel directly from crosman in August 2018. I thought the bore looked kinda rough, but figured it would be ok. The GM barrels were supposed to be good right?
I just measured it today. I've been measuring stuff for a living for 30 years. I've used all kinds if gages and have absolute faith in my measurements.
The bore at the muzzle is .245"
The bore at the breech is .250"/.2501"
In the pic, there is a .2498" pin gage in the breech end. It's a loose fit. The 9 inch long brass bar in the pic is .250" and it slides in freely, to within 1.550" of the muzzle. Almost the entire barrel is .250" !!!!!
I cast a lead slug in the barrel to measure the twist rate. It's between 1:18 and 1:19 there is some slop and the barrel isn't long enough to get a full revolution, so I did half a rev and multiplied by 2. I held the barrel in the lathe, secured the aluminum clamp/wrench pointing straight up, and pulled the slug through until the wrench pointed straight down. Never did this before.
There are 6 grooves. I can cut off a slice of the barrel and get a pic from the optical comparator at work.
SMH
Steve
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This pic might be better.
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My .50 caliber Hawken had a Green Mountain barrel..
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The lead slug has some play in the barrel, it turns freely maybe 2 or 3 degrees? The lead slug also turns on the brass adapter a couple of degrees. Need to eliminate that. Seems like the lead was a bad idea. Oh well.
I'm gonna try a jag and a piece of cloth later. Also gonna lock a collar on the rod and measure movement with a 12" dial caliper.
If I lock the aluminum wrench thing in the horizontal, I could indicate it perfectly level. Get exactly 180 degrees of rotation. Might be overkill, I don't know yet. Maybe just use a square, I only eyeballed it last night.
I can check the groove diameter and other details at work. Gonna dissect this thing.
Steve
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I measured the twist rate on the 25 Mrod barrel again today. The results I got the other day were inconsistent. There were pretty big voids in the 1st lead slug. I cast another lead slug today, this time I heated the barrel more. I also made the flats bigger on the brass piece that the slug is cast around (to keep the slug from turning) Put a few drops of oil in the bore to keep the lead slug from binding. Didn't do that the other day.
I positioned the wrench with a 1-2-3 block when the wrench was pointing down, and positioned the wrench with a square when it was pointing up. So now I'm getting very close to 180 degrees of rotation. Way better than just eyeballing it. I also locked a stop on the 3/16 dia rod, so I could check the movement with a dial caliper.
The system repeats pretty well now. Every time I push the rod home, the wrench is pointing straight down. I measured the twist rate 7 times. I rounded off the results to the nearest .005"
9.855"
9.800"
9.820"
9.860"
9.845"
9.870"
9.850"
The average was 9.843" per 180 degrees X 2 = a twist rate of approx. 1:19.7
I have confidence in this number.
Steve
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Pic b
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Pic c
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That is good stuff! Very interesting!
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Glad you like it.
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I've got a couple .25 Mrods probably from late 2017, early 2018. Would be nice if Crosman could supply a more definite date the GM barrels were phased out. I'm a little surprised that no official announcement was made. Seems like this is the equivalent of dropping LW barrels from the Challenger and not mentioning it....
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...Would be nice if Crosman could supply a more definite date the GM barrels were phased out... Seems like this is the equivalent of dropping LW barrels from the Challenger and not mentioning it....
Especially since Crosman changed the barrel spec...
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...Would be nice if Crosman could supply a more definite date the GM barrels were phased out... Seems like this is the equivalent of dropping LW barrels from the Challenger and not mentioning it....
Especially since Crosman changed the barrel spec...
I may be wrong, but it seems Crosman would rather rely on anecdotal reviews on their barrels than actually provide the specs.
The AG community has become much more knowledgeable and "sophisticated"? in recent years and Crosman would be wise to make specs available. The competition will do so and that may drive sales away from Crosman.
JMHO and I am far from an expert on any of this. So, please, take my comments for what they are worth. (chuckle)
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Steve, nice job on measuring the twist.... I think Crosman went the right way on that for shooting .25 cal pellets.... slugs not so much.... However, even for pellets it seems to me that a 0.005" choke is way too much.... ::)
Bob
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Thanks Bob,
I want to look at a slice of the barrel on a comparator. I don't know if I can get a pic of the image, it might be too dark?
