Drawbacks of a carbine?

I have only owned one .308 chambered rifle out of the 75-80 or so firearms I have owned and will never own another, they bore me...

Have a look here:

http://www.loadammo.com/Topics/October05.htm

You said there is no velocity lost from cutting a .308 barrel 6". Either way there is velocity lost. Whether or not you think it is significant is not my point. It does happen and to some people velocity does matter. To myself velocity is important as are many other things in a cartridge, I try to get the most out of every rifle I own in every aspect.
 
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crazy_davey said:
You said there is no velocity lost from cutting a .308 barrel 6".
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dont twist my words. i said that an article i had read claimed that chopping a .308 barrel from 26" to 20" resulted in no velocity loss with 168gr Match ammo, and then said:
perhaps with the relatively tame match ammo in a .308 there wasnt enough of a noticeable velocity loss from 26-20". they did (obviously) record drops in 20-18, 18-16 and below 16" velocity loss was far more dramatic.
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im still waiting for the real world results you claimed to have, not a link to a site listing theoretical decreases determined by a ballistic formula.

despite the fact that you stormed into this thread calling people 'full of sh!t' and claiming to have experience in the matter you just admitted you have never cut or chrony'd a .308 barrel.... in which case you are no more reliable a source than whatever article was mentioned - which was my point all along. ill give the article the benefit of the doubt until someone posts conflicting data or personal experience proves otherwise.
 
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crazy_davey said:
I have only owned one .308 chambered rifle out of the 75 or so rifles I have owned and will never own another, they bore me...

Have a look here:

http://www.loadammo.com/Topics/October05.htm

You said there is no velocity lost from cutting a .308 barrel 6". Either way there is velocity lost. Whether or not you think it is significant is not my point. It does happen and to some people velocity does matter. To myself velocity is important as are many other things in a cartridge, I try to get the most out of every rifle I own in every aspect.
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Thank you for the link Dave, the formulae will be handy.
 
manbearpig said:
i said that an article i had read claimed that chopping a .308 barrel from 26" to 20" resulted in no notable velocity loss with 168 grain Federal Match ammo.
nice try though.

im still waiting for your real world results, not a list of theoretical decreases determined by ballistic formulae.
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So what, you want me to post data from rifle barrels I have cut down that were not chambered in .308? Why waste any more time, you will just use that as your next argument as you already have. If you want the data that I have for the rifles I have shortened I will post some numbers tomorrow, but you probably will just argue my results. I am not really seeing the point at this time as I am arguing with a guy with absolutely no experience on the subject accept a mythical article that he cant seem to find.

manbearpig said:
the guys that cut a .308 down reported no velocity loss from 26-20" with 168gr Fed Match
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The fact is in the real world it does happen, match ammo or not, .308 or not. Why a .308 would be so special as to not be effected at all losing 6" of length is beyond me. Maybe you could explain that one to me and the others. I have data from shortened barrels on 270's, 30-06's, 300WM, 375H&h, 45-70 and soon 300SAUM. All of the ones that I have ever done were effected, some more than others but it did happen. I don't need to dig up my reloading data to know that. I also don't need to chop a .308 chambered rifle 6" to know for a fact that the velocity will be effected.

But as I said I have never shortened a .308 chambered rifle as they bore me. So maybe they are ever so magical to not lose any velocity loosing 6" of barrel. Maybe the article that you cant find would explain this amazing phenomenon.

It is quite obvious that this is going nowhere because you cant even comprehend the simple, basic concept of how velocity is lost when shortening a rifle barrel. Especially when taking 6" off, .308 or not.
 
manbearpig said:
dont twist my words. i said that an article i had read claimed that chopping a .308 barrel from 26" to 20" resulted in no velocity loss with 168gr Match ammo, and then said:


im still waiting for the real world results you claimed to have, not a link to a site listing theoretical decreases determined by a ballistic formula.

despite the fact that you stormed into this thread calling people 'full of sh!t' and claiming to have experience in the matter you just admitted you have never cut or chrony'd a .308 barrel.... in which case you are no more reliable a source than whatever article was mentioned - which was my point all along. ill give the article the benefit of the doubt until someone posts conflicting data or personal experience proves otherwise.
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You believe whatever you want. I have seen the effects of shortening a rifle barrel first hand, many times. My results wont mean anything more to you than your mythical article because they were not in a .308 chambered rifle.

