Author Topic: Shorten Hatsan barrel. (Read 6982 times))

RCO · « **on:** March 25, 2016, 05:06:43 PM »

I'm wondering if shortening the barrel will help accuracy.

From what I have read all the air is used up in a springer after around 10" of barrel. After that the pellet is just coasting. So a shorter barrel will not cause a lose of FPS.

If it takes less time for the pellet to leave the barrel, that should help with keeping the barrel on target. You have to hold it for a shorter time.

A shorter barrel should be stiffer so harmonic waves should have less amplitude.

What do you think?

dw · « **Reply #1 on:** March 25, 2016, 05:13:25 PM »

I don't know enough about the technical details to answer, but I hope a shorter barrel doesn't harm accuracy; I'm anticipating I'll soon be ordering one of the new 135QE in .22, and I understand they've shortened the barrel down several inches, to 12" if my recall is correct. Can't wait to hear the reviews on that new gun.

I shall follow this thread with interest.

Dennis

Motorhead · « **Reply #2 on:** March 25, 2016, 05:30:58 PM »

Couple issues to address ...

1st if a barrel cocker, it will take a LOT more effort to cock shorter barrel gets cut.
2nd if barrel is CHOKED, cutting barrel will remove it and in all likelihood accuracy will suffer.
3rd is that of muzzle FLIP during the shot cycle. Longer & heavier barrels tend to rise less than short ones especially when guns are magnum in power rating.

Once cut ... you can't go back ... so choose wisely.

lefteyeshot · « **Reply #3 on:** March 25, 2016, 05:31:44 PM »

That's the theory. Mendozas and also the TFM8, M12 and Bronco they make only have the first 9-10" rifled and the rest is bored out bigger. I guess to make it easier to cock.

SpiralGroove · « **Reply #4 on:** March 25, 2016, 05:36:36 PM »

Guys,
We know the AA Pro Sport has a 9.5" barrel and it retails for $779 from PA. It is a very accurate gun! So anything above that length should do fine, it's just a matter of how much care went into making the barrel?

We know most Hatsan don't miss a beat when it comes to Looks, but at times the quality control has been a bit underwhelming. So who knows, except shorter doesn't have to mean less accurate.

RCO all we know is that the harmonics will be different. Adding weight to the muzzle (brake) has shown to help accuracy when hamonic issues occur. $:-\$ I bet Bob rsterne has a post on this!

RCO · « **Reply #5 on:** March 25, 2016, 06:06:21 PM »

Flip would be addressed with metal break for weight. Cocking effort could be addressed with the muzzle break having a bored out section pass the end of the barrel. So flip and cocking is not a problem. I can cock the shorter barrels I have two.

Now for the harmonics. Along with the shorter stiffer barrel I would like to machine and try a harmonic balancer.

SpiralGroove · « **Reply #6 on:** March 25, 2016, 06:25:50 PM »

Rob,
I can't believe I haven't shot my springer's much in 1.5 years

. I personally would need to read up on barrel harmonics before I attempted what you suggest. It's way above my pay grade at this time, but shouldn't be that hard to figure out.

Good Luck

SpiralGroove · « **Reply #7 on:** March 26, 2016, 02:01:25 AM »

Hey Rob,
One last thing, I would listen to Motorhead more seriously about his item #3: Barrel Flip. I recently sold a Hatsan 95 to another member where I had cut the barrel down to 10" or so. I did the "The Cut" mainly to reduce the barrel heavy nature of the Hatsan 95, not so much because of length (even though that was what was making it heavy in the first place

)
I had added a pretty solid aluminum muzzle brake, but the gun always seemed to be a little more hold sensitive after the Cut, and I never experimented with adding more weight. The gun I sold, shot well in my 13 yard crawl space, but it may have been my mistake to think this would translate to longer distances? Was Barrel Flip a factor, I don't know $:-\$ .

I tend to have a pretty good "gut level feel" about changes I make to my guns, but I have errored too

Long Story Short--> take your time and if you cut the barrel too short - Hatsan only asks about $50/$75 for another

One of the things I've learned on my journey to becoming an "Old Timer" here on the GTA. If you choose not to listen to Bob or Scott (I can be pretty Pig Headed) you roll the dice. It's a very strong possibility you will waste a lot of your time or should be prepared to open your wallet

Also, don't make a serious mistake with HPA or you could end up with shrapnel in your Azzz.