I can defiantly measure the groove dia, groove width, land width. Give everything a good look. There must be a radius in and on all the corners.
Steve
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I don't know if these pics will show details, so I'll post a few and see.
When you look at stuff on a comparator, not all the details are clear. Things are a little blurry. Then I take pics of the blurry images with a cell phone, and then resize the pics which doesn't help.
I did this on break, it could be done better, but not today.
This is under 20x magnification. If you start at the center, and work your way right, you see .1 a little above the horizontal line, that is .100"
Look further to the right, and there's a .2, that is .200"
The kinda bold line between the .1 and the .2 is .150"
The next bold line to the right of .2 is .250"
If you follow the .250" circle all the way around, it's pretty clear that the land diameter is a little bigger than .250" That's why a .250" diameter brass rod slid into the bore with no resistance.
You can also see that the groove diameter is almost one line further out than the land diameter.
The comparator also has a digital readout, and I used that to measure the groove diameter, which is about .255"
I could check it 10 times and get a slightly different size each time. Not a huge difference, just .0001" or .0002" maybe .00025" at worst. My eyes have gotten older, and I hardly ever use comparators. And the ones I used years ago, were different. But you get the idea, you can enlarge and measure an image.
Steve
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try this one
OK, this one is pretty clear, not the pic I was describing though. One of the grooves is blown up here. The info about the line applies here too.
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I think this is the pic I was describing
Yeah, this one is pretty good. I could measure the width of the grooves in inches or degrees. Other stuff too. No time today though. You can see that the grooves are more than twice as wide as the lands. It all could be measured pretty precisely with this gizmo. You can click on this pic and blow it up pretty big.
Steve
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Just to put the info and pic together did some copy/paste
"
This is under 20x magnification. The lines on the chart are .0025' apart. If you start at the center, and work your way right, you see .2 a little above the horizontal line that is .200"
Look further to the right, and there's a .4 that's .400" the kinda bold line between the .2 and the .4 is .300"
The next bold line to the right of .4 is .500"
If you follow the .500" circle all the way around, it's pretty clear that the land diameter is a little bigger than .500"
You can also see that the groove diameter is almost one line further out than the land diameter.
The comparator also has a digital readout, and I used that to measure the groove diameter, which is about .255"
I could check it 10 times and get a slightly different size each time. Not a huge difference , just .0001" or .0002" maybe .0003" on a bad day.
"
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Yeah Kirby,
But I typed in the wrong info initially. The bore is NOT .500" it's .250"
I put in the wrong numbers.
Steve
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So it looks like 0.251" land and 0.255" groove, right?.... with a 19.7" twist.... I assume that is NOT at the choke.... To me, that seems quite large for pellets.... It would barely touch the head of a JSB King, likely not even engrave it all the way around.... if you didn't push it into the choke.... :o
Bob
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This section of barrel is from the breech end. A slice .115" thick. I was thinking about taking a sample from the muzzle end though, just for the heck of it.
I'm pretty sure the bore ID is .2502" max. Maybe .2503" but I don't think so. I turned a piece of stock .2502" and it was tight in the barrel.
The groove dia is .255"/.2553" give or take a few sub atomic particles.
Steve
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Yeah,
I was bummed out when the .250" brass rod slid right in. Woosh.... no resistance at all.
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I figured the sides of the lands wouldn't be square or sharp. A nice looking angle there.
All I need now is some really big pellets!!!!
Steve
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LW claim their barrels are 0.248"/0.254" (and smaller at the choke, obviously)….
Bob
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Yeah,
I checked the LW numbers a few times.
I wonder what their tolerances are?
Do they toss a barrel if it's .2477"??? Probably not. What are their limits to make it out the door?
I wonder how wide their lands and grooves are compared to crossman?
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A pic of the optical comparator. It's about 2 feet wide by 3 feet high.
The light goes thru the part, and an image is projected on the screen. The little table you put the workpiece on, can move left and right and up and down. The screen can rotate to check angles. The digital readouts have something like 50 millionths resolution.
Steve
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A pic of the optical comparator. It's about 2 feet wide by 3 feet high.
The light goes thru the part, and an image is projected on the screen. The little table you put the workpiece on, can move left and right and up and down. The screen can rotate to check angles. The digital readouts have something like 50 millionths resolution.
