That does not make a ton of sense so let me explain. I have an older Tikka T3 in 7mm Rem mag. I believe it is a 24" barrel. I asked my gunsmith about cutting it down because I want to use a suppressor on it. I asked him how short I could go with out losing too much velocity and energy. I was thinking 18". But would appear 21" would be the sweet spot? I would like some thoughts.
Does the suppressor make up for the cutoff barrel ballistic-ally?

No

What para said

quote:

Originally posted by parabellum:
No

Thanks, I did not think so.

It’s well documented that a suppressor can sometimes increase MV over what it is without the suppressor. I have seen it myself in a test of various AR-15 barrels I conducted years ago. When M193 ammunition was fired from a 11.5 inch barrel without the suppressor 10 shots averaged 2752 fps, and with it the average was 2786. But an average increase of 34 fps was only about 1 percent. Plus 10 shots is a small sample size, and it’s possible it wasn’t a genuine effect for some reason.

I have read possible explanations for the phenomenon such as the suppressor holds the propellant gas longer, and I suppose it might be true.

Although I don’t have other figures at hand, I have sometimes seen a slight velocity increase with other guns and ammunition, but not enough to make up for cutting a 7mm Rem Mag barrel from 24 to 18 inches. And sometimes there’s no velocity increase at all when using a suppressor. Without checking my records, I believe that’s more common than seeing any statistically valid increase.

24” with an added suppressor is on the long side, for my uses anyway. Even when it comes to ‘western hunting’ I’m not into the longer barrels. Yes I can understand the ballistic benefits, FPS increase.

Right now I have 2 rifles that share a 30 cal suppressor, 243 & 6.5 Creedmoor. With my setup I certainly wouldn’t expect any added speed, over the bare barrel.

It wouldn’t be hard to shoot 5 rounds with then without a suppressor over a chronograph, check yourself.

Once again a question here piqued my interest, so a little research.

I checked my velocity records pertaining to the following loads fired from a Tikka T3x TAC A1 rifle chambered for 308 Winchester with and without a Thunder Beast 30P-1 suppressor. All comparisons for each load were with the same lots of ammunition. ES is extreme velocity spread.

Hornady 168 grain A-MAX TAP.
Without suppressor: 2642 fps, ES 29 fps, 5 rounds
With suppressor: 2640 fps, ES 24 fps, 10 rounds
Difference +2 fps greater without suppressor.

Hornady 155 grain A-MAX Black.
Without: 2787 fps, ES 19 fps, 5 rounds
With: 2756 fps, ES 65 fps, 10 rounds
Difference +31 fps without suppressor.

Federal 168 grain Gold Medal Match
Without: 2632 fps, ES 45 fps, 16 rounds
With: 2642 fps, ES 36 fps, 12 rounds
Difference +10 fps with suppressor.

Note, however, that in all cases the velocity differences were less than the extreme velocity spreads for all but one trial. That plus the small sample sizes of the number of shots means that the velocity differences seen could have been due to chance, not any real effect of using the suppressor or not. And even if they were valid, all were so small as to be insignificant.

I also asked AI Gemini this question, which is the sort of research one should do for this issue:
“velocity change per inch of rifle barrel length 7mm Remington Magnum cartridge”

The response indicated that the average change per inch of barrel length varies with the specific load and the barrel lengths involved. This is what it said about one barrel length:

“Below 22″: 40 to 60+ fps / inch. Steeper drop-off; significant increases in muzzle blast, flash, and noise.”

According to that response, going from 22 to 18 inches could result in a loss of 200 fps as well as increasing the unpleasantness of shooting significantly due to the cartridge’s “overbore” capacity.