Pretty hard to even have a conversation with a guy who changes his posts 3-4 times before he is happy with what he said.(yes, I read it every time you changed it)

Done.
 
jedimaster said:
The plan is synthetic stocks, pistol grip on the rear, bipod on the front, cut to carbine with a Nikkon ProStaff 3-9x50 scope with a ballistic drop retical.
The stock and scope are almost a gurantee as I don't want to take the nice condition wood stocks threw the bush.
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The advantages of a carbine are lightweight and handling while in thick cover, or "the bush" as you say. A Nikon 3x9x50 w/a long range reticle will definately defeat the advantage of a shorter bbl. Lose the bi-pod and add a smaller 1.5x5 and then you are on the path to a proper carbine for hunting threw the bush.

....... or are you trying to create a tactical weapon for hunting?



.
 
Wow, HTF did I miss this?

manbearpig said:
ATM i have three 16.5" barreled .308s, as well as 22", 24", 26" and whatever length an M305 is.
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You seem to have all the answers on .308 velocities at your finger tips MBP. Please post your velocities from each .308 rifle you own all using the same factory load and I will take detailed notes on what you get.

You should be able to prove your point in short order with some chrony numbers out of what you have listed above. Why bother arguing using an article you cant seem to find when you have all the answers on hand :confused:
 
Because length is only one dimension of a barrel that is relevant to velocity, I don't know how useful it is to compare different .308 rifles with barrels of various lengths and try to come to some conclusion about the value each inch of barrel as it pertains to velocity. We know that there are fast barrels and slow barrels. We know that some barrels have more consistent internal dimensions than others, we know that some barrels have rough internal surfaces while others are glass smooth, and we know that the rate of twist has an effect on velocity. It is quite possible for a shorter barrel to have more velocity than a longer barrel. To answer the original question in a useful manner, we must consider the effect of cutting an existing barrel with a known velocity. Clearly to shorten a barrel is to remove from it's internal volume. If the volume in which propellant gasses can expand is reduced, it follows that the time the gases have to expand behind the bullet is also reduced, and that as a result there must be less velocity. As I stated before, the amount of loss is dependent on powder volume, caliber, and the sectional density of the bullet.

My .308 target rifle has a 28" barrel from a reputed maker. The Sierra manual shows that a .308 loaded with 200 gr MK has a velocity of 2450 fps with 45.5 of W-760 from a 26" barrel. During my load development, I clocked the 200 gr MK at 2484 fps with 45.0 grs of 760 and 2528 fps with 46.0 grs.

I would be inclined to think that the Sierra test barrel would not be internally identical to mine, but that they undoubtedly also use a very good barrel. It appears to me that the difference in velocity between the 26" and the 28" barrels is significant, depending on one's definition of significant. It is also interesting to note that 45.5 grs of W-760 is the maximum load listed in the manual, but that using 760 brought me to within a hair's breadth of 2700 fps when the velocity plateaued.

Again we see that there is a difference between rifles that internally should be all but identical. One difference could be the way I had my rifle chambered. The chamber is cut so that with a 200 gr MK, the bullet's boat tail enters the shoulder area of the case and the shank of the bullet makes contact with the neck of the case from the top of the boat tail forward, and when a round is chambered in the rifle, the ogive of the bullet touches the rifling.
 
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crazy_davey said:
Wow, HTF did I miss this?