Steve
Thanks for sharing. I've never even heard of this device before, let alone seen one.
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I have had a few friends with pocket comparators 7x-10x...wonder how +/- they are good for... the one I looked thru was set up for thread pitch(metric) at the time...
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I estimated my Mrod slugging it at the Breech and the muzzle and estimated 250 Bore, 252 groove... at the choke it is .2495... Fowler cheap Micrometer
http://www.fowlerprecision.com/Products/Vernier-Micrometers/0-1-Outside-Inch-Micrometer-52-229-201.html (http://www.fowlerprecision.com/Products/Vernier-Micrometers/0-1-Outside-Inch-Micrometer-52-229-201.html)
BBT are best sized to either .2495-.250 so I think I got groove size right... checked a couple .250 drill bits with the mic and they did not fit the muzzle... My other .25 slugged the same .250 /.252 at the Breech and is tighter at the muzzle /choke...think groove is around .2483-.2485 ish...
I think Fowler has pocket comparators..?
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No problem Andy.
This particular comparitor actually has a resolution of 10 millionths. I just went and looked at it. That should be good enough.
Steve
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Hey Kirby,
It's good to see the dimensions of another barrel. Quite a bit different than mine.
Maybe Fuzzy or someone else can post their dimensions.
Thanks,
Steve
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Maybe Fuzzy or someone else can post their dimensions.
I'll be able to do twist rate but have nothing capable of measuring lands and grooves.
I appreciate the detail provided. :)
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If you have a 25 Mrod barrel and are willing to check the inside diameter at the muzzle and breech, I can send you some homemade aluminum rods that range from .245"-.250"
If you would rather have delrin, I can do that.
Just carefully check the bore, and then post the results.
Steve
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If you have a 25 Mrod barrel and are willing to check the inside diameter at the muzzle and breech,
I can send you some homemade aluminum rods that range from .245"-.250"
If you would rather have delrin, I can do that.
Steve
WOW! Thanks, I appreciate it. :)
Info has been IM'ed to you.
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Mine are the old barrel 2014 and 2016... just to be clear...
I need to look not sure where I put it but have a section of the Muzzle end of a choked Airforce L.W. barrel Owen sent it to me when he cut it off... If you want it to look at under the scope am willing to send it to you... like he did for me...
pic in reply #128 https://www.gatewaytoairguns.org/GTA/index.php?topic=110616.120 (https://www.gatewaytoairguns.org/GTA/index.php?topic=110616.120)
reply #79 has Mrod and XL 725 and L.W. muzzle pics https://www.gatewaytoairguns.org/GTA/index.php?topic=110616.60 (https://www.gatewaytoairguns.org/GTA/index.php?topic=110616.60)
looks like the new .25 Mrod barrel is heavily choked 6 Land/Groove and about 25% .255 land 75% .251 groove... so the .254 BBT may be a better choice now... also with a slow twist a probable no for the 51g .25 BBT... unless the the mold is decked removing the removing tail.. :(
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Kirby
How many grooves in the 25 GM barrel?
The piece of barrel I checked on the comparator was only .115" thick. I don't need a long piece. I figured the shorter the better. I think the ends need to be square to the bore though. If you find it, sure I could measure the land width and other stuff. Compare it to the crosman. If you send me a 2 inch piece, would it be alright if I cut off .150" or so and then returned it to you?
When I got this crosman 25 barrel, I did a quick check of the bore. A .249" pin gage would not go in the breech end. A .248"pin did go. It fit pretty nice, so I figured cool, a .248" bore.
But a few days ago, when I faced off the chamber a little at a time, I saw that there was absolutely no leed, just a nice sharp burr from the factory. That's what my pin gages hit. When I got rid of the burr, a .250" rod slid right into the bore.
If you want some homemade gages .245" - .250" I could send them to you.
Steve
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shame. maybe thats why my 2018 .25 mrod shot the bbt slugs poorly. any barrel options for a mrod slug gun?
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Oh man, this is looking kind of sad. I hope this doesn't bring the end of a good run for a great rifle.
I have a 25 that is supposed to be a GM. I will try to measure it this weekend when I get back home.
