.236 vs .237 Bore Dia.?

[Chuckhunter]

I have a new barrel on order and it will have a .236 bore diameter as that is the manufactures standard, they will make a .237 bore but I would have to cancel my order and start fresh pushing my delivery time back well over a month. I'm wondering whether I should order the .237 bore as I have heard from several well known shooters plus a couple of highly respected bullet makers that the .236 barrel is likely to cause bullet failures with thin jacketed bullets. Can anyone shed any light on this issue. I'm willing to wait the extra time if a .237 bore is really what I need.

 

[jonbearman]

If the barrel maker is telling you this I would believe him as he has alot more experience at this than most shooters.Another thing about tight bore's is the pressure curve.The smaller the hole the higher the pressure.Also the bore actually should copper a little quicker. I have all .237 bore's and love them.It is the industry standard.There are bullets designed for tight bore's ,but why fix it if it isn't broke.I hope this help's jonbearman

 

[RonAKA]

If bullet explosion is the issue, then you need to consider the twist of the barrel. Bullets explode due to spin and cutting of the jacket. If you have a slow twist barrel, you probably can afford to cut a little deeper into the jacket, and produce a little more pressure.

 

[Chuckhunter]

Guess I should have pointed out that the barrel twist will be an 8 twist and it will be chambered for a dasher with the bullets to be between 105 and 108 Gr.

 

[alf]

.236" is perfect, don't change a thing.

 

[kperry]

Weather it has "canted " lands or not, will mean more than the dia. You can get by with the thin jackets more often than not, with the canted lands.

K Perry

 

[camac]

I have had Kreiger 236 and 237 8 twist and both shoot great with no bullet failures at 6BR speeds. Both were/are outstanding barrels. Nothing wrong with 237 for the long bearing surface bullets. In 308 class I like the tighter lands for shorter bullet class (155) so imagine the same would hold true for 6mm.
Berger seem to have addressed some bullet failure issues at the bullet end so may not be an issue anymore?? (Not sure though).
But remember some guys are pushing the 105-108's out at 3200+ (3350?) IN 6MM AND 243 AI's and 6 * 284's etc. Also there are barrels with 7/7.5 twist built for 115's that have been used with many 105-108's. I think the Dasher should be very safe and if not, switch bullets.

 

[RGRobinett]

Customers - the best barometer - have reported FAR fewer 'bullet issues' (especially failures) via .237 bored barrels as compared to the .236 bores. With the intent of using long for caliber (high BC) 6mm bullets, I wouldn't own a .236 bore, which engraves the jacket fully 14% deeper that the .237 bore: 14% deeper engraving probably erodes the tensile strength at greater than a linear rate. Thus, the bullets are another step closer to 'the final straw''. Why take the risk? ;D

And, from customers using the R5/C5 rifling profiles, ZERO bullet failure issues have been reported. My own [limited] experimenting bears this out - using two 1:8" twist (Broughton C5) 6mm barrels, I have been unable to create a failure - this using a 6x250 Ackley chambering. Good shootin'! RG

P.S. Oooops, I forgot: using conventional rifling profiles, both button and cut rifled, especially tight bored samples, bullet failures are not uncommon.

 

[camac]

Thanks RG good to hear from the horses mouth.

 

[dsbw]

Well well, strange how personal experiences differ!! I'm shooting two 6x47's, 108gr Bergers, 105gr Bergers, both 1 in 8 twist Bartleins, 32" finished, .236', 3100 Fps. One has 1600 shots through, the other about 1000.

I have ZERO issues with so-called bullet failure/friction issues, whatever you want to call it. I have NOT yet shot the thick jacketed Bergers, since we have not had any available until now, ONLY the original thin jackets.

Therefore, I CANNOT agree with the views here, had no such experience at all. In fact, these are the fourth and fifth 6mm barrels, I do not order them any way but .236.

 

[a6mmbrman]

I have sold over 75 6mm barrels this year all were .237". That dont mean the .236" wont work just fine. I have had such good results with .237" I wont be changing anytime soon. Get a good barrel and either will be fine.