You seem to have all the answers on .308 velocities at your finger tips MBP. Please post your velocities from each .308 rifle you own all using the same factory load and I will take detailed notes on what you get.
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were not talking about velocity loss from 20-16.5", the point was 26-20. if you scroll up to my first post on the topic it mentions velocity losses on a steep curve below 20". can you grasp the simple fact that velocity loss is not linear?

and ill spell this out for you again in big letters so its easy to understand: im not 'claiming' anything. i posted something i had read, clearly said multiple times that i had nothing to do with the test but until someone posted otherwise it seemed to make sense, and that once they did id gladly change my mind.
if someone dropped in and said 'heres an article listing the test results of cutting down a .308 barrel and the average velocity losses for every inch cut', or 'i cut a .308 barrel down from 26" to 22" last year and the average of 20 before/after shots shows __ velocity was lost' id have said 'ah - thanks' and that would have been the end of it.

but you storm in and call people 'full of sh!t' yet you have zero experience with the .308 and refuse to post anything specific other than 'im sure it will lose some velocity'. a monkey would understand that the minimal barrel length and velocity loss per inch cut is different for almost every cartridge, and you cutting back a .375 H&H Mag has absolutely no relevance here.

it took you three hours of searching last night to come back with some weak link to a ballistics formula as opposed to the actual chrony data you claimed to have all along.
how bout next time, until you have specific relevant data you refrain from being a typical internet armchair expert and keep your mouth shut as opposed to storming into a thread and calling people 'full of sh!t'. theres a dozen posts of thread progression above showing just how full of it you are.
 
Boomer said:
.........................As I stated before, the amount of loss is dependent on powder volume, caliber, and the sectional density of the bullet.
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I agree that powder volume and caliber are factors in the amount of velocity loss when shortening a barrel. To those I would add powder type(fast vs slow burn) and bullet type(short vs long bearing surface of bullets with the same weight). But I don't understand how sectional density would play a part because SD isn't normally considered in internal or external ballistics.

Can you elaborate?:)
 
When similar styled bullets of the same SD are fired at the same pressure, they have the same velocity. Eg; a .30 caliber 165 gr bullet (SD .248) and a 130 gr .270 bullet when both bullets are loaded to 50,000 lbs pressure both bullets will have the same velocity, which for the sake of argument might be 2800 fps. Going to a bullet with a higher SD might result in a smaller drop in velocity from a short barrel because that bullet would be slower to start with so when the drop of velocity is viewed as a percentage, the actual velocity drop for the slower bullet would be less.

Playing with powders of different burning rates will serve little purpose. If you get the best velocity in a 24" barrel with 4350, switching to 3031 for the same bullet in a 20" carbine will result in reaching excess pressure before you hit the velocity you expect, and as in the case with the long barrel, A very slow powder like Retumbo will bulk out before you get the velocity you want as it did in the long barrel. If 4350 gives you the best velocity with a 24" barrel, it will with a 20" barrel as well. The faster powders will be equally effected by the shorter barrel.
 
If 4350 gives you the best velocity with a 24" barrel, it will with a 20" barrel as well. The faster powders will be equally effected by the shorter barrel.

I was waiting for someone to state the above quote, which is correct.
 
Boomer - all other things being equal, at what approximate barrel length would a .308 actually start losing velocity? or is such a length far beyond the scope of factory barrel lengths (ie: 30"+)?

ie: with standard .22 LR ammo you can start to lose velocity beyond 20" barrel lengths (except in the case of CCI Stingers). obviously a rimfire is a different story than a centerfire, but im wondering if anyone has actually made barrels long enough to measure velocity drops in centerfires.
 
Send it to me. :) I'll run five rounds over my Oehler, have the barrel cut and crowned at one inch intervals, and record five shots at each new length, then send it back with the results.

Or, you could just have one of the guys down there chrony it for you before and after going to 18 1/2 inches. :cool:

The results will be the same. You are not going to lose 100 fps total, never mind 100 fps per inch.

Ted
 
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