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They're still showing in stock on Hill website
https://hillairgun.com/products/m-or-a-25-rifle-barrel/
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They're still showing in stock on Hill website
https://hillairgun.com/products/m-or-a-25-rifle-barrel/
By the note at the end of the add, I’d say it is a crosman barrel.
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Steve been looking for the L.W. muzzle bit I know I have... a touch here and there but have been exhaustingly busy...framing and sheathing with a road trip for a friend(that just happens to have a by .001 zz class set of pins) mixed in...So have not been able to find it yet... Thought I had put it in my misc barrel area... so I hope I find it soon...doing the roof today and maybe some wrap and siding...my road trip Bud is helping with the window in about an hour...
Soon will have more time to look... know I have it unless my son thru it out...
I think we need more high quality educational pics to explain the plus/minus of different types of rifling and the ability to know at least that Mrod 25 Barrel is made about a certain spec...Others should be close...
So not giving up on finding it yet...
do appreciate the offer but have access to a set of pins... I have mainly used them to make sure my Folwler mic is accurate...
right now just annoyed and embarrassed with my forgetfulness... could have sworn I put it in the misc parts box...or with my barrel collection...
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Don't worry about it Kirby. Thanks for looking though. Sounds like you need to sit in the shade and have a gallon of homemade iced tea, not beat yourself up. I've misplaced things the size of bowling balls.
Absolutely, it would be great to hear from a barrel expert. It kinda seems like making barrels is a black art in some ways. But simple things like being .001" or .002" oversize is easy to find. If you make lots of parts, but don't, or can"t check every one, a few bad ones will go out the door.
I was gonna send you a 1/4" dowell pin. They are pretty accurate and hardened. Can sorta check a mic with that if that's all you have. I might have an extra standard laying around too. If I can find it. It's probably behind the bowling ball.
It seems like the .25 cal GM barrels have 10 grooves, and the .25 cal Crossman barrels have 6 grooves. Pretty easy to count the grooves.
Steve
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touch more to do... window is waiting till tomorrow... 80* all day but muggy at 50% humidity (recent t storm) 90* now... getting to close to being 60 for this.. ;)
Back in a while...
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Green Mountain has never sold individual barrels...
They offer barrels and blanks, sold to the individual... It's literally on their website... I'm confused as to why you say this... :o
I know we're not privy to the contract between crosman and GM, but I kinda feel like once you're contract is done, the product is good for sale on the open market- kind of like when a patent runs out. I'm sure I'm wrong, as I'm not a lawyer. But it makes sense to me.
I actually lis ted the prefits that were the exception in the same sentence. All other barrels they sell are unturned blanks.
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They're still showing in stock on Hill website
https://hillairgun.com/products/m-or-a-25-rifle-barrel/
By the note at the end of the add, I’d say it is a crosman barrel.
*NOTE: According to the last New .25 caliber Marauder RIFLE I purchased, it looks like Benjamin has changed their .25 caliber barrels. Instead of 10- lands and 10 grooves (which this barrel that is for sale from hill airgun has), to the barrels that are being sold with new .25 caliber Benjamin air rifles, that now have only 6- lands and 6- grooves.
Includes: 1- New .25 caliber GM barrel (10- lands and 10 grooves), paypal fees, and free fast Priority Mail shipping, within the USA
This is the note & item description from the Hill website, unless I am reading this incorrectly, he selling the old GM barrels.
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Ken sir, Mr. Hill must have seen this thread and edited it.
I have seen the description before, and it did not state it being a GM barrel emphatically.
I think the inventory will not last for long as GM barrels are no more ;D
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Have been following this thread guys...thanks for the research. I just checked mine and I do, in fact have a 10 groove barrel. My Marauder was purchased in 2015.
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I emailed Tim a few days ago asking if it was in fact a GM. He replied yes, and then I noticed that he updated the page.
Edit: I also ordered a few for some future projects. I would not wait to order one if you want one.
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It seems like the .25 cal GM barrels have 10 grooves, and the .25 cal Crossman barrels have 6 grooves. Pretty easy to count the grooves.
Steve
Steve, which one do you consider to be a better barrel? My uneducated guess would be the 10 grooves, which would control the projectiles better. I really have no clue is why I am asking this question. Six groves could also have an advantage in some ways?