I hope that helps .................... Kirk

Gut2Fish · « **Reply #8 on:** March 28, 2016, 07:02:16 AM »

You will lose power. I've no doubt of that. What the ratio of compressed air volume to barrel volume is for optimal performance I've no idea. A potato gun is 1.5 to 1 but that's working on combustion chamber not compressed air volume.

There is no such thing as air piddling out of pressure when in a barrel unless it's so long energy was taken by friction. It's pushing that pellet all the way. If the barrel is short then the full momentum possible is not realized. Air escapes end of barrel with energy left that could have increased speed. Louder reports are unrealized velocity potential. If the barrel is too long then friction starts to take over and pellet slows. There is an optimum ratio of chamber to barrel. Volume of air at certain PSI will correspond to volume of barrel at some ratio. Imagine you can Google it.

SpiralGroove · « **Reply #9 on:** March 28, 2016, 11:37:27 AM »

Hey Garrett,
I'm no expert, we need rsterne for that, but ......
- When talking PCP's, yes barrel length is directly proportional to velocity/power.
- If were talking Springers, anything > 9.5" in barrel length only marginal affects power/accuracy.
That's why the AA ProSport costing $779 only has a 9.5" barrel.

Yogi · « **Reply #10 on:** March 28, 2016, 11:46:22 AM »

Quote from: SpiralGroove on March 28, 2016, 11:37:27 AM

- If were talking Springers, anything > 9.5" in barrel length only marginally affects power/accuracy.

Why do you say that?

The same principles apply.

Diana says that their Compact barrels shoot 20-30 fps less than their longer ones, 19" vs 15".

-Y

RCO · « **Reply #11 on:** March 28, 2016, 12:06:16 PM »

Yogi,could you show the link to that info please. I've got 2 shortened barrel rifles that I can see no drop in fps.

SpiralGroove · « **Reply #12 on:** March 28, 2016, 01:10:48 PM »

Guys,
I would have to agree with Bob's (rsterne) brief statement on this thread relative to springer barrel length and velocity/power. He doesn't provide the math to back up his statement, but he has before and I'm sure it's out there on the GTA somewhere.

http://www.gatewaytoairguns.org/GTA/index.php?topic=86268.0

Gut2Fish · « **Reply #13 on:** March 28, 2016, 01:43:59 PM »

I'll go with what Bob put out there. What your seeing is a 10-12 FPE gun's barrel length is maxed out at 10 inches. That's very believable. Something on par with Gamo and Hatsan 95 closer to 16 inches barrel length for 20 FPE gun. Now lets step that up to a 125 or 135 gun with 30 FPE. The 95 barrel is just over 17 inches. The 125 is near 20 inches. How much could one shorten that before losing velocity? Not much. As soon as lower velocity is realized the inaccuracy will rise. They will be proportionate to one another. Reason being is the air once out of barrel will travel faster than the pellet that it's no longer pushing. That unused energy will make for a louder shot and the faster air will wrap around the pellet pushing it off course. This is similar to pellet disturbance when getting close to speed of sound. The accuracy suffers as the air around pellet is disturbed by external forces. With a barrel too short that force is air pushing past the pellet. With speed of sound it's the pellet pushing through the pressure barrier.

It's my belief your accuracy will suffer. If you don't believe anything else I've stated let's go in another direction and try and think of short barrel sharp shooting guns. The longer the barrel the more accurate the shot. In twist and guidance the pellet is aided by the barrel length. The fraction of milli second lost time to aid in not moving the barrel during the shot is an interesting theory but 2-4 inches in 800-900 fps is not gaining much time.

SpiralGroove · « **Reply #14 on:** March 28, 2016, 02:12:27 PM »

Hey Gut2Fish,
Like Bob suggested, magnum springer's can benefit from longer barrels; by how much is debatable.
Keep in mind that the AA Pro-Sport with a 9.5" barrel is no slouch in accuracy.

If we compare the AA ProSport (9.5") vs. the AA TX200 (13.9" barrel): Assuming power source is = $:-\$ .
- In .177 caliber their velocities are 950 fps vs. 930 fps.
- In .22 caliber their velocities are 750 fps vs. 755 fps.