I don't want to just assume that the Crosman barrel is somehow a worse barrel than the GM. They either made the switch for a good reason or just to increase their margins only. I really don't know why they switched.
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New here.. what is GM ???
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It seems like the .25 cal GM barrels have 10 grooves, and the .25 cal Crossman barrels have 6 grooves. Pretty easy to count the grooves.
Steve
Steve, which one do you consider to be a better barrel? My uneducated guess would be the 10 grooves, which would control the projectiles better. I really have no clue is why I am asking this question. Six groves could also have an advantage in some ways?
I don't want to just assume that the Crosman barrel is somehow a worse barrel than the GM. They either made the switch for a good reason or just to increase their margins only. I really don't know why they switched.
I would bet money that the change was about margins.
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New here.. what is GM ???
Green Mountain Barrel
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Hey Keith
I don't know squat about barrels. But I can measure them pretty accurately. I haven't shot the crosman 25 cal barrel that I bought, so can't say its good or bad. I know Uncle Bob is sure you need a faster twist rate for bullets.
I think all of us here are just trying to get info. At the moment, I'm wondering if all of the new 6 groove Crossman 25 barrels are approximately the same dimension wise.
Fuzzy has GM and crosman 25 barrels, so maybe he can give us some answers. I made him some cheap, but fairly accurate plastic gages to measure the bore, but the starter in my car died today, so I never made it to the post office.
I remember reading a story about the army buying like 1,000 rifles. They tested every one for accuracy, and a handful were really exceptional. Those went to the guys who could really shoot. They also got some duds. I think the story was like 50 years old.
If you or anyone here would like a set of 6 gages, I can send you a freebie. If enough guys measure the old and new barrels, we can determine the high and low limits on bore and choke.
I meant to clarify a few days ago, that the offer to Fuzzy, was actually an offer to everyone. Don't know if I stated that clearly.
Steve
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Cool. Thanks.. i just discovered hillairgun.. anyone know which state he is in?? Is it cheaper to buy complete rifle from him or send my rifle for him to mod.. ?
Example, i am interested in benjamin marauder .25 with GM barrel.
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Hey Keith
I don't know squat about barrels. But I can measure them pretty accurately. I haven't shot the crosman 25 cal barrel that I bought, so can't say its good or bad. I know Uncle Bob is sure you need a faster twist rate for bullets.
I think all of us here are just trying to get info. At the moment, I'm wondering if all of the new 6 groove Crossman 25 barrels are approximately the same dimension wise.
Fuzzy has GM and crosman 25 barrels, so maybe he can give us some answers. I made him some cheap, but fairly accurate plastic gages to measure the bore, but the starter in my car died today, so I never made it to the post office.
I remember reading a story about the army buying like 1,000 rifles. They tested every one for accuracy, and a handful were really exceptional. Those went to the guys who could really shoot. They also got some duds. I think the story was like 50 years old.
If you or anyone here would like a set of 6 gages, I can send you a freebie. If enough guys measure the old and new barrels, we can determine the high and low limits on bore and choke.
I meant to clarify a few days ago, that the offer to Fuzzy, was actually an offer to everyone. Don't know if I stated that clearly.
Steve
Thanks Steve! If you want to send me those rods, I'll measure my two. I have two GMs. One is in use and the other is new. It would be good to know more of what I have. I can't seem to get my measurements to agree consistently. Just pm me for my address if you do.
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Have been following this thread guys...thanks for the research. I just checked mine and I do, in fact have a 10 groove barrel. My Marauder was purchased in 2015.
Hey Mike,
Thanks for confirming that a 25 Mrod barrel produced in 2015 has 10 grooves. I can say positively that the Mrod barrel I bought in August of 2018 has 6 grooves and six lands.
It would be nice to see groups at 50 and 100 yards from the respective barrels.
Steve
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Cool. Thanks.. i just discovered hillairgun.. anyone know which state he is in?? Is it cheaper to buy complete rifle from him or send my rifle for him to mod.. ?
Example, i am interested in benjamin marauder .25 with GM barrel.
https://www.ebay.com/itm/hill-airgun-5716-moderator-for-Benjamin-Crosman-and-other-air-guns-/272828288721 (https://www.ebay.com/itm/hill-airgun-5716-moderator-for-Benjamin-Crosman-and-other-air-guns-/272828288721)
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Sure thing Keith. I turn a .245", .246", .247", .248", .249" and a .250" The overall length is about 1.500" and I turn a length .650" long. I make them from .312" stock.
The ones I made for Fuzzy were within a tenth or two. Do you want aluminum or plastic?
Steve
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Steve, this is one of my most accurate guns off of the Caldwell field pod..only have about 27 yards to test, but my gf shoots dime groups. It is her favorite gun!
I think I have some pics of the targets, will look when I get back from the airport..IF I get back. We had a major fire(s) in Maui the last few days, gf had to evacuate, I got stuck on other side of Island, and some 500 people at airport night before last. should be ok as the fires are 70-90% contained https://mauinow.com/ (https://mauinow.com/)
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Sure thing Keith. I turn a .245", .246", .247", .248", .249" and a .250" The overall length is about 1.500" and I turn a length .650" long. I make them from .312" stock.
The ones I made for Fuzzy were within a tenth or two. Do you want aluminum or plastic?
Steve
IDK, whatever is best at measuring. Aluminum sounds more accurate when just guessing. Whatever is best on you. I'll send you my address.
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Which PCP air rifle you guys think the best out of the box for $350-$500 range? Reliable, accuracy, powerful, and quietness.
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Steve, this is one of my most accurate guns off of the Caldwell field pod..only have about 27 yards to test, but my gf shoots dime groups. It is her favorite gun!
I think I have some pics of the targets, will look when I get back from the airport..IF I get back. We had a major fire(s) in Maui the last few days, gf had to evacuate, I got stuck on other side of Island, and some 500 people at airport night before last. should be ok as the fires are 70-90% contained https://mauinow.com/ (https://mauinow.com/)
That's awful. You really gotta be glad you're alive.
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IDK, whatever is best at measuring. Aluminum sounds more accurate when just guessing. Whatever is best on you. I'll send you my address.
[/quote]
Aluminum it is!!!
Steve
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Which PCP air rifle you guys think the best out of the box for $350-$500 range? Reliable, accuracy, powerful, and quietness.
Other than the guns I have in my sig, I have no experience with any others e.g Kral Arms, Hatsan (one exception), Air Arms, etc. I can compare the .25 Marauder and the Hatsan Flashpup though....Marauder hands down. Especially with the GM barrel. With a spring change and heavy pellet, I was hitting about 54 FPE, quiet and accurate. Most powerful, (without getting into the big bores) easily modified, at that price range.
I actually like all of the guns I have, some are more reliable than others, some more accurate than others, some just more aesthetically pleasing than others. For me, that is one of the many attractions of airgunning!
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Steve, this is one of my most accurate guns off of the Caldwell field pod..only have about 27 yards to test, but my gf shoots dime groups. It is her favorite gun!
I think I have some pics of the targets, will look when I get back from the airport..IF I get back. We had a major fire(s) in Maui the last few days, gf had to evacuate, I got stuck on other side of Island, and some 500 people at airport night before last. should be ok as the fires are 70-90% contained https://mauinow.com/ (https://mauinow.com/)
That's awful. You really gotta be glad you're alive.
Thanks Steve, fortunately no lives or major structures were affected. We weren't in any danger perse', but I was close to some fires driving. The Emergency management community did a great job at containing these fires.
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My car starts!!!
A wire came off the solenoid. Easy fix, zero $
In February a tie rod end pulled out of the center link, or whatever they call it now with rack and pinion. Good thing I was only going 30mph. That could have been BAD. Apparently when they did an alignment, they didn't tighten the lock nut. Eventually the threads wore away.
Steve
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My car starts!!!
A wire came off the solenoid. Easy fix, zero $
Steve
That's great! Love those easy fixes.
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I just received the shipping notice from Mr. Hill. That guy really ships fast. I have ordered some parts from him on several occasions, and he is always quick.
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Currently listed as OUT OF STOCK!
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I have a few laying around both new and used. PM me if your looking for one.
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What kind of groups is everyone getting with the mrod 25 cal. Crosman barrels at 50 yards?
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What kind of groups is everyone getting with the mrod 25 cal. Crosman barrels at 50 yards?
I haven't recorded any groups in awhile, but here are all of the groups with the GM barrel I have recorded, back when I first got my .25 cal, or when tuning shortly afterwards.