So as we increase pellet weight/FPE, we can see can see the added 4" in barrel length has helped marginally. This isn't a perfect example, but at about 16/18 FPE, we see a little difference. How proportional this increase is in a Hatsan 95, 125 or 135 can be debated.

Also, keep in mind this gun has a LW barrel and is manufactured at the above lengths. I think cutting the manufactured length to 10" introduces other issues relating more to accuracy (barrel flip/hold sensitivity/harmonics) than power loss.

That's all I got on this one

.

Gut2Fish · « **Reply #15 on:** March 28, 2016, 02:25:02 PM »

Plugging some #'s in and playing around as I found it interesting and am bored. Day of boiling sap in the rain so tend to fire every 30 minutes then get inside. Any who. Using the piston diameter and sweep of hatsan 125 and barrel volume for .177 caliber it equates to a 10 to 1 ratio. All else aside as to if all that barrel volume is need let's just look at how short the barrel can be if same volume and .25 caliber. Drum roll please...tad under 10 inches long.

Something to keep in mind if cutting barrels is the caliber does indeed dictate the length of barrel. Volume is volume. Larger caliber is shorter barrel needed.

Thought it was interesting. Ok, back out to stoke the fire.

Not to steal thread or anything but what I find neat is I've always thought the 135 was too short a barrel to reach it's full potential. It has 10% more chamber volume than the 125 but only manages 5% more velocity. Since I had some area numbers of calibers already written down went and plugged in a bunch of things. The 10:1 ratio does indeed seem to hold up. Looking at other riffles set ups, in particular the Hatsan 95. If I use .177 caliber for the 95 piston volume it equates to that guns barrel length. Interesting indeed. Going back to the 135 and using same ratio and caliber I predict it would realize it's full velocity in .177 caliber if barrel was 21 inches long instead of 19.7. Not short enough to mess with accuracy yet but enough to start effecting velocity in that caliber. If this all holds up then one could surmise a 135 in .22 would realize it's full potential, in .25 possible ever so slight loss due to friction travel of that 9 inches extra barrel. 135 volume and .25 cal came to 10.5 inch barrel needed.

Physics is fun and all but think I'll watch Bob's Burgers now.

Cheers

RCO · « **Reply #16 on:** March 28, 2016, 03:29:36 PM »

I’m not arguing because I am no expert.

I don’t disagree with either of these statements Bob made. What Bob said was, “Optimum barrel lengths for springers are in the 10-16" length, depending on power.” The 125 and 95 barrels are both longer than 16”. Kirk you cut the new 95. How much velocity did you lose? Bob also said, “Your comment about shorter barrels being less susceptible to movement during recoil has merit.

Then here is what Tom Gaylord said.
As you see, barrel length is a springer is relatively unimportant. It stops affecting velocity after nine inches, or so. The only things it does affect are the distance between the front a rear sight and, on break barrels, the length of the cocking lever.
Gerald Cardew pointed out in The Airgun from Trigger to Target that only the first six inches of the barrel is needed for a spring gun to achieve maximum velocity today’s spring-piston guns probably don’t use more than the first 10 inches of barrel for top velocity.

So there are many opinions and I got several.

AudiS4 · « **Reply #17 on:** March 28, 2016, 03:59:05 PM »

I cut off 4 inches, and got zero loss in fps. Accuracy is the same aswell.

Vinícius Alves · « **Reply #18 on:** March 28, 2016, 04:55:24 PM »

the pellet is accelerated only during first 6 inches, it's well documented on the book "airguns - from trigger to muzzle"

SpiralGroove · « **Reply #19 on:** March 28, 2016, 05:23:39 PM »

Guys,
Here's what I got on my Hatsan 95 (.177) comparison. Keep in mind this is not the same gun before/after, but a comparison between two Hatsan 95's in .177 caliber 1) OEM and 2) barrel cut 1.5".

5 Shots: CPUM 7.9 grain
1) OEM - 947, 948, 947, 956 & 940
2) Cut - 949, 956, 943, 943 & my crony was acting up got ER2 five times in a row

So, small sample from a small 1.5" cut in (2) different Hatsan 95's in .177 caliber -> shows no difference.
For what that's worth

All in All - Let's quit worrying about velocity loss upon reasonably cutting ones barrel

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Shorten Hatsan barrel.

Author Topic: Shorten Hatsan barrel. (Read 6982 times))