The first groups/pic are at 25 yards, but the rest are at 50 yards. I may have been more focused on turning than groups, but this should give an idea. Some groups are when I was just testing different pellets, too. I settled with the MKIIs and is all I shoot these days. They have proven very worthy since and provide the most thump, which I like.
(https://i.ibb.co/xF2z6P4/1st-25-Cal-Synrod-Test-4-19-17.jpg)
(https://i.ibb.co/3N1MLyR/25-cal-50-yard-Groups-6-21-17b.jpg)
(https://i.ibb.co/Hzwwt9n/25-Cal-50-yard-Groups7-9-17-1of-2.jpg)
(https://i.ibb.co/wYvRgQs/25-Cal-50-yard-Groups7-9-17-2-of-2b.jpg)
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That GM barrel is a shooter I hope the Crosman barrels does the same
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That GM barrel is a shooter I hope the Crosman barrels does the same
One would think that Crosman would be standing on the highest mountain yelling this at the top of their lungs if it were.
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Raining here this AM, so had a few minutes to do the first measure. This is the crosman 25 barrel. It has 6 lands and 6 grooves.
For twist rate I get 1:19". I did it with a half rotation or 0.5:9.5"
Using the gauges I got from Steve, get 0.246" for the choke and it is a tight 0.246". They do not go deep enough to get a measure of the bore, but the choke is what I wanted to know about.
Since I had the barrel off, I opened the TP to 0.187" and deburred.
PS: I did notice some circular tooling marks about a 1/2" past the TP. They look like they had been smoothed out.
Next up will be a GM barrel from my Gen 2 Mrod, which was one of the first 100 sold.
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Rats....
I made the gages .650" long.
How long do they need to be? The longer they are, the more difficult it is to make.
I can send you longer gages, and a .2455" to get a little closer on the choke.
Steve
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GM #1: (from my Mrod)
Choke: 0.247" the pin is not quite as tight as crosman
Rifling: 10 lands and grooves
Twist Rate: 1:17"
GM #2: (purchased used, years ago from Mrod forum member)
Choke: 0.247", the pin is not quite as tight as crosman, but same as GM #1
Rifling: 10 lands and grooves
Twist Rate: 1:18"
These were both measured in gun, from muzzle, and only explaination I have why I got different twist rate.
The crown is different on the crosman 25 barrel (left most) as you can see in picture below.
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Rats....
I made the gages .650" long.
How long do they need to be? The longer they are, the more difficult it is to make.
I can send you longer gages, and a .2455" to get a little closer on the choke.
Steve
Steve,
Some numbers to compare to what you got, anyway.
I'm not sure on the right length, but my guess would be 1" or slightly longer. That should get back to the tightest part of the choke, if 0.650" wasn't far enough, and get into the bore, a half inch past the TP.
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John,
A 245" diameter gage goes into the muzzle freely. A .246" diameter gage is tight in the muzzle. The .246 would not fall out of the bore by gravity alone right?
So the actual size of the bore at the muzzle is somewhere between .245 and .246"
If I send you a .2455" diameter gage, you can narrow down the size of the choke a little more.
Will the .2455" gage go in freely?
Steve
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John,
A 245" diameter gage goes into the muzzle freely. A .246" diameter gage is tight in the muzzle. The .246 would not fall out of the bore by gravity alone right?
So the actual size of the bore at the muzzle is somewhere between .245 and .246"
If I send you a .2455" diameter gage, you can narrow down the size of the choke a little more.
Will the .2455" gage go in freely?
Steve
In the crosman barrel, the 0.245 is loose, and the 0.246 is very tight. You have to push it in with a bit of force.
Using my HF calipers, the one I labeled 0.246 measures 0.2455, and the 0.246 and 0.247 are reading 0.0005" low. That is probably the calipers.
I think we can say the crosman is 0.001" tighter in the choke than the GM.
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John
We can definitely get the bore size to within .0002/.0003"
I measured your gages with a Mitutoyo micrometer that has a .0001 Vernier scale. I went a step better with Keith's gages and measured those with an indicator mike. You can see 20 millionths with that. I clearly marked the size on his aluminum gages. I marked the size on yours too, but the writing is pretty light.
The plastic being kinda soft isn't the best gage material. It really gives you just a rough idea. Wanna try a brass gage? Or PEEK, I have some PEEK. Not sure how hard the PEEK is compared to Delrin. The Delrin can be deformed pretty easily.
I was thinking about how I measured the twist rate. I aligned the wrench/indicator with a cheap square I got at the hardware store. It could be off by a degree or maybe more. My eyes could be off a little too. And my lathe has nicks that could cock the square a little. Add it all up and it makes a difference. I figured if I really had 177 degrees of rotation, instead of 180 degrees, the twist rate would change by over half an inch. Since I only measure a half revolution and then multiply by two, any error I have is also multiplied by two. A degree wheel would give a better reading.
Steve
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Steve,
Alum or brass would be fine. Whichever is easier for you. I will just have to be careful and not push it in, like I did with the Delrin.
I re-chronied the crosman 25 barrel with JSB 25g, and seems like it loss about 20fps from what it was with GM. Not that much, and could be something else minor that changed over time.
It will take allot of bore paste to take the choke down 0.001"
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I just received the rods from Steve.
On my spare GM barrel (10 lands). The .245 is the only one that will slide into the muzzle end. it is a snug fit. On the .250 leade end, .248 is the last one that will enter the lands past the leade. So, .248 barrel lands with .245 choke lands. 1:19 twist.
On my installed GM barrel, I'm getting the same results at the muzzle end as I expected, but is not quite as tight to insert the .245. This maybe due to having thousand of rounds through it compared to the unused spare. These two barrels are roughly of the same date range. About three to four years old now.
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Keith
How about we try a .2485" gage in the breech end? Or a .2486 and a .2488? Get a little closer.
Glad the gages were long enough to reach past the chamber. I machined off my chamber to cast the lead slugs. Didn't measure it before I turned it into chips. I guessed at how long to make the gages.
I thought the Green Mountain barrels were 1:15.5 twist?
Thanks for the info.
Steve
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Keith
How about we try a .2485" gage in the breech end? Or a .2486 and a .2488? Get a little closer.
Glad the gages were long enough to reach past the chamber. I machined off my chamber to cast the lead slugs. Didn't measure it before I turned it into chips.
I thought the Green Mountain barrels were 1:15.5 twist?
Thanks for the info.
Steve
I'm game. It's whatever you feel like doing. I do thank you for your time and efforts!
As far as twist, read this thread. I have checked mine myself, but there are several pros that have done so as well and offered their input on this thread:
https://www.gatewaytoairguns.org/GTA/index.php?topic=152675.25 (https://www.gatewaytoairguns.org/GTA/index.php?topic=152675.25)
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I just read the twist rate thread. Thanks for the link. I think.
If we passed around one barrel, I wonder what kind of range the twist rate would have?
Maybe Chubby could help us?
https://www.youtube.com/watch?v=aEt80lt01vE (https://www.youtube.com/watch?v=aEt80lt01vE)
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.25 purchased from crosman 4/9/18 has the GM 10 land barrel. finally checked.
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Hey Clark
Thanks for the info. I bought my 25 Mrod barrel from crosman in August of 2018, and it has 6 grooves. So the change occurred between April and August of 2018
Steve
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it appears the barrel I was referencing in the twist rate thread is a Crosman barrel. My testing came up with 1:19 twist rate. It may or may not be as accurate as the GM barrels, but it is pretty accurate. It has a very tight choke which received a good bit of work with bore paste prior to installing in my P15. Slinging JSB 25gr around 900fps will produce easy sub 1.5" groups at 80 yards.
While the Crosman barrel may not equal the GM, it is still a good value for those of us that do barrel swaps with little to no machine shop support.....
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I contacted GM a good number of years ago about 22 cal barrels for the Mrod. I think the minimum quantity was 1000. Far more than we would ever get with a group buy.
I went to Green Mountain Rifle Barrel Co.in Conway NH. last Year ,Only 100pcs Orders for Airgun Barrels and None to fit Crosman Guns.....
WHY? You can buy a single Ruger 1022 Match barrel from Them WHY ? (Contract w/Crosman) Forbids it ????? Not Now if no more Contract w/Crosman. for .25 Barrels. Must Stop by GM again in April when Warmer There and see about A(One) .22 Barrel for a Discovery.....Franky